Overhead grab crane: purpose, principle of operation, types

An overhead crane is a crane with a load-handling mechanism, suspended from a hoist or trolley, which moves along a movable steel structure or bridge.

There are taps:

with grab and grips for containers (special);
with hook (general value);
metallurgical;
with magnet.

The design of electric grab cranes is similar to that of hooks. The only difference is the trolley: it has two lifting mechanisms: the first is for grab ropes, the second is for lifting ropes.

A grab crane consists of a bridge [2], a cabin [1] and has a special trolley [3], to which a grab [4] is suspended on steel ropes. The lifting capacity of cranes varies from 5 to 10 tons. Accordingly, the capacity of the grabs is from 1.6 to 10 cubic meters. The spans of overhead cranes are measured in meters: from 10 to 34.5 meters. The lifting height is 24 meters.

In cases where it is necessary to move or reload bulk, lump or bulk cargo, overhead grab cranes or loader cranes are used. They differ from other cranes in that they are equipped with a special grab.

Main design elements

Supports or crane tracks
along which the main mechanism moves.
The main beam
rests on supports and moves along them on special wheels in one direction.
A trolley mounted on a beam
moves in a direction perpendicular to the movement of the main beam.
Electric hoist or electric winch
, providing vertical movement of the load.
The operator's cabin
, from where the crane's movements are controlled, is fixed, as a rule, at the same height as the main beam, which provides the best possible visibility. There are models of small cranes with remote control.

The crane bridge thus consists of main or span beams connected to end beams.
A sub-carriage rail is fixed in their upper part, at the opposite ends of which there are stops to limit the extreme positions of the undercarriage. On the sides of the span beams there are platforms with railings necessary for servicing the crane mechanisms. The number of crane wheels on the end beams, thanks to which the crane itself moves, can be more than eight, which helps reduce the load on each of them and contributes to its even distribution on the crane runway as a whole.

Overhead cranes provide lifting and transportation of goods from a platform located between the main supports. Thanks to the ability to move in two mutually perpendicular directions, the cargo is accessible to them from any point. Devices such as a hook, traverse, spreader, magnet, and grab can be used as a load-handling device.

Cranes are usually designed for medium and moderate loading conditions. There are 3 groups based on load capacity:

The first
, including cranes up to 5 tons;
The second
, which includes cranes from 5 to 50 tons;
Third
- from 50 to 320 tons.

Grab crane – Great Encyclopedia of Oil and Gas, article, page 2

Grab crane

Special overhead grab cranes (Table IV.2.14) are used for transporting bulk and lumpy cargo.

Floating reloading grab cranes in river and sea ports are used very intensively.

Overhead grab cranes are produced by a number of domestic enterprises and are widely used for a variety of operations for lifting and moving bulk and lump cargo (sand, coal, ore, etc.) indoors or outdoors. The cranes are manufactured in two versions according to the location of the grab (along or across the bridge), controlled from a cabin mounted on the bridge, and are designed for heavy-duty operation.

Using a grab crane, kaolin is fed into the receiving hopper of the feeder, and then by a bucket conveyor into the wet grinding runners, where water and alumina are also supplied. About 10% of pre-ground fines from chlorinated briquettes is usually added to kaolin.

The lime paste is fed into the hopper using a grab tap, and water is supplied here under a pressure of 0 2 - 0 3 MPa. The concentrated milk prepared in the bunker is fed to a screen to remove particles larger than 25 mm, and then fed to a ball mill. Further operations are similar to those carried out for the dry method of storing lime.

For grab cranes, the compliance of the weight and capacity of the grab (taking into account the bulk weight of the material being handled) with the lifting capacity of the crane is checked. Grabs with a manual device for closing the jaws are not allowed to work.

For grab cranes, the compliance of the weight and capacity of the grab (taking into account the bulk weight of the material being handled) with the lifting capacity of the crane is checked.

The use of grab cranes for reloading bulk cargo also has disadvantages.

For grab cranes, the compliance of the weight and capacity of the grab (taking into account the bulk weight of the material being handled) with the lifting capacity of the crane is checked.

The difference between grab cranes and magnetic ones lies in the design of the lifting mechanism, which is carried out in relation to the specific features of the grabs.

