Q: what should we pay attention to when wire rope rigging is hoisted?
Answer: attention is required for hoisting rope rigging.
1. If it is a single leg hoisting belt, the hanging point must be perpendicular to the weight of the suspended object.
2. If the legs are hoisted, the hanging points should be on both sides of the goods. The hooks are heavier than the suspended ones.
3. For three-legged or four-legged hoisting, the hanging point must be symmetrically located on the plane around the cargo, and the hook is located directly above the weight of the object being lifted.
Q: how do we check whether the overload protection device of cantilever crane meets the requirements?
Answer: Cantilever crane safety protection device check overload protection device is sensitive and reliable, meet the design requirements, hydraulic overload protection device opening pressure; mechanical, electronic and comprehensive overload protector alarm, cut off the power source set point of the comprehensive error whether meet the requirements. Torque limiter torque limiter is a safety device for overloading of boom type cranes.
The sensitivity and reliability of torque limiter are checked by amplitude method or weight method, and the comprehensive error of alarming and cutting off power source setting point is checked. Limit position limiter inspects the luffing mechanism of the cantilever hoisting equipment. Whether the alarm signal can occur when the lifting mechanism and the operating mechanism reach the set position distance, and automatically cuts off the power source running in the dangerous direction.
Windproof devices should check the anemometer for cranes whose height of the hinge at the root of the boom is greater than 50 meters. Whether the anemometer can accurately alarm when the wind speed reaches the set point or the working limit wind speed is reached. Cranes operating on open-air rails should check whether the parts of rail clamps, iron shoes and anchorage devices are deformed, defective and the reliability of their respective independent operation. Drive shafts should check the automatic rail clamps for the windbreaker and the brake of the truck to realize the windbreak function and electricity under the non-anchored condition. The reliability of the gas interlock switch function.
The protective device checks whether all kinds of protective shield, guardrail, guard board and climbing ladder on the crane are complete and reliable, and the exposed cantilever crane may cause wounding and open transmission; coupling, sprocket, chain, transmission belt and other rotating parts have protective shield, and the pedestrian passage on the crane. Rainproof cover should be provided for electrical equipment of overhead cantilever crane. The control device should check whether the electrical fittings are complete, whether the mechanical fixture is firm, no loosening, no stuck resistance; whether the power supply cable is aging, exposed; insulation materials should be good, no damage and deterioration; bolt contacts, brushes and other connecting parts should be reliable; the electrical equipment and electrical components selected on the crane should be with the power supply and workers. Suitable for environment and working conditions.
Q: what is the difference between the cam controller used in the crane operation mechanism?
Answer: Cam controller is through its power contacts closed order to achieve the motor forward and reverse conversion.
When using the cam controller, the electromagnetic coil of the actuator is connected with the stator circuit of the motor in parallel, and it is connected with the motor at the same time. The master controller is a complete control system with the magnetic control panel. The commands issued by the master controller contact are starting, braking, speed regulation and commutation of the motor through the corresponding contactors on the magnetic control panel.
The master controller is often combined with two kinds of magnetic control panels, one is PQR9A and the other is PQY. The former controller is 6 ~ 0 ~ 6 gear, the latter is 3 ~ 0 ~ 3 gear. There is no big difference between the two controllers and the cam controller in the operation of the driver, only the difference in the position of the handle.
Q: how should the hook of a cantilever crane be maintained?
Answer: The hook of the cantilever crane is a wear-out part. In the normal course of use, we should pay attention to the quality of the surface and the inside of the hook. There are basically the following aspects:
1. The surface of the hook should be bright and clean, and there should be no defects such as crack, acute angle, burr, stripping and so on.
2. There should be no cracks, white spots and defects affecting the safe use of the hook.
3. Defects on crane accessories hook are not allowed to be repaired.
4. Wear of dangerous section should not reach 10% of original size.
5, the opening degree should conform to the 5.2 in GB10051.
6, the torsional deformation of the crane accessories hook is that the twist angle of the hook should not exceed 10. ;
7. The hook handle of dangerous section or hook should not be plastic deformation.
8. The thread of hooks must not corrode.
Q: what is the cause of the cantilever crane's rear tilt?
Answer: The cantilever crane which uses flexible wire rope to pull the boom to change its amplitude will produce force to make the boom tilt back when it encounters loading and unloading. This leads to an accident that the boom is over a small amplitude and the rear arm of the boom is tilting. Therefore, this kind of crane is installed with anti backwards device.
The rear tilt of boom is mainly caused by the following reasons:
1. Lifting hangers, ropes or wire ropes used for lifting have defects, which suddenly break during the lifting process; cause heavy objects to fall; or because of the improper hanging of the lifting gang, heavy objects scattered during the lifting process. All these cases will form a sudden unloading and cause the boom to rebound.
