Tuesday, 28 October 2014

The Harm Of Rail Gnawing

During normal operation, there should be a certain gap between wheel flange and orbit of bridge crane, maximum clearance for the 30-40mm. But in exceptional circumstances, flange and rail side will be under the mutual extrusion and friction, which causes the occurrence of rail biting fault and then affect the safe operation of crane.

The harm of rail gnawing can be mainly in the following three aspects. The first is to reduce the service life of the wheel and rail. For the bridge crane with serious rail gnawing, the service life of the wheel is less than 1 year, or even only a few months, while the use time of track can be only 3-5 years, much shorter than that in the normal case.
The second is to increase the running resistance. According to the determination, the bridge crane with serious rail gnawing has much larger running resistance, which can reach 1.5-3.5 times bigger than the normal running resistance. And this may cause that the load of motor and transmission mechanism increase and even overload. Bridge crane with very serious rail gnawing may has the problem that wheel rim has deformation by extrusion, which may cause a derailment accident.
The third is to do an adverse effect on the building structure. Crane with rail gnawing can easily produce lateral load, which will lead to lateral displacement of rail and looseness of the rail fixing bolt. In addition, the lateral force to the roof truss by rail can seriously affect the tray and plant stress conditions, making the roof slab bridge local loosening or fracture.

Thursday, 9 October 2014

The Working Principle Of Electric Hoist

Before the use of electric hoist, you should do the following pre inspection work. First you should ensure that there are no obstacles or float in the operator’s walking range, line of sight, or the route of heavy things. Then you should test the conditions of every part. Hand control button should be accurate and sensitive. The motor and reducer should be with no abnormal noise. The brake should be sensitive and reliable. The upper and lower limit for action should be accurate and sensitive. The hook stop nut should be tightened securely. The hook should be flexible when it rotates in the horizontal and vertical direction. The hook pulley should be with flexible rotation. The wire rope should be with no cracks, but good lubrication. And it should be arranged on the drum in neat rows, with no signs of disengaged from the pulley groove, twirl, or folding buckle. Hanging tools should be with no abnormal phenomenon.

When using the electric hoist, you should ensure it doesn’t lift or unload heavy at one side, and prohibit the use of overload. The working environment temperature of electric hoist is in the range of - 25 ~ +40 C. Electric hoist is not applicable to places with full of corrosive gas or relative humidity above 85%. It cannot replace the explosion-proof hoist, and should not be used to lift molten metal or toxic, flammable and explosive articles.

After using the electric hoist, you should make sure that the power has been cut off. And daily maintenance of it is very important.