For grab cranes, the compliance of the weight and capacity of the grab (taking into account the bulk weight of the material being handled) with the lifting capacity of the crane is checked.

Grab cranes require that all load ropes go through a stopper.

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Features and purpose

The crane with grab is designed to move soil, crushed rocks, ferromagnetic materials, metal shavings, scrap and long lengths of lumber. Such equipment is in demand in warehouses and shipbuilding docks. There are installations used for lifting various loads from the surface of reservoirs.

There are 2 types of grab working body:

With 2 jaws. The unit is used to move bulk cargo with a small fraction size.
With a large number of jaws (3 or more). The installation is designed to work with loads consisting of large fragments (stones, rock fragments, etc.)

There are 2 types of working element drive possible:

Rope type. Such installations are equipped with electrically driven winches; the crane components are moved using cables.
Driven machines in which the grab is driven by an electrical or hydraulic device installed directly on the unit. When using hydraulics, the crane has a separate pumping station equipped with a liquid supply tank.

The design of the crane installation is similar to that of general purpose lifting machines. The difference lies in the design of lifting devices and trolleys. An additional cable drum is installed on the working trolley, designed to control the working unit. A similar solution is found on magnetic installations. The cable drum is driven by a working mechanism, which ensures equal speeds of unwinding and rewinding of cables and electrical wiring.

Mechanical grabs use trolleys with a double drum mechanism. One section is responsible for raising and lowering, and the other is responsible for opening and closing the bucket.

The characteristics of grab installations include:

load capacity;
working bucket capacity;
permissible density of transported cargo;
direction of opening of the bucket (along or across the guide bridge);
speed of movement of the bucket up and down and movement of the bridge;
type of power supply;
machine operating conditions (indoors or outdoors);
ambient temperature at the height of the working elements;
type of control (from the cabin, from the remote control or combined).

Advantages

All products have a lot of advantages:

long period of operation with a 20-year warranty;
high level of security;
possibility of installing manual or radio control;
excellent productivity at work;
quick access to all components, interchangeability of parts;
high quality materials and workmanship.

Overhead cranes are certified in accordance with TR CU 010/2011 “On the safety of machinery and equipment”. When designing a crane, we take into account the operating temperature, work intensity and other factors that affect the crane’s performance. We will advise you on the details and install it on site.

Mostovoy

The overhead grab crane is equipped with a special beam along which the unit with the grab winch mechanisms installed on it moves. The box beam can be single; there are installations with a double guide. At the ends of the beam there are running trolleys that move along guide rails. The overhead crane is equipped with lifting winches equipped with electromagnetic hydraulic brakes, ensuring quick stopping.

The magnetic grab crane is distinguished by the installation of 2 load-handling devices - with electromagnets and a standard bucket. The units are mounted on a common or separate trolley. Excitation coils are installed on the magnetic section, which create a field when electrical voltage is applied. The technique is used when moving ferromagnetic materials and standard bulk cargo, as well as scrap steel.

The operator's workplace is equipped with a separate adjustable seat with joysticks installed on the armrests. The remote control allows you to perform manipulations from the cabin or from a distance from the grab crane.

To increase safety, the grab is equipped with:

a limit switch that automatically turns off the lifting mechanism;
sound alarm;
limit contact switches limiting the travel of the trolley;
built-in thermal switches to protect electric motors;
contact travel limiters;
work area lighting system.

Kozlova

The grab gantry crane is a type of bridge crane. The span of the machine is mounted on supports equipped with wheeled trolleys. The units move along rail tracks laid on concrete foundations. Visually, the supports resemble trestles, which is what gave the cranes this designation. There are semi-gantry-type installations, one of the sides of which rests on special racks, and the other on crane tracks.

To move the installation, movement mechanisms mounted on single-wheeled or balancing trolleys are used. There are various designs of gearboxes and couplings for connecting output shafts and wheel axles. The trolleys use band brakes to ensure quick stopping.

Shipping

Transportation of overhead cranes is carried out in different ways, but most often delivery is carried out using railway platforms. The main beams are shipped assembled. Parts of bridge structures that have large spans are transported in 2 or 3 sections.

