RamAir95TA
13-02-2013, 11:45 PM
Hi guys. Long time reader, first time poster.
I am an operating engineer for a produce freezing plant. We have a very large Frigoscandia blast tunnel freezer. The system is a bottom-feed recirculating system using large Evapco aluminum coils (10 total, stacks of 2 in 5 individual compartments). Temp is -40 F. Defrost is hybrid consisting of hot gas defrost (90psig) and water defrost (water is at 55 F). Total cycle is 22 minutes. Each pair of coils is defrosted independently of eachother throughout the day with the first coil defrosting 4 times per day, the second pair 3 times per day, third pair 2 times per day, and the fourth and fifth coils once per day, PLUS a complete end-of-shift defrost for ALL coils simultaneously.
The plant manager wants to heat our washdown water supply for sanitation purposes, however the vessel that contains this water is also used for freezer water defrost. He would like to heat the water to 120 F. Safeties on the recirculator are set at 150psig.
How will aluminum coils at -40 F fair being sprayed for 7-8 minutes of 120 F water? We have had 3 coils crack over 10 years due to rapid pull-downs in the beginning of the shift so this is certainly a concern.
How about coil steaming and/or excess snow build-up? And what about LPR pressure on the final defrost? Really don't need safeties popping and the National Guard showing up...
Thoughts? Thanks! :)
-Joe
I am an operating engineer for a produce freezing plant. We have a very large Frigoscandia blast tunnel freezer. The system is a bottom-feed recirculating system using large Evapco aluminum coils (10 total, stacks of 2 in 5 individual compartments). Temp is -40 F. Defrost is hybrid consisting of hot gas defrost (90psig) and water defrost (water is at 55 F). Total cycle is 22 minutes. Each pair of coils is defrosted independently of eachother throughout the day with the first coil defrosting 4 times per day, the second pair 3 times per day, third pair 2 times per day, and the fourth and fifth coils once per day, PLUS a complete end-of-shift defrost for ALL coils simultaneously.
The plant manager wants to heat our washdown water supply for sanitation purposes, however the vessel that contains this water is also used for freezer water defrost. He would like to heat the water to 120 F. Safeties on the recirculator are set at 150psig.
How will aluminum coils at -40 F fair being sprayed for 7-8 minutes of 120 F water? We have had 3 coils crack over 10 years due to rapid pull-downs in the beginning of the shift so this is certainly a concern.
How about coil steaming and/or excess snow build-up? And what about LPR pressure on the final defrost? Really don't need safeties popping and the National Guard showing up...
Thoughts? Thanks! :)
-Joe