12 replies to this topic

[mm217]

Dear All,

1- According to your comments on http://www.cheresour...ssurizing-line/, as safety issue, it's not recommended to use bypass line around ESDV, but in our project which is compressor station, ESDV's are used both as XV's and ESDV's so for start-up they have bypass lines!. On inlet line; it has ESDV on by pass line too. i mean two ESDV's in parallel. (at the ESD of END of station it's only double block and bleed to back pressurization of equipment at start-up) . Is there any strong standard that i use to reject this configuration of valves, or you may help me to better understand it.

2- I confused about using ESDV's!!!! i know that ESD command can consists open or close commands. But i thought that all of ESDV would be closed by ESD. IF i want to open the valve by ESD command what type of valve should i use?


Thanks a lot.

[fallah]

mm217,

General comments:

-ESDV and SDV are normally on-off ball valve
-ESDV to be reset locally
-Considering by pass for ESDV isn't normally authorized
-Two ESDV's in series are normally considered in each stream incoming/outgoing a fire zone

Your case may be based on your project specification and if you want to get more help you should submit detail information (PID, safety system,...).

Fallah

[mm217]

mm217,

General comments:

-ESDV and SDV are normally on-off ball valve
-ESDV to be reset locally
-Considering by pass for ESDV isn't normally authorized
-Two ESDV's in series are normally considered in each stream incoming/outgoing a fire zone

Your case may be based on your project specification and if you want to get more help you should submit detail information (PID, safety system,...).

Fallah

Fallah;

as you said, i think project specification could impose a lot of regulations.
but i want to know is it correct to open ESDV by ESD command?! we have one ESDV which will be opened by ESD. We used to use BDV instead of ESDV when we wanted to open the valve by ESD command.

[paulhorth]

mm217

You have asked two questions.
(1) I have seen a number of examples on projects in the North Sea and elsewhere, where the large ESDV on an inlet pipeline is provided with a small (2 inch) bypass line, to allow pressurisation and pressure balancing across the big valve before it is opened. This is acceptable if the small bypass line is also provided with a ESDV. So in the event of an emergency shutdown, both valves are closed and the upstream source of pressure is isolated, the facilities are safe.
The small valve is opened by manual reset, and the large valve is opened after a pressurisation procedure, sometimes with a pressure difference permissive signal being required.
The outlet from the facilities generally does not have a bypass line round the ESDV.

(2) In my experience, valves classed as ESD valves are ALWAYS fail-closed and can not be opened by an ESD signal. As you said, valves which open on ESD are BDVs, which are fail-open.

Paul

[fallah]

Fallah;

as you said, i think project specification could impose a lot of regulations.
but i want to know is it correct to open ESDV by ESD command?! we have one ESDV which will be opened by ESD. We used to use BDV instead of ESDV when we wanted to open the valve by ESD command.

mm217,

ESDV is normally be opened (reset) locally not by ESD command.

Indeed, BDV would be opened by EDP command (Emergency Depressurization) which depending on its level is implemented on ESD or DCS systems.

Fallah

Edited by fallah, 04 January 2012 - 06:04 AM.

[mm217]

mm217

You have asked two questions.
(1) I have seen a number of examples on projects in the North Sea and elsewhere, where the large ESDV on an inlet pipeline is provided with a small (2 inch) bypass line, to allow pressurisation and pressure balancing across the big valve before it is opened. This is acceptable if the small bypass line is also provided with a ESDV. So in the event of an emergency shutdown, both valves are closed and the upstream source of pressure is isolated, the facilities are safe.
The small valve is opened by manual reset, and the large valve is opened after a pressurisation procedure, sometimes with a pressure difference permissive signal being required.
The outlet from the facilities generally does not have a bypass line round the ESDV.

(2) In my experience, valves classed as ESD valves are ALWAYS fail-closed and can not be opened by an ESD signal. As you said, valves which open on ESD are BDVs, which are fail-open.

