Wooden decking of crane passages. General information about the installation of overhead cranes
The need to install special platforms for inspection and maintenance of mechanisms located outside the crane, the Crane Rules (Article 229) provide only for single-girder (support and suspension) and double-girder suspended cranes, if they are installed in a building and do not have platforms and galleries located on the actual tap. In other cases, the feasibility of constructing platforms is determined by the organization designing the installation of cranes or the enterprise operating them.
Platforms can be stationary or mobile. In stationary sites, the distance from the flooring to the lower dimension of the crane being serviced must be at least 1800 mm, however, at this distance, access to the mechanisms is very difficult. To create normal service conditions, this distance can be reduced by installing a locking door on the stairs with automatic electric locking, which removes voltage from the main trolley wires of the repair area.
The staircase must have a door, when opened, the trolley section in the landing area is automatically de-energized. The trolls are turned on after the crane is repaired using a switch in the repair area. For the electrical diagram for blocking the entrance to the repair site, see 7. 13.
Approximate solutions for stationary repair sites are shown in Fig. 4. 16-4. 22.
The requirement for the repair site door of single-girder and double-girder suspended cranes, when the distance from the floor of the repair site to the lower parts of the crane is less than 1800 mm and when the current supply to the crane is carried out not by trolley wires, but by a flexible cable. In this regard, the need for a locking device to automatically relieve tension from the flexible cable in this case
Figure 4.18 Repair platform at the end of the span for overhead electric single-girder cranes with control from the cabin with a lifting capacity of 1-5 tf with a span of 4.5 to 10.5 m: 1 - platform; 2 - chain; 3 - emphasis; 4 - cabin
should be determined taking into account the number of cranes operating in one span, the method of operating the cranes (from the cabin or from the floor) and the possibility of taking other measures to prevent people from entering the repair area while the cranes are operating and running into them. The repair site is designed for a uniformly distributed crane load of 20U kgf/cm2, and the site area designated
Figure 4.19. Repair site at the end of the span of overhead electric single-girder cranes with control from the cabin with a lifting capacity of 1-5 tf with a span from 13.5 to 23.5 m (1-4, see Fig. 4. 18):
for repair of electric hoists, on the concentrated weight of electric steel of the corresponding load capacity. For two beam overhead supporting cranes, it is advisable to provide in the repair car (see 7.5) areas for inspection and changing the running wheels of the crane, if there is a distance of at least 600 mm from the end part of the crane to the wall of the building. Access to such sites is provided from the crane bridge or through a hatch in the deck that is closed during operation of the cranes. Access to such a repair site is subject to a permit.
Bridge cranes controlled from the cabin (except single-girder and suspended) must be equipped with cabins for servicing the main trolley wires and pantographs if they are located below the deck of the bridge gallery (Article 230 of the Crane Rules). The hatch for entering this cabin from the bridge deck must be equipped with a lid with a lock.
The dimensions of the cabin for servicing the main trolleys and their pantographs are not regulated and are usually taken as 1000X1400 with a height of at least 1800 mm. The cabin area should not be less than 800X800 mm. The cabin must be fenced with railings at least 1 m high with a continuous hem along the bottom and a height of 100 mm. It is suspended at a distance of 1000-1100 from the axis of the crane rail. When power supply is carried out by cable, the cabins are not arranged. The cabin floor is covered with a dielectric mat.
Figure 4.20. Repair site for suspended two- and three-span electric single-girder cranes with a lifting capacity of 1-5 tf (1-3 - see Fig. 4. 18)
The supporting overhead electric crane has a crane bridge that spans the span of the building and rests with running wheels on the rails of the crane track. Most often, double-beam bridges are used, which are a frame structure consisting of two spatially rigid main beams with rails laid on them for moving a cargo trolley and two end beams adjacent to the main beams at the ends of the span.
On the main beams there are fixed platforms that serve to accommodate the crane's movement mechanisms, electrical equipment cabinets and the passage of the driver and repair workers. All platforms have railings. The end beams are also equipped with railings and are used for fastening axle boxes with running wheels, with which the crane rests on the rails of the crane runway. At the ends of these beams there are buffers and limit switches that limit the movement of the crane along the rail track.
For ease of service metal constructions cranes are equipped with galleries, platforms and stairs. The width of free passage through the gallery intended for servicing mechanisms and electrical equipment is usually at least 500 mm for cranes with a central drive and 400 mm for cranes with a separate drive. On a gallery intended for installation of trolley wires, the width of the passage between the railings and the devices supporting the trolleys, as well as current collectors, is set to at least 400 mm. The flooring of the gallery, repair and landing areas is made of metal or wood along the entire length of the gallery or area. Metal flooring is made from steel corrugated or perforated sheets with holes with a diameter of no more than 20 mm.
Platforms, galleries, end beams, as well as a cabin for servicing trolley wires of overhead cranes are fenced with railings at least 1 m high with a continuous fence in the lower part with a height of at least 100 mm. The latter allows you to eliminate the involuntary fall of tools and spare parts from the crane bridge when servicing the crane. Railings and fences are also installed on the end sides of cargo trolleys, and in the absence of a gallery - along the bridge on the longitudinal sides. The hatches of the gallery flooring and repair areas are equipped with conveniently opening covers. If the cover is hinged, then the angle between the hatch cover in the open position and the deck does not exceed 75°. The dimensions of the hatch are at least 500X500 mm.
Stairs for access from the floor to platforms and galleries are made with a width of at least 600 mm, and the distance between steps is no more than 300 mm. If the height of the ladder on the crane is less than 1.5 m, a ladder width of 500 mm is allowed. Stairs for exiting the cabin to the crane bridge gallery can be made at least 350 mm wide. Inclined stairs with an angle of inclination to the horizon of 75° or less are equipped with railings and flat steps made of corrugated or smooth steel sheets with fused relief; The width of the steps must be at least 120 mm. On vertical stairs, as well as on stairs with an angle of inclination to the horizon of more than 75°, at a height starting from 3 m, arched fences are installed. These fences are located at a distance of no more than 800 mm from each other and are connected by at least three longitudinal steel strips.
General information about the installation of overhead cranes
When installing overhead cranes, assembly units are enlarged, delivered to the installation site and laid out in the operating area lifting devices, rig, lift the enlarged elements onto the crane tracks, assemble and calibrate the mounted cranes.
The choice of installation method for bridge supports depends on their design and weight, installation location: inside or outside the building, delivery time by manufacturers, construction readiness of the facility, building frame design, as well as the type and characteristics of lifting machines available to the installation organization.
The most widely used methods for installing overhead cranes are: – using tower or jib rail cranes designed for installation building structures buildings; – using jib self-propelled cranes; using building frame structures, including pulleys, attached to columns or mounting beams resting on two adjacent trusses, less often - directly to the trusses.
IN Lately The method developed by the Giprometallurgmontazh Institute for installing cranes, fully assembled in the lower position, using conveyor line equipment for the assembly and installation of building roofing blocks is becoming widespread.
The previously widespread method of mounting cranes using masts is currently used only in cases where there are no other lifting devices or mechanisms available or cannot be used, for example, workshop conditions do not allow the use of a self-propelled crane, and the structure of its frame does not allow the installation of an assembly beam.
The main disadvantages of this method are the greater labor intensity compared to others (1.5-1.8 times), metal consumption, duration of work, as well as the need to install braces to secure the mast inside the workshop.
Recently, the method of installing overhead cranes using hydraulic lifts designed by the Giprotechmontazh Institute has begun to be introduced.
Consolidation of assembly units of overhead cranes.
The order of enlarged assembly and the degree of enlargement of crane assembly units are determined by the work execution plan (WPP), depending on the chosen installation method and the terms of delivery of the cranes.
The purpose of the enlarged assembly of structures, mechanisms and electrical equipment of overhead cranes is to perform the maximum volume of assembly work in the lower position and, accordingly, reduce to a minimum the number of operations performed at height. That's why the best option is one in which a bridge is lifted onto the crane tracks, completely assembled in the lower position, together with the trolley installed on it, or the bridge is lifted separately, and then the trolley. However, it is often not possible to lift and install a fully assembled crane bridge on the crane tracks due to the insufficient lifting capacity of the existing mechanisms and devices, the limited under-jib space of the self-propelled cranes used, and the inability (due to lack of space) to deploy the assembled crane bridge in a horizontal plane above the crane tracks . In addition, it is not always economically feasible to manufacture stands and arrange sites for assembling crane bridges.
Most often, crane bridges are mounted in two or four assembly units; the trolley is mounted in one enlarged unit and the control cabin is mounted in the other.
Enlarged assembly of bridges. Metal structures of bridges are enlarged in the lower position in cases where the bridge is lifted onto crane tracks in one block. To do this, at the enlarged assembly site (if space allows) or at a site specially allocated for this purpose, as close as possible to the installation site, racks for assembling bridges are installed. The racks must have a horizontal surface; two parallel rails are laid on top of them, the distance between which is equal to the span of the crane, and the length is 2.5-3 m greater than the base of the crane on each side.
The crane bridge is assembled on the racks using self-propelled jib or operating overhead cranes (if the site is located in the workshop). In this case, if the bridge is supplied by the manufacturer separately in the form of two main and two end beams (Fig. 74, a), four assembly joints of the main beams with the end beams are assembled. If the bridge is supplied in the form of two main beams together with parts of the end beams (half-bridges), assemble the joints connecting the parts of the end beams: two - if the main beams are supplied for installation with halves of the end beams (Fig. 74, b), and four if The outer parts of the end beams are attached to the main beams, and their middle parts (inserts) 3 are supplied separately (Fig. 74, c).