If the lifting mechanism has a small load capacity, the carts are transported assembled. Production requires heavy-duty trolleys; they are transported in units. The frame and lifting mechanism are transported separately; if necessary, the balancers are moved from place to place.

The choice of transportation method depends on the size of the crane. If it is large, the structures are transported on separate railway platforms. It is possible to organize a coupler of 2 elements, but they are suitable for delivering cargo whose length does not exceed 17 m. For this purpose, platforms are used whose lifting capacity is 50 tons and 60 tons.

If the loads are oversized, you need to pay attention to the quality of their securing

It is important to take into account loading conditions. The parts of the crane must be securely fixed in place; to do this, wooden beams are placed under them

This reduces the mobility of the elements; they do not move during transportation. The crane is fixed to the platform using guy wires. It is necessary to make a strength calculation, determine the effective dynamic loads and the magnitude of the impact of inertial forces

The parts of the crane must be securely fixed in place; to do this, wooden beams are placed under them. This reduces the mobility of the elements; they do not move during transportation. The crane is fixed to the platform using guy wires. It is necessary to make a strength calculation, determine the effective dynamic loads and the magnitude of the impact of inertial forces.

If railroad tracks cannot be used for transportation, the crane is loaded onto semi-trailers. To transport them, powerful tractors or tractors are used. The enterprise must choose appropriate courses of action.

Why and how often should you clean your well?

A reliable well house, of course, significantly limits the entry of debris into the well, but even it cannot completely protect the water from contamination. Fallen leaves and branches, not to mention dead animals and birds, cause significant deterioration in water quality as a result of the decomposition process. The rate of siltation also depends on the characteristics of the aquifer. In soft clay soil, silt forms noticeably faster than in hard rock. This slows down the flow of water and, accordingly, reduces the flow rate of the source.

Experts recommend clearing the bottom of silt at least once every five years. However, in some cases, cleaning the well using a grab or other device may be necessary earlier, which is facilitated by the following symptoms:

significant turbidity of the water as a result of a violation of the tightness of the seams or poor performance of the filter layer;
the appearance of clay deposits at the bottom due to the ingress of surface runoff;
significant reduction in source flow;
a noticeable increase in the bottom level;
deterioration in the taste characteristics of water.

If any of these symptoms have been noticed, or cleaning measures have not been carried out for more than five years, then it is better not to put off cleaning for a long time and carry it out as soon as possible. Especially if you regularly use water from a well for drinking and cooking.

Single rope grabs

Single-rope machines are usually called those in which both working movements (ascent or descent, closing or opening) are carried out by one traction element, mainly a rope. Single-rope designs can be automatic (with a bell) or manually controlled when deployed.

Currently, single-rope automatic ones (with a bell) are not used due to the complexity of the design.

In Fig. Figure 1 shows a single-rope Ginstalmost grab. The grabs consist of jaws a, middle crossbar b, upper crossbar c and jaw crossbar e.

Traverse b is guided by a bar. Latches are installed in the traverse d. The grab is suspended from the crane hook by means of a special cross-beam d. For smooth opening, an oil brake e is used, connected to the cross-beam b and jaws a. In the closed position, traverse d is closed with traverse b (Fig. 2, C). If you pull the rope k, the levers M and N will take the position shown in the dotted line. The beveled supporting surfaces of the latches p, under the influence of their own weight, slide off the traverse g, the latter lowers, and the grab opens. When lowering it onto the material of the traverse hook d, and along with it the traverse b is lowered until the latter reaches position a (Fig. 2, B). The latches move from position I to position II, and lever N, under the influence of its own weight, falls into the gap between both latches, taking its previous position (Fig. 2, A); traverse g closes with traverse b, and with further lifting of the hook the grab closes.

The speed of opening and closing of the jaws is controlled by an oil brake (Fig. 3), which is a cylinder with cavities A and B, connected by a valve that regulates oil flow. When opened, oil flows from A to B through valve L, which is adjusted using a set screw. Spring R (Fig. 2, B) holds the lever in its position and only by the force of the rope k can it be compressed and the latches p open.

It is advisable to use single-rope ones where the same reloading device must be used for reloading both bulk materials and piece goods. This occurs in foundries, on construction sites, in slag ditches when cleaning steam locomotives, etc.

