Turbine inlet On/Off Valve

[cheme112]

I need to know what is the effect of having ON/OFF valve on the steam inlet TO turbine in fail close vs. fail open?
The purpose of the turbine is to drive rotary pump continuously. There is a 2" ball on/off valve on the steam inlet to the turbine.
Most of the turbine inlet valves are fail open.

 

[georgeverghese]

If this valve is in safety shutoff service, it should be FC. Else this can only be an operational or control valve in on / off service.

 

[rotw]

If the turbine begins to over speed, the main steam inlet flow to turbine must be shut off immediately ; if not it will add energy to the rotor sustaining its acceleration with a risk on machine mechanical integrity ; safety / hazard consequences including potential catastrophic failures can occur because of turbine over speed.

 

[crshears]

Most turbines I've dealt with have an overspeed trip built right in, often directly acting upon a separately-actuated valve that functions independently of any other shutdown system. If that is the case here, overspeed trips should not become part of this discussion.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]