Assembly joints are assembled in two stages: first, using mounting (assembly) bolts, and after alignment and elimination of distortions, finally, using welding, clean bolts or rivets in accordance with the instructions in the working drawings.
When assembling a bridge installed according to the diagram shown in Fig. 74, and, first, end beams with wheels or balancers are installed on the rails laid on the racks and fixed (temporarily secured) in the desired position. After this, one of the main beams is inserted between the end beams until the holes for the mounting bolts in the joints are aligned and they are connected with bolts. Then the second main beam is also installed and connected to the end beams.
Assembly of crane bridges supplied according to the diagrams shown in Fig. 74, b, c, begin by installing half-bridges with wheels or balancers on the racks. If bridges are supplied according to the diagram shown in Fig. 74, c, then the middle parts of the end beams - inserts - are installed between the half-bridges. Then the half-bridges are brought together and the holes for the mounting bolts in the butt plates are aligned according to the marking scheme, after which they are connected with bolts.
74. IOSG crane delivery diagrams a - separate main and end beams: b - main beams with halves of end beams; c - main beams with the outer parts of the end beams and inserts; 1 - main beam; 2 - end beam; 3 - insert
Before assembly, the surfaces of the butt elements are thoroughly cleaned of dried soil, paint and rust, and the surfaces of the welded butt elements are cleaned to a metallic shine. When assembling joints, it is necessary to achieve maximum coincidence of the holes and not allow them to be adjusted by tension using conical mandrels, as this creates additional stresses in the metal. The tightness of the butt pads is checked with a feeler gauge: the probe plate with a thickness of 0.1 mm should not pass between the pad and the body of the end beam.
Riveted joints are assembled by driving mandrels (plugs) into the holes (for the rivets), which are used to evenly fill 10-15% of the holes on each side of the assembly joint. At the same time, mounting bolts are installed, which are used to evenly fill 20-25% of the holes. The nuts on the bolts are not tightened completely.
For assembling installation joints, except lifting cranes, use lever winches, jacks, as well as simple devices for temporarily securing bridge elements in the desired position: supports, linings, brackets, shoes, etc.
After assembling the bridge, platforms are attached to the outer walls of the main beams, stairs and fences are installed.
The crane bridge assembled on mounting bolts is verified by checking and comparing with those indicated in the drawings or passport: the squareness of the bridge, the crane span, the track of the load trolley, the construction lift of the bridge, the installation of trolley rails and running wheels of the crane.
The squareness of the bridge is checked in one of two ways: by the difference in diagonals or by the alignment method (using a theodolite). Diagonals are measured at symmetrical points of the bridge, which can be the intersection points of the longitudinal and transverse axes of the running wheels; practically they are carried out on end beams or bogie rails (Fig. 75), but in this case the dimensions a and a’, b and b’ must be respectively equal to each other. Measurements of diagonals are often carried out at points transferred to the end beams from vertical tangents to the circumferences of the flanges of the running wheels. If the squareness of the bridge was checked at the manufacturer (about which a corresponding entry is made in the crane passport), then during installation, measurements of the diagonals are made according to the control marks marked on the end beams or bogie rails. The difference between the diagonals of a rectangular bridge should not exceed 5 mm.
75. Scheme for aligning a crane bridge using a tape measure
76. Scheme of alignment of a crane bridge using a theodolite
1 - theodolite; 2-5 - wheels; 6 - reticle
For large crane spans, this method of checking is not accurate enough, since it measures long lengths tape measure requires constant tension of the steel tape; In addition, it is almost not always possible to measure diagonals on the crane bridge. In these cases, the second method is more often used, which is as follows.
At point A, at the distances indicated in Fig. 76, install the theodolite, and at point B - sighting Mark 6. Align the sighting axis of the theodolite with the center of the sighting mark, after which the theodolite telescope is rotated 90° in the horizontal plane (along the limb) and secured. Then measure the distances X\, Xr, X3 and X4 from a plumb line installed along the sighting axis of the theodolite to the end surface of the wheels along a chord passing through points removed from the axis by at least 300 mm. The chord length is assumed to be the same on all wheels. After this, the theodolite is transferred to point A’, and the target mark to point B’ and similar measurements are made on the wheels.
The condition for the rectangularity of the bridge is the equality of the dimensions xx and x4, Xg and x3, as well as xb, taken between wheels 3 and 4, 2 and 5. The permissible deviation of these dimensions from each other is 3 for flanged wheels, and 4 mm for flanged wheels.
The second method also allows you to simultaneously check the misalignment of the running wheels in the horizontal and vertical planes, since the difference in dimensions xx and X2, Xb determines the misalignment in the horizontal plane, and the difference in distances from vertical plane to similar points located at the ends of the vertical chord, characterizes the skew in the vertical plane.
In the first method of checking the squareness of the bridge, wheel misalignments are determined in the same way, but instead of a theodolite sighting line, a string and a plumb line are used. Deviations of the end surfaces of the wheels from the horizontal and vertical planes should not exceed i mm per 1000 mm of wheel diameter. The same tolerance is established for the deviation of the ends of the wheels from the general plane.
If deviations from the squareness of the bridge exceed the specified values, then the misalignment must be eliminated.
Most common fix geometric shape crane bridges is as follows. At one of the corners of the bridge with a larger diagonal, a stop is placed to prevent its longitudinal and lateral movement, and at the other corner there is a jack. Having loosened the tightening of the mounting bolts, direct the force of the jack along the axis of the main beam, which is moved until the difference in the diagonals becomes zero or within the tolerance. Another way to correct the shape of the bridge is to fix one end beam and move the second one in the direction of the axis of the crane track rail.
The permissible deviation of the crane span LK, measured in the middle of the supporting surfaces of the running wheels for cranes with LK up to 40 m, is ±6 mm, for cranes with LK more than 40 m - ±7.5 mm.
The deviation in the joints of bogie rails 2 in plan and height should not exceed 1 mm, and the gap at the joints should be no more than 2 mm.
The permissible gap between the base of the bogie rail and the spacer or the upper chord of the beam depends on the type of rail and can be at the edges of the base (see size g in Fig. 77) from 0.75 mm for the P4 rail to 2.5 mm for the SKR140 rail. In the middle part of the sole, this gap should not exceed 0.3 mm (P4) to 1 mm (skr140).
Distortions of the running wheels exceeding the above tolerances are eliminated using spacers installed between the plates and axle boxes of the wheels in the end beam or balancer, ensuring that the position of the wheels corresponds to the dimensions obtained during assembly at the manufacturer and recorded in a special form, attached to the crane passport.
The final connection of assembly joints by welding is performed by welders certified according to the rules of Gosgortekhnadzor at a temperature not lower than minus 10 ° C in compliance with the technical requirements of the manufacturer.
Clean bolts used for connecting assembly joints must have a length of the unthreaded part of 8-10 mm less than the thickness of the package of elements being connected. Insert them tightly into the holes using a hammer. The tightening of the bolts during final assembly of the joints should ensure a tight fit of the parts being connected. In a tight joint, a 0.1 mm thick probe can be inserted between the parts to a depth of no more than 20 mm at any joint.
Riveting is done using hand pneumatic hammers. This is a very labor-intensive and difficult operation, so they strive to perform the maximum amount of riveting work in the lower position, before lifting the assembly units onto the crane tracks.
Before riveting begins, tighten the clean bolts that secure the linings at the joints.
Then the holes for the rivets are checked with a gauge with a diameter 1.5 mm smaller than the nominal diameter of the hole and the burrs on the edges of the holes are removed, while the depth and width of the countersinking of the holes should not exceed 1.5 mm.
The enlargement of crane half-bridges consists of installing the chassis and the drive of the movement mechanism (if they are supplied separately), as well as platforms. Sometimes, during the enlarged assembly of crane half-bridges installed according to the diagram shown in Fig. 74, c, in the middle, parts of the end beams are placed on one of the half-bridges to reduce the amount of assembly work at height. This enlargement scheme is used when it is possible to rotate the enlarged half-bridge in a horizontal plane during lifting.
The running gear of the crane movement mechanism, in which the main beams rest directly on balancers with running wheels, is installed by rolling them along rails under the main beam, and after aligning the holes, they are connected by an axle (connecting shaft).
The installation of the running gear of cranes, in which the main beams rest on the main balancers (Fig. 78), begins with attaching small balancers with running wheels to them. To do this, small balancers are first installed and temporarily secured on the rails, to which the main balancer is fed on the hook of the lifting mechanism. The axles are inserted into the aligned holes in the main and small balancers. Then the main balancer, assembled with small ones, is fed by the same lifting mechanism to the end of the main beam, laid on sleeper linings, and after aligning the holes, they are connected by an axle.
The position of the balancers with wheels is adjusted by spacer rings installed on the axle on both sides of the balancer in accordance with the factory markings. Incorrect installation spacer rings or their absence can change the span of the crane, which is unacceptable. The installed balancers are checked for jamming by rocking them on their axes.
The drive of the crane travel mechanism is assembled after installation and alignment of the chassis, and the alignment and connection of the output shaft of the gearbox with the axis of the drive wheel in the end beam or balancer - after the final connection of the mounting joints of the bridge metal structures. The most difficult operation when assembling the drive is the alignment of gear couplings of the MZ and MZP types (with an intermediate shaft). Condition correct connection shafts is their alignment and absence of distortions (within tolerances).
78. Scheme for hanging balancers on the main beams
1 - hook of the lifting mechanism; 2 - main beam; 3 - holes; 4 - main balancer; b - small balancer
79. Scheme for determining misalignment and radial displacement of couplings
a - MZ type; b - MZP type
When assembling MZ type couplings (Fig. 79, a), the radial displacement a, which characterizes the misalignment of the connected shafts, and the misalignment, determined by the linear value s - tn-n or the angle с, are controlled. The quantities a, m and n are determined at four points (in two mutually perpendicular planes). The highest permissible value is 0°30.
