Instruments and safety devices for overhead cranes. Safety devices and sensors for overhead cranes: what and why? Overhead cranes must be equipped

Depending on the type of crane and type of drive (electric, mechanical), the crane is equipped with a number of instruments and devices that ensure its safe operation:

Limit switches- for automatic stopping of crane mechanisms with electric drive. On mechanically driven valves, limit switches are not used.

Interlock contacts- for electrically blocking the door to the crane cabin from the landing platform, the hatch cover, and the entrance to the bridge deck. All crane doors and guards are blocked by its release device. If any contact is broken, the tap cannot be turned on.

Load limiters- to prevent crane accidents associated with lifting loads weighing more than their lifting capacity. Installation of the device is mandatory on jib, tower, and portal cranes.

Skew limiters- to prevent dangerous distortion of metal structures of gantry cranes.

Load capacity indicator- installed on jib-type cranes, in which the lifting capacity changes with the change in the boom radius. The device automatically shows what the crane's lifting capacity is at the set boom radius. This helps prevent the crane from being overloaded.

Angle indicator- For correct installation jib cranes, except those operating on rail tracks

Anemometer- tower and portal cranes should be equipped with it. It shows the wind speed. The operation of the cranes must stop if the wind speed is above 15 m/s, and when installing elements with a large windage when the wind speed is above 10 m/s.

Anti-theft device- on cranes operating on surface rail tracks to prevent them from being blown away by the wind.

Automatic dangerous voltage alarm- is triggered when the crane boom approaches live wires and power lines. They are equipped with jib cranes (except for railway ones).

Support parts- they are equipped with bridge cranes, tower cranes, portal cranes to reduce dynamic loads on metal constructions in case of damage to the axles of the running wheels.

Stops- installed at the ends of the rail track to prevent the lifting machine from leaving them, as well as on jib cranes, with a variable boom reach to prevent it from tipping over.

Sound signaling device- installed on cranes controlled from the cabin or remotely. They are installed on cranes controlled from the floor.

Dimensional requirements for the installation of cranes moving along overhead rail tracks



The horizontal distance between the protruding parts of a crane moving along overhead tracks and buildings, stacks of cargo and other objects located at a height of up to 2 m from the ground must be at least 700 m, and at a height of more than 2 m - at least 400 mm. These distances must be maintained along the entire length of the rail track and in any position of the rotating part of the crane. The vertical distance from the counterweight console to the platforms where people may be located must be at least 2 m.

PRACTICAL WORK No. 10

Selection and calculation of a tower crane

The choice of tap (Fig. 10) is influenced by:

1. Nature and scope of the structure.

2. Weight of mounted elements.

3. Time frame for installation of the structure.

4. Methods and ways of organizing work.

5. Specifications tap.

Rice. 10. Tower crane diagram

Q = G gr + G basic G base = 10% · G gr

H k = h 1 + h 2 + h 3 + h 4

h 1 – height of the installation area, m,

h 2 – minimum permissible distance 0.5, m,

h 3 – load height, m,

h 4 – height of slings, m.

To calculate the reach of a tower crane, we take the most distant point.

L = b + 0,7 + R, Where R– radius of rotation of the tail section, R≈ 4 m.

Q= 5 t.

The height of the installation area is 12 m.

Q= 5 + 10% · b= 5.5 t.

N cr = h l + h 2 + h 3 + h 4 = 12 + 0.5 + 0.4 + 3.5 = 16.4 m.

L = b + 0,7 + R= l8 + 0.7 + 4 = 22.7 m.

We select a faucet.

Task options

No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m
0,4 11,5 1,3
0,2 8,5 1,4
7,5 0,5 12,5 1,6
9,5 1,7
4,5 8,5 1,5 13,5 1,8
5,5 1,1 13,5 3,6 1,9
3,5 9,5 0,7 6,3 14,5
6,5 1,2 6,8 2,5
10,5 0,8 2,5 15,5 2,7
7,5 0,9 2,2

Calculation of self-propelled cranes



The diagram of the self-propelled crane is shown in Fig. eleven.

Rice. eleven. Self-propelled crane diagram

h w ≈ l.5 m,

A≈ 1.5 m,

h≈ l.5 m,

Δ ADE ∞ Δ ABC,

, DE = A.E. · = ( H c – h w)( b/2 + 1 m)/ h 4 + h 5,

L = DE+ D.F.

