3 replies to this topic

[Ghasem.Bashiri]

Dear Sir, Madam
Is there any difference between Car Seal Open/ Car Seal Closed and Locked Open/Locked Close during development of P&ID.?
I read somewhere that CSO/CSC is old terminology and should not use anymore.
Ghasem.Bashiri@gmail.com

[djack77494]

Ghasem,
I do not agree with the statement that CSO/CSC is old technology. CSO/CSC and LO/LC are two different things. Which one to use depends on your facility's preference. In my experience CSO/CSC is more common and is most often preferred (even today). A car seal, typically constructed of a sturdy plastic, prevents the inadvertant opening/closing of a valve. Seals should not be removed unless specific administrative procedures are followed. Locked open/closed valves serve the same purpose but add another level of security. That is because a much stronger means is used to secure the valve position (a chain & metal lock).

My experience suggests that operators and maintenance people hate locked valves. Extra inconvenience is encountered whenever the need to operate the valve arises. Very little added security is purchased for the added cost and inconvenience. It's also an added inconvenience for management, who are now charged with maintaining a secure lockbox while also providing suitable access to the keys. Ultimately, either method can be defeated, but only by those who would deliberately violate procedures. Both work fine if there is no conscious effort to defeat their purpose. Suggestion: Save yourself & your plant the money and inconvenience and use car seals.

[JoeWong]

It's reported that the PSV outlet manual block valve can "self-close" in the even of relief due to uneven pressure force distribution. It is advisable to provide "proper lock" to secure the position of manual block valve at full open position. Car seal would be much weaker than a proper lock.

"...operators and maintenance people hate locked valves. Extra inconvenience is encountered whenever the need to operate the valve arises...". This relates to operator personality, awareness and education level... I would include the plant operator background as one of the important factor to determine if lock and car seal would be provided.

[Qalander (Chem)]

It's reported that the PSV outlet manual block valve can "self-close" in the even of relief due to uneven pressure force distribution. It is advisable to provide "proper lock" to secure the position of manual block valve at full open position. Car seal would be much weaker than a proper lock.

"...operators and maintenance people hate locked valves. Extra inconvenience is encountered whenever the need to operate the valve arises...". This relates to operator personality, awareness and education level... I would include the plant operator background as one of the important factor to determine if lock and car seal would be provided.

Dear Ghasem Bashiri Hello,
May I just add that it is the need which makes the things happen or decided about.
One has to be careful in design if extra-ordinarily reliable system dependent on human intervention or control are employed and they are not easy to operate or easy to access they become in a way useless or redundant and finally in-operable.
Careful decision-making striking a balance between the two extremes of 'Extremely good design' and 'Extreme ease of operation and maintenance' has to be ensured without sacrificing the necessary Process Safety Level.
Accordingly the situation may dictate use of CarSealOpen/ CarSealClose Relief Valves or Lock/Unlock methodology or Duplicated (Double Relief) Valves Methodology; although demanding some extra resource.
Hope this helps
Regards
Qalander