Question re DVC 6200 and SOV

Hi EE365 members, I received this question by email and wanted to see what you think... thanks!

I have a question about a Fisher 5200 DVC installed on a SIS valve with a solenoid.

The DVC is configured as ETT (energize to trip) while the solenoid is configured DTT (deenergize to trip). The valve is a trip valve with no control function.

So my question is, in case of a SIS trip demand, will the DVC do anything i.e. can we consider the DVC and the solenoid as 1oo2 voting to cut of the air supply and trip the valve.

The opposite situation, if the DVC was set as DTT in this configuration would it be considered 1oo2 with the solenoid.

Appreciate you guidance.

  • Dear Jim,
    Good question.
    It is possible for DVC6200 SIS mounted pneumatically in series with SOV can be considered as 1oo2 voting approach (for pneumatic path) in both ETT (Energize to Trip) or DTT (De-energize to trip) option, taking valve to safe state either by DVC or by SOV or by both.
    To claim 1oo2 approach (in pneumatic path), DVC and SOV are mounted pneumatically in series, in case of safety DEMAND, for ETT option, DVC needs to get upper end of electrical power (i.e. if operated by 4-20mA signal, for ETT, it will be 20mA), whereas in case of DTT, it will get lower end of signal (4mA) at the time of Safety Demand.
    Hope this helps.