1.
Main Components of Refrigeration plants
▪ Compressor
➢ Reciprocating single or two stage compressor is commonly used for compressing and
supplying the refrigerant to the system.
▪ Condenser
➢ to cool down the refrigerant in the system
➢ for liquefied gas
▪ Drier
➢ consists of silica gel to remove any moisture from the refrigerant
▪ Solenoids
➢ to control cold room temperature
➢ Master solenoid is provided in the main line
➢ Other solenoid is present in all individual cargo hold or rooms.
▪ Expansion valve
➢ to control amount of refrigerant flow to the evaporator
▪ Evaporator unit
➢ act as a heat exchanger to cool down the hold or room area
▪ Thermostatic Expansion Valve: TEV:
▪ Main Functions:
➢ control amount of refrigerant flow to the evaporator
➢ maintains a constant super heat of refrigerant at the
evaporator outlet about 6.6℃.
➢ Prevention of Liquid flow into Compressor.
▪ Why Equalizing Connection is fitted?
➢ In some plant having large Evaporator or Multi-circuit
Evaporator,
➢ excessive pressure drop across Evaporator occurs increase the Superheat.
➢ To counteract this an Equalizing Connection must be provided at TEV
➢ A direct connection between below of Bellow and suction piping of Compressor,
➢ This is called Equalizing Line.
▪ Safety devices on Refrigeration Plant:
➢ LP cut-out switch/ LP cut-in switch
➢ HP cut-out switch
➢ LO LP cut-out:
➢ Liquid shock valve on Compressor cylinder head.
➢ Bursting disc on cylinder head
➢ Bursting disc on Condenser or Relief valve on
Condenser.
➢ Condenser cooling water LP cut-out.
➢ Master solenoid valve:
➢ diff pressure
▪ Refer plant survey:
➢ General examination of machinery and testing under working condition.
➢ The log examined, to ascertain successful operation during voyages.
➢ Compressor and prime mover to be open-up and examined.
ဘံု
▪ Air in the system Cold room tem တက္မယ္
▪ Indication: compressor long time run
➢ Abnormal and jumping of Compressor discharge pressure gauge reading
➢ Sight glass shows small air bubble
➢ Compressor will over heat
➢ Increase Cold room temperature
➢ Compressor will be running longer than normal.
▪ Remedy: လေဝင်ရင်ဘာေုပ်မေဲ
➢ Pumping down the plant
➢ Then purge air at the top of Condenser
▪ How to carried out Pumping down
➢ Close liquid stop valve at Condenser outlet.
➢ Pumping down the entire charge into Condenser,
➢ Until suction pressure is just above zero, and then stop Compressor.
➢ Shut Compressor discharge valve
➢ Cool down the Condenser content, by running cooling water for some period.
➢ Then purge air at the top of Condenser, through purging valve until refrigerant gas appears
at the valve.
Causes လေဝင်ရလ ာအလ ာင််းရင််း
➢ Charging တုန်းက ကကောင်း ကကောင်း purging မလုပလု ို့
➢ Lo sump ဖြညတဲ.အခါ ကလပါသော်းလု ို့
➢ during O/H
➢ Pipe လင
ု ်းဖပြုဖပင ရင
➢ Dehydrator မော purge 0r silica jil ဖြြုတလဲ
➢ After repair job ကလဝငတယ
▪ Moisture in the system:
▪ Indication:
Flooding back ျဖစ္ ရင္ ဘယ္ လို သ
➢ Choke at Expansion Valve.
Increase suction pressure
➢ Compressor tends to stop by H.P. cut-out.
Suction မွာ liquid ရက
ို သ
္ ံျကွာားရမယ္
➢ Check Dehydrator Indicator
Oil in the sys မွာ compressor sweating ျဖစ္
▪ Remedy:
Running cool ျဖစ္
➢ By renewing Drying agents.
Suction pipe မွာေရခဲ
➢ prevent air in the System
▪ Oil in the system
▪ Indication:
➢ Compressor will be running longer than normal.