Notes

Grab
- article from the Great Soviet Encyclopedia.
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Load-lifting and transporting machines at construction materials factories/
V. P. Balashov
Read also: Devices for sharpening knives: which ones are used at home
- M: Mechanical Engineering - 1987 - 384 p., ill.
Grab // Explanatory dictionary of the Russian language: in 4 volumes / ch. ed. B. M. Volin, D. N. Ushakov (vol. 2-4); comp. G. O. Vinokur, B. A. Larin, S. I. Ozhegov, B. V. Tomashevsky, D. N. Ushakov; edited by D. N. Ushakova. - M.: State Institute "Soviet Encyclopedia" (vol. 1): OGIZ (vol. 1): State Publishing House of Foreign and National Dictionaries (vol. 2-4), 1935-1940.
↑ 1 2 3 4 5 6 7 8 Berkman I.L., Rannev A.V., Reish A.K.
- Universal single-bucket construction excavators, School - M: Higher School, 1977, 384 pp., ill.
↑ 1 2 3 4 5 P. N. Ushakov, M. G. Brodsky
- Ref: Cranes and elevators of Industrial enterprises, 1974, 352 pp., illus.
↑ 1 2 3 4 5 6 7 8 9 P. Z. Petukhov, G. P. Ksyunin, L. G. Serlin
- Special cranes - M: Mashinostroenie, 1985, 248 p.

Types of general purpose overhead cranes

Bridge support cranes come in the following types: single-girder and double-girder manual hook cranes, as well as electric hook cranes.

Bridge support cranes come in the following types: single-girder and double-girder manual hook cranes, as well as electric hook cranes. Single-beam manual hooks consist of one beam, which is connected to the end beam. It is in this place that the wheels are mounted. To ensure that the bridge is sufficiently strong and rigid, the end and span beams are connected by struts. The wheels are made to rotate by the transmission shaft and gear, which extend from the traction wheel with a chain.

Worm steel is used for the load lifting mechanism. Double-girder manual hook cranes consist of two beams, which, as in single-girder cranes, rest on end beams. The movement mechanism is represented by a wheel with a chain. The design of the trolley has a frame with wheels. The cart is driven by a sprocket wheel. The frame has a mechanism for lifting loads, equipped with a brake with wheels and a chain.

Single girder electric hook cranes. Here the cargo trolley is represented in the form of electric ropes. The bridge also has one beam, which is supported by box-type end beams. The ends of the beam are braced, which are designed to enhance strength and rigidity. Movement occurs using a separate drive, that is, each wheel is equipped with a drive separately from the other wheel.

This type of crane does not have a brake, as the movement speed is very low. All crane mechanisms are powered via a cable. This type of crane can be controlled either using the control panel or from inside the cabin. Double-girder electric hook cranes have a bridge and a load trolley. The bridge has a movement mechanism, and the cargo trolley has almost all the mechanisms found in the cranes. This includes a load lifting and movement mechanism, a crane control system, and much more. The control is similar to the control of an electric single-girder crane, that is, both using the control panel and from inside the cabin.

Electric magnetic overhead cranes. Their design is the same as that of electric hook cranes. Only this type of crane has a magnet that is attached to the hook. The magnet supplies direct current with a voltage of 220V. The magnet on the crane can be removed and the crane can then be used as a hook crane.

Electric grab overhead cranes. The device is the same as that of hook cranes. The only exception is the device of the trolley. It has two lifting mechanisms: one for lifting the grab ropes, and the other for lifting the load.

Electric hook overhead cranes designed for lifting large loads. The device is the same as that of double girder cranes.

Electric hook overhead cranes designed for lifting large loads. The device is the same as that of double girder cranes. The bridge of such cranes must be located on eight wheels. This ensures significantly less load on the wheels. In order for the crane to be rotated, the hinges are in contact with the rails. The rails, in turn, have some deviation. Movement is ensured using a separate drive.

The crane can be controlled remotely if the crane operates in workshops that do not contain explosive substances, toxic gases, or substances that destroy metal and cause erosion. There are three types of remote control. Control using a special remote control, using a remote control that can be rearranged, and using radio control.