Example

Cargo weight Q= 8 t.

Height of installation area h 1 = 10 m.

Load height h 3 = 0.2 m.

Sling height h 4 = 3.5 m.

Object width b= 20 m.

Constant values:

Chassis h w = 1.5 m.

Distance to crane axis A= 1.5 m.

Height of pulley block h 5 = 1.5 m.

Stock, h 2 = 0.5 m.

Boom height: Hс = h 1 + h 2 +h 3 + h 4 + h 5 = 8 + 0.5 + 0.2 + 3.5 +1.5 = 13.7 m.

DE = (H c – h w)( b/2 + 1 m)/( h 4 + h 5) = (13.7–1.5)(14/2 + 1)/(3.5 + 1.5) = 19.52 m.

L= 19.52 +1.5 = 21.02 m.

We select the KS-5473 crane.

Task options

No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m
0,2 8,5 1,3
0,4 9,5
0,5 3,5 1,5
0,6 0,8
0,8 10,5 0,7
0,7 4,5 0,9
0,9 5,5 0,6
9,5 6,5 0,5
6,5 1,1 5,5 0,4
17,5 1,2 3,5 0,3

Calculation of jib cranes

General scheme a crane with a jib is shown in Fig. 12.

Rice. 12. General diagram of a jib crane

DE = A.E. · B.C./AB = (H c – h w)1 m/ h 4 + h 5;

L = DF + DE + b/2;

Q = G gr + G basic; G base = 10% G gr;

H k = h l + h 2 + h 3 + h 4.

The selection of boom equipment for cranes with jib (without jib) is carried out depending on the dimensions of the object:

1. When installing single-story industrial buildings we take a crane with one main boom and work on minimum height equal to approximately 5 m.

2. We do not calculate boom reach.

Let us determine the type of jib crane, the design diagram of which is shown in Fig. 14.

Rice. 14. Jib crane diagram

Initial data:

Q g = 1.5 t; weight of equipment: Q snap = 0.1 Q= 0.15 m.

Q = Q g + Q equipment = 1.5 + 0.15 = 1.65 t.

Height of installation area h 1 = 7.2 m.

Load height h 3 = 0.3 m.

Sling height h 4 = 3.5 m.

Object width b= 9 m.

Constant values:

Chassis h w = 1.5 m.

Distance to crane axis A= 1.5 m.

Height of pulley block h 5 = 1.5 m.

Stock h 2 = 0.5 m.

DF= 1.5 m.

H k = 7.2 + 0.5 + 0.3 + 3.5 = 11.5 m.

H c =H To +h 5 = 11.5 + 1.5 = 13 m.

m.

L = DF + DE + b/2 = 1.5 + 2.3 + 9/2 = 8.3 m.

We select the MKG-25.01 crane.

Task options

No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m
0,5 6,5 2,5
2,5 0,2 4,5
0,7 7,5
3,5 0,5
1,2 0,2
4,5 1,4
1,5 5,5 1,2
5,5 1,8 1,4
6,5 1,5
1,8

Calculation of a crane without a jib

We take a tap without a jib (Fig. 13).

Rice. 13. Crane diagram without jib

Initial data:

Q= 4 t, including weight of equipment:

Q snap = 0.1∙ Q, T;

h 1 = 5; h 2 = 0,5; h 3 = 0,3; h 4 = 3.5 m; h 5 = 1.5 m; h w = 1.5 m; b= 5 m;

H k = h l + h 2 + h 3 + h 4 = 9.3 m;

H c =H To +h 5 = 9.3 + 1.5 = 10.8 m;

.

;

We select a crane brand MKG-16M.

Task options

No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m No. Cargo weight Q, T Height of installation area h 1m Load height h 3m Object width b, m
4,5 5,5 0,2 4,5 5,5 0,2
0,4 0,4
5,5 6,5 0,5 5,5 6,5 0,5
0,6 0,6
7,5 0,7 4,5 7,5 0,7
4,5 0,8 0,8
9,5 0,9 5,5 9,5 0,9
5,5 8,5 8,5
1,2 4,5 1,2
1,4 9,5 1,4

Annex 1

MINISTRY OF EDUCATION AND SCIENCE OF RUSSIA


Practical work No. _______

Appendix No. 2

MINISTRY OF EDUCATION AND SCIENCE OF RUSSIA

Federal state budget educational institution
higher vocational education

"Izhevsk State Technical University named after M.T. Kalashnikov"

(FSBEI HPE “IzhSTU named after M.T. Kalashnikov”)

Faculty of Quality Management

Department of Life Safety

Course work by discipline

"Safety technological processes and equipment"

Subject ___________________________________________

2.12. Safety devices and devices

2.12.1. Instruments and safety devices of cranes must comply with these Rules, state standards and other regulatory documents.

