The crane consists of Description of the principle of operation and arrangement of overhead cranes of various types

Posted on 11/26/2012

Crane types

Among the designs of load-lifting cranes, boom-type cranes, bridge-type cranes, cranes with carrying ropes and stacker cranes are distinguished.

1. Boom-type cranes are called cranes with a load-handling body suspended from the boom or a cargo trolley moving along the boom.

These include:

a) jib cranes - jib-type cranes with a jib fixed on the frame of the undercarriage or on a turntable placed directly on the undercarriage frame;

b) tower cranes - boom-type cranes with a boom fixed in the upper part of a vertically located tower;

c) portal cranes - boom-type cranes, rotary, on the portal;

d) semi-portal cranes - jib-type cranes, rotary, on a semi-portal;

e) mast cranes - jib-type cranes, swivel, with a boom hinged on a vertical mast with lower and upper supports. At the same time, for cable-stayed cranes, the upper support is fixed by means of rope braces, and for rigid-legged cranes, it is rigidly fixed;

f) jib cranes - jib-type cranes, the lifting body of which is suspended on a console connected to the column or the supporting part of the crane or on a trolley moving along the console. The group of jib cranes includes column-mounted, wall-mounted jib, mobile jib and bicycle crane.

2. Bridge-type cranes are called cranes with a load-handling body suspended from a cargo trolley, to a swivel boom on a cargo trolley or hoist moving along a mobile bridge.

These include:

a) bridge cranes - bridge-type cranes with direct support of the bridge on the elevated crane runway;

b) gantry cranes - bridge-type cranes with the support of the bridge on the crane track with the help of two support columns;

c) semi-gantry cranes - bridge-type cranes with the bridge resting on the crane track on one side directly, and on the other - with the help of a support rack.

3. Cranes with carrying ropes are called cranes with a lifting body suspended from a cargo trolley moving along carrying ropes fixed on supports. For cable cranes, the carrying ropes are fixed in the upper part of the supports, and for cable bridge cranes, at the ends of the bridge mounted on support posts.

4. Stacker cranes are called cranes equipped with a vertical column with a device for stacking goods moving along it. At the overhead stacker crane, the column is suspended from the cargo trolley moving along the mobile bridge, and at the rack stacker crane, the vertical column moves in the aisle between the racks.

In addition to the classification of cranes by design, there are classifications according to other criteria:

according to the design of the load gripping body and according to the purpose - hook, clamshell, magnetic, magnetic clamshell, traverse, cranes with paws, multi-magnetic, multi-grab, multi-loading, pin, pile, hardening, foundry, landing, cranes for stripping ingots, well, forging, container and etc.;

if possible, move - stationary, attached, self-elevating, adjustable, radial, mobile, self-propelled, trailed;

according to the design of the undercarriage - rail, railway, walking, automobile, cranes on the chassis of an automobile type, caterpillar, tractor, pneumocoded, floating;

according to the type of mechanism drive - manual, mechanical, electric, hydraulic, pneumatic, cranes with a combined drive.

All about cranes. General information.

Crane - hoisting machine of cyclic action with reciprocating movement of the load gripping body; used to lift and move loads. The cycle of work of the load-handling device consists of the capture of the load, the working stroke for moving the load and unloading, and the idle stroke for returning the empty load-handling device to the place of receiving the load. P. to. Movements can be both working and installation for periodically changing the position of the crane, boom, etc. The main characteristic of P. to. is the carrying capacity, which is understood as the largest mass of the lifted load, and in the case of replaceable load gripping devices, their mass included in the total load.

Depending on the design and the adopted scheme of work, P. to. are rotary and non-rotary. Slewing cranes can be mounted on rails - railway and rolling rail cranes; on a trackless course - pneumatic, automobile and caterpillar P. to.; on the walls and roofs of buildings - wall-turning and roofing; on pontoons and ships - floating and ship. There are also rotary P. k., moving along two rails located at different levels (at the bottom and at the top), - the so-called. bicycle cranes. Railway, pneumowheel, automobile and caterpillar rotary P. to. are often united by a common name - jib self-propelled cranes. The rotary part of the P. to. rests on a column (a crane on a fixed or on a rotating column) or on a turntable with wheels, rollers or balls (a crane on a turntable). The rotary part can be in the form of a high tower - tower cranes, masts - mast-jib cranes (stiff-legged and cable-stayed). It can be installed on the portal - portal cranes. Rotary P. to. can have a constant or variable departure (the distance of the load from the axis of rotation of the crane), which is changed by swinging the jib (boom) or moving the cargo trolley along it.