General purpose overhead cranes can also be suspended. They are single-span, double-span and three-span. Such cranes are very convenient because they are small in size, they can be installed anywhere in the workshop, they can cover large spans and ensure the movement of a trolley from one crane to another. These cranes are also used in hard-to-reach places where it is not possible to operate with any other type of crane.

Manual single girder single span cranes have a beam attached to the bottom of the end beams. A manual hoist is used as a lifting mechanism. Electric single girder single span cranes also have a support beam attached to the lower end beams.

Both driven and non-driven electric hoist trolleys serve as the movement mechanism. The taps are made without butt locks, but a power cable must be present. Electric single girder double span cranes differ from single girder electric cranes only in that the main girder is attached to three cross girders.

Excavators

Rope grabs

On mechanical cable excavators, both double-jaw grabs and grabs with a large number of jaws are used - the number and shape of the jaws depend on the type of material being handled. However, the basic diagram of their operation does not differ from the diagram of a double-jaw grab.

Description

For a grab used on a mechanical excavator, a dragline lattice boom is used. Three types of grabs are produced for excavators: light, medium and heavy. In this case, the mass of the grab used should be greater, the denser the soil. However, the heavier the grab, the less soil it can lift for a given equipment stability, which affects its productivity.

Device

To prevent twisting of the ropes and significant swinging of the grab when turning the platform, a pull-out device called a damper is used. The damper acts on the bucket with a pull rope. A constant rope tension, independent of the position of the grab, is created by the weight of the load moving inside the boom along the guides, to which the rope bending around the blocks is attached. Some excavators use a friction mechanism for opening the bottom of the bucket, on the drum of which a rope is attached.

Advantages and disadvantages

The disadvantage of the rope grab is the inability to develop dense soils: the load from the mass of the grab is not enough to crash into the ground.

Hydraulic grabs

On hydraulically driven excavators, special rigidly suspended grabs are installed, which are mounted on the handle of a backhoe instead of a bucket.

Advantages and disadvantages

The main advantage is the ability to create the necessary pressure when cutting into the ground and, regardless of its mass, to develop dense soils.

Classification by number of blades

Depending on how many blades the grab has, they are classified into multi-jaw and double-jaw.

Double-jaw crane for German production from Ural Stahl

Grab overhead cranes with multi-jaw grabs are mainly used for the purpose of moving stones, as well as for working with other materials that are difficult to scoop. Also, for scooping various cargoes, ship holds or wagons, cranes are used, which are equipped with special scooping grabs. But the most popular are the cranes that are equipped with a two-rope, two-jaw grab.

Multi-jaw grab

As a rule, a grab overhead crane with a rope grab is equipped with a winch that has two drums. The locking drum winds the locking rope while winding the supporting rope.

There are designs that are equipped with a pair of independent winches. Rope grabs are manufactured in single-rope, double-rope and four-rope versions. The last two types allow you to perform unloading operations without weight in any position. Thanks to this, the duration of reloading work is reduced.

The grab overhead crane, which is equipped with a hinged grab, is equipped with a locking mechanism, and it is built into the grab. In this case, a rope winch is installed on one of several traverses, which is equipped with a hydraulic or lever-screw tightening system. With the help of this type of overhead cranes, cargo is transported using a hook.

Construction of a double girder overhead crane

The movable bridge of the crane consists of 2 parallel beams of a box-shaped, solid-wall or lattice structure, depending on the load capacity.

Due to the connection with the transverse end beams on which the chassis is located, the double-girder overhead bridge crane moves along the rails of the crane tracks in the upper part of the production workshop or external overpass. The rails are mounted on crane beams, which are attached to building columns or ground supports.

Lifting of cargo is carried out by a lifting mechanism of a cargo trolley moving along the bridge. The trolley has a welded frame, is equipped with one or two lifting mechanisms with a gearbox and a moving device with a low-speed shaft to evenly distribute the load on the running wheels.

The overhead crane is driven by gear motors operating synchronously. Electricity is supplied via trolleys laid along the span and supplied to the hoist through a flexible cable. The crane is controlled from the cabin, or from a radio remote control on the floor.