2.12.2. Cranes must be equipped with operating movement limiters to automatically stop:

a) the mechanism for lifting the load-handling member (except for electric hoists equipped with a torque limit clutch) in its extreme upper and lower positions. The lower position limiter of the load-handling member may not be installed if, according to the operating conditions of the crane, it is not necessary to lower the load below the level specified in the passport;

b) the mechanism for changing the departure;

c) the mechanism of movement of rail cranes (except for railway ones) and their cargo trolleys, if the speed of the crane (trolley) when approaching the extreme position can exceed 30 m/min. The movement mechanisms of tower, gantry cranes and overhead loader cranes must be equipped with limiters, regardless of the speed of movement;

d) mechanisms for moving overhead, gantry, cantilever, portal cranes or their load trolleys operating on the same crane track.

The specified devices must also be installed if it is necessary to limit the stroke of any mechanism, for example, a rotation mechanism, extension of the telescopic section of the boom or sections when installing a crane, mechanisms of the load-handling member, or lifting the cabin.

2.12.3. Limit switches installed on the crane must be switched on in such a way that it is possible to move the mechanism in the opposite direction. Further movement in the same direction is allowed:

for travel mechanism overhead crane s when approaching a landing pad or a dead-end stop at the lowest speed provided by the electric drive;

for the mechanism for lowering the boom of a jib crane into the transport position (without load).

2.12.4. The limiter of the mechanism for lifting a load or boom must ensure that the load-handling element stops when lifting without a load and the gap between the load-handling element and the stop for electric hoists is at least 50 mm, for other cranes - at least 200 mm. When the load lifting speed is more than 40 m/min, an additional limiter must be installed on the crane, which operates before the main limiter, switching the circuit to a reduced lifting speed.

2.12.5. For grab cranes with separate drives of the lifting and closing winches, the limiter(s) must (must) turn off both motors simultaneously when the grab reaches its extreme limit. top position.

2.12.6. Limiters of movement mechanisms must ensure that the motors of the mechanisms are turned off at the following distance to the stop:

for tower, portal, gantry cranes and bridge loaders - no less than the full braking distance;

for other cranes - at least half the braking distance.

When installing mutual travel limiters for the movement mechanisms of bridge or jib cranes operating on the same crane runway, the specified distance can be reduced to 500 mm. The braking path of the mechanism must be indicated by the manufacturer in the crane passport.

2.12.7. Jib-type cranes (except for cantilever cranes) must be equipped with a load capacity (load moment) limiter, which automatically turns off the mechanisms for lifting loads and changing the reach in the event of lifting a load whose weight exceeds the load capacity for a given reach by more than:

15% - for tower (with a load moment up to 20 tchm inclusive) and portal cranes;

10% - for other faucets.

For cranes with two or more load characteristics, the limiter must have a device for switching it to the selected characteristic.

2.12.8. Overhead cranes must be equipped with load limiters (for each cargo winch) if overloading is possible due to production technology. Cranes with a variable load capacity along the length of the bridge must also be equipped with such limiters.

The load limiter for overhead cranes should not allow overload of more than 25%.

2.12.9. After the load limiter has been activated, it must be possible to lower the load or activate other mechanisms to reduce the load moment.

2.12.10. Jib cranes must be equipped with working movement limiters to automatic shutdown mechanisms for lifting, turning and extending the boom at a safe distance from the crane to the power line wires.

2.12.11. Overhead cranes with a lifting capacity of more than ten classification groups (mode) of at least A6 according to ISO 4301/1, tower cranes with a lifting capacity of more than 5 tons, portal, railway and jib cranes must be equipped with recorders of their operating parameters. Tower cranes with a lifting capacity of up to 5 tons inclusive must be equipped with devices for recording operating hours.

2.12.12. To prevent their collision with obstacles in cramped working conditions, jib cranes must be equipped with coordinate protection.