Fixed cranes include fixed cranes of the span type (overhead cranes and reloaders), as well as wall-mounted console cranes. Overhead cranes have a retractable bridge that moves along rails laid on the walls of buildings or on special overpasses outside the building. A cargo trolley with a lifting winch moves along the bridge; in some designs, the cargo trolley is equipped with a swivel boom. Wall-mounted console cranes consist of a cantilever wall truss and a trolley moving along it with a lifting winch. Loaders are similar in design to overhead cranes, but their bridge has high supports (legs) that move along ground tracks. For large spans they are called overhead loaders or dock levellers, and for short spans they are called gantry cranes. However, there is no clear division. Bridges of loaders can have fixed or retractable consoles; a trolley or a slewing crane moves along the bridge. Console loaders designed for loading (unloading) ships, the so-called. coastal console loaders, can also be installed on ships (ship loaders). A special type of loader is a cable crane, in which the cargo trolley is moved by means of a traction rope along a carrying rope stretched between 2 reel towers or stationary masts. A variety of cable cranes are bridge-cable cranes, in which the carrying rope is attached to the ends of the bridge truss. Monorails are structurally close to crane devices, the trolleys of which have lifting mechanisms.

In modern construction conditions, helicopter cranes with devices for capturing cargo are also used. With their help, work in hard-to-reach areas

Application areas of cranes Overhead cranes are typical production equipment. workshops, power plants, closed and open warehouses. Their carrying capacity reaches 500-600 tons, spans (distances between the axes of the crane rails) - 50-60 m, the possible height of the load - 40-50 m and in a special version up to 500 m; bridge speed (working movement) -30-160 m/min, cargo trolley - 10-60 m/min, load lifting up to 60 m/min.

The bridge can accommodate 2 cargo trolleys on one or two (adjacent or double-row in height) tracks. General-purpose bridge cranes include hook, magnetic, clamshell, and magnetic clamshell cranes. Hook single-girder cranes of the simplest type (see Beam crane), supporting and suspended, have a self-propelled electric hoist as a cargo trolley. A special group includes metallurgical bridge P. to. (casting, filling, well, for "undressing" ingots, etc.), which are equipped with special load gripping devices and mechanisms for controlling them. One of the varieties of overhead P. to. - A stacker crane with a cargo trolley having a rotary column, along which a fork gripper moves, carrying a package of cargo on a pallet and allowing stacking and dismantling of package stacks.

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An overhead crane is a mechanism that is used to move goods. For the 80s. 20th century there was a peak in the production of devices, Soviet factories produced from 6,000 to 7,000 pieces of equipment every year. In the 90s. the volume of production fell, and today no more than 1,500 cranes are produced in all countries of the former USSR.

Overhead crane device

The overall structure of the overhead crane is reliable, manufacturers make the main components and other structural elements of high-quality steel. The lifting machine consists of the following:

1. Bridge. This is a movable structure, it has a large load.
2. Tal (mobile cart). She moves across the bridge.
3. gripping devices. It can be a magnet used to lift loads, a grapple or a device used to carry containers.

Devices for capturing goods are installed on a trolley, equipment is used in all areas of the national economy. Most often it is used to move heavy or bulky goods. In all other cases, enterprises can get by with cranes of lower capacity.

Bridge mechanisms can be found at construction, industrial sites, ports, workshops of enterprises. The equipment is operated in any climatic zones. It is often installed indoors, but it is also suitable for outdoor work.

The advantage of the systems is that they can operate at the entire height of buildings, and the disadvantage lies in the stationarity of the lifting devices.

If we talk about the general device, the bridge is a one- or two-beam structure along which a cargo trolley moves. Electrical equipment is located on the bridge, and the mechanisms that are used to move goods are on the trolley.

Brake system

In order to hold the load on weight and regulate the speed of its lowering, a brake is used. This mechanism is necessary to quickly stop moving parts of a structure, such as a trolley or a bridge.

Manufacturers equip models with the following braking systems:

• block;
• disco drums.

Shoe brake consists of 2 shoes, which are located on both sides of the pulley. This position allows you to evenly distribute the load on the shaft. The brake pulley is mounted before the gearbox, which makes braking easier.

The role of the brake pulley is performed by the clutch, it connects the electric motor to the gearbox. The brake is mounted so that its pads clamp the part of the clutch connected to the gearbox.

The brake mechanism must be closed by a load. To do this, it is installed on the lever so that it does not move to the side and does not fall. A spring can be used to close. In this case, it is placed in a sleeve, it can also be equipped with a centering rod.

The brake must be protected from moisture. In order for the mechanism to work better, a brake band is riveted to the brake pads. This increases the friction between the pulley and shoe.

The cart can move at different speeds. If it does not exceed 32 m/min, the device for moving goods need not be equipped with a brake system. Under these conditions, braking occurs independently, the braking distance is not exceeded.

All braking systems can be divided into locking and descending. The former are used to stop the device, and the latter are necessary to slow down the descent of the load.

The braking system can be of the following types:

• open;
• closed.

Manufacturers can equip the hoist with closed brakes, in which case the brake will be released only at the moment the engine is started. In other positions, the mechanisms will be inhibited.