You can familiarize yourself with the diagram of a double-girder overhead crane on our website.

The double girder overhead crane has the following main characteristics:

operating mode (“A”) - a total of 6 gradations, from “rare” to “very heavy”. The indicator depends on the combination of the class of use and load of the crane;
load class (“Q”) is divided into “light”, “moderate”, “heavy”, “very heavy”;
class of use (“U”) - divided into 9 positions, depending on the number of operating cycles over the entire service life of the PMG.

The main characteristics must be taken into account when choosing the parameters of a double-girder overhead crane before purchasing, in order to prevent premature wear and failure of the hydraulic transmission unit under excessive loading.

To avoid making a mistake with your choice, seek advice from our specialists.

Parameters of Double Girder Electric Overhead Cranes

lifting capacity – from 1 to 500 tons (includes the mass of the cargo, taking into account the lifting device and container);
lifting height – from 3 to 52 m;
lifting speed – from 2 to 40 m/min;
trolley moving speed – from 40 to 60 m/min;
crane speed – up to 125 m/min;
span length – from 4.5 to 34 m (distance between the axles of the crane wheels);
temperature range – from -40 to +40°С (depending on operating conditions and climatic design of the crane);
type of placement – U1, U2, U3 (outdoors, under a canopy, indoors);
execution - explosion-proof, fireproof, tropical, special (equipped with load-handling mechanisms).

Price and reviews

The price of stationary grab cranes depends on the span length, lifting capacity and range of auxiliary equipment. The minimum price of the product starts from 2 million rubles. Used equipment is estimated at 1-1.2 million rubles. When purchasing such products, you should take into account the correspondence of the overall dimensions of the old and new warehouse space.

The cost of renting a crane is included in the price of renting warehouses; there are no offers for separate use. Self-propelled grab units based on wheeled or tracked excavators are available for rent. The cost of operating such machines is in the range of 2-3 thousand rubles per 1 hour of work.

I work as an operator of a clamshell bridge installation installed in the workshop of a ship repair plant. The unit has a hydraulic bucket and a separate load magnet. To control the work, a small-sized remote control is used. The use of such a device simplifies the operation of the installation. The crane is under warranty, there are no complaints about the work.

Alexander, Moscow region

A Soviet-made mechanical crane is in operation, used for reloading sand-salt mixtures. Initially, the machine was equipped with a mechanical control system, which included numerous relays and contact groups. Instead, an electric throttle drive with thyristor control was installed, which increased the reliability of operation. The crane requires periodic maintenance; no breakdowns have been noted over several years of operation.

What is a beam crane and its use in the modern world

A beam crane is a machine that is designed to carry out work to ensure loading, as well as work to ensure unloading. Often such machines are used in various warehouses, they are also used in port areas. Such machines operate in open space. As a working body, this machine can use not only a hook suspension for lifting piece goods, but also on such machines they use clamshell buckets, which open and close using a rope system and pulley blocks. These devices - grabs - are used for loading and unloading various bulk materials, such as coal, sand, crushed stone, asphalt and other similar materials. Modern companies specializing in the production of industrial capacity are now experiencing a real surge in activity. Of course, because their equipment is now in great demand. The hero of our story is just from such a list. The leaders in production are large, established companies, such as CJSC Trading House Lifting and Transport Equipment, for which beam cranes Yekaterinburg are the primary area of production

This company also installs them at the customer’s site, which is also important. Let us now take a closer look at the very structure of this complex production element.

The suspended beam crane itself is a machine, the main frame of which is made of angle profiles and channels welded together, which together form a lattice structure. There is also an option with a frame design in the form of a beam. A cargo trolley is installed on it, which moves along rails installed along the crane frame. Lifting equipment (winch) is installed on this cargo trolley. This equipment, like the entire machine, is electrically driven. It consists of an electric motor that transmits torque through a clutch (on top of which a brake (block type) is installed) to a gearbox (helical). And from the gearbox, the moment is transmitted to the drum. Transmission is provided through the connection of two gear coupling halves of the gearbox and the drum.

The drum ensures by its rotation that the rope winds and runs away from it. Steel rope. At the end of the rope, a working body is installed, which, as noted earlier, can be either a hook suspension or a rope grab. What kind of working body a given crane has is determined by its purpose, or in other words, where it works.

