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Summary
A recent incident in Eastern Canada caused a signal to display an aspect “less restrictive than required”. This problem was caused by the “wrong side” failure of a Neutral Bias GRS B1 vital relay. The results of the investigation confirmed the “sticking” action affecting this neutral bias relay was identical to the symptoms previously observed on the slow release type B1 vital relays.
This relay was referenced in the GRS Safety Notice dated August 18, 1995 but had not yet been serviced in accordance with GRS’ recommendations. Transport Canada is hereby reminding all stakeholders that the GRS Safety Notice dated August 18, 1995 concerns ALL B1 vital relays manufactured from 1960 to 1985, including slow release, neutral bias and other types of B1 vital relays.
Description
GRS/Alstom has identified a problem with B1 vital relays manufactured from 1960 to 1985. This problem is caused by the transfer of material between the copper-silicon residual screw and the cadmium-tin plated core head, which can cause the residual screw to adhere to the core head. When this occurs, the relay may fail to drop in the way it was designed when energy is removed from the coils.
According to GRS/Alstom, the problem is more likely to occur when the relay is normally in the energized position and under certain conditions (temperature, frequency of operation, operating current).
Side view of a B1 vital relay showing point of contact between the residual screw and the core head.
B1 vital relay on a test rack without cover. The arrow indicates the
position of the residual screw 1
B1 vital relay with armature removed exposing the core plate. The arrow indicates the point of contact with residual screw (dark point on the core plate)
History
On March 22, 1985 GRS issued a safety bulletin concerning B1 vital slow release relays manufactured between 1967 and 1981 advising of the possibility of material build up on the residual stop screw.
On September 6, 1991 GRS issued a second safety bulletin concerning B1 vital slow release relays used in highway crossing warning systems covering all relays manufactured prior to 1985 or more than 8 years old, and recommended a rebuild of the relay as per their instructions issued at the same time.
Then on August 18, 1995 GRS issued a third safety bulletin concerning
ALL B1 VITAL RELAYS superseding both March 22, 1985 and Sept. 6, 1991 bulletins. In this bulletin, Alstom/GRS recommended that
ALL B1 VITAL RELAYS manufactured between January 1960 and December 1985 incorporating screw Part No. 20360-012-00 be modified in accordance with their instructions by replacing the copper-silicon residual screws with stainless steel screws. The August 18, 1995 bulletin concerned
ALL B1 VITAL RELAYS used in highway crossing warning systems and train traffic control systems.
In 2000, following a preliminary investigation by the Canadian Transportation Safety Board regarding a similar incident with a slow release B1 vital relay, Transport Canada launched a nation-wide awareness program. At the time, emphasis was placed on slow release B1 vital relays, as they were associated with a higher risk of failure.
On March 12, 2001 Alstom issued an information update concerning ALL B1 vital relays. To assist the railways in prioritizing their efforts, they identified relays with higher frequency of operation, higher operating current and relays manufactured between 1970 and 1980 as those having a higher risk of failure.
Conclusion
Transport Canada is hereby reminding all stakeholders of this safety issue and the GRS Safety Notice dated August 18, 1995 concerning
ALL B1 vital relays manufactured from 1960 to 1985, including slow release, neutral bias and all other types of B1 vital relays. B1 vital relays play a critical role in crossing warning systems and signal traffic control systems. Their proper functioning is crucial to safe railway operations.
The timely application of the manufacturer’s recommendations described in their bulletin or the implementation of other risk attenuation measures is imperative to prevent the adverse effect of relay failure, which could lead to an unsafe condition. Transport Canada is also concerned that failures may go unnoticed.
Additional References
Notification requirement
Notification requirement will be communicated to each railway under separate cover.
For additional information feel free to communicate with one of Transport
Canada Rail Safety office (http://www.tc.gc.ca/rail/offices.htm).
1. Pictures included in this document are from a different relay than
the one found to be defective. These pictures are only included to support the
understanding of the issue and show the particular area of the relay affected by
this problem.
Rail Safety Bulletin (RSB-ENG-0701): B1 Vital relays referenced in the GRS Safety Notice is available in PDF format (file size
158kb) which will download in approximately 2 minutes and 09 seconds on a 28.8 connection and may be viewed using Acrobat Reader (version 3.0 or higher).
Note: Portable Document Format (PDF) formats may be viewed using version 3.0
or higher of the Adobe® Acrobat Reader. This reader may be downloaded free of
charge by visiting the
Adobe® web site.
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