2. Because of the failure of the lifting height limiter, the coil yard accident happened, resulting in the breakage of the wire rope; or directly to the boom after the traction force, resulting in the boom after the accident.
3. The control failure of the luffing mechanism and the failure of the luffing limit switch result in the luffing of the boom during the luffing process.
4, due to the impact of wind disasters, the crane's rear tilt accident is caused during the lifting process.
In order to prevent similar accidents, China's hoisting machinery safety regulations clearly stipulate that mobile cranes and wall cranes should be installed anti-tilt device.
Most of the anti tilt devices currently used consist of two parts. First, the luffing limit switch is limited by the amplitude limiting switch installed near the hinge point of the boom. Sometimes the boom drives an amplitude indicator through a connecting rod mechanism, and a position switch is set on the amplitude disk to limit the position. Then a mechanical device is used to stop the boom. The safety rope and the bumper are two commonly used anti backwards devices. The safety rope uses the calculated length and strength of the wire rope, one end is fixed on the turntable, the other end is fixed on the boom, through the length of the wire rope, the inclination angle of the boom is limited.
The disadvantage of this anti roll back device is that it can not play the role of buffering and shock absorption, and the impact vibration is larger. Bumpers are often used to reduce vibration and impact. The working principle of the bumper is that the upper end of the bumper is articulated on the boom and the lower end is articulated on the turntable; the bumper is a telescopic mechanism with a sleeve, which extends and contracts with the dip of the boom; a buffer spring is installed in the sleeve, which has the functions of cushioning, shock absorption and limit of the boom. The bumper also adopts hydraulic and oil gas combination, which has better damping and cushioning properties than springs.
Q: what is the difference between electric hoist and hand hoist?
Answer: Electric hoist is mainly composed of motor, transmission mechanism and drum or sprocket. Electric hoist is mainly divided into wire rope electric hoist and chain electric hoist.
Usually driven by conical rotor motor with brake (or cylindrical rotor motor with electromagnetic brake). Electric hoist is suitable for working in the environment with temperature - 25oc~+40oc, humidity < or = 85%, altitude below 1000m, no fire, explosion danger and corrosive medium. It is forbidden to lift molten metal, toxic, flammable and explosive. Goods.
But electric hoists like riot-proof wire rope hoists and metallurgical wire rope hoists can be used in such high-risk environments. Like most electric hoists are suitable for AC three-phase, 50Hz, 380V, there are also some small electric hoists can use two electric; intermediate electric hoists in the use of the working level of each mechanism to improve the level, its rated lifting capacity must be reduced by 20%.
Electric hoist is operated by a person using buttons to follow the ground or in the driver's room or using wired (wireless) remote control to generate power to lift the weight, electric hoist can be used alone, but also with manual, chain or electric car assembly together, suspended in the roof of the building or the beam of the crane. Use. Electric hoist is a light and small lifting appliance that is widely used. It is characterized by small size, light weight, large bearing capacity, often installed in electric single-girder gantry crane and suspension crane, used to lift and move goods. The main types of electric hoist are wire rope electric hoist, chain electric hoist, metallurgical wire rope electric hoist, miniature electric hoist and explosion-proof electric hoist.
Hand hoist and wrench hoist are both called manual hoist, specifically, the use of human pull and pull to lift the weight.
Q: what does the fixed column swing arm need to check before starting?
Answer: the inspection items of fixed column boom crane before starting are as follows:
1, remove the debris in the test site, and have enough test space and space.
2. Check the installation and lubrication of all mechanical parts, connecting parts, protective devices and lubrication systems. The results should meet the requirements of the Installation and Use Instructions and relevant regulations.
3. Check the reliability of wire rope end fixing and the correctness of wire rope winding direction in drum and pulley.
4. Check the wiring of hoist, intermediate conductive device, sliding wire, transformer and the electrical wire of each motor is correct, whether there is loosening phenomenon, and check whether the ground is good.
Question: According to the starting switch after the electric hoist (can be divided into chain electric hoist and wire rope electric hoist) does not work how is it?
Answer: The main reason why the electric hoist doesn't work after pressing the starting switch is that the hoist doesn't turn on the rated working voltage, so it can't work. Generally, there are three situations.
(1) Whether the power supply system to the electric hoist power supply, the general test pen test, such as no power, wait for power after the work;
(2) The electrical damage of the main and control loops of the hoist, the disconnection of the line or the poor contact of the hoist, will also make the hoist motor unable to be energized. In this case, it is necessary to repair the main and control loops. In order to prevent the power supply of the main and control loops to the three-phase motor from being short of phase, the motor will be burned down, or the hoist motor will suddenly run on electricity, causing harm. Must disconnect the hoist motor from the power supply line, only to the main and control circuit power supply, and then start and stop the switch, check and analyze the operation of the control electronics and lines, repair or replace the defective electrical appliances or lines, when the main and control circuit fault-free, can be re-commissioned;
(3) The voltage at the motor end of the hoist is more than 10% lower than the rated voltage, and the starting torque of the motor is too small, so that the hoist can not lift the goods and can not work. When checking, the voltage at the input end of the motor is measured by a multimeter or voltmeter. If the voltage is too low to start the motor, it is necessary to use the electric hoist after the system voltage is restored to normal. Reed. Sometimes, the voltage of the Hulu motor is normal, and the gourd is not working. There are other reasons to consider.
