COP - Oil purger vessel

COP - Oil purger vessel

What is a CPO:
CPO stands for Cool Products Oil recovery vessel.

The CPO is an oil recovery vessel for the high-pressure side of an ammonia refrigeration system. The vessel works in the way it separates oil droplets out of liquid ammonia. The vessel contains a large pool of liquid ammonia with a very low velocity where the oil droplets separate out of the ammonia liquid, settles in the bottom and is lead to a vertical drop leg from where it can be returned to the compressors or drained from the system.

How do we get an offer for a CPO?:
We will send you an offer for a CPO vessel when we have the necessary information and a contact person information.

To give us the correct information please download the questionary form from the following link here and fill in the information asked for.

Save the file and send a copy to:
Lars Vetter
Ph: direct +49 175 203 7736
Mail: LV@atlas-s.de

Special advantages of the CPO:
A big advantage with this system is the oil has not been on the low pressure side of the system where all the contaminants like water, decomposed oil, and nitro compounds (amides) are concentrated. It means the oil returned to the compressors from this point will be just as good and same quality as oil returned from the oil separators on the compressors.

Disadvantages of the CPO system:
The clear disadvantages with the CPO are the large quantity of ammonia liquid which is needed on the high-pressure side of the system and the price of the quite large high-pressure vessel needed for this.

Making two vessels in one solution:
Introducing an extra big vessel on an ammonia refrigeration system is quite expensive. Bothe the vessel and the necessary extra piping and valves will increase the cost of the system. But the increase on overall cost will often be much lower if the CPO function can be built into vessels which is needed anyway on the system. This will of course increase the cost and the size of the vessel needed but normally not nearly as much as if the CPO system is built into a system in a separate vessel. Making such a combined vessel solutions can significantly reduce the extra cost of building an ammonia refrigeration system with the CPO oil recovery system included.

Examples of combined vessels can be:

  • High pressure receiver with build in CPO system
  • Priority vessel for liquid cooled oil coolers with build in CPO system
  • High pressure float valve pilot receiver with build in CPO system

How efficient is the CPO system?:
The CPO system works on the principle that the oil will not dissolve in the ammonia liquid but stay as small droplet in the ammonia liquid. The droplets have a higher density than the liquid ammonia and can be separated by gravity separation more or less the same way as liquid and gas in a liquid separator. The separation calculations related to oil droplets separation in ammonia liquid are more complex than liquid separation in gas and demands special knowledge and some empirical values based on tests and experience.

The separation of droplets can be done very efficient and will leave nearly no oil droplets at all in the liquid ammonia going to the Low-pressure side of the system. The oil leaving the compressors as oil vapor because of the high temperatures in the discharge gas will be condensed into oil droplets in the condenser and by this also separated from the liquid in the CPO vessel.

However, the oil dissolved in the high-pressure ammonia liquid cannot be separated. How much or we could say how little oil there will be dissolved in the high-pressure liquid will depend on the base oil type used on the system and the state of decomposition of the oil.

  • Oils based on synthetic PAO oils will dissolve very little into the ammonia liquid.
  • Oils based on mineral oils will dissolve very little into the ammonia liquid.
  • Oils based on synthetic Alkyne Benzene oils will dissolve in a higher degree into the ammonia liquid, but exactly how much is unknown.

Broken down oil components and nitro compounds will dissolve much more in the liquid ammonia and might pass through the CPO vessel dissolved in the ammonia liquid. But the oil will only decompose in the presence of oxygen (air) and water. So if the air and water is efficiently kept out of the ammonia refrigeration system for example by using the CPA air purgers and the CPW water separation units oil decomposing is avoided and oil decomposition products will not be present.

Properties​
Questions?

If you are interested in this product or have any questions, please contact us.

Get an offer for a CPO

To give us the correct information please download the questionary form from the following link here and fill in the information asked for.

Save the file and send a copy to:
Lars Vetter
Ph: direct +49 175 203 7736
Mail: LV@atlas-s.de

Application drawings of CPO