When assembling MZP type couplings (Fig. 79.6), the radial displacement a and distortions e-b-c are controlled.
Allowable values of a, s, b, c and e depend on the sizes (numbers) of the couplings; they are indicated in technical documentation manufacturer.
During the alignment process, the shafts being connected are aligned, i.e., their alignment is achieved and distortions are eliminated, after which the couplings are finally assembled.
Lastly, the electric motors and brakes are installed, the position of the electric motors is verified, their shafts are aligned with the gearbox shafts and secured to the under-motor plate or frame.
The brake must be installed so that its center coincides with the center of the brake pulley. Non-parallelism and misalignment of the surfaces of the pads relative to work surface pulleys should not exceed 0.1 mm per 100 mm of pulley width, and radial runout - 0.05 mm per 100 mm of pulley diameter.
Integrated assembly of trolleys. Crane trolleys with a lifting capacity of up to 50 tons inclusive are supplied by manufacturers fully assembled and ready for installation on the crane bridge.
Crane trolleys with a lifting capacity of 80 tons and above are supplied as separate assembly units according to the following schemes: – the trolley frame assembled with the movement mechanism, the main and auxiliary lifting mechanisms - assembly units; – half of the frame with a travel mechanism (without running gear) and the main lift mechanism, half of the frame with an auxiliary lift mechanism and with the running gear of the travel mechanism; – the entire trolley frame, movement mechanisms, main and auxiliary lifts - as assembly units; – the trolley frame is in parts, the movement mechanisms, the main and auxiliary lifts are in separate assembly units.
Obviously, the largest amount of work on the enlarged assembly has to be performed when delivering trolleys according to the last of the above schemes (this is how crane trolleys with a lifting capacity of 200/32 tons and above are supplied). The larger assembly of the trolley is carried out on a special stand with rails or on a crane bridge. You can assemble the trolley on a sleeper cage, and then carry out the final alignment of the running gear of its movement mechanism on the crane bridge. First, assemble the trolley frame (if it is supplied by the manufacturer in separate parts) on mounting bolts and install the running gear of the travel mechanism: wheels or balancers.
When assembling the frame, check its squareness by measuring the diagonals at the points marked with risks at the manufacturer during the control assembly of the trolley or directly at the installation site. The difference between the diagonals should not exceed 3 mm.
After this, check the correct installation of the running wheels or balancers in the same way as the running gear of the crane movement mechanism. In this case, in addition to the skew of the running wheels, the displacement of the vertical plane of symmetry of the running wheel from the same plane of the rail, which is allowed no more than 2 mm, is checked, as well as the support of the trolley on the bogie rails with all wheels (the centers of the running wheels must be located in the same horizontal plane ) and the base of the trolley, measured on one side and the other, the tolerance of which is ±2 mm. After alignment and elimination of distortions of the frame and chassis, gellings are performed final assembly frames are riveted or welded in accordance with the instructions in the manufacturer's drawings. Sometimes the running gear of the trolley movement mechanism is assembled on an inverted frame, which is then tilted into the design position.
After riveting or welding the trolley frame, the movement mechanism is finally assembled: the gearbox is installed (preliminarily), the gear couplings and shafts are assembled and aligned, and they are also connected to the wheels, after which the gearbox is secured. Then install the brake and electric motor with a coupling half made in the form of a brake pulley, center the shafts of the electric motor and gearbox, the brake and secure them with bolts. If it becomes necessary to place the coupling half on the electric motor shaft, this is done with light blows of a wooden or copper hammer, while the opposite end of the shaft is given a stop; the coupling half is preheated to 60-80 °C.
The assembly units of the lifting mechanisms rest on processed plates, so there is no need to adjust their height position with pads.
The main lift mechanism is assembled in the following sequence: a drum with block bearings and a stand is installed (after they are aligned and fastened, the locking wedges are hammered in and secured by electric welding), small gears of an open gear and a gearbox, and then an electric motor and brake.
The assembly of the auxiliary lift mechanism begins with the gearbox, and then installs the drum, electric motor and brake.
When installing the drums of the main and auxiliary lifting mechanisms Special attention should be given correct assembly and alignment of open gears.
The gear teeth of the gearbox output shaft must be evenly recessed between the teeth of the driven gear of the drum. When aligning, it is necessary to ensure the interaxle distance specified in the drawings and the absence of misalignment of the axes.
Correct assembly is determined by the maximum deviations of the side clearance and center distance, as well as the size of the contact patch of the teeth, which is checked for paint.
Electric motors and brakes are installed after complete assembly and alignment of the mechanisms. At the same time, gear couplings and shafts are assembled and aligned. The misalignment and mutual displacement of the shafts of electric motors and gearboxes must be within the tolerances specified in the manufacturer’s drawings, and in any case must not exceed the value permissible for a gear coupling of the corresponding number.
After assembling the crane bridge or enlarging half-bridges, as well as after assembling the trolley, before lifting the assembly units onto the crane tracks, electrical equipment is installed. This work is performed by a team of electricians who, in accordance with electrical installation drawings, install terminal and adapter boxes, stands for electrical devices, and lay electrical wiring harnesses in boxes and metal sleeves.
Then install electrical devices (transformers, starters, resistance boxes, etc.), making sure that the width of the passages between them and the railings of the bridge site fencing is at least 400 mm. After this, connect the ends of the electrical wiring to the terminals of the electrical equipment, and install the grounding of the electrical equipment and electrical wiring.
Control cabins for overhead cranes are usually installed with high degree electrical installation readiness. But sometimes the electrical installation of the cabin has to be done at the installation site, including the installation of a protective panel, controllers, lamps, limit and emergency switches, buttons, terminal and junction boxes.
Also, before lifting the bridge (or half-bridges) of the crane, crane lighting fixtures are installed and connected.
If assembly units are enlarged away from the installation site of overhead cranes in the design position, then after enlargement they are transported to the installation area along railway tracks on platforms, special carts or by vehicles on trailers. When the consolidation assembly site is located near the installation site of overhead cranes, the assembly units are delivered to the installation area by pipe layers.
In the installation area, assembly units are laid out in accordance with the chosen installation method and depending on the availability of free space on the site.
If there is enough space, the assembly units of the frame are brought into the installation area in their entirety and laid out in such a way that the heaviest of them are within the range of action of the lifting devices and there is no need to drag them to lift them into the design position.
If, due to lack of space for layout, all crane assembly units cannot be delivered to the installation site, they are supplied according to an agreed schedule, specified before the delivery of each enlarged unit. The most effective is “installation from wheels”, i.e. lifting crane assembly units directly from Vehicle.
Slinging. This operation is very critical in production rigging work and must be carried out in strict accordance with G1PR, which indicates the slinging schemes of assembly units and the diameter of the rope used for the manufacture of slings. The slinging pattern can be changed or the rope replaced only with the permission of the organization that developed the PPR.
Crane assemblies must be rigged by experienced riggers.
When choosing a slinging unit and the number of rope threads in a sling, they tend to use slings with as few threads as possible by increasing the diameter of the rope, but not more than 39 mm, since it is difficult to tie knots with a large diameter rope, especially when slinging with a “dead loop” knot, and splice the ends of the rope with a straight knot (“figure eight”).
When lifting assembly units of small mass, slinging is performed with a universal or lightweight sling.
When lifting heavy assembly units, a steel rope of such length is used for the sling that is necessary for slinging according to the accepted scheme.
The ends of the ropes in these cases are connected with straight or bayonet knots, as well as with the help of various clamps.
The beams of box-section bridges are raftered with various units (Fig. 80). A simple ring knot (Fig. 80, a) is made with universal slings or from pieces of rope.
Most often, beams are stropped with one or two “dead loop” (noose) knots (Fig. 80, b, c). Since the beams are lifted together with the platforms and elements of the movement mechanisms, the center of gravity of the lifted assembly unit is shifted from the axis of symmetry of the beam section by the amount K. Therefore, when slinging, the “dead loop” unit is shifted (see Fig. 80.6) by this amount, which can be determined by calculation or, as is done in practice, by trial lifts to a height of 100 mm with subsequent re-slinging, if the need arises. Sometimes, for the same purpose, an auxiliary sling with a spacer is used (see Fig. 80, c), which absorbs the overturning moment caused by a shift in the center of gravity.
80. Slinging beams of box-section bridges
a - a simple ring knot “in the girth”; b - displaced “dead loop” knot; c - a “dead loop” knot with an auxiliary sling; g - a knot with an overlapping thread; 1 - bridge beam; 2 - bracket; 3 - sling; 4 - lining - 5 - platform: 6 - hook or bracket of the lifting mechanism; 7 - spacer; 8 - auxiliary sling; 9 - overlapping thread; 10 - compression
The beams of heavy-duty cranes are often slung with a knot with an overlapping thread 9 (Fig. 80, d), which ensures reliable fixation of the threads of the main sling and in which this knot differs from a simple ring knot. In these cases, an auxiliary sling is also used. To ensure the stability of the beam being lifted, the distance L between the slings or the spacing of the branches of one sling must be no less than half the height of the beam I, i.e. L> >0.5 R.
To protect the rope from damage from the sharp edges of the lifted loads, stock metal pads or wooden pads are placed under it.
In some cases, the crane manufacturer or installers (in agreement with it) weld eyelets (with reinforcement elements) to the upper chords of the beams to attach the movable block of the hoisting mechanism (Fig. 81). In these cases, there is no need for rope slings, and the movable block of the pulley block is attached to beam 1 using pin 5, fixed in the holes of the eye and eyelet of the block.
