22 replies to this topic

[_1angelia23]

Dear friends
Updating is required to a CPF. The capacity of the existing flare not updated for it is limited. To avoid overloading it,in case of instrument air failure, Contractor put air accumulator on the PVs to delay opening of the vent valves partially, but he soon found it deepens the problem instead of solving it.
your technical point of view!

Edited by _1angelia23, 05 April 2024 - 12:14 PM.

[fallah]

Dear friends
Updating is required to a CPF. The capacity of the existing flare not updated for it is limited. To avoid overloading it,in case of instrument air failure, Contractor put air accumulator on the PVs to delay opening of the vent valves partially, but he soon found it deepens the problem instead of solves it.
your technical point of view!

 

Hi,

 

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

 

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

 

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

[Pilesar]

Nitrogen bottle backup systems in critical places might help.

[_1angelia23]

Dear friends
Updating is required to a CPF. The capacity of the existing flare not updated for it is limited. To avoid overloading it,in case of instrument air failure, Contractor put air accumulator on the PVs to delay opening of the vent valves partially, but he soon found it deepens the problem instead of solves it.
your technical point of view!

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

I've been reviewing API 521
and adding air accumaltors to deal with this case is proposed with some attention.
If they used mechanical stop for PVs, how can they deal with BDVs, even with existing RO?

Edited by _1angelia23, 05 April 2024 - 09:02 AM.

[fallah]

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

I've been reviewing API 521
and adding air accumaltors to deal with this case is proposed with some attention.
If they used mechanical stop for PVs, how can they deal with BDVs, even with existing RO?

 

 

Hi,

 

I think what you have read in API 521 is relevant to back up provision for emergency valves such as BDVs or ESDVs/SDVs; not all control valves. And yes, these emergency valves can be equipped with air bottles to keep the valves active in the IA failure.

 

The proposed mechanical stop just is used in PVs to limit the gas flow rate to the flare in case of an overpressure following to a process upset. 

[_1angelia23]

Nitrogen bottle backup systems in critical places might help.

Thank you Pilesar, same as local instrument air bottles

Edited by _1angelia23, 05 April 2024 - 09:31 AM.

[_1angelia23]

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

I've been reviewing API 521
and adding air accumaltors to deal with this case is proposed with some attention.
If they used mechanical stop for PVs, how can they deal with BDVs, even with existing RO?

Hi,

I think what you have read in API 521 is relevant to back up provision for emergency valves such as BDVs or ESDVs/SDVs; not all control valves. And yes, these emergency valves can be equipped with air bottles to keep the valves active in the IA failure.

The proposed mechanical stop just is used in PVs to limit the gas flow rate to the flare in case of an overpressure following to a process upset.

Thank you
Is it possible to use RO instead of Mechanical stop?

[fallah]

 

 

Hi,

I think what you have read in API 521 is relevant to back up provision for emergency valves such as BDVs or ESDVs/SDVs; not all control valves. And yes, these emergency valves can be equipped with air bottles to keep the valves active in the IA failure.

The proposed mechanical stop just is used in PVs to limit the gas flow rate to the flare in case of an overpressure following to a process upset.

Thank you
Is it possible to use RO instead of Mechanical stop?

 

 

Hi,

 

Yes RO can be used instead; but it would always (even in normal conditions) limit the flow which isn't favorable while mechanical stop just limit the flow after it will going to pass a prespecified value.

[_1angelia23]

Dear friends
Updating is required to a CPF. The capacity of the existing flare not updated for it is limited. To avoid overloading it,in case of instrument air failure, Contractor put air accumulator on the PVs to delay opening of the vent valves partially, but he soon found it deepens the problem instead of solves it.
your technical point of view!

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

It deepens the problem because after adding it valve is not opening immediately

[fallah]

 

 

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

It deepens the problem because after adding it valve is not opening immediately

 

 

Hi,

 

Mechanical stop is nothing to do about the valve's opening speed; it just prevent the valve to be more opened beyond a prespecified opening area.

[_1angelia23]

Hi,

In general, IA failure as a common failure scenario cannot totally be removed by mentioned solutions...

How did the contractor find using air accumulator deepens the problem? Please elaborate more...

Why didn't they use mechanical stop on PVs to limit the relevant incoming gas to the flare system?

It deepens the problem because after adding it valve is not opening immediately

Hi,

Mechanical stop is nothing to do about the valve's opening speed; it just prevent the valve to be more opened beyond a prespecified opening area.

i mean about adding air accumulators for PVs not mechanical stop

Edited by _1angelia23, 05 April 2024 - 11:05 AM.

