Emergency Removal of a Main Steam Line Plug: A Case Study

Preferred Engineering has decades of experience with the Main Steam Line Plug, and sometimes unique situations arise that make our our expertise in installation and removal especially important.

A recent project required us to employ an MSLP Emergency Removal tool during the installation process. One of the latch mechanisms on the plug jammed during the plug installation, and no amount of effort could release the installation tool from the main steam plug. This can occur when an incorrect load is applied to the hoist cable following the transfer of the lift point socket. In this case, the rigging appeared to have the correct load prior to unlatching, but when the latch was moved to unlatch, the latch rotated slightly until it bound and stuck.

Shaking the rigging and manipulating the chain fall up and down did not manage to free the latch, so we employed a special feature of the installation tool, a “split hook” that is designed to free a stuck latch. The Emergency Removal tool is designed to be lowered to the installation tool, allowing the screws holding the hook halves together to be loosened to free the latch mechanism.

To use an Emergency Removal tool, the latch hook needs to be as horizontal as possible. We found that loosening the two outer screws was not difficult in this case, but once the jacking screw was turned, the pole seemed to lock onto the latch hook. This was due to the pneumatics set to Un-Latch, which bound the tool in the jacking screw head. By selecting “Latch,” the cylinders pushed the latch hook level, and the tool was able to be easily removed. Then the “un-latch” function was selected, and the tool was able to be removed from the Plug.

The Emergency Release tool is made up of a machined hex bolted to a light duty pole adapter. The machined hex on the last batch was cut at the high end of the tolerance, and crews indicated that it would not fit into the Hex Head Cap Screw (HHCS). This is easily remedied by a light filing to remove a few thousandths of material from the hex faces.

The Emergency Release tool might not be a frequently used device, but it is well worth keeping on hand so you don’t have to come up with a makeshift solution under the gun. When needed, this tool is critical to fast repair and recovery. Contact Preferred Engineering for more information about the MSLP and all our related installation support services.

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