The assembled crane bridge is slinged using ring units as shown in Fig. 82. To prevent deformation of the bridge during the lifting process, pipe spacers, adjustable in length, are installed between the main beams.
Crane trolleys are slung behind the frame beams so that the branches of the sling that go around the equipment parts do not damage them (Fig. 83).
Trolleys with a small carrying capacity are slung with universal slings or tied with a rope under the frame (Fig. 83, a, b). If there are special sling devices on the trolley frame - bosses, axles, staples, etc., then the slings are attached to these devices. Heavy-duty crane trolleys are slung behind the main frame beam, which connects the side beams. In Fig. 83, c shows that the trolley is slinged with two slings: the main one, tying the main beam of the frame, and the intermediate one, tied to the main sling and going to the hook or bracket of the movable pulley of the lifting mechanism. Other schemes for slinging heavy trolleys are also used - without intermediate slings.
81 Attaching the chain hoist to the eye
1 – bridge beam; 2 - reinforcement: 3 - eye; 4 - block clip earring; 5 - finger
82. Crane bridge sling diagram 1 - end beam; 2 - sling; 3 - lining; 4 - main beam; 5 - spacer
83. Slinging diagrams for overhead crane trolleys
A. b - universal or rope sling under the frame; c - main and intermediate slings; 1 - intermediate sling; 2 - main sling
Lifting crane assembly units onto crane tracks. This operation is the most critical operation during the installation of overhead cranes and must be carried out in strict accordance with the PPR (with installation diagrams and instructions for ensuring safe conditions production of work). The installation diagram can be changed in cases where it becomes impossible (according to various reasons) the use of lifting mechanisms originally provided for in the project, or when the situation at the installation site changes.
The most difficult operation for lifting crane assemblies is lifting main beams, half-bridges and fully assembled bridges.
There are two main methods of installing them on crane tracks: – lifting a half-bridge (the main beam or the entire bridge) above the crane tracks in a position where it is oriented along the span or at a certain angle to its longitudinal axis, then turning it in a horizontal plane and lowering it onto the crane tracks .
The possibility of installing a half-bridge in this way is determined by the distance from the axis of the crane rail to the wall of the building, as well as the width of the half-bridge; – raising the half-bridge in an inclined position - “fish”, when one side is ahead of the other. After one side passes the crane beam, the half-bridge is retracted or pulled to the same side and the second side of the half-bridge is carried past the second crane beam, and then the half-bridge is lowered onto the crane tracks.
The sequence of lifting crane assembly units depends on the degree of their enlargement and practically does not depend on the lifting mechanisms used for this purpose.
So, if a crane is mounted with two half-bridges (main beams with end parts), then one half-bridge is first lifted onto the crane tracks, then the other, the assembly joints are connected, after which the crane trolley is lifted and installed on the bridge, followed by the control cabin.
Another version of this scheme is often used, when the half-bridges raised and installed on the crane tracks are spread to a distance exceeding the width of the trolley by 400-600 mm, then they are raised between the spread half-bridges above the trolley rails, after which the half-bridges are brought together, the mounting joints are connected and the trolley is lowered onto bridge.
If a crane bridge is assembled from two main and two end beams, then first they lift onto the crane tracks and temporarily fix one end beam on them, then the second, then, in turn, lift the main beams and join them with the end beams, after which they lift and install the trolley on the bridge, and then mount the cabin.
In cases where the half-bridge of a crane, in which the main beams rest on balancers, cannot be lifted together with them (the load capacity of the existing mechanisms is insufficient), first the balancers with balancer trolleys are lifted and temporarily secured on the crane tracks. Then one main beam is lifted and its ends are connected to the balancers, the second beam is also lifted and installed on the balancers, after which the end beams are alternately lifted and joined to the main beams. The sequence of installation of the trolley and control cabin is the same as in the first of the schemes discussed above, including lifting the trolley between the separated half-bridges, bringing them closer together, connecting the joints and lowering the trolley onto the bridge.
The smallest number of lifts in cases where overhead cranes are installed in the design position with two or one mounting block: in the first case, a bridge and a trolley, in the second - when a completely assembled crane (together with a trolley attached to its bridge) is installed on the crane tracks.
Regardless of the sequence in which the overhead crane is assembled on the crane tracks, the final connection of the assembly joints on the crane bridge should be performed only after its alignment, which is carried out in the same way as when assembling the bridge in the lower position.
During the assembly process, half-bridges are moved along crane tracks using manual lever winches (mounting traction mechanisms). The guy ropes are controlled manually during the process of lifting, turning and installing half-bridges on the crane tracks (with a hemp rope). The exception is guy ropes, with the help of which the half-bridge is moved to the side when lifting in an inclined position - “fish”. These guys are made from steel rope and are controlled using hand lever winches.
84. Scheme of lifting a half-bridge with two cranes
1 - tower crane BK-1000; 2- half-bridge of the mounted crane; 3 - crane SKR-1500
The most effective for lifting assembly units of overhead cranes are tower or jib rail (type SKR) cranes, which are used to assemble building frame structures. This method is possible when overhead cranes are supplied before or during the construction of the building frame. In these cases, the installation of assembly units or cranes fully assembled in the lower position is carried out simultaneously with the installation of building structures of the building before its ceiling, or an opening is left in the ceiling sufficient to supply half-bridges and trolleys through it to the installation site; subsequently the opening is closed.
Depending on the location of the tower cranes on construction site when the lifting capacity of one crane at the required hook reach is not enough, the assembly units of overhead cranes are lifted by two tower cranes (Fig. 84).
The advantages of this method are that, Firstly, there is no need for other lifting machines, secondly, the possibility of combining the installation of the building frame and bridge cranes, which allows them to be put into operation in advance and then used not only when installing equipment, but also before that - when constructing foundations for it . The use of tower cranes, in addition, makes it possible to install overhead cranes at high altitudes, for example, in the high-rise part of oxygen converter shops, in the “shelves” of mine headframes, etc.
The main factor hindering the widest adoption of this method is the late delivery of overhead cranes, that is, after the construction of the building frame, when the tower cranes have already been dismantled.
In addition, Fie can always be mounted on any overhead crane assembly due to the insufficient lifting capacity of a tower crane at the required reach of its hook.
The use of erection jib self-propelled cranes to lift assemblies of bridge bridges onto crane tracks is one of the most common methods of installing these cranes.
The conditions for using self-propelled cranes inside a building for this purpose are: – openings in the building for the crane to pass into the installation area; – leveled and compacted platforms for installing cranes on them; – sufficient load bearing capacity ceilings of basements and canals in the crane passage area; – the presence of self-propelled cranes with load-height characteristics that ensure lifting and installation of the elements of the mounted crane into the design position; These characteristics include the lifting capacity, which at a given hook reach must correspond to the mass of the load being lifted, as well as the under-jib space (dimension a in Fig. 85), which must ensure lifting of the elements of the mounted crane without resting them on the boom and be at least 200 mm.
In addition, the installation crane must fit with its boom into the dimensions of the building in which the bridge crane is installed: the distance h (see Fig. 85) from the top of the boom in its highest position to the roof must be at least 200 mm.
85. Diagram of installation of half-bridges of an overhead crane on crane tracks using one installation crane
86. Scheme of lifting an overhead crane trolley using two self-propelled cranes
1 - tap; 2 - traverse; 3 - sling; 4 - spacer between the main beams of the bridge; 5 - crane bridge; 6 - crane beam; 7 - arrow
87. Scheme of lifting a crane bridge using a self-propelled crane with special boom equipment
Often limited underjim space and lifting capacity at the required hook reach are the main obstacles to lifting a completely assembled bridge or trolley with one erection crane. In such cases, large elements are lifted with two cranes (Fig. 86). Sometimes, specially manufactured boom equipment is used for this purpose (Fig. 87), which is a tubular boom with a traverse, the reach of which makes it possible to place a fully assembled crane bridge in the space under the boom, and when the boom is in a vertical position, the installation crane has maximum lifting capacity.
In Fig. Figure 85 shows a diagram of the installation of two half-bridges 2 and 3 of an overhead crane on the crane tracks using an assembly crane. The dotted line marks the position of the assembly crane when lifting half-bridge I, as well as the initial positions of both half-bridges. The bridge bridge according to this scheme is assembled as follows. First, the half-bridge is lifted from its original position, deployed in a horizontal plane over the crane tracks and lowered onto them, and then, using mounting traction mechanisms, it is driven to the position shown in the figure. Then the assembly crane moves to the right, to the position marked by the position, and with its help the half-bridge is lifted and installed on the crane tracks in the same way as the half-bridge.
The bridge is assembled depending on the adopted trolley installation scheme: if it is supplied to the bridge from the side, then the half-bridges are joined immediately after they are lifted onto the crane tracks; if the trolley is lifted between spread half-bridges, then they are joined after the trolley is raised above the trolley tracks and before the trolley is lowered onto them. In this case, the assembly crane for lifting the trolley is installed under the spread half-bridges in the middle so that its boom is directed along the half-bridges, and the cargo pulley is located above the center of mass of the trolley. After installing the trolley on the crane bridge, it is released from the slings and the assembly crane is driven away, simultaneously lowering its boom between the half-bridges.
When the lifting capacity of one crane is not enough, the half-bridges are then turned around and installed on the crane runways by two assembly cranes. In this case, the half-bridge is slung from both sides, raised above the crane tracks and, alternating between maneuvering the booms and changing crane positions, the half-bridge is deployed in a horizontal plane, after which it is lowered onto the crane tracks.
