Anti Surge Control Valves - Which Style is Best?

[Hawkeye86]

I am relative new to the industry and I am trying to get a better understanding of Anti-Surge Control Valve applications, specifically for natural gas compressor stations.

I am trying to get a better understanding of the benefits of utilizing different valve styles in this application (globe vs. ball vs. axial) Is one style really better than the other and why? They all same to have the capability to meet closing and noise requirements with the correct actuation, instrumentation and internal trim, but why one style versus the other?

 

[pmover]

definitely not a ball valve . . . unless you meant a v-ball. ball valves are not designed for throttling or process control purposes - mainly On/Off control.

globe valves are acceptable . . . then again, it depends upon process operating parameters (i.e. flow and dP requirements). the mfg compressor curves are what is needed to determine ASV. Fisher, Valtek, Masonelian, etc.are a reputable mfg's of ASVs with various trims available to meet the requirements.

the more important criteria are actuator, flow measurement device (location too!), and valve response times.

good luck!
-pmover

 

[JLSeagull]

The valve selection depends upon the process conditions and other situations with noise high on the list of issues. Some that I have bought within the last decade or so range from standard Emerson cage valves, Neles severe service ball control valve with aerodynamic noise attenuation and CCI drag valves - priced in the same order.

 

[Hawkeye86]

Thanks for your response.

I completely understand that any type of control valve selection is based on application and process conditions. However when selecting between Emerson, Neles and CCI what are the determining factors? With each valve style there are unique features and benefits. I would think the following for this particular application:

Globe (such as CCI)
-Generally Higher Noise Attenuation (when compared to other valve styles)
-Linear motion provides short strokes (so faster closing time????)

Rotary Ball (such as Neles)
-High turn down so the ball style valve is able to maintain control during all operating conditions (max flow during surge or min flow start up)
-Higher capacity size for size compared to globe valves, reducing the compressor stations footprint

I'm not too sure when axial style fall into the mix.

I guess my question is, besides the process conditions what tips the scale on what valve style to use? Is it always noise? (If a compressor is already operating at 105 dBa, how important is an ASV's noise attenuation, when it is only in control during a surge) Does the compressor style (centrifugal or axial) influence the valve style decision?

 

[BigInch]

Sound is additive.

I think control during surge would be more important.

I doubt that the difference in valve style or size will affect the size of the compressor station's footprint.

 

[JLSeagull]

Rhetorically, it makes no sense to treat noise for a control valve at 93 dB with a machine operating at 103 dB. Regardless our client specifications usually ignore these realities. We like to provide valves with noise levels below 85 dBA. We can treat up to 9 dB or so excess noise with insulation etc.

Both the recent CCI and Metso Neles ball valve applications were applied to existing units with very high actual noise in operation (not noise prediction). The CCI valve was used because the existing valve was breaking pipe supports. pipe, etc. More complex treatment is required as the noise approaches 100 dB. Above about 108 dB the noise may cause mechanical damage. Above about 114 dB the damage is severe. These are throw-down levels. I don't have any scientific data that shows 107 to be OK and 108 to be bad. However the reality is that data far in excess of 100 dB breaks stuff - an unpleasant thing to happen in an ethylene unit.

 

[BigInch]

There are often cases where machines are inside enclosures and valves are outside.

 

[bcd]

The metal seated ball valve has an advantage when cost and weight are primary considerations. Greater Cv of ball valve means it can be smaller to obtain same flow. Drawback is speed of response and controllability. Longer actautor stroke to obtain 90 degree rotation increases deadband. The ball constantly rubbing against the seats causes stiction which makes small changes in ball movement more difficult. Stiction.

Globe valve is just the opposite. Fast response. Fine, accurate control, but bigger, heavier, and more expensive.