For example: the motor is burned down, maintenance needs to replace the motor; long-term use of the hoist, poor maintenance and other reasons to make the brake wheel and the end cover rust, starting the brake wheel can not be removed, the motor only "hum" sound, can not rotate, the hoist can not work. At this time, the brake wheel should be removed, cleaning the rusted surface, and then re-commissioning; serious motor sweeping, will also make the motor does not rotate, found this situation, should stop using, must be overhauled or replaced motor to ensure the normal work of the hoist. In addition, it is strictly prohibited to overload the use of electric hoist in production. When the goods are overloaded, the hoist can not lift the goods, the motor only emits a "hum" sound, but not running, serious motor will burn down, or even cause an accident, at this time should immediately stop, lighten the goods, so that the hoist in the rated power to work.
Q: comparison and difference between fixed column cranes and gantry cranes?
Answer: The fixed-column jib crane is characterized by its lightness, simplicity and large working space, but its lifting tonnage is smaller than that of the gantry crane.
Again, we should pay attention to safety, have experienced engineers to operate, fulcrum control is not good, there is a certain risk, and then do a set of adjustable height bumper to withstand the vehicle before and after the two sections.
The gantry crane is characterized by large lifting tonnage, good safety, but occupies a large space, and can support the type of vehicle is also limited.
Generally used for car selected column crane with a set of safety bracket, truck on the choice of gantry crane, relatively safe.
And now used in cars began to popular a kind of scissors, buried in the ground, when not used with the ground is flat, larger space, but more expensive, construction is also more troublesome than fixed-column crane, to dig trenches.
Q: how do we install crane tracks?
Answer: requirements for track girder installation before track laying.
1 Requirements for concrete track beams (1) Track beams must be manufactured to ensure that the position deviation of reserved bolt holes along the transverse and longitudinal beams is less than 5 mm, the diameter of bolt holes is 2-7 mm larger than the diameter of bolts, and the top of the beams should be flat, but not smooth.
(2) The installation deviation of the track beam must satisfy the following requirements, otherwise the track beam must be adjusted before it is allowed to be leveled with concrete.
The deviation of the position of the beam to the design axis is less than 5mm.
2. The deviation of the elevation of the top of the beam to the design elevation is +10mm-5mm.
3. The displacement error of the bolt and the reserved bolt on the beam is less than 5mm.
(3) construction requirements for concrete leveling layer
(1) the strength level of concrete leveling layer is C30, and the thickness is 30 ~ 50mm.
(2) Before the construction of the concrete leveling layer, the installation deviation of the track beam should be checked according to the requirements, and if it does not meet the requirements, the track beam should be adjusted.
(3) According to the measured elevation of the track beam surface, a suitable control elevation of the top of the concrete leveling layer is determined, and a datum point of the control elevation is set every 214-310m on the track beam.
(4) Measuring with instruments, adjusting the elevation of the datum point, determining the datum line of the height of the top of the leveling layer, and then installing formwork to remove debris from the top of the track beam and the bolt hole, and plugging the upper opening of the bolt hole.
After watering, the concrete can be poured.
_The top of the leveling layer must be leveled and calendered, and there must be no exposed or uneven stones. The method of placing cement mortar on the surface is not allowed to leveling.
_In construction, the top surface of leveling layer must meet the following requirements: the unevenness of the top surface within the width of 400 mm at the bolt site is less than 5 mm; the difference of the top surface elevation at the internal affairs bolt site of any 610 m length is (+) 3 mm; and the difference of the top surface elevation along the bolt site is (+) 5 mm.
_The concrete should be mechanically stirred, and the maintenance should be strengthened during construction. The track installation can only be carried out when the strength of concrete blocks reaches 75% design value.
2 requirements for steel structure track girders
(1) the perpendicularity of the track beam is less than h/500 and H is the beam height of the track beam.
(2) the lateral bending of the track beam is less than l/1500, and the net 10mm and L are the girders of the track beam.
(3) the vertical direction of the track beam is less than 10mm.
(4) The deviation between the position of the track beam and the designed positioning axis is less than 5 mm. If the deviation does not meet the requirements, the track beam should be adjusted before the track can be installed.
