Quote Originally Posted by AmmoniaMike View Post
Describing the entire system in one sitting will be very difficult but it is essentially three systems with one common high pressure side. The three systems are like this:
Spiral freezer system is run by one RWF II 399 Frick 600 hp compressor set at 12" Hg suction: Glycol and water chiller system is run with a RXF 58 Frick 134 hp compressor set at 24 psig suction: Plant cooling is run using a RXF 68 Frick 165 hp compressor and a RXF 50 Frick 123 hp compressor set at 39 psig.
The condenser for the complete system is a Frigid Coil/Imeco IDC 1200-2S evaporative condenser. Condensing pressure set by PLC based on relative humidity and temperature. I don't think I can go into the entire system at one go so I will break it down by system.
The freezer system's compressor is set up as follows:
suction pressure: 12" Hg
suction temp (typical) -13F
suction superheat (typical) 31F
discharge pressure: between 120 and 160 psig (depending on weather)
discharge temp (typical) 164F
Discharge superheat (typical) 89F
Oil pressure (typical) 114 psig
oil temp (typical) 113F
oil cooled by thermosyphon no pump
compressor capacity (typical) 65%-80% (average about 70%)
Compressor also hooked up to an economizer whose main duty is to cool liquid in a coil from the +25 recirculating vessel to -14F before going to -45F recirculating vessel. The liquid is pumped from the +25F recirculating vessel. The liquid in the economizer vessel is supplied from the HP receiver and the vapour is taken in by the 600 hp compressor. The suction line from the economizer is also supplied with a cross over 1 1/4" HA4AS, 1 1/2" FLGS set at 40 psig which goes to the suction of the +25F recirculating system (compressors for this side are set at suction of 39 psig).
The liquid cooled in the economizer then goes to the -45F recirculating vessel. From there it is pumped to the spiral freezer which has 4 of 62 ton capacity coils. The freezer is maintained at -35F. The coils are set to defrost individually in this order A, C, B and D. Time intervals from start up are set at 90, 120, 150 and 180 minutes respectively and 35 minutes between unit defrosts. The defrost cycle is set to 10 minutes pumpdown, 2 minutes soft HG and 15 minutes HG (at 70 psig for the hot gas) and 5 minutes drying. C and D are the bottom two coils and A and B are the top coils. The freezer is an Aerofreeze 185 ton unit set at 4:1 recirculating ratio at -40F ET. This is getting pretty long so I will leave the rest of the system for another day
As an aside the frost on the coil wasn't noticed by the operators because when freezing hot chicken from the oven the bare metal in the freezer tends to get frosted from all the steam comming off the chicken at the infeed of the freezer so it isn't readily noticable at that end. The real give away was the lack of frost on the suction valve on the roof that had no frost on it at all since the liquid valve was closed to that coil. Everyone was too busy looking at the valve assembly for coil B and no one looked at the other valve assemblies
The guys were too focused on the problem with temperatures rising when B went into defrost and all assumed the problem was with that coil.
It isn't clear for me how economiser hooked up. Does it have level control or it has TXV?
As far as I understand every coil in spiral freezer defrost every 2 hours. If it is true, you have clear over defrosting. You have 2 coils to freeze the product. One coil on defrost. Second coil(right after defrost) run for 30min to remove the heat of this coil defrost. Typically 90% of defrost heat goes to the freezer and you have to run this coil to remove this heat. Do you have any frost on the coil before defrosting? Probably, very little. That is why you didn't notice the poor operation of one coil.
What is the settings of your condenser? Minimum allowable head pressure, wet bulb approach...
By the way chicken should cooled before going to the spiral freezer, otherwise you waste a lot of energy. Do you have full production? Why compressor load just 70%? Do you have any storage room for the frozen chicken?