Closed brakes are the most commonly used because they last longer than open brakes. If they fail, then their breakdown is easier to notice. Open braking systems can complement closed ones. Using them, the crane operator will increase the accuracy of moving goods.

Bridge mechanisms can be used to move dangerous goods. These include poisonous and explosive substances, as well as molten metal and acids. In this case, the mechanisms are equipped with 2 brakes. They act autonomously, replacing each other.

Lifting mechanisms

Manufacturers equip cranes with lifting mechanisms, they are placed on a crane trolley. The system consists of the following elements:

1. Electrical engine.
2. Load ropes used to lift or lower a load. Winding drum.
3. transmission shafts.
4. Horizontal gearbox.

If the company plans to move loads weighing more than 80 tons, then the crane must be equipped with an additional gearbox. If the need arises, it can be replaced by a reduction gear. In order to increase traction, a chain hoist can be used. This device consists of several blocks that are wrapped around with a rope or cable. Crane operators often use a double multiple chain hoist.

The crane cannot work without a gearbox, they are divided into the following types:

• bridge traffic devices;
• lifting mechanisms;
• cargo carts.

Manufacturers equip cranes with gearboxes in planetary and deployed versions. The deployed type is used most often, it is equipped with cylindrical wheels. The design of the mechanism, when compared with the planetary, is simpler. Such systems are cheaper to repair.

Crane tracks

The crane moves on railroad tracks laid on the ground. They can be narrow-gauge (P18, 24, 38) and designed to form a wide gauge. In the latter case, products P4, 50, 65 are used.

To move the hoisting mechanism, square guides can be used. They are made of steel, products are distinguished by rounded edges. They are designed for operation of cranes with a lifting capacity of 20 tons and above.

To move the overhead crane, two-tee beams are used as tracks. To connect their ends, double-sided pads and bolts are used, but the elements are often connected by welding. When installing beams, attention should be paid to the quality of laying. There should be no displacement of elements. Only in the case of correct installation, the crane will work without failures, and worn rails can be easily replaced.

electrical equipment

The power supply of the crane is carried out in 2 ways:

• trolley lines;
• installation of electrical cable.

Systems of the first type are required for the operation of heavy-duty mechanisms. The tire is placed at a height of more than 3.5 m from the floor level, to the bridge deck should be at least 2.5 m.

In the second case, a flexible electric cable is brought to the crane, it is suspended on a carriage. The cable system is simpler, it is easier to operate. Its installation will cost the enterprise cheaper, but it must be taken into account that it is less reliable. The trolley line is used to move the bridge beam, and the cable system is better suited for the operation of the crane trolley.

Strict requirements are imposed on electricians, because the number of operations that a crane operator performs in 1 day is in the hundreds. They are associated with the acceleration of the cargo trolley, its braking, turning on and off additional devices, unloading, loading or moving containers and goods from one place to another.

During operation, there is a need for emergency braking, so the elements of the crane are subject to high loads. All systems must be in working order, the safety of the crane operator and other people depends on this.

The following equipment is used to organize the movement of the trolley, the bridge and the movement of goods:

1. Electric motors. The heavy duty mechanism is equipped with 3 or 4 powerful devices, 2 of them are placed on the trolley. They are designed for lifting and lowering the load, as well as moving the trolley along the bridge beam. Another 1 or 2 engines are responsible for the movement of the beam along the rail tracks.
2. Controllers and other devices, such as magnetic starters. They are used to control electric motors.
3. Devices to help control the holding brakes. These are pushers and electromagnets.
4. Remedies. These include load limiters.

Auxiliary equipment is required to operate the crane. It includes spotlights and heating devices. The group includes measuring equipment and sound alarms. Tools are widely used, they are needed to perform repair work.

A cargo trolley is necessary in order to lift loads, move them along the bridge, and then install them in a new place. Crane nodes are located on a steel frame, it is rigidly connected to the wheels. The operation of the device is carried out by drives. The trolley is moved by the main and auxiliary electric motors. It is additionally equipped with a current collector, there are blockers that regulate the lifting height.

In production, a situation may arise when an emergency stop of the trolley is required. Emergency braking is performed by buffers.

Cantilever bogies are used on single-beam bridge mechanisms. Double beams are equipped with devices that move along the lower and upper chords of the beams.

Principle of operation

Bridge mechanisms differ from other systems in that they rely on a crane runway during operation. It is made from railway rails or square sections, they are made from high-quality steel.

The carrier beam moves along the rails, they are laid on overpasses inside workshops or open areas industrial enterprises. The cargo trolley moves along the bridge, it is equipped with a winch for lifting loads.

Companies often need to expand the functionality of lifting mechanisms, in this case, cranes are supplemented with different devices. It can be a set of magnets of different power or grabs. The acquisition of additional mechanisms makes it possible to use overhead cranes not only in the organization of industrial production, but also to perform work in warehouses and in the construction industry.