Paul

Paul;

You absolutely understood my case. As you said inlet ESDV in our project has bypass line for pressurization with pressure difference permissive signal to open the main ESDV. But on outlet ESDV, bypass line has Globe & Ball Valve (Not ESDV) and bypass line is required for back pressurization too. Indeed, it is a compressor station, and outlet ESDV is after the aircooler.
1)Do you think if it is enough to "locked close" the bypass valves or they must be replaced by ESDV (the same as the inlet ESDV).

2) The Valve on the main GAS Line to bypass the whole "compressor station" is already an ESDV type. As the ESD command of compressor station shut down the station this valve will be opened to bypass the compressor station. According to your comment i should change the type from ESDV, because it will be "opened" by ESD not "Closed".


That was really kind of you to concern my problem.

mm217

[paulhorth]

mm217,

(1) In my view, if the bypass round the outlet ESDV is locked closed, then that is sufficient and a ESDV on the bypass is not necessary - but you need to check with the ESD philosophy for the facility, and with the safety engineering group. This is the kind of problem which should be raised and discussed in a HAZOP.

(2) I don't think the bypass valve around the compressor station should be opened on ESD. Consider, when the compressor is running, the downstream pressure will be much higher than the upstream pressure, so there is a large DP across this bypass valve in the reverse direction. If you did succeed in opening the bypass valve against this pressure difference, the gas would flow backwards or would slam against a check valve. Wthout the compressor running, the flow downstream will fall, and the pressures along the pipeline will change. Better to wait until the downstream pressure has fallen sufficienly, and open the valve on a manual signal. The valve then becomes a motorised valve (XV) not a ESDV.

Paul

[tkeung]

I agreed with the above, in addition two ESDV's in parallel ensures the plant is blocked in during ESD.


The bypass ESDV allows you to pressurize downstream equipment during startup. For a manual bypass, I have seen a ball and globe valve used in series, for the purpose of throttling.

[mm217]

mm217,

(1) In my view, if the bypass round the outlet ESDV is locked closed, then that is sufficient and a ESDV on the bypass is not necessary - but you need to check with the ESD philosophy for the facility, and with the safety engineering group. This is the kind of problem which should be raised and discussed in a HAZOP.

(2) I don't think the bypass valve around the compressor station should be opened on ESD. Consider, when the compressor is running, the downstream pressure will be much higher than the upstream pressure, so there is a large DP across this bypass valve in the reverse direction. If you did succeed in opening the bypass valve against this pressure difference, the gas would flow backwards or would slam against a check valve. Wthout the compressor running, the flow downstream will fall, and the pressures along the pipeline will change. Better to wait until the downstream pressure has fallen sufficienly, and open the valve on a manual signal. The valve then becomes a motorised valve (XV) not a ESDV.

Paul

Paul;
I really thank you for your comments. I should check it with project team.
Thanks every body for cooporation.

mm217

[sv10491]

i have a question.i need to pressurise a gas pipeline.with inlet pressure being atmospheric.we need to bring up the pressure to 98kg/cm2 g.what are the equations to be used.the question is that how much time will it take to bring the pressure to desired pressure.
basically need to find out a relation between pressure and time and integrate.plz do help as soon as any one can.
thanx
regards

[sv10491]

The above query is also related to the ball valve in the by pass section of the main gas pipeline.
do reply back asap!
in a hurry!!

[ankur2061]

sv10491,

You have skyjacked the original topic which is against the rules of the forum. What is more, your topic is unrelated to the original post, which makes it even more unacceptable. Please start your own thread for your topic. I will wait for a couple of days for you to post your new query in a new thread otherwise I will request the main administrator to delete your posts which have no relation to the original post.

Regards,
Ankur.

Edited by ankur2061, 15 July 2012 - 11:07 PM.

[sv10491]

Ankur,
i am sorry for the trouble.I am new to this forum.i am extremely sorry.
nyways i have started a new thread.
if u cn,have a look at it.
the topics name is pressuristaion in gas pipeine.
sorry for the unconvenience.
my apologies
regards