The longitudinal movement of the cargo trolley along the frame is provided by an additional drive, which moves the trolley using a rope. There is one more element worth noting here.

Able to quickly lift heavy loads without putting operating personnel at risk. An electric hoist is a suspended type lifting device with an electric drive. It is used to move objects vertically and horizontally.

The entire frame with the cargo trolley is mounted on two racks. These racks come with double support or single support. Also racks can be rigid or flexible. It can be made of profiles, that is, it can be lattice, or it can also be made of a tubular structure.

The movement of the crane is ensured by wheels for moving on rails, which are installed at the bottom of the crane racks. Each wheel block is equipped with an individual electric drive. The movement itself is carried out on rails.

A cabin for the crane operator is also installed on the frame, from where he operates the machine; usually the cabin is located under the frame.

The faucet is powered by electricity, which is supplied through high-voltage wires.

sprosi.com.ua

Rope grabs

Ropes and drum winches allow the production of mechanical force without a rigid kinematic connection between the gripping elements when closing and opening the jaws. The control of a single-rope grab is available to the crane operator from the cab. The equipment is suitable for handling bulk materials and piece goods. Changing the load-handling attachment is carried out without wasting time by removing the bracket from the hook of stationary and mobile cranes. Mounted on an excavator or loader.

Operating principle of a single-rope grab:

It descends with its mouth open and is inserted into the load.
The load is grabbed and the jaws close.
Lifting, moving to the unloading point.
The opening of the jaws occurs upon contact with the surface - loosening the tension of the rope opens the closing latch.
When lifting, the bucket is emptied and ready for the next cycle.

There are accelerated unloading options:

Self-unloading - at a given height, the hanging bell automatically opens the latch of the bucket blades.
Unloading at an arbitrary height - the stopper is controlled from the ground or from the cabin (disabling the blocking by a tensioning cable device).

Multi-rope load grippers are more efficient to use due to the ease of control. With the integration of the pulley system, the power characteristics when raking and deepening the jaws when digging loose soils are improved.

Description of the operating principle and design of overhead cranes of various types

This is a lifting machine, the gripping device of which is located on a mobile trolley (or hoist), which in turn moves along the bridge. The latter is a movable structure made of high-strength steel. An overhead crane can be equipped with various gripping mechanisms: a bucket, a magnet, a grab, a device for lifting containers, and so on.

The peak production of these lifting machines occurred in the 80s of the twentieth century: 6,000-7,000 models of various lifting capacities rolled off the assembly lines of Soviet factories every year.

Since the 2000s, overhead cranes have been produced in quantities of up to 1,500 units (if we count manufacturers from all countries of the former Union). But they are made by specialized factories that develop and offer new solutions for specific construction tasks.

Main criteria for choosing a grab loader:

The maximum weight of the load with which work is expected. It is important that this parameter is also correlated with the capabilities of the chassis on which the loader is mounted.
Reach of the grab boom. It determines the optimal operating area of the unit, the range of movement of the gripper with a load, as well as the stability of the machine during operation.
The design of the chassis itself. With larger wheels, the stability of the grab loader increases. Excavators in this sense have advantages over tractors, since in them the grab gripping device is mounted on the side opposite to the blade. Thus, the latter is a kind of counterweight.
Maximum permissible temperatures at which operation is expected. At external temperatures below -30 degrees, the hydraulic drive of the unit loses its functionality, so you should choose options with a mechanical drive of the grab.
Loader bucket size. This parameter is especially important if the machine is intended to be used primarily for road construction work.

Grab loaders are very versatile mechanisms that can come to the rescue when other loading equipment is inappropriate. Choosing a model suitable for purchase or rental is not so difficult - you just need to follow the above recommendations.

Classification of overhead cranes

Classified by design:

Support cranes, the bridge structure of which rests directly and from above on the rail track along which it moves.
Suspended - models attached to the rail track from below, to its shelves.
Gantry cranes are cranes whose bridge is mounted on a rail track using supports.