Overhead crane classification

The industry produces different overhead cranes, but all of them can be divided according to the following key features:

• Areas of use;
• way of moving;
• constructions;
• types of load-handling mechanism.

If we consider the classification by scope, we can distinguish the following types of overhead cranes:

• for workshops;
• construction;
• transport;
• deck systems.

Depending on the design, lifting systems are divided into the following:

• beam;
• two-beam.

According to the method of movement, there is the following classification:

• supporting cranes;
• suspension mechanisms.

If we consider the mechanism that is used to capture cargo, then we can distinguish modern clamshell and special systems. The same group includes foundry and magnetic devices. In industry, there is often a need for hooks.

By design

On this basis, all lifting mechanisms can be divided into the following:

1. Support. They rely on a rail track laid on the ground and move along it.
2. Gantry. The installation of such a bridge on the rail tracks is carried out using supports.
3. Suspended. Such devices are held by the rails from below.

Enterprises should choose mechanisms, focusing on the needs for the movement of goods.

By load capacity

There are models of the following types:

• lifting loads up to 5 tons;
• up to 50 tons;
• 300-320 tons

Faucets have different prices.

By appointment

Manufacturers produce mechanisms that are divided by purpose into the following:

1. General. They are designed to solve typical construction tasks.
2. Special purpose. With their help, crane operators will perform lifting operations that require special treatment.

The organization, when choosing a mechanism, must take into account the purpose of the goods. If they are classified as dangerous, their movement will be different.

Drive type

On this basis, all bridge-type cranes can be divided into the following:

1. Manual. The movement of cargo is carried out by a winch.
2. Electric, which work from the network.

Enterprises can choose from domestic and foreign models.

Shipping

Transportation of overhead cranes is carried out in different ways, but most often delivery is carried out using railway platforms. Shipment of the main beams is carried out in the collection. Parts of the bridge structure, which have large spans, are transported in 2 or 3 sections.

If the lifting mechanism has a small carrying capacity, the trolleys are transported assembled. In production, heavy-duty trolleys are required, they are transported in knots. Separately, the frame and the lifting mechanism are transported, if necessary, the balancers are moved from place to place.

The choice of transport 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 coupling of 2 elements, but they are suitable for the delivery of cargo, the length of which does not exceed 17 m. For this purpose, platforms are used with a carrying capacity of 50 tons and 60 tons.

If the goods are oversized, it is necessary to pay attention to the quality of their fixation. It is important to take into account the technical conditions of loading. Parts of the crane must be securely fixed in place, for 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 with braces. It is necessary to make a calculation for strength, to determine the acting 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. For their transportation, powerful automobile tractors or tractors are used. The enterprise must choose the appropriate course of action.

Mounting and dismantling

Installation of the crane requires preliminary work, they begin with the installation of crane tracks. They are laid on a flyover or on the ground. There are 3 mounting options:

1. Step by step. It is based on the assembly of nodes, it is carried out on crane tracks.
2. Expanded assembly. Large elements are collected on the ground, and then raised to the required height. This is the case with electrical equipment and mechanisms.
3. Full block. This method is based on a complete assembly, it is carried out on the floor. The bridge is assembled as a whole, then the installation is carried out, the technology requires powerful equipment.

Installation work should be carried out by specialists, they also dismantle the overhead crane, make grounding. It requires strict adherence to safety standards. They resort to it when it is necessary to replace the old lifting mechanism. It is also necessary after the completion of work on the site.

There are several options for dismantling, each of them depends on what is supposed to be done with the crane next. If it is subject to disposal, crane beams are removed from it. The structure is freed from the cable, the electric bridge motor is removed, the cables are wound up. Span beams and other components made of metal are sent for scrap.

If the crane is transferred to another place, the traveling mechanisms of the overhead crane and devices for moving goods are disconnected from it. In this form, the structure is transported to the work site, where it is reassembled.

Overhead crane applications

The operating instructions contain information about the scope of use of load lifting devices. When choosing a model, you should pay attention to the operation manual of the crane, the scope may be as follows:

1. Working with loads on a permanent or temporary basis in conditions where there is no current supply. The organization can purchase manual overhead and overhead cranes.
2. Transportation of goods in production shops, warehouse complexes and other industrial sites. Support and suspension models of electric cranes are useful for performing the work. Devices with a carrying capacity of 10 tons, 15 tons and 20 tons are in demand.
3. On construction sites, cranes MK 5, MK 10, double-girder Demag and other models are used.
4. To work with bulk cargo, it is necessary to use grabs, so when choosing devices, you need to pay attention to the technical characteristics.

With the help of bridge systems, other loads can also be moved; for this, the crane is supplemented with equipment with magnetic properties.

Maintenance, repair and modernization

Repair of overhead cranes is not often required, because the design has a long service life. Much more often you need to fix minor problems, adjust the operation of the device. Before starting the shift, the driver must check the condition of the crane.