2.12.13. Cranes, except those controlled from a pendant control panel, must be equipped with an audible warning device, the sound of which must be clearly audible in the area where the crane is operating. When controlling the crane from several posts, it should be possible to turn on the signal from any of them.

2.12.14. Gantry cranes and overhead loader cranes must be designed for the maximum possible skewing force that occurs during their movement, or be equipped with an automatic skewing limiter.

2.12.15. Cranes with electric drive, except for cranes with electric hoists that have a second load-bearing brake, must be provided with protection against falling loads and booms in the event of a break in any of the three supply phases electrical network.

2.12.16. Overhead cranes must be equipped with a device for automatically relieving tension from the crane when entering the gallery. For cranes operating indoors, trolleys with a voltage of no more than 42 V may not be switched off.

For overhead cranes, the entrance to which is provided through the bridge gallery, the door for entering the gallery must be equipped with such a blocking.

2.12.17. The door to enter the control cabin, which moves with the crane, on the side of the landing platform must be equipped with an electrical lock that prohibits the movement of the crane when open door. If the cabin has a vestibule, then the vestibule door is equipped with such a lock.

2.12.18. For magnetic cranes, the electrical circuit must be designed in such a way that when the voltage is removed from the crane by the contacts of instruments and safety devices, the voltage from the load electromagnet is not removed.

2.12.19. For tower cranes with a fixed tower and for other cranes where the cabin is located on the rotating part of the crane, to prevent the possibility of pinching people when moving from the rotating part to the non-rotating part, a device must be provided that automatically turns off the motor of the rotating mechanism when the hatch or door is open.

2.12.20. Cranes whose lifting capacity varies with changes in reach must be provided with an indicator of the lifting capacity corresponding to the reach. The scale (display) of the load capacity indicator must be clearly visible from the crane operator’s (driver’s) workplace (hereinafter referred to as the crane operator). The load capacity indicator may be part of the electronic load limiter.

When calibrating the scale of a crane's lifting capacity indicator, it is necessary to measure the reach on a horizontal platform with a load on the hook corresponding to a certain reach, and make a mark on the scale after removing the load.

2.12.21. The crane angle indicators (inclinometers, alarms) must be installed in the jib crane cabin. In the case when the crane's outriggers are controlled outside the cabin, an additional crane angle indicator must be installed on the fixed frame of the crane.

2.12.22. Tower cranes with a height to the top of the tower head of more than 15 m, gantry cranes with a span of more than 16 m, portal cranes, overhead loader cranes must be equipped with a device (anemometer) that automatically turns on an audible signal when the wind speed specified in the passport for the operating condition is reached tap.

The installation location of the device should be selected in accordance with regulatory documents.

2.12.23. Cranes moving along a crane track on outdoors, must be equipped with anti-theft devices in accordance with regulatory documents.

Overhead cranes operating outdoors may not be equipped with anti-theft devices if, when the crane is exposed to the maximum permissible wind speed, accepted according to GOST 1451 for the crane's non-operating state, the braking reserve of the moving mechanisms is at least 1.2 according to regulatory documents.

2.12.24. When using rail grips as an anti-theft device, their design must allow the crane to be secured along the entire path of its movement.

2.12.25. Machine-driven anti-theft devices must be equipped with a device for manual activation.

2.12.26. Cranes moving along a crane track and their trolleys must be equipped with elastic buffer devices to soften possible impacts against stops or against each other.

2.12.27. Cranes (except for electric hoists) and cargo trolleys moving along the crane runway must be equipped with support parts in case of breakage of the wheels and axles of the running devices.

For monorail trolleys with a trailer cab, the supporting parts must be installed on the cab chassis. When the cabin and lifting mechanism are suspended from a common frame, support parts are installed on each undercarriage.

Supporting parts must be installed at a distance of no more than 20 mm from the rails (riding beams) on which the crane (trolley) moves, and must be designed for the greatest possible load on these parts.

2.12.28. Jib cranes with variable reach and flexible boom suspension must have stops or other devices installed to prevent the boom from tilting.

For tower cranes, such devices must be installed if, with a minimum reach, the angle between the horizontal and the boom exceeds 70°.