Two assembly cranes lift the half-bridges in an inclined position - “fish” (Fig. 88). After one side of the half-bridge is raised above the crane tracks, by turning the crane booms, the half-bridge is moved to this side and the second side of the half-bridge is raised above the crane tracks. Then, by turning the crane booms in the opposite direction and changing their lifting height, a half-bridge is installed on the crane tracks.
88. Scheme of lifting a half-bridge using two erection cranes
According to those shown in Fig. 85 and 88 schemes lift the main beams of bridges onto the crane tracks with the difference that according to the second of these schemes, the ends of the main beam should be raised above the end beam or balance beam (and not the crane tracks), which are installed before the main beams.
89. Scheme of installation of the end beam on crane tracks
1 - end beam; 2 - corner; 3 - clamp; 4 - I-beam; 5 - column; 6 - crane rail
When installing assembly cranes from the side of the half-bridge platforms, if necessary, these platforms are not installed or the decking and railings of the fences are cut out in the places where the crane booms pass.
In Fig. 89 shows a diagram of the installation of an end beam or balancer on crane tracks, when the crane bridge is assembled from four beams (two of which are together with the chassis) or from four beams and balancers, lifted separately.
For temporary fastening of end beams or balancers on crane tracks, use various devices, one of which is shown in Fig. 89. It includes an I-beam and a bracket consisting of an angle and a retainer made in the form of a plate with a T-shaped cutout. The clamp is welded to the angle, and the angle to the upper chord of the end beam. The I-beam is also welded to the workshop column. The clamp, while holding the end beam or balancer on the crane track, does not prevent their movement along the crane rail, which is necessary for performing operations to connect the main beam with the end beam or for attaching the balancer to it.
The end beam (or balancer) is installed on the crane runway according to the diagram as follows. First, an I-beam device along with brackets is attached to the workshop columns above the crane tracks. Then the end beam is lifted with an assembly crane and installed on the crane runway. Without removing the sling, weld the corner of the bracket to its upper chord (or the balancer body), after which the beam is freed from the sling. The second end beam of the bridge (or balance beam) is also installed, after which, using one of the methods described above, one main beam is raised and joined to the end beams, then the second. If the main beams rest on balancers, then, lifting them one by one, connect their ends to the balancers, and then raise the end beams and join them to the main ones.
Most in a simple way installation of crane trolleys is the installation of a fully assembled trolley in the lower position directly onto the crane bridge with one or two installation cranes installed on the side of the bridge. If the characteristics of existing self-propelled cranes do not allow this, the trolley is installed by lifting it between the spread half-bridges, as described above.
When the lifting capacity of self-propelled cranes is not enough to lift the trolley in this way, it is mounted in separate assembly units: first, the trolley frame with the movement mechanism and the auxiliary lifting mechanism is installed on the crane bridge, and then the assembly units of the main lifting mechanism are lifted and mounted on its frame.
90. Installation diagrams for mounting beams
91. Mounting beam
1 - support steel slick; 2 - overlay; 3 - I-beam; 4 - pipe; 5 - rib; 6 - farm; 7 - tap block; 8 -
chain hoist
After the trolley, the crane cabin is installed. To do this, cut a hole in the flooring of the working platform of the crane bridge in the center of the cabin fastening for the passage of the assembly crane hook, and install it in the parking lot indicated in the installation diagram. After this, having secured the cabin, they lift it to the design position and attach it to the crane bridge.
When, for various reasons, it is impossible to use tower or jib self-propelled cranes, assemblies of overhead cranes, especially heavy ones, are lifted using pulleys suspended from the building frame structures or from mounting beams resting on these structures. This installation method requires mandatory pre-amplification building structures, except in cases where this reinforcement is provided for in advance when designing the building frame.
One of the ways to lift assemblies of bridge cranes with the help of building frame structures is to hang two or four pulleys, respectively, from the tops of two or four columns of the building, with the help of which the half-bridges, or the entire assembled crane bridge, are lifted “fish”, in some cases - along with a trolley secured to the bridge so that it does not move during lifting. With this installation scheme, the running threads of the pulleys are directed down along the columns, where the branch blocks are connected, and through them to the winches located behind the workshop or inside the workshop at a distance from the installation site. The disadvantages of this method are the need for large quantities rigging and winches, as well as ensuring the stability of columns against forces for which they are not designed. Therefore, this method is rarely used. Sometimes pulleys are suspended from two adjacent trusses, with spacers placed between them.
The most widespread method of lifting assembly units of overhead cranes using pulleys suspended from mounting beams resting on two adjacent trusses 5 (Fig. 90, a), or on two auxiliary beams b (Fig. 90.6), which rest on neighboring farms. With the help of mounting beams, which are also called repair and installation beams (since they are used to lower and lift crane assembly units during their repairs in existing workshops), up to 60% of all overhead cranes in metallurgical workshops are installed. Much more often the first version of this method is used, when the beam rests directly on the workshop roof trusses along the longitudinal axis of the span.
92. Scheme of the assembly beam pulley
1 - movable block holder; 2 - poly branch, spasta; 3 - fixed block holder; 4 - mounting beam; 5 - tap-off block; 6 - column
93. Scheme of lifting a half-bridge using a pulley suspended from a mounting beam
1 - roof truss; 2 - fixed block holder; 3 - ropes; 4 - movable block holder; 5 - sling; 6 - lining; 7 - half bridge
Currently there are a large number of beams various designs, of which the most widespread are beams of I-beam (made of one or two T-beams), box-shaped (made of sheet) sections, as well as beams of a lattice structure: the two side walls of such a beam are lattice trusses.
In Fig. 91 shows a general view and installation diagram of a mounting beam made of two I-beams connected by strip overlays and reinforced with ribs. The pulley is suspended from a pipe fixed to the upper flanges of the I-beams and inside of which a round piece of wood is inserted. The beam is installed on the ridges of the trusses using support tables.
The load capacity of the mounting beams is from 30 to 160 tons, the length (most often used) is 6 and 12 m.
Unified beams for the repair and installation of overhead cranes in workshops of ferrous metallurgy enterprises have a design similar to that given above. Their load capacity is 50, 70 and 100 tons, the diagram of their pulleys and the direction of the running thread are shown in Fig. 92.
A chain hoist suspended from an assembly beam is used to unload assembly units from vehicles on which they are delivered to the installation area.
Depending on the load-carrying capacity of the mounting beam and the mass of the crane assembly units, the main beams, half-bridges, and entire beams are lifted using pulley hoists. assembled bridges(followed by turning them in a horizontal plane over the crane tracks), as well as overhead crane trolleys (Fig. 93).
Since the mounting beams are installed along the axis of the span, the end beams or balancers are lifted onto the crane tracks using two pulleys suspended from the tops of opposite columns of the workshop building.
94. Scheme of installation of a bridge bridge using a mounting beam
1 - mounting beam; 2 - design position of the half-bridge; 3, 7 - mounting traction mechanisms; 4, 13 - chain hoists; 5 - design position of the end beams; b - initial position of the end beam: 8 - initial position of the half-bridge; 9 - initial position of the trolley; 10 - temporary fastening device; 11 - tap block; 12 - sleeper flooring; 14 - guy wire of hemp rope; 15 - intermediate position of the half-bridge
First, using pulley hoists, devices 10 are lifted and attached to the columns to temporarily secure the end beams on the crane runways (see above). Then the end beams are lifted and installed, using one of the pulleys as a load and the other as a guy. After this, the half-bridges are lifted with a pulley hoist, turning them in a horizontal plane and joined to the end beams (one of the half-bridges is not shown in the figure).
Having assembled the bridge, it is moved to the side by two mounting traction mechanisms, after which the trolley is raised with a pulley system above the level of the bogie rails and, using the traction mechanisms, the bridge is rolled under the trolley and lowered onto the rails. Then the cabin and other elements of the crane are installed. The chain hoist diagram is shown in Fig. 92 fixed pulley block is tied to top part columns, the running thread is directed down along the column and through the outlet block AND onto the winch.
Fully assembled installation of overhead cranes using the conveyor method. This method, in which overhead cranes are fully assembled in the lower position, and then lifted and installed on crane tracks using conveyor line equipment for the assembly and installation of building roofing blocks, is the most progressive and gives the greatest effect in large volume works on installation of cranes on site. The conveyor method makes it possible to organize the in-line assembly of cranes with a high degree of installation readiness, including performing the maximum amount of electrical installation and commissioning work in the lower position, and therefore reduce to a minimum the volume and duration of work performed at height after installing the crane on the crane runways.
A prerequisite for using this method is the installation of overhead cranes during the construction of the workshop building, since in order to move, lift and install fully assembled overhead cranes on crane tracks, equipment is needed that is used to carry out similar operations with coating blocks, i.e. lifts, jib rail cranes, portals, etc.
In Fig. 95 shows a diagram of the organization of the installation of overhead cranes using the conveyor method using a jib rail crane 1 (intended for the installation of roofing blocks of a workshop building) to move the fully assembled overhead crane 2 from the enlargement site to the span in which it is to be installed, as well as to lift the crane and installing it on iodine crane tracks.
Assembly units of cranes supplied for installation are unloaded from vehicles and laid out on the storage site using one or two pipe layers, which then move the crane elements to the site for assembly within the range of the crawler crane. This crane is used to install the end and main beams on the assembly stand and the crane trolley on the bridge after its assembly. The sequence of operations for assembling and aligning the bridge is outlined above. The assembled overhead crane is rolled to the other end of the stand into the range of the rail crane using an electric winch. Here they perform electric installation work, after which the overhead crane is carried by a rail crane to the stand and for installation of the cabin. Using a truck crane with the help of a traverse, the crane operator's cabin and the cabin for servicing the trolleys are mounted, and mounting cradles and ladders are hung.
