8 Most Common Problems Found in Ship’s Refrigeration System

One of the few machinery systems which need to run continuously on ships is its refrigeration plant. As a lifeline for all perishable food items and temperature-sensitive cargo, refrigeration plant is one of the most important systems on ships which requires utmost attention of engineers at all times.

However, just like all other machinery on ships, the refrigeration system can also get into some trouble from time-to-time. Some of these problems are common but require immediate attention. Mentioned below are eight most frequently seen problems in the ship’s refrigeration plant:

Reefer Plant on Ship

1. Compressor Starts But Stops immediately

When the compressor in the reefer circuit starts and suddenly stops, it can be because of the following reasons:

Reasons Solutions
Low pressure cut out gets activated Ensure that all the suction line valves are in open condition, the refrigeration is properly charged and the low pressure cut out is not defective
Defective oil pressure cut out Check for the proper functioning of oil pressure cutout and replace the defective cutout
Defrosting timer is getting activated frequently If the defrost timer is getting activated frequently, leading to a cutout of the compressor, check and repair defrost timer
The lube oil level is below the required level This can be because of leakage of lube oil from seal or carryover of oil. Rectify the leakage and refill the oil level
Foaming of oil leading to the reduced oil pressure Ensure no foaming takes place, renew the oil if required
Motor overload cutouts are activating Ensure that electrical motor trips are working properly

2. Compressor Start and Stops Frequently

If while maintaining the correct temperature of the ship’s provision room or reefer cargo, the reefer compressor is frequently cutting-in and out, then such problem needs to be sorted out immediately. The most normal causes for such operation are:

Reasons Solutions
Wrong Setting of Cutouts: It may be because the high pressure (HP) cutout is set too high or LP cutout is set too low Check and change the setting to advisable limit
Differential Setting Span is Small: The low pressure (LP) cut out is provided with starting and stopping pressure setting. If the setting span is too small, it will lead to frequent cut-in and cut-out of the compressor Change the setting and increase the span between starting and stopping compressor pressures.
Defective Valves: If the compressor discharge valve is leaky or the line solenoid valve is not closing properly, this will lead to variation in sensor pressure and result in frequent cut-in and cut-out of the compressor. Replace all the defective valves
Clogged Suction Filters: Compressor is provided with a filter in the suction line. If that is clogged, it will lead to frequent LP cut out Clean the filter

 

3. The compressor is Running Continuously

The function of the compressor in a refrigeration system is to act as a pump to circulate the refrigerant in the cooling circuit. It can happen that to maintain the cooling temperature in the rooms, the compressor is running continuously. If this happens following can be the causes for the same:

Reasons Solutions
Refrigerant not sufficient for cooling evaporator Ensure thermostatic expansion valve is working properly and clean the filters inside TEV
Thermostat low-pressure cut-out not activated at low temperature/ pressure Correctly set the LP cut-out to correct setting
Refrigerant charge is low in the circuit Check for leakage of refrigerant and charge with required refrigerant

 

4. Unusual Sound from Compressor

One of the most common problems in any machinery is abnormal sound coming from some of its parts. This may be due to trouble with mechanical components inside the compressor or due to the reasons stated below:

Reasons Solutions
The capacity control setting is too high, leading to knocking sound during starting Reduce the capacity control setting
The oil pressure is low Ensure that the oil level is maintained and no foaming of oil is developed. Replenish or refill the lube oil if required
Incorrect alignment of compressor and motor Check the alignment and set motor and compressor in one line
Loose foundation Ensure that the compressor foundation is secured and all foundation bolts are checked for tightness
Loosening of the driving belt Ensure to check the elasticity of the belt and renew if the belt is slack

 

5. High Compressor Discharge Temperature

It may happen that all the provision rooms or cargo holds are maintained at the correct temperature, but in doing so the discharge temperature of the compressor is going above the limit. This problem may arise due to the following reasons:

Reasons Solutions
Excessive suction temperature due to less refrigerant in the circuit Recharge the circuit to maintain refrigerant quantity in the circuit. Ensure TEV is set properly and supplying enough to the evaporator, else degree of superheating will result in an increase of suction and discharge temperatures of the compressor
The leak in the discharge valve leads to the generation of heat Renew the leaky valve
Leak in the safety valve Renew safety valve
Open bypass between suction and discharge Control the bypass to avoid this