To ensure trouble-free operation, the overhead crane is equipped with the following instruments and safety devices: limit switches; buffer devices; a load limiter or a mass measuring device indicating the mass of the load being lifted; locking devices; devices that prevent collisions between overhead cranes operating on the same crane tracks; a device to prevent the sling from falling out of the cargo hook; sound and light alarms and means of collective protection against electric shock.

Limit switches are used to automatically disconnect the load lifting mechanism from the electrical network when the hook suspension approaches the main beams of the bridge, as well as when approaching the end stops of a crane or cargo trolley at a rated speed of more than 32 m/min (Article 160 of the Rules). After stopping the mechanism, the limit switch should not prevent the mechanism from moving in the opposite direction (see 161 of the Rules). A limit switch is an electrical device with contact pairs, when opened, the power supply circuit of the electric drive of any actuator is broken, for example, the drive motor of the trolley movement mechanism and the drive of its brake. The circuit can be broken by the contacts of the limit switch or, at the signal of the limit switch, by the contacts of other electrical devices: relays, contactors, starters, etc.

Lever and spindle limit switches are used in overhead electric cranes. Lever switches are triggered by contact with some kind of stop, for example a trip line, and usually serve to limit movement in one direction. In addition to limiting the movement of crane mechanisms, such switches are used to disconnect current-carrying trolleys when service personnel enter galleries, stairs and crane service areas. These switches serve to block the door of the crane control cabin, which does not allow the crane mechanisms to be turned on when the door is open (Article 167 of the Rules).

Spindle switches are used mainly to limit the lifting height of a load-handling device and are designed to limit its movement up and down in both directions.


Rice. 6. Limit switches:
A - general form switch KU-701; 6 - its kinematic diagram; c - KU-704; d - KU-703; d - KU-706

Electric overhead cranes domestic production equipped with lever limit switches of types KU, NV, V and VK, which de-energize the coils of the main and reversing contactor of the motor control circuits in the electrical circuits of the mechanisms. KU switches provide opening or closing of the electrical circuit. Closing electrical circuits when the drive motor is turned off, according to the Rules, is allowed only for signaling and control devices. The KU switch (Fig. 6, c) has a cast housing in which cam washers 2 are fixed on shaft 1 (Fig. 6, b). Roller 3 of lever 4 interacts with washers 2. The roller is constantly pressed against the washers by spring force 5. On the lever 4, a jumper 6 is installed, which closes, when washers 2 act on roller 3, contacts 9 of the electrical control circuit for the motor of the crane mechanism. With this design, the KU switch works to close the electrical circuit. When using it to open an electrical circuit, roller 3 is installed on axis 10, and spring 5 is moved to the N.C. position. The latch 7 and the spring-loaded pawl 5 serve to return the drive lever of the KU-701 switch to its original position, and for switches KU-704 and KU-706 - to fix the position of shaft 1. In the design of the KU-703 switch, the latch and pawl are absent. The operating levers of the switches can be installed in various positions.

Limit switches of the KU-703 type (Fig. 6, d) are used on load lifting mechanisms. These switches are activated when the load suspension reaches its highest position. Switch types KU-701, KU-704 and KU-706 are installed on the crane movement mechanisms. They are triggered when their drive levers are acted upon by a ruler or a special stop mounted on a cargo trolley or on a crane track. The limit switches of the travel mechanisms are installed in such a way that their motors are turned off at a distance equal to at least half the braking distance of the mechanisms.

The safety of people involved in crane operations is also ensured by interlocking devices that automatically remove voltage from exposed live parts and de-energize the crane. Typically, the simplest limit switches of the VK type are used for this purpose. On electric bridge cranes they are installed on the exit hatches from the cabin, on the doors in the end fences of the galleries (Fig. 6.4).

Before exiting the cab onto the crane gallery, the crane operator must turn off the main switch - de-energize the crane. If for some reason the crane operator does not turn off the switch, and there is no interlock, then this creates a danger of electric shock. The purpose of the locking device is to eliminate this danger in such a situation.

Figure 6.4 – Locking device at the entrance to the crane gallery

The exit from the cabin to the crane bridge is through a hatch in the gallery floor. When the lid is opened, a switch installed on the hatch breaks the electrical circuit and de-energizes the trolleys. The same purpose is used for the locking device on the doors in the end railings of the crane galleries. The door entering the overhead crane cabin must also be equipped with an electrical lock to prevent the crane from operating when the door is open.