Diagnosis of an overhead crane, as well as current repairs, must be performed by specialists. They carry out the following list of works:

• Maintenance;
• diagnostics of the mechanical department;
• inspection of additional equipment;
• replacement of worn devices;
• bearing check;
• node adjustment.

Minor problems can be eliminated at the enterprise, and major breakdowns require analysis of the structure. If necessary, specialists can upgrade devices. Work is carried out in accordance with the requirements of GOST.

Specialists can replace the hook suspension or cable suspension, check the safety devices and devices, and inspect the suspended equipment.

Repair work is of the following types:

• planned;
• overhaul;
• emergency.

Planned is carried out in order to prevent breakdowns. In the course of work, the master performs fault diagnosis, lubricates the mechanisms, and adjusts the nodes. The technical examination of the overhead crane is being carried out.

Overhaul includes a wide range of works. It is needed for cranes whose service life has already expired. Emergency repair is needed when the device is out of order. The master determines the malfunction and eliminates it as soon as possible.

Wiring diagram

The electrical circuit of the overhead crane depends on the model of the device, but the following main points can be distinguished, which are paid attention to:

1. When drawing up a circuit, a specialist must take into account options for protecting the system from voltage drops.
2. The crane is protected from overloads. Mechanisms for emergency braking and stopping the engine should be provided.

The wiring diagram is required in order to repair electrical equipment. It consists of special characters that characterize nodes. Rectangles represent moving contacts, solid circles represent fixed elements. Sweeps mean drum controllers. Their position is set by lines running parallel. They are numbered at the top.

Price and reviews

The industry produces general-purpose electric overhead cranes and other devices. Their cost is influenced by the equipment and load capacity of the overhead crane. Used devices are cheaper, but you can save money by buying a new model of domestic production, rather than a foreign-made crane. A crane of 10 tons can be bought for 200 thousand rubles, there are models whose cost reaches 2 million rubles.

When choosing a mechanism, you need to consider that many brands require a crane track. Small businesses can purchase an overhead overhead crane or a mechanism with a lifting capacity of 5 tons.

Mikhail, 47 years old, Kaluga.

Overhead cranes on fixed supports were chosen for the enterprise for a long time. We found 1 device, the price is affordable. Now there are no problems with loading.

Igor, 36 years old, Yakutsk.

LOAD-LIFT CRANE, a cyclic machine designed to lift and horizontally move a load held by a load-handling device until it is unloaded. Crane working inside a confined working area(construction site, workshop, terminal, warehouse, etc.). The main characteristic of a crane is its lifting capacity, which is understood as the largest mass of the load being lifted.

History reference. The simplest lifting machines used in earthworks in construction, mines and mines were made of wooden parts and had a manual drive until the end of the 18th century. By the beginning of the 19th century, wearing parts began to be replaced with metal ones. In the 1820s, the first hoisting machines made entirely of metal appeared, first with a manual, and in the 1830s with a mechanical drive. The first steam crane was created in Great Britain in 1830, a crane with a hydraulic drive - in the same place in 1847. An electric motor was used for cranes in 1880-85 almost simultaneously in the USA and Germany; in 1895 an internal combustion engine was used. The cranes had a bridge truss, a single-engine drive.

Load-lifting cranes of the modern type began to be produced in Russia at the end of the 19th century at a number of factories (Putilov, Bryansk, Kramatorsk, Nikolaev, etc.). In the 1920s, a new branch of transport engineering was created with specialized factories producing cranes for various purposes. The main direction of production development is the introduction of automated control, increasing the load capacity, specialization and ensuring the reliability and safety of crane equipment.

Classification. Cranes differ in design, type of load handling device corresponding to the nature of the work performed, the specified trajectory of the movement of the load; the angle of rotation of the working bodies, the running gear, by the type of drive mechanisms. A variety of designs of load-lifting cranes provides their wide application. According to the characteristic features of the design, load-lifting cranes are divided into overhead, jib and special ones, often created on their basis.

Overhead cranes have a truss structure along which a cargo trolley moves with a load gripping device suspended on it by means of ropes (hook suspension, lifting electromagnet, grab, etc.). The trolley moves across the truss structure, based on bridge beams, which can move along a special crane track laid on a flyover or load-bearing beams of a workshop, warehouse, etc. (Figure 1). The cranes of this type include a gantry crane, the cargo trolley of which is mounted on rigid racks (Figure 2). The entire structure moves along a rail track or a concrete base. The lifting mechanism of the crane is a hoist or winch mounted on a cargo trolley. The trolley movement mechanisms can have a traction flexible drive (chain or rope) or drive wheels mounted on the trolley frame or on running beams, having special balancing bogies and drives with shoe or disc brakes. The lifting capacity of typical overhead cranes is 500-600 tons; gantry - up to 1600 tons.

