4 replies to this topic

[chizonweke]

Hi,

I understand that Vessels are normally specified for full or partial vacuum to allow for steam out operations.

However, I wish to know if this requirement is also a requirement for piping, valves and instrumentation as well.

Thanks.

[vinay]

The piping, isolation valve (ist isolation valve from vessel) normally sees the steam out condition & hence need to be designed for steam out condition . Instruments like Level Transmitter, Pressure gauge etc need not be designed for steam out condition as they can be isolated during steam out with the isolation valve provided at inlet. If a instrument can not be isolated /removed during time of steam out then only it needs to be designed for such condition ( i doubt if any one does so) .

Regards,
Vinay

[JoeWong]

The piping, isolation valve (ist isolation valve from vessel) normally sees the steam out condition & hence need to be designed for steam out condition . Instruments like Level Transmitter, Pressure gauge etc need not be designed for steam out condition as they can be isolated during steam out with the isolation valve provided at inlet. If a instrument can not be isolated /removed during time of steam out then only it needs to be designed for such condition ( i doubt if any one does so) .

Regards,
Vinay

There is potential of valve leakage or passing. I doubt credit should be taken for valve isolation.

[vinay]

Dear Joe,

Steam out of vessel is done by isolating & blinding all the other nozzles of the vessels apart from Vent ( which is open) & the steam inlet nozzle. Blinding is also essential if the vessel is to be man entered. As the blind is present after 1st isolation valve all the downstream piping after the valve need not be designed for full vaccum . Again the philosophy can be different in different companies.

Regards,
Vinay

[JoeWong]

Dear Joe,

Steam out of vessel is done by isolating & blinding all the other nozzles of the vessels apart from Vent ( which is open) & the steam inlet nozzle. Blinding is also essential if the vessel is to be man entered. As the blind is present after 1st isolation valve all the downstream piping after the valve need not be designed for full vaccum . Again the philosophy can be different in different companies.

Regards,
Vinay

I have limited experiences in such service but i have the following question. Maybe an experience engineer in operation can assist :

Should you open the nozzle, put the blind in place, then conduct steam out ?

I guess if you can follow above sequences, then probably you are right.

OR

all the nozzle isolation valves the special type arrangement (can't remember the name) where you have double valving with spade/blind and purging nozzle in it.

I guess if above arrangement is provided, then probably you are right.