At the same stand, the movement mechanisms of the crane and trolley are tested, and the pulleys of the lifting mechanisms are also stored.
95. Scheme of organizing the installation of overhead cranes using the conveyor method using a jib rail crane 1 - rail crane SKU-1500R; 2 - fully assembled edge bridge; 3 - truck crane; 4 - crawler crane; 5 - platform for crane assembly; 6 - electrical installation platform; 7 - pipe layer; 8 - platform for storing crane elements; 9 - mounting traction mechanism; 10 - safety rope; 11, 12 - stands
96. Scheme of organization of the conveyor method of installation of overhead cranes
using the portal t - site for enlarged assembly; 2 - crawler cranes; 3 - fully assembled overhead crane; 4 - portal; 5 - testing area for assembling workshop coating blocks
Then, using a rail crane, the finally assembled overhead crane is moved to the span of the workshop building and installed on the crane tracks, unfastening is carried out, after which two traction mounting mechanisms 9 move the overhead crane inside the workshop.
Other variants of the described method for installing overhead cranes are also used, which depends mainly on the equipment for lifting and moving the coating blocks and which is used when installing overhead cranes. In Fig. 96 shows a diagram of the organization of the conveyor method for installing overhead cranes using a portal on which blocks of building coverings are moved from site 5 for assembling these blocks to a given workshop span.
In this case, on the other side of the portal tracks from the landfill, an enlarged assembly site is set up, on which, with the help of two crawler cranes and mounting traction mechanisms, all assembly work is carried out, including the installation of a fully assembled trolley on the crane bridge. Here, electrical installation work is carried out and the mechanisms are tested, pulleys are stocked, after which the fully assembled crane is lifted by crawler cranes and installed on the portal, which is moved to a given workshop bay. Having joined the rails of the portal with the crane rails of the workshop, the crane is moved into the span using mounting traction mechanisms.
Installation of lubrication systems for crane mechanisms. Lubrication systems are installed in accordance with the drawings, marking diagrams and instructions of the manufacturers.
Installation of individual lubrication systems consists of checking the cleanliness of the inner surface of the bearing housings, the serviceability of the lubricators, installing them in place and filling them with lubricant.
Centralized lubrication systems are installed in the following sequence: – a lubricating hand pump (lubrication station) and feeders are installed and secured to the supporting surfaces; – install and connect the main pipeline assemblies, branches from them to feeders and branches from feeders to lubricated points; – fill the pipelines with lubricant; - set up and test the system.
Before installing the system, you must ensure that the pump and feeders are working properly, as well as that the internal surface of all pipeline elements is clean (no dirt, rust). Manufacturers in most cases supply all elements of lubrication systems completely ready for installation in place.
However, if, upon acceptance for installation, dirt or rust is found on the inner surface of pipeline assemblies and bends, then they must be washed and pickled in baths. Pickling is also mandatory after welding to remove scale formed on the inner surface of the pipeline in the welding zone.
Etching is carried out in solutions of sulfuric, hydrochloric or phosphoric acids. Etching in solutions of sulfuric or hydrochloric acids consists of the following operations: etching itself, washing, neutralizing the remaining etching solution, washing, drying and lubricating the etched surfaces. For etching, use 20% sulfuric acid solutions at a temperature of 50-80 ° C or of hydrochloric acid at a temperature not exceeding 40 °C, since at more than high temperature the release of hydrogen chloride vapor from baths with hydrochloric acid increases. The etching time depends on the condition of the inner surface of pipeline units and bends, on the temperature of the solutions and can be from 2 to 24 hours. Sometimes etching is carried out in a mixture of acid solutions of the following composition: sulfuric acid - 60 g per 1 liter of solution, hydrochloric acid - 40 g/ l, urotropin - 6 g/l, table salt- 25 g/l at a temperature of 40-50 °C.
The quality of cleaning is monitored visually. If the surface has not been cleaned sufficiently, then spots and individual areas of undissolved oxides are visible on it; a well-cleaned surface has a steel-gray color, while an overetched surface has a black color.
After etching, the nodes and bends are removed from the solution and held above the bath to drain the solution, and then transferred to a bath of water in which they are washed, then transferred to a bath with a 3-5% soda or lime solution to neutralize the remaining etching solution in for 1 hour.
After neutralization, the products are washed in a bath of hot water heated to 80-90 °C and air dried.
The dried etched surface must be lubricated with oil, as it again very quickly corrodes. For this purpose, pipeline units and bends are immersed in a bath of oil, and after removal from it, they are placed on racks in an inclined position to drain the oil for 2-3 hours.
All of the above operations are performed without interruption; upon completion, the ends of the nodes and bends are closed with plugs.
Etching in solutions phosphoric acid differs from the one described above in the absence of such operations as washing, neutralizing and lubricating the etched surfaces with oil.
Pipeline components and bends that have been previously cleaned of contaminants are first etched in a 15-20% solution of orthophosphoric acid at a temperature of 50-60 °C for 6-12 hours (depending on the condition of the internal surface of the products), checking the quality of cleaning in the same way as and when etching in solutions of sulfuric or hydrochloric acid, and then transferred to a bath with a 2% solution of the same acid, having previously drained the remaining etching solution into a bath with a 15-20% solution. In a 2% solution of orthophosphoric acid, a thin phosphate film is formed on the surface of steel products after etching, which passivates (covers) the metal surface and protects it from corrosion for several months. In a bath with such a solution, pipeline units and bends are kept for 1-2 hours at a temperature of 50 ° C, after which they are removed from the solution, the residue is allowed to drain back into the bath, placed on a rack and dried compressed air, previously cleaned of moisture and oil and, if possible, heated (to speed up drying). Then the ends of the products are closed with plugs to prevent dirt from getting inside, as well as water, which destroys the protective film. The surface etched and covered with a passivating film has a dark gray color with a barely noticeable greenish tint.
Lubricant feeders, for which the warranty period has not expired and no defects were found during external inspection, are installed in place and secured to the crane structure with screws that tightly attract the feeder to the support.
If the warranty period has passed, but no defects are found, the feeders are tested for leaks with mineral oil at the test pressure specified in the passport for 2 minutes in each of the extreme positions of the pistons.
In this case, oil should not leak through the rod seals and plugged connecting holes in the housings, and its leakage through any of the outlets to the lubricated points should not exceed three drops per minute. Feeders must operate and dispense the required amount of lubricant when the pressure difference in the main lines is not more than 1 MPa and the number of piston strokes is not less than 6. The movement of pistons and spools must be smooth, without jamming along the entire stroke length. Testing and checking for operation is carried out by injecting lubricant into each line in turn. Feeders that fail testing are sent for repair and new ones are installed instead.
Pipelines of the systems are assembled from units and bends manufactured at the manufacturer. When the manufacturer supplies piping as straight pipe sections and piping parts separately, installers construct the main piping assemblies and bends themselves from pre-etched pipes.
Pipeline connections are made mainly on conical pipe threads using union nuts and fittings (elbows, tees, couplings). The use of sealing agents in these joints in the form of whitewash, red lead and tow is not allowed; They are assembled on nitro varnish of the NTs brand or bakelite varnish of the LBS brand. Often, pipe bending is used instead of angles, and inserts made by welding are used instead of tees; Thus, the bends from the lines to the feeders and from the feeders to the lubricated points are in many cases made curved, and the branches are connected to the lines through threaded fittings welded to the latter.
Pipelines are also connected by welding, but it is necessary that the welded joint be between two threaded joints. This allows, after assembling the pipeline, to dismantle the section with welded joint and pickle it. If the welded joint is made in a socket or with a coupling welded outside the joint, then pickling after welding does not need to be done.
Having installed the system, the pipelines are blown with compressed air to remove solid particles that got inside when assembling the joints, and then they are filled with lubricant using a pump, supplying the lubricant first through one main pipeline and then through the other. One of the main requirements when carrying out this operation is to remove air from the pipelines. Air entering the system disrupts normal operation. To do this, during filling, the opposite end of the pipeline is opened and only after 0.5 kg of lubricant comes out of it is closed.
As the pipeline is filled, the outlets to the feeders and the feeders are charged with lubricant, for which purpose the plugs installed on these outlets are removed one by one before purging. The taps are connected to the feeders only after 50-100 g of lubricant comes out of each tap. The feeder is considered charged when 10-20 g of lubricant comes out of it. After this, the feeder is closed with plugs. The taps from the feeders to the lubricated points are charged as follows. The taps are disconnected from the feeders and lubricated points, blown with compressed air and filled with lubricant using a hand pump until 50-100 g of contaminated lubricant comes out of the free end of each tap, which is removed. After this, the outlet is installed in place.
Having filled the system, they begin to set it up, which consists of checking the operation of the feeders and determining the pressure required for their operation. The operation of the feeders is checked by alternately injecting lubricant into both lines.
When pumping into the first line, all rods must be in top position, when pumping into the second - in the lower. If there is a discrepancy in the position of the rods, the branches from the main pipelines to part of the feeders are swapped so that the rods of all feeders are in a raised or lowered position when pumping lubricant into one of the two lines.
The pressure at which the system should operate is determined by a pressure gauge at the moment the most remote feeder is activated plus 0.5 MPa. After checking the operation of the feeders and determining the operating pressure, the pipelines are subjected to a hydraulic test with test pressure. A pump is used for this high pressure, which is used to inject lubricant alternately into the first and second main pipelines. The test pressure in each pipeline is 1.2 times the working pressure, it is maintained for 20-30 minutes. During this time the pressure drop should not exceed 10%.