Models are classified according to their load capacity:

The first group - those working with a weight of up to 5 tons;
The second group - lifting up to 50 tons;
The third group - designed for a weight of up to 300-320 tons.

According to their purpose, clans are classified into:

General - solve standard construction problems;
Special - provide specific lifting operations.

By type of drive there are:

Manual - Required to operate a winch to perform work tasks.
Electric - they operate without operator participation, from the network.

Varieties

The grab overhead crane can have different designs. First of all, they distinguish:

Rope cranes (drive winches are used, to which they are connected using ropes);
Drive cranes (equipment in which the drive is located directly on the grab).

In addition, cranes are classified by grab type. They can be:

double-jawed (usually used for bulk materials);
multi-jawed (for lump raw materials, such as stones).

Grab cranes have become widespread in industrial facilities.

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General principles of operation of machine winches

Mechanical devices were used to more efficiently move goods by our distant ancestors. Today, it is difficult to imagine many modern processes without their use.

Requirements for electric gantry cranes

Gantry cranes are used at construction and industrial sites to transport goods to heights. They are subject to a number of requirements described in GOST 27584-88.

Types of winches and their purpose

A winch is one of the simplest and most convenient lifting mechanisms. It can be manual and electric, universal and automotive.

General structure of an overhead crane

The bridge design of each model is very simple: it is a connection of two box-section spans with end beams. Together they form a rail track, with stops at the ends to block the movement of the trolley.

Each span beam has 2 horizontal chords

upper
lower.

Support cranes are installed on the first one, and suspended cranes are installed under the second one. The span beam also has large and small diaphragms for stability and more uniform load transfer. In order to be able to service the overhead crane, special platforms are mounted on the span beams.

A trolley moves along the rail track - in the general case, a frame with mechanisms for moving and lifting loads attached to it. The assembly diagrams for each unit are usually unified.

The frame itself is the intersection of longitudinal and transverse beams with the flooring. The trolley can also be equipped with a fencing buffer, hook lift limiters, and a ruler for fixing extreme positions. It typically weighs between 0.2 and 0.4 times the lifting capacity (Q) of an overhead crane.

The trolley moves through a movement mechanism equipped with cylindrical wheels and made according to one of the unified schemes. It can have a central drive for both wheels at once or separate for each, a mounted gearbox and a brake. And the wheels themselves can be not only cylindrical, but also conical, with the apex mounted both on the outside and on the inside (in the latter case, only non-drive ones).

Applications of overhead cranes

Carrying out periodic, one-time or permanent lifting operations in the absence of current supply. In such cases, manual overhead cranes, both overhead and support, are especially in demand.
Lifting and moving operations in large indoor areas, for example, in production workshops, machine rooms, warehouses. In such cases, the relatively high performance of electric overhead cranes is convenient; both support and suspended models are in demand.
Lifting work on small construction (and other) sites, both open and closed. In such conditions, it is more advisable to install and use manual, support or overhead overhead cranes.
Operations with bulk cargo - for their implementation it is necessary to use models equipped with grabs.
Work on lifting and moving loads with magnetic properties - this requires electric, usually support bridge cranes.

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Specifications

The operational capabilities and scope of such devices are determined by the following characteristics:

the size of the boom increase (it is measured in meters and ranges from twenty-five to forty meters);
load lifting height (individual cranes can lift loads one hundred meters or more);
load lifting speed (this parameter reaches 200 m/min);
a parameter that determines the rotation of the tower (from 0.2 to 1 rpm);
speed of movement of the chassis.

The listed parameters are determined by the list of tasks to be solved. All types of tower cranes comply with the accepted classification. It is approved by existing standards.

The marking includes a sequence of capital letters and a set of numbers. The first three letters indicate the type of product. For example, K (crane) B (tower) M (modular). The following numbers indicate: group number, type of base model, serial number of the entire unit.

The group number determines the magnitude of the load moment.
The appearance of the base model indicates whether the tower is rotating or not. Numbers from 01 to 69 indicate mechanisms with a rotating turret. Rooms 71 to 99 with fixed tower.
The serial number of the design indicates design changes.

At the end of the marking the climatic version of the specific product is indicated. For example, the letter “U” indicates the use of a crane in a temperate climate, “HL” in a cold climate.