Jib cranes have the most diverse design: equipped with interchangeable booms of various lengths, telescopic or truss (straight or curved), providing the necessary scope of work; equipped with specialized lifting equipment (cargo trolley or hoist); depending on the place of work, they have appropriate support and running devices. According to the design features and the location of the boom, cranes are distinguished, designed to perform certain work. Distinguish portal cranes (Figure 3) with the installation of an arrow on a slewing portal or self-propelled cranes with a running gear with an automobile or caterpillar drive; tower - with the location of the boom in the upper part of the structure (sometimes on the portal) of the tower; cable-stayed - with a boom on a foundation support with fastening of its upper end with rope braces, mast - with a rigid fastening of the boom; cantilever - with a permanent fastening of the boom on the wall, column (Figure 4) or on a movable cart; bicycle - with a trolley moving along a floor single-rail track and held by its upper guide. To change the length (outreach) of the boom when it is hinged on the support, cranes are equipped with a winch. Tower structures are made in the form of lattice or tubular sections connected by flanges, with the possibility of their extension from below or from above to change the height of the load. The stability of the crane is usually ensured by the use of counterweights. Rotation (rotation) is carried out on roller or ball slewing devices by a drive with a gear rim or with a cable transmission. In the construction of high-rise buildings (100-300 m), attachable cranes are used with attachment to the wall of the tower building and building it up from above, and at a height of more than 300 m - mobile tower cranes, based on the building structure from above and self-lifting with the help of a winch having a large chain hoist mechanism multiplicity. The lifting capacity of mobile cranes is from 40-300 tons, of special assembly cranes - up to 1600 tons.

Figure 3. Gantry crane with articulated boom and grapple.

Special cranes are designed to perform lifting and transport or technological operations, often carried out in special conditions. Such load-lifting cranes have the necessary mechanisms that perform specified technological operations, perform specific movements and are equipped with special load gripping devices. For most of them, the base is a bridge-type structure, which is complemented by special equipment - clamshell, magnetic clamshell, special lifting equipment, for example, ladles for molten metal, stackers. For work in large areas (terminals, container sites), bridge loaders equipped with spreaders (Figure 5) are used to capture and securely hold the cargo; cable bridge cranes, which are similar in design to gantry cranes, but have a larger bridge span, one of the supports is often connected to the bridge with a hinge, which increases the service area. In ports, warehouses for bulk materials and timber, portal cranes are used, which have an arrow mounted on a full-turn platform mounted on a portal moving along crane rails. Works on cleaning the bottom of reservoirs are carried out from floating jib-type cranes, which are also most often equipped with turntables and form a single structure with the ship's hull (pontoon). They are used in ports, docks and in the construction of hydraulic structures, for lifting heavy loads (up to 2500 tons). Self-propelled cranes have structures of towers and booms similar to tower cranes, for stability they are equipped with outriggers (outriggers). Such load-lifting cranes are used for reloading heavy piece and bulk cargo, are used in the installation of high-rise structures, the construction of bridges, the removal of rubble, the elimination of accidents, etc.

Design features. Cranes are divided into: stationary; attached, attached to a structure under construction; adjustable (with moving them from one place to another manually or with the help of other machines); mobile, moved from one working position to another under its own power (on automobile, pneumatic-wheeled, caterpillar and railway platforms) or with the help of a tractor (trailed). The undercarriage can be supported from above on crane rails (support) or suspended on the lower I-beams of a special crane track (suspended). The drive of all mechanisms, as a rule, is individual from electric motors of three-phase AC 380 V or (if necessary, smooth speed control) direct current received from a generator set or from a diesel engine. To ensure safe operation, all cranes are equipped with automatic limiters for load capacity, lifting height, load moment on the boom, limit switches for the extreme positions of the working bodies. To stop the operation of the crane in strong winds, wind pressure indicators with an alarm are used that turn off the drives, and anti-theft grippers - rail clamps. Stops for buffer devices (shock absorbers, hydraulic stops) are installed at the end of the rail tracks. For work on rough terrain, cranes are equipped with roll indicators, and near power lines - with light and sound signaling devices about the dangerous approach of the crane to the lines.

The operation of the crane is controlled by a push-button panel "from the floor" or by power controllers or controllers located in the cab. In most cranes, control is provided by a crane operator, and in an automated mode - using a computer. When working in hazardous conditions or with insufficient visibility from the cab, remote control is carried out.

Depending on the purpose and design, cranes can have different lifting heights, for example, for overhead cranes 50-60 m; operating speed of the bridge 30-160 m/min; cargo trolley up to 60 m/min; for jib cranes, the boom lifting speed is 1-3 minutes; boom reach 60-100 m.

Lit.: Cranes: In 2 books. / Under the editorship of M. P. Alexandrov. M., 1981; Petukhov P. 3., Ksyunin G. P., Serlin L. G. Special cranes. M., 1985; Zertsalov A.I., Pevzner B.I., Benenson I.I. Stacker cranes. 3rd ed. M., 1986; Vainson A. A. Hoisting and transport machines. 4th ed. M., 1989; Alexandrov M.P. Lifting machines. M., 2000.