[fallah]

Hi,

Mechanical stop is nothing to do about the valve's opening speed; it just prevent the valve to be more opened beyond a prespecified opening area.

i mean about adding air accumulators for PVs not mechanical stop

 

 

Hi,

 

Would you please elaborate more about using air accumulator for PVs, say, by a simple sketch?

[_1angelia23]

Hi,

Mechanical stop is nothing to do about the valve's opening speed; it just prevent the valve to be more opened beyond a prespecified opening area.

i mean about adding air accumulators for PVs not mechanical stop

Hi,

Would you please elaborate more about using air accumulator for PVs, say, by a simple sketch?

https://ibb.co/2gCvBqr

[fallah]

 

 

Hi,

Would you please elaborate more about using air accumulator for PVs, say, by a simple sketch?

https://ibb.co/2gCvBqr

 

 

Hi,

 

If the air accumulator connects to the line of IA by a pressure regulator can do the job at IA failure same as IA and has no negative effect on PV's opening speed. But if there would be many PVs in a plant it might not be logical providing one air accumulator for each PV.

The negative point of using air accumulator, is limitation of its usage time duration (due to its pressure depletion) which is around 30-60 min.

[_1angelia23]

Hi,

Would you please elaborate more about using air accumulator for PVs, say, by a simple sketch?

https://ibb.co/2gCvBqr

Hi,

If the air accumulator connects to the line of IA by a pressure regulator can do the job at IA failure same as IA and has no negative effect on PV's opening speed. But if there would be many PVs in a plant it might not be logical providing one air accumulator for each PV.
The negative point of using air accumulator, is limitation of its usage time duration (due to its pressure depletion) which is around 30-60 min.

Thank you, what is the purpose for adding pressure regulator from your point of view here? I need to know how without the pressure regulator the accumulator delays the opening
In brief what if we have pressure regulator? and what if we don't?

Edited by _1angelia23, 05 April 2024 - 03:42 PM.

[fallah]

Hi,

If the air accumulator connects to the line of IA by a pressure regulator can do the job at IA failure same as IA and has no negative effect on PV's opening speed. But if there would be many PVs in a plant it might not be logical providing one air accumulator for each PV.
The negative point of using air accumulator, is limitation of its usage time duration (due to its pressure depletion) which is around 30-60 min.

Thank you, what is the purpose for adding pressure regulator from your point of view here?

 

 

Hi,

 

To regulate the accumulator outlet air pressure on the PV actuator equal to the pressure of instrument air header now it's supposed has been failed.

[_1angelia23]

Hi,

If the air accumulator connects to the line of IA by a pressure regulator can do the job at IA failure same as IA and has no negative effect on PV's opening speed. But if there would be many PVs in a plant it might not be logical providing one air accumulator for each PV.
The negative point of using air accumulator, is limitation of its usage time duration (due to its pressure depletion) which is around 30-60 min.

Thank you, what is the purpose for adding pressure regulator from your point of view here?

Hi,

To regulate the accumulator outlet air pressure on the PV actuator equal to the pressure of instrument air header now it's supposed has been failed.

l need to know how it effects on opening the valve if we keep it

[breizh]

Hi,

Consider this link: https://www.vatvalve...le=en&region=TH

Will it help?

Breizh

[_1angelia23]

Hi,
Consider this link: https://www.vatvalve...le=en&region=TH
Will it help?
Breizh

useful, breizh, thanks

[_1angelia23]

You can see this arrangement which l think is appropriate
https://ibb.co/KXRfS56
It is for fail close

But the arrangement in my case is

https://ibb.co/b7r5QHC
For fail open

Edited by _1angelia23, 06 April 2024 - 07:20 AM.

[fallah]

 

 

Hi,

To regulate the accumulator outlet air pressure on the PV actuator equal to the pressure of instrument air header now it's supposed has been failed.

l need to know how it effects on opening the valve if we keep it

 

 

Hi,

 

It affects same as what IA affected before failure...

[_1angelia23]

Nitrogen bottle backup systems in critical places might help.

Your opinion, pilesar about using mechanical stop instead of air accumulator, is that possible in case of IA failure?

Edited by _1angelia23, 06 April 2024 - 02:40 PM.

[_1angelia23]

Hi,

To regulate the accumulator outlet air pressure on the PV actuator equal to the pressure of instrument air header now it's supposed has been failed.

l need to know how it effects on opening the valve if we keep it

Hi,

It affects same as what IA affected before failure...

For mechanical stop,Fallah, it is not possible in this case,
Because it makes valve pre-determined in open or close position, so we need to keep the valve in close position in 30 minutes to avoid the multiple sources simultaneously and then will be opened

Edited by _1angelia23, 06 April 2024 - 07:09 PM.