Remote safety system shutdown though radio link
Process control authority Bela Liptak brings in specialists to answer a reader's question regarding if there are any TUV restrictions or recommendations in IEC 61511 for shutdown of a safety system.
IN ONE of our offshore project we are doing remote shutdown of the wellhead platform from a nearby FPSO. The shutdown system is Siemens PCS-7. We have fiber optic link between ESD system in FPSO and the ESD system in wellhead platform. The command from FPSO is sent through this fiber optic serial link. It is a soft signal from FPSO ESD controller to wellhead platform ESD controller. The fiber optic link is a dedicated link between two controllers and as per Siemens safety manual, shutdown in this way is allowed.
There is a 2.4 GHz radio link also between two platforms DCS system. Client is requesting to include a back-up shutdown command from FPSO through this radio link to wellhead platform DCS and then to wellhead platform shutdown system (pl. note that PCS-7 is an integrated system where control and safety controllers sits on the same system bus).
From my experience I know that normally shutdown through radio link for a safety system is not allowed. But I may be wrong also. I want to know exactly if there is any recommendation in IEC 61511 or other standards regarding this matter. Is there any TUV restriction also? Appreciate if you throw some light in this matter.
A.K.Hait, Senior Engineer, Technip
THE LNG shipping industry is working on specifications for wireless shutdowns on ship to shore. A few places have experienced some problems (such as transient interference), but should be ironed out. I would expect acceptability in appropriate marine codes to follow.
I would recommend going ahead particularly as a backup system, because we need experience to forge technology ahead. You may run into roadblocks from the "certified " equipment followers, but since I am not a big fan of the certification process anyway, I suggest you do a rigorous a hazard analysis and charge on.
Dr. Harry H. West, PE, Adjunct Professor, and Mary Kay O'Connor, Process Safety Center, Chemical Engineering Department, Texas A&M University