Cranes can be seen at any construction site. It is there that they extend their powerful paws. Movable machines, like the crane shown in the picture, they can extend their hydraulically operated telescopic boom up to 130 feet and lift 45 tons of construction materials with ease.

By removing the moving part of the boom inside, such a crane is made the size of an ordinary truck and simply goes further where it is needed. The winch mechanism controls the cable lowered from the boom. A load is attached to this cable with a hook. When the winch begins to wind the cable, the load rises. The system of multiple pulleys and cables between the hook and the boom reduces the effort that must be applied to the winch in order to lift the load.

To balance a heavy load

When cranes lift heavy loads, they rely on cantilever beams or stabilizers to keep from tipping over. Each such beam acts as the fulcrum of the balance beam. With its help, the load being lifted is balanced by the weight of the crane itself. Retractable support beam legs are made of steel, aluminum or nylon. Each leg can be individually raised and lowered until the crane is in the desired position.

Lowering and lowering the boom

Two hydraulic cylinders control the movement of the boom. One cylinder raises and lowers the boom, while the other lengthens and shortens it.

Hook, rope and truck crane block

Block with a hook with a lifting capacity of 20 tons

7 pass block

Watching the crane. On-board computers monitor the operation of the crane: the weight of the load, the angle of elevation and length of the boom, the angle of the crane itself and, in some models, even the speed of the wind.

Truck Crane Load Moment Diagram

The upper diagram shows that the more the boom is extended in the horizontal direction, the less load the crane can carry without the risk of tipping over.

lecture

Cranes

Cranes called universal hoisting machines of periodic action, consisting of a frame and mechanisms mounted on it, with the help of which goods are moved in vertical and horizontal directions at a short distance.

Cranes consist of mechanisms: lifting a load in the form of a winch, in combination with a chain hoist and a device for capturing the load; movement, by means of which the crane frame or any part of it is moved relative to the path of its movement; changes in the position of the cargo grip relative to the frame and rotation of the rotary part of the crane frame. Each mechanism can have a separate drive or be connected to a common group drive.

Cranes are used for loading and unloading of heavy machines, goods transported in packages, containers, metal and precast concrete structures, etc., as well as for warehouse operations with these goods. When equipping cranes with special grippers and grabs or when transporting goods in stacks, cranes are successfully used for loading and unloading bulk bulk bulk cargo, and when equipped with electromagnets, for loading and unloading various products made of steel and cast iron.

Cranes, depending on the design, are divided into:

bridge type (overhead, stacker cranes, gantry, reloading) that can lift the load and move it within a rectangular area;

boom type (on railway, automobile, pneumatic wheels, etc.), which serve the warehouse area in a circle.

Overhead crane

(prepare Fig. 1.1.)

consists of a bridge made of main (longitudinal) and end (transverse) beams welded together, and moves along an elevated rail track laid on crane beams fixed on the consoles of the building (workshop) or overpass columns.

The supply of electricity to power the drives of the crane mechanisms is carried out through contact wires with current collectors-trolleys sliding along them or through an electric cable trailing behind the crane (trolley).

An overhead crane serves almost the entire area of ​​the workshop (except for narrow longitudinal strips near the walls of the workshop), which is its main advantage. In addition, the overhead crane moves along the elevated crane track, so it does not occupy the usable floor area of ​​the workshop or site. The lifting capacity of the crane does not depend on the position of the cargo trolley relative to the bridge and the height of the load. The overhead crane is simple in design, reliable in operation and easy to operate. The disadvantages of overhead cranes include the need to install special crane tracks at elevations.

gantry crane

in a simplified form, it is an overhead crane based on racks and designed to move along the ground rail track. Outwardly, it resembles a four-post portal (mounting goats), from which it got its name. The main element of a gantry crane is a bridge fixed on two pairs of supports with bolts. Depending on the relative position of the bridge and its supports, there are non-console, one- and two-console cranes.

In railway transport, gantry cranes are widely used for reloading containers, heavy loads, metal, timber and building materials, as well as various other bulk cargoes.

In gantry cranes, as well as in overhead cranes, three independent operations are implemented: lifting - lowering the load to the required height, moving the load along the crane bridge across the serviced area and moving the load by the crane along the serviced area.

Gantry crane mechanisms are driven by electric motors, lifting devices are mounted on carts similar to overhead cranes, or electric hoists are used.

Basic parameters for overhead cranes.

Crane span(m) - the distance between the planes passing through the middle of its wheels (or between the axes of the rails) is determined by GOSTs, depending on the type of crane. The outreach of a gantry crane console is the distance from the axis of the skeleton support to the end of the console.

Working reach of the console- the same distance, but to the extreme position of the hook.

lifting height called the distance between the lower and upper position of the hook in meters.

