About the authorWinter Operation - Ammonia Refrigeration
By now many of the States in the upper midwest have experienced very cold weather. As some have found, winter time presents some occasional challenges for starting or operating an ammonia refrigeration system.
When this occurs many report an issue of not being able to keep the compressor(s) running. Another common complaint is the discharge pressure is too low. Both are related. When the ambient temperature decreases even an evaporative condenser operating dry can be troublesome. With the low temperatures and a lot of exposed pipes in the condenser coil the refrigerant condenses very quickly. This is further aggrevated by the start-up condition where you are only starting one compressor, because the suction pressure will rapidly decrease if you start too many.
This entire situation is a result of low liquid feed pressures to the expansion devices. If the liquid feed pressure is too low, the expansion device has very little flow capacity. Consequently, with little to no liquid flow through the expansion device the evaporator does not have sufficient liquid to boil. Hence, lower than normal suction pressures to keep the compressor operating.
This situation is a bit like the old addage: Which came first? The chicken or the egg?
If you cannot deliver a sufficient quantity of liquid to the evaporator(s) at an adequate pressure it is difficult to build suction pressure to keep the compressors operating.
This past week one of our clients experienced this in two different facilities. One system experienced start-up issues and one had no problems with the cold weather. The system that did not have any issues with the cold weather was recently modified with methods developed by us.
If you are experiencing similar conditions and want to implement a reliable soltuion, please contact us.
Tags: ambient temperatures, condensing temperature, discharge pressure, operating issues