➢ Very difficult to cool-down the room temperature due to excessive oil in piping system
➢ Causing flooding back
➢ Low level in sight glass
➢ Decrease compressor pressure
➢ Incorrect Condenser and Evaporator temperature differentials
▪ Remedy:
➢ Pump down the system charges into reservoir
➢ Totally shutdown the whole System.
➢ Then blow out the collected oils inside piping and evaporator.
➢ if necessary, renew Compressor piston rings or oil separator, and replenishment of oil
▪ causes; Compound oil ်းု တယ် Blow out ဘာနဲ. ေုပ်မေဲ
➢ Ringမလ ာင််းေု ို့ လေ
➢ Separator မလ ာင််း ေု ို့ Nitrogen
➢ Sum oil level high ဖြစ် ေု ို့ လ ာ် zone
➢ Suction pressure ထ ် Crank case press တအာ်းဖမင်ေ
ို့ ာမယ် system ထဲဆပ
ီ ါမယ်
▪ Overcharge. ျမင့္ ေအား ခဲ ဘက္ overcharge
▪ Indication:
➢ Increase suction and discharge pressure
➢ Cause compressor running cool
➢ Frost at suction line
➢ Causing flooding back
▪ Remedy
➢ Prepare reception facility
➢ Then transfer until normal discharge pressure
➢ Pump down system charges into reservoir and purge out excessive refrigerant from vent
valve
▪ Undercharge: က် တက္ ဘူစီ ျကွာ လမ္.မည္
▪ Indication:
➢ Decrease discharge pressure
➢ Increase cold room temperature
➢ Large bubble in sight glass
➢ Increase in running period
➢ Hot Compressor/ Condenser discharge pipe.
▪ Remedy:
➢ Carried out recharging until normal level
➢ Test leak
➢ After rectification of leak points, recharging if necessary.
▪ Short cycling: ၃ ခါ ခ်ပ္ light load ေလ်ွာ.ခ်င္လို့
➢ Choke of dehydrator, TEV filter and TEV Suction cut in 4 bar cut out 2 bar
➢ Light load
Dif 2 range 4
➢ High Leak points in the system.
▪ Causes: Discharge 15
➢ Abnormal operation of TEV.
➢ Overcharge of the system.
➢ Moisture in the system owing to dirty Dryer.
▪ What is short cycling:
➢ Causing start and stop frequently
➢ Malfunction in L.P cut-in/ cut-out.
➢ Excessive icing up at Compressor Suction
▪ (Drain Period) 168. Defrost Method
➢ System stop
➢ Warm / Hot water
➢ Electric Heater "ON"
➢ Hot gas by pass
▪ Defrost Sequence
➢ Defrost sequence is done by Defrost Timer.
➢ This timer consist of 3-set dial
➢ Top dial (Defrost cycle setting , Eg → 12 hr – 2 time per day)
➢ Second dial (Defrost heater on period setting, Eg → 30 Minutes)
➢ Base dial (Drain setting)
▪ When defrost cycle setting reach
➢ system auto stop
➢ Liquid Solenoid valve stop
➢ Evaporators fan stop
➢ Defrost Heater ON as per time setting period.
➢ Then drain period
➢ After defrosting take place restarting the plant in normal operation.
169. Refer Suction Suction valve ? Discharge valve
▪ Deflective Suction Valve
➢ High Suction Pressure
➢ Low Discharge Pressure
➢ Continuous Running of Compressor
➢ Noisy of operation
➢ Insufficient cooling effect.
▪ Deflective Discharge Valve
➢ High Suction Pressure
➢ Low Discharge Pressure
➢ Continuous Running of Compressor
➢ Noisy of operation
➢ Insufficient cooling effect.
➢ High suction pressure when compressor stop
➢ Warm Cylinder Head
➢ High Discharge Temperature
▪ 170. Refer flooding back
➢ Liquid Refrigerant back to compressor suction side , is call flooding back.
▪ Causes
➢ Over charging
➢ TEV malfunction
➢ Solenoid valve malfunction.
