2 replies to this topic

[Sherif Morsi]

Hi,

 

I am currently reviewing WHCP vendor documents. Wellhead wing, master and SCSSV are hydraulic actuated valves operated by pneumatic pilot valves.

 

When a process shutdown signal is initiated, Wing valve, Master Valve and SCSSV valve (all hydraulic) are closed in a timely sequence. A pneumatic signal is sent to the pilot valves inside the panel, hence closing the valves on the hydraulic lines feeding the actuators.

 

My question is: When you close the valve, the line will still be pressurized hence the valves on the wellhead will not close. How can I make sure that pressure is already released for the valve to close?

 

Thank you

[Art Montemayor]

 

Sherif:

 

What is “Whcp”?  Please don’t use acronyms without first defining them.

 

Your process description is difficult to understand.  Do you mean to state the following:

Your wellhead valves are all actuated by a hydraulic system;

• The Wellhead wing, master and SCSSV (what is “SCSSV?) valves are “oil to open” (hydraulic pressure keeps them open);
• An independent pneumatic system operates the block hydraulic valves pressurizing the operator on the wellhead valves;
• When the pneumatic air pressure closes the hydraulic oil pressurizing the wellhead valves, the valves are supposed to spring back to the normally closed position;
• What happens to the pressurized oil that is blocked in between the pneumatic block valve and the wellhead operators?  How can the wellhead hydraulic operators spring back to their normally closed positions if their hydraulic lines are still pressurized?

If the above is what you mean to state, then the answer is simple.  The pneumatic block valve on the hydraulic lines pressurizing the wellhead operators must be a 3-way valve that acts to block the oil while venting the trapped oil back to the oil reservoir.  This should all be carefully explained in your operating manual and depicted on your P&ID.

 

Please verify with an accurate and detailed sketch in order to confirm what is installed.

[Sherif Morsi]

Art,

 

Sorry for the inconvenience;

WHCP is Wellhead Control Panel

SCSSV is Surface-Controlled Subsurface Safety Valve

 

My understanding is that each oil operated valve installed on the wellhead has two hydraulic connections; one inlet providing pressurized oil to the actuator and one outlet for the returning oil from the valve to the oil reservoir (installed on the panel).

 

Referring to the attached schematic:

1. When a pneumatic operated valve closes, this inhibits pressurized oil from the wellhead valves (master, wing, safety) and the valve will spring back to its normally closed position (according to your explanation). As an example: if air supply on port M8 is closed, HV1-2 will close and the hydraulic supply will be cut off at port M5 supplying the wing valve with pressurized oil. What would make the wing valve spring back and closes since that portion of the line still contains pressurized oil?
2. Another question: the same question as above but for the pneumatic side, if pneumatic supply is cut-off from a pneumatic valve, what would make the valve fail if that portion still contains compressed air and there is no way to relief this pressure (see the portion of the line between SL2-1 and HV1-1)?

 

Thanks,

Sherif

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