(5) the height difference of the top rail of the same cross section within the same span is less than 10mm at the support, and other locations are less than 15m.
(6) the height difference of the top rail between the 2 adjacent columns is less than l/1500, and 10mm L is the track length of Liang Deliang.
(7) the adjacent 2 track beam joints, the height difference of the top surface of the 2 rail girders is less than 1mm, and the lateral misalignment of the 2 rail girders is less than 3mm.
3 crane rail joint
3.1 preparation before welding
Crane rail joints before welding, should carefully clean the groove and nearby oil, rust and other dirt, until exposed to metallic luster. According to the principle of equal strength, the welding material matches the alkaline electrode, and its grade J857 (national standard 4.2 track welding deformation control rail end pre-padded height, according to the type of rail, length and fixing conditions and environmental temperature and other factors, adopt pre-pad, with copper pad plate and carbon steel plate to pad the end of the rail 30-40 mm, using the already made. Good bolts and pressure plate and other connectors, tighten the nut so that the rail is fixed on the track beam, each rail joint near at least four fixed points. When the bottom of the rail is welded, loosen the pressure plate, reduce the pad at the end of the rail to 20 mm, and then tighten the pressure plate nut. When welding the rail waist, gradually reduce the height of the pad, when the rail waist welded, should remove all the pad, and loosen the pressure plate, at this time the rail joint should have a small warp value, in the process of welding the rail head, according to the rail flatness, decide whether to tighten the pressure plate nut. In the whole welding process, it is necessary to check the deformation of rail joint with straight steel ruler at any time, and adjust the height of the joint and tighten the compression plate at any time to control the deformation of rail joint. When fixing the rail joint before welding, the gap between the ends of the two rails is upper wide and lower narrow, and the gap between the two rails should not be less than 12 mm, nor should it be too wide, generally controlled in the range of 15-18 mm. When adjusting the fixed rail joint, in addition to ensuring the size of the end clearance, the two rail ends must be aligned, and there must be no distortion or stagger. Before and during welding, the position of the middle line of two rails should be strictly checked and ensured on one line, so as to prevent the bending of the rail after welding. The rail fixed by hook bolt can be fixed by temporary clamp according to the above method when welding the rail joint.
The welding sequence of rail joints is from bottom to top, first rail bottom, then rail waist, rail head, layer by layer for surfacing, then repair the surrounding. The range of the two track ends is 40 mm, and the preheating and interlayer temperature are controlled at 300 ~350 C. Welding (backing): Current 120A to 130A to prevent carbon steel backing plate from burning through and melting the copper backing plate, thereby reducing the difficulty of removing the copper backing plate, shortening the track air cooling time, in order to maintain the interlayer temperature and prevent quenching; after each layer can use (130 + 15) A, each layer must be cleaned up to continue welding;
Rail waist welding: current 130 ~ 140A, welding upward from the lower part of the waist, pay attention to slag cleaning.
Rail head welding: current 130 ~ 140A, the copper bracket will be installed after the start of welding, pay attention to each layer of slag once; after the welding seam around the full weld repair treatment.
3.3 points for attention in rail welding process
When applying each welding wave, especially when applying each welding wave at the bottom of the welded rail, l electrode should be used to complete the welding, avoiding welding electrode and arc breaking in the middle, the welding direction of the front and rear two welding waves should be opposite, and the welding work of each rail joint should be carried out continuously so that the rail end can be welded at a higher temperature (300 ~350). After welding, when the stress relief heat treatment has not yet cooled, rain water should be prevented from getting wet; hot copper plate can be taken off stained water to cool, so as to be reused next time.
3.4 elimination of stress heat treatment (flame heating method)
Stress relief heat treatment of rail end after welding is an important measure to improve welding quality. It is necessary to adopt this measure for welded track at relatively low temperature, such as winter construction, etc. It is necessary to pay special attention to the heating quality of the rail bottom when the whole section of the track is heated evenly. The temperature of stress relief heat treatment is 620 ~650 C, and 40 mm on both sides of the weld can be calculated as the range of stress relief heat treatment. When the temperature of stress relief heat treatment reaches, the constant temperature heating must be guaranteed to be more than 20~30 minutes, and the needle blanket should be used to keep the cotton wrapped up and keep the temperature cool slowly until normal temperature.
3.5 leveling treatment of rail joints
After the welded joints of rail have been heat treated and cooled to atmospheric temperature, the welds on the top and both sides of the track are ground. When the welding bump is too large, grinding is done with a grinding wheel grinder until it is even with the rail head, and then the surface is polished.
3.6 track joint treatment for expansion joint of factory building
There are usually two kinds of rail joint treatment at expansion joint of workshop: one is connected by splint or fishtail plate, the track is connected by 45 degrees inclined joint, and the gap is 10mm. The other is a splice splint made of rail head, with a clearance of 50mm.