12 replies to this topic

[fallah]

Dear All,
Is it considered the Antisurge Valve of compressors in horizontal run? If so,why?
Regards

[Majid-Process]

Hi
It should be installed in horizontal run and the line slope down stream of anti surge valve should be towards KO drum which anti surge is connected to. No pocket is allowed in piping and if reducer is required it should be eccentric type.

Cheers

[fallah]

It should be installed in horizontal run

Why?

[djack77494]

fallah,
I don't think it much matters whether the takeoff for an antisurge/recycle line is located in a horizontal or a vertical section of the piping. The valve should be as close to the compressor outlet as practical and pockets must be avoided (as previously noted). Practical piping considerations, such as valve accessibility often suggest a location. Also, I have seen installations where the valve outlet went directly to the compressor inlet line. Here the configuration is very important. Remembering that there may be lengthy periods of time where there is no flow in the antisurge line, you must avoid the possibility of condensate forming and being sent to the compressor suction. If you'd like to discuss this further, please confirm my assumption of a centrifugal compressor.
Doug

[fallah]

Dear Doug
Your assumption regarding centrifugal compressor is right.Do you think it does'nt matter the antisurge valve would be installed in horizontal or vertical run?
Regards

[JoeWong]

Good engineering practice is to install anti-surge control valve in horizontal to avoid liquid accumulation which possibly lead to issue like corrosion, liquid slug, etc.

[ashetty]

It is normally good practice to install the antisurge valve in horizontal run.The valve accessibility is also very important.Since the ASV is a very critical component in many applications it is neccesary to periodically check in the feild whether the actual % opening is the same as shown in the control room.Also valve stroking is regularly done for ASVs in gas processing facilities to check valve response to a step change in instrument signal from thr DCS or SCADA,for checking the response of the valve.All this dictates that the valve be in horizontal run and be accessible easily for operators.Of course as pointed out earlier liquid-hold up in pockets and corrosion are also important issues.

[djack77494]

I don't mean to hijack this thread, but my most recent compressor project had the first stage ASV in a short pipe segment coming off vertically from the compressor outlet piping (which was in an elbow just past the vertical compressor outlet). It's been a while since that job, but I remember we had a very sharp compressor expert reviewing all that was done, and he was OK with this solution. I will say that the pipe segments were very short and that we were concerned about keeping condensate out of the compressor suction, but we thought the ultimate solution was acceptable. Could anyone explain why they disagree with this if they, in fact, do disagree? Thanks.

[ashetty]

I don't mean to hijack this thread, but my most recent compressor project had the first stage ASV in a short pipe segment coming off vertically from the compressor outlet piping (which was in an elbow just past the vertical compressor outlet). It's been a while since that job, but I remember we had a very sharp compressor expert reviewing all that was done, and he was OK with this solution. I will say that the pipe segments were very short and that we were concerned about keeping condensate out of the compressor suction, but we thought the ultimate solution was acceptable. Could anyone explain why they disagree with this if they, in fact, do disagree? Thanks.

Hello DJack,

Quite honestly, my answer regarding the ASV placed in horizontal run is only based on what i have seen and come across.If the compressor expert has other opinions he might have a basis for it.Liquid hold up really shouldnt be an issue for vertical piping, because the ASV is normally located upstream of the compressor aftercooler,and as the tempratures are quite high here i`m not sure about liquid formation even at higher pressures.So slugging and corrosion might not be an issue.Its just that ive never seen ASVs installed vertically.

[fallah]

the ASV is normally located upstream of the compressor aftercooler

Dear Ashetty,
I have seen many cases the ASV located downstream of the compressor aftercooler named :"Cold Recycle Valve Arrangement".

[ashetty]

the ASV is normally located upstream of the compressor aftercooler

Dear Ashetty,
I have seen many cases the ASV located downstream of the compressor aftercooler named :"Cold Recycle Valve Arrangement".

Dear Fallah,

I agree..which is why i have stated "normally" not "always".Hot recycle will increase inlet gas temperature and reduce compressor efficiency.Anyway for expensive machines hot recycle maybe a better idea.It depends on your application.Also check if aftertercooler outlet temperature has been calculated at above the dew point temperature of the gas at the corrosponding pressure (For all operating cases). Anyway depending on your case..ie. ASV upstream or downstream of aftercooler you could deciede if condensation/slug/corrosion is an issue.

[JoeWong]

There are

i) Cold anti-surge / capacity recycle which normally downstream of compressor discharge cooler recycle back to Compressor suction scrubber.
ii) Hot anti-surge directly downstream of compressor discharge back to compressor suction.

Requirement of (i) and/or (ii) is subject to anti-surge valve charateristic, system volume, settle-out condition, system response etc. This is always determine upon Compressor Dynamic Simulation.

I am not surprise with the "Compressor Expert" has no issue with installation of anti-surge valve in vertical orientation.

i) If the fluid is lean or dry enough and has not possibility of condensation when recycle valve is passing or opened
ii) Wet fluid from upstream of suction scrubber may diffuse and condensed on the recycle line. However, probability and potential accumulation is low.
iii) The possible accumulated liquid volume is low even though it is happen.
iv) Fluid is not corrosive
v) Fluid will not freeze or form hydrate when it is cooled to minimum ambient
vi) Fluid is not possible crystallize, solidify, self-polymerize (when it is accumulated
vii) agreement from Anti-surge control valve (ASCV) incharge

A typical example which would demand for no liquid accumulation and self-draining :

Booster compressor from production separator or slugcatcher
i) Vapor is wet (with H2O)
ii) Vapor may contain free water
iii) Free water formed and accumulated will freeze
iv) In cool ambient below 20 degC, gas contain hydrate former i.e. methane may form hydrate
iv) Present of CO2 and H2S and wet. A very good condition for corrosion especially stagnant area. Not only metal loss due to corrosion, pitting and crevice corrosion may occur

This is good engineering practice to install ASCV in Horizontal run to minimise and avoid any unexpected condition.

[djack77494]

Thanks all for your inputs.
Doug