antisurge system requirement

[rotw]

thread124-130176

Reference to this thread above.

Why antisurge valve is not present in (some) recycle reformer gas centrifugal compressor ?

Thanks for any insight

 

[LittleInch]

If there is no possibility of a closed valve or control valve in the discharge side piping then there is no requirement for a recycle line. This is quite rare, but can happen in some reformer cases.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[rotw]

Thanks LittleInch for your feedback.
Can you please elaborate a bit on that.

1/ If there requirement of by pass line is not possible, then how the compressor is protected in case of surge?
2/ Why the reformer as so specific then ? They are subject to same risk to have unexpected process upset, temporary variations of process parameters (flow, inlet/outlet pressure), etc. or not ?
3/ From where comes the impossibility to have a by pass line with a control valve ? it is just an addition piece of pipe with control valve that could safeguard the machine in case something unexpected occurs?

Thanks again for your response

 

[sshep]

Hey rotaryworld,

Surge is caused by low inlet volume (left of surge line). The anti-surge valve creates more inlet volume by recycle. The process and the controls can be such that recycle is not needed to stay out of surge, and so the anti-surge valve might be omitted.

I don't really know the application or i would have commented earlier- i.e. what is the control objective, what flow or pressure? Centrifugal compressors can generally be manipulated in the following ways: speed, vanes, inlet valve, outlet valve, or recycle (same as anti-surge which you obviously don't have). Some ways (like suction throttling) are better for staying out of surge than others.

Best wishes,
Sshep

 

[silebi66]

Dear Rotaryworld
If the compressor's operating curve exist in the minimum flow and maximum head condition (compressor is not able to overcome the system resistance) - surge point.
It to be installed the Spill-back from discharge to suction line, and its to be required for flow or pressure control in the discharge piping. In my limited experience, I never saw any compressor without
spill back line.

Thank you.

 

[rotw]

silebi66,

I've never seen too but other mention in rare cases (reformers).
That's why I ask for people feedback on such rare cases, eventually to know more.