Zero blocking. All motor control circuits on cranes have zero blocking. It allows you to turn on the line contactor and apply voltage to the controllers when all controllers are brought to the zero position. If this condition is not met and any of the controllers is not set to the zero position, then the contactor of the protective panel will not turn on and the mechanism will not be pulled out arbitrarily.

However, practice shows that if safety rules are violated, even if there is an automatic lock, an accident can occur.

For example, an electric overhead crane moves along the bay of a workshop with castings suspended from a hook. At this time, a crane operator is coming to meet him along the crane track. Having reached the crane, without any warning, he opens the door in the end fence and goes out onto the gallery. What happens? When the doors are opened, the lock is activated. The crane stops. But he was moving at high speed, and the load suspended from him, due to inertia, moves first forward due to the oblique tension of the rope, then makes a reverse movement - the load swayed. And people were working in the workshop in the same flight - and the accident became inevitable.

Limit switches and interlocking devices are only effective at low speeds. If the speed exceeds 80 m/min, the lever limit switches cannot serve reliable protection. In these cases, other traffic restriction systems are used.



The Ural Polytechnic Institute has created a photoelectric hitchhiker designed to safely stop overhead cranes moving towards each other at high speed. Hitch-hiking; is activated when the cranes approach a distance equal to the sum of the longest braking distances. This device can be used mainly in enclosed spaces. Another system for stopping cranes moving towards each other is made using radar sensors, with the help of which the cranes are de-energized when approaching a dangerous distance.

Overhead cranes must be equipped with load limiters that prevent overloading by more than 25%.

If lifting cranes are controlled from the cabin, from a remote control or remotely, then they are equipped with a mechanical or electrical signaling device.

The main purpose of safety instruments and devices is to ensure accident-free and reliable operation GPM, ease of maintenance and increased productivity. To ensure operational safety, collective protective equipment is widely used: alarms, safety limiters and braking devices, as well as fire-fighting equipment and means of protection against electric shock.

Basic requirements for instruments and safety devices:

· durability, reliability and trouble-free operation of the device;

· ease of repair and adjustment;

· small dimensions and weight;

· automatic switching off and then switching on of mechanisms, regardless of the duration of the PMG stop;

· lack of possibility of switching or special adjustment due to changes in the operating mode of the PMG or load;

· Possibility of using devices of various designs.

For safe operation The following devices and safety devices are installed on the lifting mechanism:

· Load capacity limiters (load moment) are designed to ensure the safety of PMG operation in cases of breakdowns of individual elements and mechanisms due to overload. They automatically turn off the mechanisms for lifting the load and changing the boom reach in the event of lifting a load whose weight exceeds the permissible load capacity (for a given reach). The excess lifting capacity can be no more than 10% for jib, tower and railway cranes, 15% for portal cranes and 25% for overhead cranes. After the load limiter has been activated, it must be possible to lower the load or activate other mechanisms to reduce the load moment.

Load limiters are:

- Mechanical type (OGB-2; OGB-3, ONK-M). They are installed on cranes with a constant boom length and consist of a force sensor, an angle sensor; control unit and alarm panel. The operation of the limiter is based on the principle of comparing the force measured by a force sensor installed in the boom-lifting mechanism with the maximum permissible force value set by an angle sensor, which is connected to the boom. If the operating force exceeds the maximum permissible for a given flight, the limiter is activated, i.e., a red light on the alarm panel lights up and a command is given to actuating mechanism, which disables the mechanisms for lifting the load and lowering the boom.

- Microprocessor based. They have great technical and information capabilities. These devices together make it possible to perform several safety functions, such as limiting the load capacity, limiting the movements of crane structures near power lines and various obstacles, and registering the operating parameters of the PMG in the memory unit. The most widespread following types devices: ONK-140; ONK-160; OGM-240. The operating principle of the limiter is based on sequential polling and conversion analog signals from sensors of primary information in digital code, determination of the angle of inclination and length of the boom, calculation by digital methods of departure, lifting height and actual weight of the load, followed by comparison with the maximum acceptable values stored in the limiter’s memory in the form of load characteristics. The choice of cargo (protective) characteristics, i.e. the relationship between the weight of the load and the reach is made by the limiter depending on the operating mode and type of boom equipment. If exceeded permissible load At this departure, the initial control commands for the locking devices are generated.

