Updating the Mark V communication interface overload issue

Mark V goes haywire, shuts down F-class unit’s lube-oil pumps caught many in the industry by surprise when it was published in CCJ ONsite May 3, 2017 judging from the social media and online user-group chatter we were told occurred the days following, a passing mention by a GE engineer at a recent meeting, and a call from Scott Muster of Turbine Technology Services (TTS).

What the editors learned in the past two weeks came in too late to include in the article with the same title appearing in CCJ’s 1Q/2017 print edition which just went in the mail. The material that follows updates CCJ’s coverage on the subject, which was based on the industry alert Abel Rochwarger, chief engineer at Gas Turbine Controls, shared with the editors for publication.

GE Power responded to the article with Product Service Information Bulletin (PSIB) 20170519A, “Mark V Communication Interface Overload—Loss of Lube Oil.” The overview for that document states, “A recent loss of lubrication event on an F-class unit using Mark V controls has highlighted the need to communicate the capabilities of the Mark V controller in the context of today’s demanding applications.” The OEM said the Mark V controller was released in 1991 and has accumulated more than 200-million operating hours in a variety of applications with a good record for safety and reliability.

In basic terms, “heavy command traffic” was cited by the OEM as the cause of the accident described. GE said laboratory testing confirmed that symptoms similar to those observed can be recreated by increasing network traffic significantly above the recommended limit of 10 commands per second from all sources.

The PSIB recommended that owner/operators not make changes to lube-oil pump controls without first consulting GE. It also referenced four background documents on communications protocols. Plant personnel who do not have a copy of 20170519A should contact their GE representative for one.

Online discussion revved up after GE released the PSIB. TTS’s Muster contacted CCJ after learning of customer concerns. He told the editors that his company’s Turbine Monitoring System (TMOS), which is a direct replacement for existing Mark V <I> and <HMI> systems, actively manages and regulates the transfer of instructions from all site devices (BOP, DCS, SCADA, operator stations) to the Mark V, ensuring that the type of communication overload associated with the lube-oil failure is not possible.

Muster said the TMOS has been in the field since 2001 and has maintained an “outstanding record for safety and reliability for more than 60-million operating hours.” More material pertinent to this discussion is available on the TTS website.

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