Safety Alert

Reyrolle LM, 11 kV Switchgear

Circulation

Mine Owners
Mine Managers
Coal Mine Unions
Inspectors

Safety Circular

Dear Sir

Mine Managers should note the enclosed information relating to the use of Reyrolle LM, 11 kV switchgear. The problem outlined can lead to the circuit breaker failing to correctly remove power when a fault occurs and this can be a danger to anyone in the vicinity of the switchgear. If you have this type of switchgear in use at a mine then the manufacturers, or persons competent to carry out the necessary modifications, should be contacted without undue delay.

Yours faithfully

S P Wing
HM Principal District Inspector of Mines

LM23T, LM36T and LMI Switchgear
Information, recommendations and instructions

Summary

This document relates to EA SOP 206 raised on type LM23T, LM36T and LMI Switchgear circuit breakers and the long term maintenance of dashpot washers.

This information does not apply to type lmt2 switchgear

Background - Dashpot Buffer Washer

SOP 206 was raised following an internal fault on a LM23T circuit breaker manufactured in 1974. Investigation has revealed this was probably due to the opening spring dashpot piston seizing within the cylinder resulting in incomplete travel of the main contacts.

The dashpot contains a PVC buffer washer which is immersed in oil and over a long period of time, the plasticizer in the PVC can migrate into the oil, in some cases causing shrinkage and hardening of the washer. Subsequently the washer could become loose and displaced and due to the impact of the piston it could disintegrate.

LM23T/LM36T/LMI Circuit breakers were manufactured between 1960 and 1976 and can be easily identified from the data label by the article number. 861A ------ and/or a constructional number X2 to X22.

LMT2 Circuit breakers NOT AFFECTED were manufactured between 1973 and 1997 and can be identified from the data label by an article number 971A ---- and/or a constructional number X30, X31, X32 or X33.

Recommendations / Inspection / Actions

Although the incident rate is low (second recorded incident) the consequences could be severe therefore all buffer washers over 12 years old should be replaced.

This affects LM23T, LM36T and LMI Switchgear, all use the same type buffer washer.

A replacement buffer washer is now available of superior material which will have a life of at least 20 years.

For further information please contact:

Reyrolle Switchgear
Tel. No. 0191 4015494
Fax No. 0191 4015573