- Load capacity indicators. Cranes whose lifting capacity varies with changes in boom radius must be provided with a lifting capacity indicator. This device contains a scale (display) with an arrow, from which the crane operator can determine the permissible load weight at a given boom angle. The sign must be clearly visible from the crane operator's workplace. In modern PMGs, the load capacity indicator is, as a rule, part of the microprocessor load limiter.

· Limit switches. A limit switch is a device with electrical contacts, when opened, the circuit of the electric motor and brake drive is interrupted directly or using an auxiliary control circuit. Limit switches are divided into lever and spindle. Lever switches provide one-way limitation; two-way limiting requires two switches. The switch is activated by touching the lever with the stop of the moving mechanism. Spindle switches are connected to the rotating shafts of mechanisms and are used for bilateral limitation.

Limit switches are installed on the PMG to protect the transition of mechanisms beyond the limit positions. Some cranes cannot start moving at the first position (speed) of the controller. Therefore, further movement in the same direction is allowed for the traveling mechanism of the overhead crane when approaching the landing site at the lowest speed allowed electrical diagram. In this case, the lowest speed should be understood as the minimum speed allowed by the electrical control circuit after the crane starts moving.

· Limiter for the load or boom lifting mechanism. It is a limit switch with a limit bracket (KB), installed at least 200 mm from the uppermost position of the load-handling member. When the crane suspension rests on the limit bracket, the HF is turned on and the upward movement of the load-handling member stops. The lifting mechanism of the load-handling member will only work for lowering. If, when installing the HF on the hydraulic machine, the distance between the hook suspension and the HF lever is reduced, then when lifting the HF load, due to the inertia of the spring, the rope may not work and the rope will pull the hook suspension all the way, and the hook suspension (load) may break and fall in the area work.

If, due to operating conditions, it is necessary to lower the load below the level specified in the passport, then a limiter for the lower position of the hook suspension is installed in the lifting mechanism (it turns off the mechanism if 1.5 turns of rope are wound on the drum).

· Other safety devices:

A PMG with an electric drive must have drop protection and arrows in the event of a break in any of the three phases of the power supply network. Such protection is provided, as a rule, by the use of normally closed type brakes in the mechanisms, which are automatically activated in the event of a phase failure or power failure. In the most critical cases, a phase loss protection device (PPD) is used.

For jib cranes with flexible suspension, the booms (using jib ropes) must be installed stops or other devices that prevent the boom from tilting back. Tower cranes must be equipped with such devices if, at a minimum reach, the boom angle exceeds 70°.

Protective means protection is used to prevent access to easily accessible, moving or energized electric current parts of the GPM. They protect all types of gears (gears, chains, etc.), couplings and drums located near the crane operator’s workplace or in passages, shafts of the movement mechanism of cranes and other systems (if the latter are located in places intended for the passage of service personnel). Exposed live parts are also subject to fencing.

In addition, during operation, hydraulic and hydraulic machines are used: alarm systems . They can be of two types. This is a signal painting of moving elements of lifting equipment, dimensions of transport openings, differences in the plane of the floor, fences, corners of walls, hatches, floors, steps of stairs, as well as audible warning alarms on cranes controlled from cabins or from a remote control.

Safety requirements for electrical equipment of cranes. Electrical equipment of the gas and hydraulic machine includes electric motors, mechanisms and control devices, lighting systems, heating devices, and for cranes with electromagnetic load grippers - electromagnet power systems.

Current supply to electric motors can be carried out using trolleys made of rolled steel or wire round section, flexible cables and ring current collectors (when powering rotating mechanisms). The limited use of flexible cables is due to the fact that they can only be used in machines moving short distances and at low speeds. The supply of voltage from the external network must be carried out through an input device, with which the voltage can be removed. Since an insulation breakdown may result in the appearance of voltage on non-energized structural elements, they must be grounded.

The specificity of grounding systems is the use of crane tracks as grounding devices (where they exist) and special chain devices that slide at cranes on a vehicle on the ground or on the road surface. When the network voltage is restored after another power outage, special (zero) protection is used.

Fire-fighting equipment . Carbon dioxide fire extinguishers must be installed in all rooms where hydraulic machinery is located, technically maintained, repaired, as well as in crane operator cabins.

Safety devices are sealed after manufacture, repair, and adjustment by responsible specialists in order to prevent access and damage to the devices by unauthorized persons.