Cooling Standby Compressors

[Thealanator]

We are planning to add compressor capacity. Compressors will operate intermittently. There are lots of ideas related to cooling. One proposal says get two coolers-each cooler sized to handle the total compressor load (1 cooler for 4 compressors). Another proposal says turn off cooling water to a compressor when it is not running and use a VFD to ramp down pump speed. Another proposal (don't expect it to fly) says use one pump/cooler per compressor.

Presently we just leave the cooling pumps on 24/7. Tower fans/bypasses respond to temperature as required.

A concern seems to be developing about energy conservation. I am worried that attempts to save some energy will end up compromising reliability.

How do others deal with compressor cooling?

 

[JJPellin]

What type of compressor? What gas is being compressed?

Johnny Pellin

 

[BigInch]

Hummm. I could turn that problem into a nice raise on my paycheck. Not only is 24/7 probably unnecessary, these days it's irresponsible, both to the environment and your stockholders.

What's wrong with 4 separate coolers, no space? That will save you the most energy. When it comes to savings energy over the lifetime of the plant, the fewer you have running the better. The gas pipeline companies I worked for all had individual coolers for each compressor. Energy cost is every day for 20 to 40 years. Coolers are a one time hit.

Figure out how much money you can save for the next 20 years running only what you need and see how many separeate coolers that money will buy.



What would you be doing, if you knew that you could not fail?

 

[Thealanator]

Space is a problem, but it is interesting to hear about 1 cooler/compressor.

Compressors are recips. Gas is helium.

 

[zdas04]

For multi-stage compressors, inter-stage coolers kind of have to be on the skid. For modular set ups (e.g., a site has 14,000 hp of compression, but chooses to do it with 14 compressors each with 1,000 hp that they move from site to site like Lego blocks) all the coolers have to be on the skid. For engine-driven compressors, the jacket water and lube oil cooling need to be on the skid.

For an electric driven, single stage compressor, the only cooling load is the after-cooler (assuming a recip that relies on radiation from the sump to cool frame oil), so setting one after-cooler to serve four compressors probably makes good economic sense (I'd size it for two compressors running).

David

 

[rakuday]

Hi,

You have mentioned that you are planning to add capacity, does this mean you already have some compressors?. What is the type of cooling systems in those compressors? To start with, select a similar cooling arrangement of the existing system. This would help gain confidence in operating the added facility and avoid experimentation.

Secondly, it is always better to have separate coolers for each compressor. This would minimize the interdependence of the system and will be easy for maintenance also. By sizing the coolers for multiple compressors, you will be over designing and under-utilizing them (cooling system as a whole).

Please note that general rule of thumb is, only 20% of cost is incurred in the initial investment of the compressor and about 80% of the cost goes into operating them for the lifetime. So the selection of the compressor package is very critical. If the cost appears to be high, spend some time to evaluate the energy cost of operating the system for about 15-20 years and choose between the low investment – high operating cost and high investment – low operating cost.

Running the cooling pumps 24/7 (without using them) is equivalent to a crime . Imagine this; every minute the system runs unnecessarily, you are intentionally throwing your money in the drain.

Finally, I would prefer to have a system which provides me flexibility in usage and also saves energy in the long run, even though the initial investment is high.

Thanks