Outstanding points in control system in Tandem Compressors Arrangement

[e43u8]

Hi Everyone,

I want to know the outstanding points/loops in Tandem Commpressors Arrangement, say three compressors on the same shaft, such as recycle line antisurge system flow control system...and so on. Appreciated if someone would submit a briif on this request...

 

[rotw]

What do you mean ?

Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[e43u8]

My mean is clear...

I want to know the required control loops such as number of anti surge line, flow control loop, pressure and temperature control loops and so on...

Appreciated if you can submit a typical PID for tandem centrifugal compressors arrangement, say three compressors on the same shaft, showing mentioned required control/protection loops/systems...

 

[rotw]

What do you mean by 'three compressors on the same shaft' ??


Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[e43u8]

Have you heard about tandem compressors arrangement?

My case is three compressors, each one as a stage, on the same shaft with a gas turbine as driver...

 

[rotw]

Are you saying the three compressors are on same shaft which is driven by Gas turbine.
What do you mean by shaft?

Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[georgeverghese]

This forum doesnt provide full fledged engineering consultancy type deliverables, which is what you appear to be after. We can help with any specific queries and doubts you may have. For a full narrative and definitive control scheme, you should prepare a bid quality SOW doc which outlines the service of this compressor and any other info you think may influence this design for local engineering companies.

 

[e43u8]

@rotw
We are discussing about a type of compressors arrangement hence what do you mean when you are asking "What do you mean by shaft?"?

 

[rotw]

You gonna have to explain what is meant by "'three compressors on the same shaft' ?" if you want to get any meaningful help.
You need help - not me. Make a sketch if you want.

Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[e43u8]

@rotw
Please find attached a sketch of the tandem compressors arrangement but for two compressors...

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/raw/upload/v1573114755/tips/Tandem_Compressors_hbilqi.docx[/url]

 

[rotw]

Your drawing is still unclear, so we still have to go by guessing - probably your compressors are not on same shaft.
You are probably talking of three process sections each associated to a single shaft, and all shafts connected by way of couplings. Which means this would be three casings.
That is a different story that three process section on same shaft, which would typically mean all are embedded in a single compressor casing. In practice, I have not seen more than two sections on a single shaft, except in multiple injection/extraction configurations. These configurations are often found in petrochemicals, refinery, LNG applications (example: propylene/ethylene or ammonia refrigerant compressors).
If each process section has a dedicated shaft / casing, then this is more of basic case for anti-surge control.
Yet, there is no such thing as a standard arrangement. Often each process section is equipped with a dedicated anti-surge valve, but not always. In some applications, you may have three process sections / casings which share a single combined anti-surge loop.
I suggest you simply need to start understanding how to set up an anti-surge control system for a single process section. That is your basic building block. If you google it, you will find lot of information about the process flow schemes, instrumentation, optional arrangements, etc.. etc.

 

[e43u8]

Thanks rotw,

Actually i'm not exactly aware if three compressors are connected by way of coupling; and all info mentioned by client is limited to: three compressors are arranged in Tandem Configuration first two compressors are in a casing and the third one in another casing. These arranged compressors are intended to be applied in an associated gas gathring system in an oilfield area. I'll try to get more info about the compressors connections.
I'm well aware of control system of one compressor but want to know the control system for such mentioned arrangement.

 

[rotw]

"first two compressors are in a casing and the third one in another casing". So, you do not have all compressors on same shaft. You have two casings coupled by a flexible coupling. The flexible coupling is obviously there. We generally do not apply rigid couplings between single-shaft compressors.

There is no standard anti-surge valve configuration. If you are considering an anti-surge loop per each process section, you just have to study well/define the configuration for a single compressor section (e.g. location of cooler, location of flow meter, type of flow meter, measured process variables, etc.), because it is likely that you are just going to repeat / apply the same concept to each section. It is not rocket science, plenty information in google on that.

Life is not about waiting for the storm to pass. It's about learning dance in the rain.

 

[e43u8]

Thanks rotw,

I'm thinking to consider three anti surge loops for three compressors each one starting from tapping at downstream of each compressor's discharge cooler and terminated to upstream of same compressor suction drum. What's your opinion on these anti surge loops configurations?