(end of first hour)

Technical accessories of overhead cranes

At cargo yards, overhead cranes with a lifting capacity of 5 ... 32 tons are used, equipped with hook suspensions, swivel heads, semi-autoslings, autoslings, grabs and electromagnets. They are designed for medium and heavy duty applications. Cranes with a lifting capacity of more than 10 tons usually have two lifting mechanisms: main and auxiliary.

Gantry cranes KK-6 and K.K-5 are used at container sites for processing medium-tonnage universal containers with a gross weight of 3 and 5 tons. Cranes KDKK-10 and KPB-10M are used to work with heavy cargo at the cargo yards of stations, as well as for processing containers. Cranes KKS-10 and KK-12.5 are used for processing long heavy cargoes, such as timber, rolled products, building structures. Cranes KK-20 and KK-32 are designed for handling containers weighing 10.20, 32.5 tons.

STACKING CRANES

(briefly talk about stacker cranes; refer to the literature - Grinevich, Riedel and my training manual)

Jib cranes

Railway jib cranes

Railway cranes move within the serviced warehouse or cargo area along the railway track with a distance between the rail heads of 1520 mm on their own and fit into the gauge of the rolling stock, and are transported over long distances as part of a train at a speed of up to 80 km/h. The crane is controlled by the driver and his assistant, some cranes are controlled by one driver. They are designed for transshipment, sorting and assembly work in coal yards, freight yards, freight railway stations, ports, locomotive depots and all kinds of construction and assembly sites. Railway cranes are full swing mobile cranes. Railway cranes are classified:

by type of power plant - steam, electric, diesel-electric, diesel and with carburetor internal combustion engines;

by the number of engines - single and multi-engine;

by the number of axles of the chassis - two-, four- and six-axle;

in terms of carrying capacity - light (with a carrying capacity of up to 10 tons), medium (with a carrying capacity of 10, 16, 25 tons), heavy (with a carrying capacity of 45, 50, 60, 75, 100, 125, 150, 250 tons).

Diesel-electric cranes KDE-161, KDE-162, KDE-163, KDE-251 are equipped with a main 15 m boom with a hook and, on special order, can have additional equipment, a 5 m insert for extending the boom up to 20 m, a forest grab or grab with a set of ropes, a cargo electromagnet with a motor-generator station for its power supply.

(refer to your manual and to Grinevich, Riedel)

Truck cranes

A distinctive feature of automobile cranes is the placement of the crane installation on the chassis of serial vehicles. In the freight industry of railways, truck cranes are used for a small amount of work. The advantage of truck cranes is their high mobility, which makes it easy to relocate them from one object to another. Truck cranes are issued with mechanical, electric and hydraulic drives.

(refer to your faucet manual)

Specifications of cranes

(prepare Fig.1.3.)

load capacityQ - the largest permissible mass of the working load, which the crane is designed to lift under the specified operating conditions (i.e., depending on the reach) while maintaining the necessary stability margin. For jib cranes, the lifting capacity varies depending on the outreach - the highest lifting capacity corresponds to the smallest outreach. The load capacity at a smaller reach is called nominal, it exceeds the load capacity at the longest reach by several times. When determining the load capacity, not only the mass of the lifted load is taken into account, but also the mass of the load gripping devices and devices.

Load characteristic (fig. 1.3) - graphical dependence of the crane lifting capacity on the outreach of the load gripping device. On the vertical axis of the graph of the load characteristics, the load capacity of the crane is plotted on a scale, and on the horizontal axis, the size of the departure. The points of intersection of lines drawn parallel to the axes form a curve that shows the change in the lifting capacity of the crane depending on the reach. Each type of crane has its own load characteristics.

Naturally, the closer the weight of the lifted load is to the weight corresponding to the reach of the boom on which the work is performed, the more fully the crane is used and its productivity is higher.

Lifting or lowering speed - the distance traveled vertically by a load per unit of time. The performance of lifting operations largely depends on the values ​​of the speeds of lifting and lowering the load.

Transport speed crane movement - the speed of movement of the crane in the transport position. (only applies to jib cranes)

Duty cycle (cycle time)- the time spent from the moment the load is lifted to the moment the next regular load begins to be lifted.

Sustainability called the ability of the crane to resist the forces tending to overturn it. A free-standing crane is subjected to the following forces (see Figure 1.2): The weight of the crane G, lifted weight Q, wind force W, the force of inertia, determined by the value of the moving mass and the speed of its movement.

performance The crane is called the amount of work performed by him for any period of time, for example, for 1 hour of work, shift, month or year, and, accordingly, is hourly, shift, monthly and annual.

Hourly productivity P(t/h) can be determined by the formula

П= 3600/ T c G

where 3600 is the number of seconds in 1 hour;

Tts - duration of one working cycle, s;

G is the mass of cargo moved during one working hour, i.e.

The productivity of the crane is higher, the greater the load is moved by the crane and the shorter the duration of the working cycle.