3 replies to this topic

[rha257]

Hello All,

The topic of anti surge valve seems like a very subjective topic and each end user interprets the function of an anti surge valve differently. It is pretty obvious that the anti surge valve main function is to prevent a surge condition which could lead to complete compressor failure.

However, I had a meeting with an end user and a major compressor OEM and they were discussing the design of the anti surge valve to handle full recycle and hence the valve must handle maximum compressor flow i.e. stonewall flows to ensure the machine protection.

What I fail to understand is that how can the anti surge valve save the machine in a stonewall/choking scenario? Why should the anti surge valve open and recycle flow back to the compressor in a stonewall condition? Doesn't that make the problem even worse? My understanding is that a stonewall condition is not a real problem that is faced with centrifugal compressors and moreover I always that a flow controller and a discharge throttling valve (I.e. anti choke valve) can be utilized to increase the back pressure on the compressor discharge so that the compressor can reduce the flow accordingly which will lead to a higher discharge pressure which ultimately pushes the operation point to the left, away from the stonewall line. What do you guys think about this topic? Please note that this a GT driven centrifugal compressor.

Also, what are the real consequences of oversizing the anti surge valve especially that the end user is requesting a 30% extra CV to be considered for the anti surge valve on top of the full recycle condition?

[breizh]

Hi,

I believe the document attached could support your work and understanding about anti surge  (sizing of the valve and set up )

 

Good luck

Breizh

[Bodhisatya]

Hello All,


However, I had a meeting with an end user and a major compressor OEM and they were discussing the design of the anti surge valve to handle full recycle and hence the valve must handle maximum compressor flow i.e. stonewall flows to ensure the machine protection.

What I fail to understand is that how can the anti surge valve save the machine in a stonewall/choking scenario? 

Also, what are the real consequences of oversizing the anti surge valve especially that the end user is requesting a 30% extra CV to be considered for the anti surge valve on top of the full recycle condition?

 

(a) Are you sure ,that is what the OEM meant ,AntiSurge and Stonewall are two opposite extreme ends of operation for a dynamic machine.

( Anti Stonewall Valves are generally located at Compressor Discharge ,normally 100 % open ,starts throttling when the operating point starts moving far right.Suggested reading would be Compressor Control Corporations User Manual.

© Practice is to select a Cv ( Valve with Linear Characteristics ,and possibly Noise reduction trim) that is 2 times of Normal Calculated Cv or 1.5 times of Rated Calculated Cv ,easily caters the 30 % flow rate as wanted by your customer.

 

Regards

Bodhisatya.

[rha257]

 

Hello All,


However, I had a meeting with an end user and a major compressor OEM and they were discussing the design of the anti surge valve to handle full recycle and hence the valve must handle maximum compressor flow i.e. stonewall flows to ensure the machine protection.

What I fail to understand is that how can the anti surge valve save the machine in a stonewall/choking scenario? 

Also, what are the real consequences of oversizing the anti surge valve especially that the end user is requesting a 30% extra CV to be considered for the anti surge valve on top of the full recycle condition?

 

(a) Are you sure ,that is what the OEM meant ,AntiSurge and Stonewall are two opposite extreme ends of operation for a dynamic machine.

( Anti Stonewall Valves are generally located at Compressor Discharge ,normally 100 % open ,starts throttling when the operating point starts moving far right.Suggested reading would be Compressor Control Corporations User Manual.

© Practice is to select a Cv ( Valve with Linear Characteristics ,and possibly Noise reduction trim) that is 2 times of Normal Calculated Cv or 1.5 times of Rated Calculated Cv ,easily caters the 30 % flow rate as wanted by your customer.

 

Regards

Bodhisatya.

 

Thank you for the response. 

 

What is the definition of the normal calculated Cv? At which point on the compressor performance map is considered to calculate this Cv value? Is it the design point at 100% speed?

 

Also, to clarify, the OEM was stating that an anti-choke valve is not feasible and is not always a good idea. Alternatively, they want to use the anti-surge valve during a stonewall condition so that the higher compressor discharge pressure (e.g. 3 bar) goes back to the suction and mixes with the lower compressor inlet pressure (e.g. 1 Bar) and have an intermediate pressure at the suction (e.g. 1.75 Bar) and this should re-stabilize the compressor operating point and push back to the left of the curve. What do you think about this explanation?

Edited by rha257, 26 January 2020 - 09:53 AM.