6.  Evaporator Coil Icing
Another common problem in reefer system is the icing of the evaporation coils which may happen due to:

Reasons Solutions
Too low-temperature setting Increase the coil temperature by adjusting TEV or it’s the sensor
The coil capacity is less Install large capacity evaporator coils
Defrost is not operational Check if the defrost system is functioning at regular intervals

 

7. Reduced Cooling Capacity

If the cooling capacity of the plant has reduced and it is not being able to maintain the provision room or cargo hold temperature, the following may be the causes:

Reasons Solutions
Inadequate refrigeration Charge refrigerant in the circuit
Insufficient or damaged insulation in the room Check and renew the insulation
Room or hold is over packed Ensure that the room is not filled above its capacity
Malfunctioning solenoid or TEV Check the functioning of these valves and renew if not functioning properly
Poor thermostat location that senses cold temperatures Place the sensor of the TEV in proper location i.e discharge of the evaporator
Room door is kept open Ensure to close the door while exiting the provision room

 

8. Reducing oil level in the compressor

If the oil level in the compressor crankcase of the refrigeration system is reducing within short intervals, this indicates leakage or increase in consumption of lube oil due to the following reasons:

Reasons Solutions
Nozzle or filter clogged Ensure that the nozzle in oil return line or filter in solenoid valve is cleaned and not choked
Foaming of oil due to liquid in the suction line Foaming of oil may arise due to liquid refrigerant entering the crankcase. Replenish oil and troubleshoot the cause of liquid in the suction of the compressor
Drive side seal leaking The compressor is provided with oil seal at the drive side. Ensure it is not leaking and renew it if required
Worn out piston rings/ liner leading to oil carryover in the system Renew the compressor piston rings or liner

 

Do you know about any other common problems seen in the ship’s refrigeration plant? Let us know in the comments below.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

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View Comments (21)

  • Found very good Information and shared with Engine staff on board mainly for juniors knowledge and training to TME .

    Many Thanks and heartily appreciate .

  • Very good technical information in a capsule from.
    Waiting more similar information in near future,

    Keep it up Marine In Sight.

    Ranjit
    Elect Supt
    Eagle International Shipping USA

  • Very good technical information.

    Today I read many articles in the Marine Insight and now, I will share information and I will indicate to my maritime engineer friends this website.

    Thanks.

    1st Eng. Fabio Pantoja
    ECO, Brazilian Division

  • Hi I have a Danfoss compressor that runs fine but does not cool Gas levels fine but when I switch on it immediately draws 18 amps of power 240v. It is shorting somewhere????? Can you advise and if so what do I need to replace. Thanks Alan.

  • Can you recommend an on line course or another course for ships refrigeration trouble shooting and repair for marine engineers?

  • thanks for good remarks about refrigeration system faults.
    but Im doubt about icing on suction line of compressor.if its an indication of under charge or over charged system?pls leave your comments

  • That's a wonderful information it has improved on my knowledge .keep it up, you can be every good lecturer. I also needed information on hermetic scroll compressor eg. daikin reefers compressor

  • Hi. Im busy trying ti troubleshoot a fault on provision cooling plant. The system cuts off and says high pressure. But seawater discharge and all the valves r working fine..when it does this, the fridge evaporators won't function either on manual..

    • @Cyrus: H.P cutout needs to be reset manually, otherwise plant will not start. There can be many reasons including -dirty condenser, wrong HP setting, Refrigerant overcharge, Liquid refrigerant backed up in the receiver, defective water regulating valve etc.

  • Meet room and vegetable room are normal. But fish room temperature not reducing from -7 expansion valve change by other
    Many time collect gas in condensor even manual also compressor operated till 0.1 bat to collect oil from the system. Pls reply.

    • @Jaspal: Icing on the evaporator can be due to following reasons -
      Ripped or broken door gasket
      • Door left open for long
      • System is low on refrigerant
      • Improper adjustment of TEV
      • Condenser is dirty
      • Improper defrost timer
      • Evaporator drain is choked or improper vent
      • Heater not functioning
      • Faulty evaporator fan

      Do check our premium ebook on Marine refrigeration system - https://learn.marineinsight.com/eBooks/e-marine-refrigeration-system/

  • Hello
    The page offers great help! Thanks to your contribution.
    Can you please advise what equipment is used for detection of leaking Freon 134a; both hand-held and for integration on to an automatic warning system on board of vessels?

    Await your reply

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