Diagnostics and repair of marine refrigerators

Refrigeration systems on ships are used to store the products during the long time. Some ships also have one or a few refrigerated cargo compartments for transporting general cargo. Refrigeration ships are used exclusively for transporting cooled or frozen cargo. Refrigeration units on fishing or fish-processing ships have technologically-difficult implementation.

Marine refrigeration equipment is created on the basis of stationary units but in a so called ‘marine’ implementation that implies some changes in construction and replacement of some materials to reduce weight and dimensions, increase the fault-tolerance in ship motions and vibration, cooling by sea water. Cooling of quick-freezing machines and ice engines is usually direct, while cooling of holds (and tweedecks) is indirect. Direct expansion refrigeration is unadvisable due to the problems with preventing coolant leakage related to constant and heavy vibrations and ship body deformations. During the cruise it is almost impossible to get into the refrigerated cameras.

Marine refrigeration systems are divided to: industrial that provide the implementation of industrial (technologic) processes — freshy-caught fish cooling and storage, generation of ice for fish cooling, freezing and storing frozen fish, cooling and storage of salt-cured fish and canned fish; provision systems used for storing provision for ship crew and passengers. Ships with unrestricted navigation also feature a refrigeration system for air conditioning.

Currently the most popular refrigerant coolant is R22 that provides cooling at rather low temperatures in excessive boiling pressure. This allows benefiting in the size of compressor cylinders and provides other advantages. The cylinder capacity of a compressor working on R22 is approximately 60% from the cylinder capacity of a compressor working on R12 in all other conditions being equal.

Approximately the same benefit is brought by using R502 coolant. Due to the lower compressor delivery temperature there are less chances for grease oil coking and injection valves breakages.

All mentioned refrigerant coolants do not cause corrosion and can be applied in hermetic and semihermetic compressors. R502 agent used in electric engines and compressors implies smaller impact on laques and plastic materials. Currently this promising coolant is rather expensive. That is why it hasn’t gained wide popularity yet.

Cooling mediums are used in big air conditioning units and refrigerators for cooling cargo. The coolant circulates through the evaporator, and then it is transported to the cooled room. Coolant is used when the cooling system is big and branched to avoid the need in the circulation of big amount of expensive refrigerant agent that has very high penetration quality and can leak through the smallest looseness. That is why it is very important to reduce the number of pipe connections in a system to a minimum. Air conditioning systems usually work on fresh water that can contain a glycol solution.