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Environmental Code of Practice for Elimination of Fluorocarbon Emissions from Refrigeration and Air Conditioning Systems

Mobile Refrigeration

5.1 Design
5.2 Servicing
5.3 Equipment Conversions
5.4 Operator Education

The general principles found in Sections 2, 3, and 4 Commercial/Industrial, Residential Systems and Domestic Appliance and Mobile Air Conditioners (Automobiles) are also applicable to the Mobile Refrigeration section.

The scope of this section includes refrigerated transport trucks, trailers, refrigerated rail cars, intermodal containers, ships, and air transport.

5.1 Design

The equipment manufacturer should ensure that the design of mobile refrigeration units incorporates a series of proven features that will eliminate emissions to the atmosphere and minimize servicing.

5.1.1 Compressors

Compressors generally do not leak from design faults, but rather due to installation, vibration, and contamination.

Mobile refrigeration design should incorporate a high degree of physical protection of associated equipment attached to the compressor, e.g., gauge and cutout connections, oil return, oil drain, oil level sight glass, relief valve, condensing coils, and connecting pipe work. The physical environment that mobile refrigeration equipment must operate in is much more severe than for fixed systems like those found in buildings. It is essential that there is good access for cleaning.

Mechanical Seals (Open Drive) . The unique environmental, geographic, and extreme hot and cold temperature conditions that mobile refrigeration equipment is subjected to can damage mechanical seals and compressors. Adequate protection should be provided to prevent leaks and emissions.

Mechanical Shaft Seals. There are several factors that can lead to the premature failure of mechanical seals and result in leakage, such as the exposure of refrigerant and oil mixtures to various contaminants, and physical factors as previously mentioned.

High Head Pressure. High head pressure is caused by high [37 °C (98.6 °F)] outside ambient air temperatures, air in the system and/or condenser coils blocked with bugs, fluff, dirt, and debris. Higher than normal operating pressure can cause leaks, emissions, and premature equipment failure. In addition, the presence of air and moisture can cause acid generation and oil breakdown that can lead to premature equipment failure and refrigerant leakage.

Design features should include a method to alert the operator of potential problems before they occur, so that corrective actions can be taken before failure.

Seal Design . New replacement refrigerants and their oils have little or no ability to tolerate moisture.

Double-faced mechanical seals and single-carbon seals with improved features that keep the carbon in a oil-coated state help prevent leakage.

The mechanical shaft seal design should minimize oil seepage and work towards eliminating external refrigerant loss.

On larger systems, separate oil pumps are recommended to lubricate the seal before startup. On smaller open compressor refrigerant systems without an auxiliary oil pump, the lack of lubrication on shutdown can cause the faces of the seal to stick together. Subsequent damage on the next startup can be prevented by rotating the shaft by hand and lubricating the seal.

Vibration. Vibration stress leaks can be minimized by using:

  • antivibration mountings,
  • heavy-duty insulated clamps,
  • proper maintenance to eliminate vibration,
  • metal braided vibration eliminators between fixed piping and components that are subjected to movement, and
  • a minimum number of soldered joints to reduce potential leaks.

Mobile Refrigeration Design Features . Design features should include:

  • operator-friendly control panels with self-diagnostic abilities;
  • self-reseating pressure-relief valves vented to the outside;
  • the use of adequate isolation valves and access fittings to facilitate maintenance, repair, recovery, and recycling of refrigerant.

5.1.2 Condensers on Ships

The condensers found on ships are the same as those found in commercial and industrial applications. To prevent fouling and scaling of the primary refrigeration condenser, a secondary heat exchanger is used which uses sea water to absorb the heat being rejected and to cool the refrigerant condenser cooling water. Sacrificial anodes should be placed in the sea water heat exchanger to help prevent corrosion. Use of resistance alloys is also recommended. Both the condenser and the heat exchanger should incorporate designs to allow easy cleaning and maintenance.

Water Velocity. Excessive water velocity through the tubes of shell-and-tube units can cause vibration or erosion failures, and should be avoided.

Water Conditions. Proper water treatment and filtration will help minimize effects of corrosion or erosion that can cause failures too.

5.1.3 Pipelines and Connections

All pipelines should be designed so that the number of joints are minimal. Welded or flanged piping and fittings are preferred over screw connections.

5.2 Servicing

5.2.1 Planned Preventative Maintenance

Particulate matter and other types of soiled materials (contaminants) can damage the refrigeration system and lead to leaks by allowing moisture into the system, resulting in contamination of refrigerant and oils.

Planned preventative maintenance is the key to minimizing breakdowns, down time, and increasing overall dependability. This is very important when at sea or on the road. System cleaning is a very important part of planned maintenance.

5.2.2 Regular Planned Preventative Inspections

Refrigerated transport should incorporate regularly planned preventative maintenance inspections into its vehicle maintenance safety inspection program.

As the production and importation of CFC is phased out and it is essential to have a leak-free system to avoid shut down due to lack of refrigerant, expenditure for retrofitting existing equipment, and possible premature capital for new equipment using alternative refrigerant

Only trained qualified certified service persons using the manufacturers service check sheets and service procedures can ensure that the unit is leak-free and is operating at peak efficiency.

An annual inspection check sheet should be developed by systems owners, that can travel with the unit. This annual inspection sheet will also verify that the equipment was leak-free as of a certain day and by whom it was serviced. Any repairs that were required to bring the system up to leak-free standards should be noted.

5.3 Equipment Conversions

The principles and procedures outlined in previous sections should be followed. See Sections 2.8 and 3.6 and the following sections.

5.4 Operator Education

The vehicle or system operator should understand the basic principles of how the refrigeration system works and the normal operating parameters of the unit. Parameters may include temperatures, pressures, oil levels, sight glass inspection, and/or visual inspection of the moisture indicator.

The operator should know the basic components that make up the unit, how to start and stop the unit, and how to pump it down and isolate the refrigerant charge if necessary.

Logs of inspections should be kept with each unit. These can be invaluable in helping the service person diagnose some types of problems.

A good operator knows his/her equipment and watches for oil leaks (a sign of refrigerant leaks) on the bottom of fittings and connections.