Installation of lifting ropes. A critical operation during the installation of cranes is the reeving of ropes on lifting mechanisms, in which the following requirements must be met: ensuring the safety of the rope during its installation; prevention of unnecessary internal stresses caused by reeving conditions; correct initial laying of the rope on the drum of the lifting mechanism.
Damage and the formation of additional stress in the rope can occur if it is unwinded incorrectly from coils or drums. When reserving, it is necessary to follow the order of wiring the rope, one end of which must sequentially go around all the rollers in the block cages and then be attached to the drum. The second end is also attached to the drum or to the upper block holder. The rope can be laid manually or using the substitution method.
In Fig. 97 shows the reeving of the pulley mechanism of the main lifting mechanism of an overhead crane using the replacement method. A drum or reel with rope 1 is installed under the overhead crane on supports in which they can rotate freely. The movable cage of the pulley block 5 with a hook suspension is fixed in the lower position along the axis of the crane. An electric winch 6 is also installed under the crane, on the drum of which a thin rope is wound.
This rope is manually passed through all the rollers of the pulley block and connected to the end of the design rope wound on drum 1. Then, turning on the electric winch, a thin rope is passed through all the rollers in the opposite direction, but with the design rope, which thus replaces the thin rope in the pulley block rope.
97. Scheme for reeving a chain hoist using the replacement method
a - work organization diagram; b - reeving diagram; 1 - drum with rope; 2 - fixed block holder; 3 - drum of the lifting mechanism; 4 - overhead crane trolley; 5 - movable block holder; 6 - electric winch
When reserving great importance It has precise definition length of the rope, otherwise the hook will not rise to the required height or will not reach its lower position.
If the hook according to the project falls below the workshop floor level (in the presence of buried rooms), the length of the rope must be increased by the distance from the floor to the lower position of the axis of the movable cage, multiplied by the multiplicity of the crane pulley.
When retrieving new ropes, the pulley often gets twisted. Twisting can be eliminated in two ways: by first rolling out the rope over its entire length into one straight line when reeling, or by unwinding the pulley.
In the second method, lift the load, the mass of which is 30% of the mass of the largest load, by 150-200 mm and allow the pulley to twist freely, only keeping the load from accelerating. In this case, the number of revolutions of the lower block cage is counted until the pulley stops rotating.
After securing the rope to the drum, the hook is raised and lowered several times, thereby evenly distributing the twist along the entire length of the rope.
Features of installation of metallurgical cranes are determined by design features bridges, trolleys and mechanisms for performing special technological operations. The sequence and rules for performing all assembly operations during the installation of metallurgical cranes are set out in detail in the manufacturers' instructions, so the procedure for installing enlarged assembly units of these cranes is discussed here.
When installing mullion loading cranes after assembling the bridge on the crane tracks (or lifting the assembled bridge), the frame of the main trolley with the chassis and mechanisms for moving, turning and lifting the column is lifted onto the bridge. At the same time, the lower part of the main trolley is assembled, starting from the control cabin. The cabin is installed on the working platform on supports. Before installation and fastening on the control platform, the column is cleaned of the preservative coating and checked for straightness and absence of nicks; the curvature of the column faces should not exceed 1 mm over a length of 1 m. After securing the column to the site, a frame with mechanisms is inserted into it and installed along the swing axis. Then the trunk with the mouthpiece is assembled.
After assembling the lower part of the main trolley, the shaft is put on the column using a self-propelled crane or pulleys tied to the frame of the main trolley. The shaft with the column is secured in a vertical position (for stability) with braces or racks. Then a traverse with a suspension of the column lifting mechanism is put on the head of the column and secured.
After this, the shaft assembly with the column and cabin is lifted and secured to the frame of the main trolley.
The shaft is lifted with pulley hoists suspended from the trolley frame or mounting beam, or with a column lifting mechanism.
Installation of foundry cranes differs from installation of cranes general purpose in that first the main bridge is assembled on the crane tracks, then the auxiliary bridge, after which the trolleys are mounted. Bridges of heavy casting cranes are assembled on crane tracks from half-bridges or individual elements, when the weight of the elements (balance trolleys, bridge beams) and the load-carrying capacity of the existing mounting mechanisms do not allow them to be enlarged into half-bridges. Such cranes are most often mounted using pulley hoists suspended from mounting beams. For the same reason, the main trolleys of heavy casting cranes are mounted on the crane bridge from enlarged assembly units, and the auxiliary trolleys are assembled entirely, in the form in which they arrive from the manufacturer. For slinging the main trolleys of casting cranes, a device from the Giprometallurgmontazh Institute is often used, consisting of a traverse, which, through four sliding rods, is hingedly connected to two shoes placed under the middle beam of the trolley frame.
When installing cranes for stripping ingots, after assembling the bridge and installing the trolley on it, a shaft, previously assembled with a cabin, platforms and ladders into one enlarged assembly element, is suspended and secured to it.
Specific to these cranes is the attachment of a mechanism for ejecting ingots with pliers, which, as a rule, comes from the manufacturer assembled. Layed in a horizontal position near a special repair pit 4.6 m deep, this mechanism is lowered into the pit using a pulley suspended from a beam on the trolley frame, or the main lift mechanism.
If the ejection mechanism arrives disassembled, it is assembled in a horizontal position next to the repair pit and lowered into it. After this, the crane bridge and trolley are installed above the repair pit so that the ejection mechanism can be lifted and inserted into the shaft directly from the pit without moving it in the horizontal direction.
If by this time the installation of the main lifting mechanism of the crane trolley has not yet been completed, then the ejection mechanism is lifted with the same pulley with which it was lowered into the repair pit. Having lifted the mechanism along the guides of the shaft, it is temporarily secured and further work is carried out after the installation of the main lifting mechanism and electrical installation work is completed.
When the main lift mechanism is operating, the ejection mechanism is mounted as follows.
Lifting ropes are attached to the drum, they bend around the blocks of the ejection mechanism and are first secured to its balancer. The ropes of the pliers control mechanism are passed through blocks and secured to the levers of this mechanism and to the drum. Then the ejection mechanism is raised from the pit to the lower design position (at maximum pliers opening) and temporarily secured in the shaft on two beams placed under the protruding parts of the cartridge. After this, the freed ropes are pulled and reattached to the balance beam and levers (without cutting off their ends). Having raised the ejection mechanism to the upper design position (with a minimum opening of the pliers), the ropes are attached to the counterweight for balancing the pliers control mechanism.
The technology for installing well (clamp-type) taps is similar to the technology for installing taps for stripping ingots.
Dismantling of overhead cranes is carried out in most cases using self-propelled jib cranes or pulleys suspended from mounting beams. Assembly masts are used much less frequently for this purpose (for the same reasons that they are rarely used for the installation of cranes).
It is promising to use hydraulic lifts designed by Giprotechmontazh for dismantling overhead cranes.
Cranes may only be dismantled if there is a specially developed PPR.
Before starting dismantling work, carry out preparatory activities, including: – preparation of the required lifting mechanisms and equipment, including installation of winches, linking of pulleys and branch blocks, installation of devices for temporary fastening of end beams or balancers on crane tracks, etc.; – preparation and installation of scaffolding necessary for dismantling the crane; – fencing off the hazardous work area and preparing a site for placing the removed crane assembly units.
By installing shoes under the wheels of the crane and trolley to prevent their spontaneous movement,
and having de-energized the crane mechanisms, they begin to disassemble it.
First, the trolley is slung and removed from the crane bridge. If the load capacity of the existing mechanisms and equipment is less than the mass of the assembled trolley, then it is disassembled into the minimum required number of elements and removed one by one.
For the same reasons, the crane bridge is removed entirely or disassembled into two half-bridges or another number of elements in accordance with the PPR.
Operations for disassembling the bridge are performed in the reverse order of its assembly.
The mounting pads are removed by gas cutting, having previously secured the main beam (or half-bridge), which is to be removed first, and temporarily securing the end beams or balancers to the crane tracks.
The lowering of half-bridges, individual beams or an assembled bridge is carried out according to schemes reverse to those adopted during the installation of the crane.
TO category: - Installation of loading cranes
The size of the galleries is regulated by the Crane Regulations. The width of free passage through the gallery should be:
a) for cranes with transmission drive - at least 500 mm;
b) for cranes with transmissionless or manual drive - at least 400 mm.
For the same cranes on galleries intended for the location of trolley wiring, the width of the passage between the railings and the devices supporting the trolleys, as well as current collectors, must be at least 400 mm.
The requirements of the Rules for Cranes do not apply to the bridge crane gallery located on the side of the current supply if the current supply to the electrical equipment of the trolley is made by a flexible cable. The console holding the cable can cross the entire width of the bridge gallery. The exit hatch to the bridge deck of such a crane must be equipped with a lock that automatically relieves tension from the flexible cable when entering the bridge deck.
The distance from the end railings of the crane bridge to the protruding parts of the cargo trolley when it is in the extreme position is not regulated. To increase the service area of the crane, this distance is sometimes taken to be less than 400 mm. All these requirements also apply to gantry cranes and mobile cantilever cranes.
Bridge cranes controlled from the cabin (except for single-girder and suspended cranes) must be equipped with cabins (platforms) for servicing the main trolley wires and pantographs, if they are located below the bridge gallery deck. The hatch for entering this cabin from the bridge deck must be equipped with a lid with a lock.
The dimensions of the cabin for servicing the main trolleys and their pantographs are not regulated and are usually accepted as 1000 x 1400 (Komsomolsk-on-Amur PTO plant) with a height of at least 1800 mm. The cabin area should not be less than 800 x 800 mm. The cabin must be fenced with railings at least 1 m high with a continuous hem along the bottom to a height of 100 mm. With flexible current supply, platforms are sometimes not arranged.
