How to ensure the safety of the jack in use?

Jack is a single-action lifting machinery. It can ensure the accurate lifting height, jacking process without shock and vibration. Several jacks can be linked, can reach hundreds of tons of lifting capacity; jack can also be used for multiple repetitive lifting, to achieve a large lifting height. Therefore, the construction industry is widely used in equipment installation and maintenance work.


Jack according to its principle of action and construction characteristics can be divided into: rack jackscrew jack and hydraulic jack. As the spiral jack structure is simple, safe and easy to operate with a self-locking function; hydraulic jack several of the same type can be used together to jack up a heavy object, high efficiency, load up to, therefore, more widely used in the construction industry.

1. the check before use.


① check its rated lifting capacity should be greater than the load.


② several jacks used jointly, require synchronous operation, and each capacity of not less than 1.2 times the calculated load.


③ spiral jack and rack jack before use should be a detailed check of the screw, nut and rack at the wear and tear, there are broken teeth or tooth wear amounting to more than 20% of the original tooth thickness, prohibit the use. Hydraulic jack before use should be 110% of the overload test. In the test so that it is jacked up to the highest position and maintain 20 minutes, observe that the jack does not occur abnormalities, before use.


④ The minimum height of the jack should be less than the bottom of the object or the net height of the force application point.


⑤ jack maximum stroke should be greater than the thickness of the pad plus the elastic deformation of the pad stack.


2. the use of safety requirements


① foundation should be stable and reliable, solid and flat (commonly used thick steel plate and sleeper pad).


② jack to prevent, should make the load of the weight line of action and jack axis as far as possible to maintain the same. Strictly prevent the risk of collapse due to substrate deflection or load horizontal displacement and jack deflection, tilt.


③ jacking point of force should be selected in the top of the object has sufficient strength of the part, to prevent the top of the deformation caused by the point of force damage.


④ The top of the jack should be padded with a flat, oil-free board (pad iron plate will slip).


⑤ not overload jacking; not allowed to extend the handle to force the hydraulic jack overload.


⑥ When the screw jack lifting sleeve appears red warning line, no more jacking.


⑦ lifting heavy objects, should be up with the heavy objects below the pad pillow pallets; decentralization, should be gradually drawn out. The distance between the insurance pillow stack and the heavy object is generally not more than 3cm to prevent accidents.

⑧ when jacking large objects (such as beams), both ends should be separately landing and taking off. When one end of the landing, the other end must be padded and placed firmly.


⑨ in the synchronous use of more than 2 jacks, should pay attention to make each jack load balance, not to exceed the rated load. To the same command, with the same up and down, so that the weight lifting and lowering smoothly, without the risk of tilting.


⑩ hydraulic jack lowering, should pay attention to the slight opening of the throttle can be slowly put down, not suddenly put down.

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