Steel Plant Metallurgical Bridge Crane - Hook Problem

Steel Plant Metallurgical Bridge Crane - Hook Problem
 

The 100 ton double-girder bridge crane is the most important and most commonly used important equipment for lifting, transportation and other operations in large-scale iron and steel metallurgy enterprises in my country.
 

Bridge cranes are commonly known as "crane". The "overrolling" accident of bridge cranes is also called "hook going to the sky", which is one of the vicious accidents of bridge cranes.

When the accident happened, the fixed pulley block was crushed and the steel wire rope was damaged and scrapped;
 

"Overroll" accidents also account for a large proportion of lifting accidents, and the resulting economic losses and even casualties are very serious. Therefore, careful prevention and control must be carried out.

Analysis of the Causes of "Overrolling" Accidents
 

It is generally believed that as long as the limit switch of the 100 ton bridge crane works well, "overrolling" accidents will not occur, which is a wrong understanding. Even when the limit switch itself is normal, there are still many reasons that can cause the "hook to go to the sky".
 

For example:
 

Mechanical reasons - insufficient tightness of the brake, "overwinding" caused by the swing of the limit ruler;
 

Electrical reasons - short circuit of the operating line, grounding, wrong wiring, adhesion of the main contacts of the contactor, damage to the controller components or "overwinding" caused by excessive clearance;
 

The reasons for the operation - the wrong position of the controller handle, the "overwinding" caused by the excessive swing of the hook group during operation, etc.
 

At the same time, we can't believe in the so-called double limit setting, because for the "overwinding" accident caused by the non-limit switch itself, no amount of limit switches will help.
 

It can be seen that the control of "over-roll" accidents is a comprehensive task, and the simplicity and one-sidedness of understanding must be overcome in order to achieve a more comprehensive and effective containment of accidents.
 

Accidents under harsh working conditions, some iron and steel metallurgical enterprises, mining enterprises, machinery manufacturing enterprises, the operating environment of bridge cranes is very harsh. For example, the thick smoke from various smelting furnaces has already occurred, and the driver can only be aware of it after causing serious consequences.

So, How To Control It?
 

During the operation of the crane, when the hook group rises, as long as it hits the limit horizontal ruler (no matter what causes "overwinding", the hook group must first hit the horizontal ruler or other to disconnect the normally closed point in the corresponding limit switch Indirect action link), when the limit horizontal ruler starts to lift, causing the normally closed point of the limit switch to be disconnected, at the same time, the normally open point of the alarm device linked with it is closed, and the electric horn sounds. The driver must be aware of it and take immediate action. Emergency control measures can avoid the occurrence of "over-rolling" accidents.
 

This kind of alarm device can be used after appropriate improvement in other types of limit control systems; and cranes working in non-dense smoke and strong noise environments must also be equipped with alarm devices to achieve intrinsic safety.

Fast speed. high frequency. The main gear of the bridge crane used under long-stroke working conditions is relatively fast, the fork is frequently started, and the lifting height is often close to or reaches the limit height. For cranes working under such conditions, the limit device must be sensitive. Ding and accurate positioning.

Accident prevention under normal working conditions
 

1. First of all, adjust the brake to maintain proper tightness, otherwise, the brake is too loose, which may cause "overwinding" accidents caused by inertial operation. Frequently test whether the limit switch is sensitive and reliable, and prevent limit control failure caused by point adhesion, shaft abnormality and other reasons.
 

2. It is forbidden to forcibly lift the contactor armature to continue working when the suction noise of the protection plate and the contactor armature is too high or the main contactor circuit is faulty and cannot be sucked in, because forcibly pushing the contactor armature will cause the auxiliary limit control to fail.
 

3. When adopting double-limit one-worm gear and one-foot-type configuration, the positioning of the worm gear or the limit should be about 20cm lower than the limit position of the three-foot-type, so that it can be used for sub-section control, and the fork can protect the limit of the ruler-type ．
 

4. Always pay attention to whether the limit operation circuit is normal. Prevent limit failure due to short circuit of line groups and grounding, and prevent "overwinding" caused by incorrect wiring. Do a good job in the maintenance of the soil circuit to prevent the limit failure caused by the adhesion of the soil contact and the sticking of the contactor armature.

5. Educate the driver that the controller handle should be straightened during operation, and the driving hook set should be stable to prevent accidents such as "hook going up to the sky" caused by misoperation or illegal operation.