The crane bridge must be fenced on four outer sides (along the perimeter) with railings 1 m high with a continuous fence installed to a height of at least 100 mm to prevent the fall of tools or parts during inspection and repair of mechanisms and electrical equipment of the crane.
On the trolley side, railings are not installed on the bridge galleries and end beams.
In this regard, it is dangerous to be on a crane bridge made of lattice trusses, in which the gallery deck is located at the level of the trolley rails, since you can fall into the span between the trusses. Cases of people falling from crane bridges have been reported exclusively on cranes with lattice trusses. In addition to the noted drawback (lack of proper fencing of the galleries), on such cranes the passage along the flooring is restricted due to the location of the movement mechanisms on it, which also poses a danger to operating personnel. For box girder cranes, the gallery deck is located below the level of the trolley rails, so passage through such galleries is not dangerous.
To prevent accidents on cranes of old designs, where the passage through the gallery is restricted, it is necessary to arrange bypass platforms at the locations of the electric motor and gearbox of the bridge movement mechanism or transition bridges with railings. Precautions should also be taken to ensure that the worker's feet do not slip on the flooring when crossing.
Installing a railing along the bridge from the trolley side causes difficulties in servicing and repairing the trolley mechanisms, since it is necessary to climb over the railing.
The crane trolley must be fenced at the end sides with railings 1 m high with a continuous hem along the bottom to a height of 100 mm. Railings on one of the longitudinal sides of the trolley should be installed if there is no gallery along the crane bridge on that side, for example, when there is a flexible power supply to the trolley.
For trolleys and end beams, it is allowed to reduce the height of the railings if the dimensions of the building do not allow the installation of railings with a height of 1 m.
Popular articles
|
195. The crane must have easy access to the cabin. Overhead cranes must have safe exit on the crane trolley. For single-girder and suspended double-girder overhead cranes, galleries or platforms on the crane are not required if there is a repair platform in the span in which it is installed.
196. On the taps bridge type and mobile console cranes in the presence of a gallery intended for servicing electrical equipment and mechanisms, the width of the free passage should be:
A) in the area where movement mechanisms with a central drive are located - at least 500 mm;
B) in the area where movement mechanisms with separate drives are located - at least 400 mm.
In the area where trolleys are located, the width of the passage between the handrails and the devices supporting the trolleys, as well as current collectors, must be at least 400 mm.
In the spans of buildings in which supporting overhead bridge cranes with classification group (mode) A6 are installed, as well as on trestles for cranes (except for single-girder and suspended double-girder cranes), galleries must be arranged for passage along the rail track on both sides of the span.
197. Galleries for passage along the rail track must be equipped with railings on the side of the span and on the opposite side in the absence of a wall. A gallery on an open overpass can be equipped with railings with a height of at least 1100 mm only with outside(opposite the span).
198. The width of the passage (clear) along the gallery for passage along the rail track must be at least 500 mm, the height - at least 1800 mm.
199. Where columns are located, a passage must be provided on the side or in the body of the column with a width of at least 400 mm and a height of at least 1800 mm. It is not permitted to leave an unfenced section of the gallery near the columns.
200. When constructing a passage inside a column 1000 mm before approaching it, the width of the passage along the gallery should be reduced to the width of the passage in the column. Each gallery must have access to stairs at least every 200 m.
201. Repair sites must provide convenient and safe access to the mechanisms and electrical equipment of the crane.
202. When the distance from the floor of the repair site to the lower parts of the crane is less than 1800 mm, the door to enter the repair site must be equipped with a lock and automatic electrical interlock that relieves tension from the main trolleys of the repair site.
203. Instead of constructing stationary repair platforms, it is allowed to use mobile platforms that can safely withstand the load specified in their passport.
204. Overhead cranes controlled from the cabin (except for single-girder and suspended double-girder cranes) must be equipped with cabins (platforms) for servicing the main trolleys and pantographs, if they are located below the deck of the crane gallery. Cranes with cable current supply are not required to be equipped with the specified means of access.
205. The hatch for entering the cabin for servicing the main trolleys from the bridge deck must be equipped with a cover with a device for locking it.
206. The cabin for servicing the main trolleys must be fenced with railings no less than 1100 mm high with continuous lining along the bottom 100 mm high.
207. The size of hatches installed for entry into the flooring of walk-through galleries of repair and other areas should be at least 500 x 500 mm. In this case, the hatch must be equipped with an easily and conveniently opening lid.
208. The angle between the hatch cover in the open position and the deck should be no more than 75°.
209. To enter the control cabin of an overhead, mobile jib crane, as well as an electric cargo trolley moving along an overhead rail track, a landing platform with a stationary ladder must be arranged.
210. The distance from the floor of the landing area to the lower parts of the ceiling or protruding structures must be at least 1800 mm. The floor of the landing area must be located at the same level as the floor of the cabin or vestibule if the cabin has a vestibule. The gap between the landing platform and the threshold of the cabin door (vestibule) when the crane stops near the landing platform must be at least 60 mm and no more than 150 mm.
211. It is allowed to install a landing platform below the level of the cabin floor, but not more than 250 mm in the event that when the landing platform is located at the same level with the cabin floor, the height clearance (1800 mm) cannot be maintained, as well as when the landing platform is located at the end of the building and the impossibility of maintaining the specified gap between the cabin threshold and the landing platform.
212. When constructing a landing platform at the end of the rail track below the level of the cabin floor, it is allowed for the cabin to collide with the landing site (but not more than 400 mm) with fully compressed buffers. The gap between the landing platform and the lower part of the cabin (vertically) should be in the range from 100 mm to 250 mm, between the cabin and the landing platform fence - in the range from 400 mm to 450 mm, from the side of the cabin entrance - in the range from 700 mm up to 750 mm.
213. Entry into the control cabin of an overhead crane through the bridge is allowed only if direct entry into the cabin is impossible for structural or production reasons. In this case, the entrance to the crane must be arranged in a specially designated place through a door in the bridge railing, equipped with an electrical lock and an audible alarm.
214. The flooring of galleries, platforms and passages must be made of metal or other durable materials, meeting fire safety requirements. The flooring should be installed along the entire length and width of the gallery or platform.
215. The flooring must be made in such a way as to prevent the possibility of feet slipping. In the case of decking with holes, no hole size should exceed 20 mm.
216. Galleries, platforms, passages and stairs located in areas where trolleys or bare wires are located, regardless of the presence of entrance locks, must be fenced to prevent accidental contact with trolleys or bare wires.
217. Platforms and galleries, end beams of bridge-type cranes, intended for access and (or) servicing of cranes, must be fenced with railings with a height of at least 1100 mm with a continuous fence along the bottom with a height of 100 mm.
218. On the end beam and trolley of an overhead or mobile jib crane, the height of the handrail can be reduced to 800 mm if the dimensions of the building do not allow the installation of handrails with a height of 1100 mm.
219. Railings and guardrails along the bottom should also be installed on the end sides of the trolley of bridge-type cranes, and in the absence of a gallery - along the crane bridge and on the longitudinal sides of the trolley.
220. The posts on the landing platform, to which the railings or landing structure fastening structures are attached, located at a height of more than 1100 mm from its flooring, must be at least 400 mm away from the cabin.
221. The end beams of bridge-type cranes having a width of no more than 300 mm, as well as cranes that use an electric hoist as a lifting mechanism, may not be protected with railings if, according to the operating manual (instructions), their end beams are not intended for servicing the crane .
222. Stairs for access from the floor to platforms and galleries of overhead cranes must be at least 600 mm wide. The width of stairs located on the crane, with the exception of stairs with a height of no more than 1500 mm, must be at least 500 mm.
223. Stairs with a height of less than 1500 mm located on the crane, as well as stairs for exiting the cabin to the gallery of an overhead or mobile console crane, can be made with a width of at least 350 mm.
224. The distance between steps should be no more than 300 mm for steeply inclined stairs and 250 mm for inclined landing stairs.
225. The pitch of the steps must be maintained along the entire height of the stairs. The steps of steeply inclined stairs must be at least 150 mm away from the metal structures of the crane.
226. Stairs for access from the floor to landing, repair platforms and galleries for passage along the rail track must be located so as to prevent the possibility of pinching the personnel on them by a moving crane or its cabin, and must be free and safe for personnel movement. It is not allowed to clutter these stairs and store foreign objects on them.
227. On steeply inclined stairs, guards in the form of arcs must be installed, starting from a height of 2500 mm from the base of the stairs. The arcs must be located at a distance of at least 800 mm from each other and connected to each other by at least three longitudinal strips.
228. The distance from the stairs to the arc must be at least 700 mm and no more than 800 mm with an arc radius of 350 mm to 400 mm. Arc guards are not required if the staircase runs inside a lattice column with a cross-section of not more than 900 x 900 mm or a tubular tower with a diameter of not more than 1000 mm.
229. The installation of steeply inclined stairs above hatches is not allowed. When the height of stairs is more than 10 m, platforms must be installed every 6 - 8 m. When stairs are located inside a tubular tower, such platforms may not be arranged.
230. Inclined stairs located on cranes (except for jib-type cranes) must be equipped with railings on both sides with a height of at least 1100 mm relative to the steps and have flat metal steps width of at least 150 mm, eliminating the possibility of slipping.
231. Stairs for entering platforms for servicing jib-type cranes must be stationary and (or) folding (retractable) with a handrail height at the entrance to the platform of at least 1500 mm.
232. Steps must be at least 320 mm wide with steps from 250 mm to 400 mm. The height from the surface of the floor or platform to the first step should be no more than 400 mm.