2021 RETA Breeze September-October

CHASING BTU ' s By Jeff Welch, P.E., Welch Engineering Corp.

Now that the economy is slowly crawling out of the doldrums, there is a chance that you may be called upon to re-start an ammonia refrigeration system that has been idle for a few years. What to look for and a suggested check list was the topic of a recent phone call from my good buddy Jake Farley. Here is a rundown of what we hashed out. Let’s start with the assumption the ammonia was removed upon shut down. ammonia charge or nitrogen. Most likely all of the safety relief valves are in need of their five year change out. So now would be a good time to purge the system from the low points, drain the oil pots, plug the relief valve connections, pull a vacuum and perform a pressure/leak test. Once the system is pronounced tight, install new relief valves. If that is the case, who knows what replaced the ammonia? Air, a trace

Most likely the condenser fan belts are in need of replacement and all bearings should be greased. The compressor shaft seals may have dried out and simply need a good run with fresh oil or a replacement. Fresh oil in the compressors will get rid of any contaminants. Dry run the control system to be sure the solenoid valves are functioning. Test the spray water pump and condenser fans. Test the evaporator fans. Make sure that the solenoid valves | were not manually opened for the prior de-commissioning and return them to automatic. At this point it should be safe to take on a new ammonia charge and slowly start the system section by section. If the system was open to atmosphere, there is a high probability there will be

some light surface rust on the inside of the system. Check and clean all of the strainers frequently until they are clean upon inspection. After operating for a while have the ammonia checked for water. This should have been removed in the evacuation process, but it is always good to check. Have an oil analysis done on the compressor(s) oil to ensure that it is free of contaminants. During the initial month of operation, be especially vigilant regarding bearing temperatures and noises. If corrosion occurred in the bearings while idle, their life upon restart will be brief.

Originally run in the 2014 September/October issue.

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