➢ Excessive oil in the system.
➢ Excessive frost on evaporator (1/4 thickness)
▪ Prevent
➢ Liquid short valve
➢ Regular maintenance Suction & Discharge Valves.
➢ Solenoid Valve
➢ Correct amount Refrigerant charging.
➢ Correct function TEV
➢ Avoid excesses Lub of crank case.
➢ Oil separator
➢ Dryer regular maintenance
➢ Defrost timer malfunction.
➢ Master solenoid valve malfunction.(compressor outlet)
➢ Regular malfunction.
▪ Reefer Gas Charging and liquid Charging
suction valve နဲ. Compressor ျက ား
▪ Gas Charging
➢ weight bottle
➢ Gas Charging connection is between, & suction valve and Compressor
➢ Connect the bottle and Charging valve with connection pipe
➢ Purge out air from connection pipe and tighten the screw cup
➢ Fully open the bottle valve but still close Charging v/v
➢ Plant in operation
➢ Close the condenser out let valve
➢ check suction pressure and slowing open Charging valve
➢ Check level in condenser Sight glass
➢ When required level reach, close the charging valve
➢ And then pump down the system
➢ After that close the compressor discharge
➢ Cooling water keeps running for some time
➢ Purging air from purging valve at condenser
▪ Liquid charging
Condenser outletနဲ. Dehydrator ာ်း
➢ Firstly, weight the gas bottle
➢ Connect the bottle and charging valve with connection pipe
➢ Purge out air from connection pipe and tighten the screw cup
➢ Purge out air from connection pipe and tighten the screw cup
➢ Compressor in operation
➢ Close condenser outlet valve
➢ check suction pressure open the & suction valve slowly
➢ Check level in condenser Sight glass
➢ When required level reach, close the charging valve
➢ And then pump down the system
➢ After that close the compressor discharge
➢ Cooling water keeps running for some time
➢ Purging air from purging valve at condenser
➢ Calculate the amount of charged refrigent and entire the engine room log book and ODS record
book
▪ properties of a Marine Refrigerant? HIGH ၂ NON ၅ Low Low လိုက္ တည္ ျမဲ လြယ္ကူ ေစ ားေပၚ ယူ
➢ High Critical Temp
➢ High latent heat of vaporization
➢ Non-Corrosive (system loving)
➢ Non-Solvent (to oil and impurities)
➢ Non-Flammable (for obvious reasons).
➢ Non-Explosive (Obviously).
➢ Non-Toxic
➢ Low Boiling Point
➢ Low condensing pressure
➢ Stable
➢ Easy Leak Detection (by odor or color).
➢ Cheap and Easily available.
➢ Environment Friendly.
▪ Refrigerant Compressor Oil
➢ Refrigerant Compressor Oil is a highly refined naphthenic mineral oil
➢ primarily for use in reciprocating and rotary screw compressors in refrigeration systems
using ammonia, carbon dioxide, or non-HFC refrigerants.
▪ features & Benefits
• Excellent low-temperature properties
• Wax-free
• Good oxidation stability
• Low carbon-forming tendency
• Good lubricity
• Light color
▪ Function
▪ HP
• It Fitted at discharge side of compressor
• It will stop compressor if excessive pressure in the system
• By this way prevent the system damage
• high pressure cut out is need manually re-set
▪ LP
• It Fitted at suction side of compressor
• LP cut out is controlled automatically
• Such as when the suction pressure drops stops the compressor and
• when the suction pressure rises again starts the compressor.
• To prevent vacuum in the system
▪ High pressure (HP) cut out and low pressure (LP) cut out in refrigeration system?
▪ HP cut out
• Occurs due to dirty or chocked condenser tubes.
• malfunction of consider cooler valve operation.
• low cooling water pressure
• Also, can cause. cooling water failure
• Due to liquid flooding back
▪ LP cut out
• Operate the solenoid valve is closed when the cool room temperature reaches its desired
temperature (setting temperature)
• Can cause when expansion valve is chocked.
• Under charge
