2-position 3-way solenoid valve via DCS and ESD

[knapee]

Could any professional engineer help me out ?
How could I decide the solenoid valve type(three way, four way, five way) used in specific process situation?

The solenoid valve usually is NC to avoid valve fail
as power failure happen. The attached drawing shows that
the signal will from 1->3->valve as the solenoid be activated ,and the signal will from valve->3->2 vent.

Not sure my explanation for this drawing is right ? The operator can reset this valve(through DCS), and also DCS(circle with letter I) can be sent a signal to control the valve.


Is operator can use ZSO/ZSC hand switch to send signal to safety interlock to open/close this valve ? Or any better explanation for this type of solenoid valve design?

Thank you very much.

 

[xnuke]

Your description of the solenoid operation is correct. Port 1 is the NC port, port 2 is the NO port, and port 3 is the common port C. I haven't seen the circle with the letter I used before - I'm guessing it is an interlock either from or to the DCS, but it isn't really clear from the drawing.

However, the ZSO and ZSC are position switches on the valve that indicate whether the valve is fully open (ZSO) or fully closed (ZSO). They are not hand switches that allow manual operation of the valve, so the operator cannot use them to change valve position. If there is a manual operator on the solenoid valve or on the main valve, it isn't shown on the sketch.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[koba78]

Thank you very much for your reply.

Base on this sketch, in my understanding(please advised my
if I am wrong),

1) The ZSO and ZSC can send signal to ESD (saftey interlock) to show the open/close singal on the DCS panel.

2)Reset button located on DCS may be actived by operator to function the solenid valve then ZSO/ZSC be actived.

3)The ESD have a higher prioterity than (circle I,DCS interlock)
This kind of valve may used in storge vessl level control or batch silo control.

Thank yon.

 

[ICLL]

In answer to your questions:

1. Yes
2. Your question doesn't make sense in English. I think that what the sketch is trying to convey is that the ESD system includes a software latch whenever the trip condition is activated. This latch prevents the solenoid from automatically re-energising when the trip condition has cleared and thus preventing control from resuming; the operator must make a conscious decision to reset the latch when he is happy that the condition that has caused the fault has cleared. (There would almost certainly also be logic that would prevent such a manual reset if the condition had NOT cleared, but you can't show everyhting on a P&ID.)

I think you are not understanding what the ZSC and ZSO are. These are simply positon feedback switches. They are quite "dumb" and don't care if the valve is moved via the control function or via the trip function. Typically they play no part in the actual valve control and only provide indication.

The control system symbol showing Open/Close probably just refers to the valve position indication on the HMI. It might refer to a command to open and close the valve, but this is unlikely, as it's control valve, not an on-off valve.

3. Yes, the ESD system can dump the air from the valve regardless of what the DCS control is trying to do and thus has a higher priority. (I assume the valve is fail closed).