Cleaning Suction Strainers
When putting a new unit into operation, you should
clean the suction strainers after a few hours of operation.
Refrigerants have a solvent action and will loosen any
foreign matter in the system. This foreign matter will
eventually reach the suction strainers. After a few days
of operation, the strainers will need another cleaning.
Inspect them frequently during the first few weeks of
plant operation and clean as necessary.
The suction strainers are located in the compressor
housing or in the suction piping. The procedure for
cleaning the strainers is as follows:
1. Pump down the compressor.
2. Remove the strainer and inspect it for foreign
3. Dip the strainer screen in an approved solvent
and allow it to dry.
4. Replace the strainer and evacuate the air from
5. Test the housing for leaks by wiping up all oil
and then using a halide leak detector.
Sometimes a compressor cannot be pumped down
and is damaged to the extent that it has to be opened for
repairs. If so, you should first close the suction and
discharge valves. Then allow all refrigerant in the
compressor to vent to the atmosphere through a gauge
When you must remove, replace, or repair internal
parts of the compressor, observe the following
1. Carefully disassemble and remove parts; note
the correct relative position so that errors will not be
made when you reassemble.
2. Inspect all parts that become accessible.
3. Make certain that all parts and surfaces are free
of dirt and moisture.
4. Freely apply clean compressor oil to all bearing
and rubbing surfaces of parts being replaced or
5. If the compressor is not equipped with an oil
pump, make certain that the oil dipper on the lower
connecting rod is in the correct position for dipping oil
when the unit is in operation.
6. Position the ends of the piston rings so that
alternate joints are on the opposite side of the piston
7. Take care not to score gasket surfaces.
8. Replace all gaskets.
9. Clean the crankcase and replace the oil.
The compressor discharge line terminates at the
refrigerant condenser. In shipboard installations, these
condensers are usually of the multipass shell-and-tube
type, with water circulating through the tubes. The tubes
are expanded into grooved holes in the tube sheet to
make a tight joint between the shell and the circulating
water. Refrigerant vapor is admitted to the shell and
condenses on the outer surfaces of the tubes.
Any air or noncondensable gases that may
accidentally enter the refrigeration system will be drawn
through the piping and eventually discharged into the
condenser with the refrigerant. The air or
noncondensable gases accumulated in the condenser are
lighter than the refrigerant gas. They will rise to the top
of the condenser when the plant is shut down. A purge
valve, for purging the refrigeration system (when
necessary), is installed at the top of the condenser or at
a high point in the compressor discharge line.
Cleaning Condenser Tubes
To clean the condenser tubes properly, first drain the
cooling water from the condenser. Then disconnect the
water connections and remove the condenser heads. Be
careful not to damage the gaskets between the tube sheet
and the waterside of the condenser heads. Inspect tubes
as often as practical and clean them as necessary, using
an approved method. Use rubber plugs and an air lance
or a water lance to remove foreign deposits. You must
keep the tube surfaces clear of particles of foreign
matter. However, you must not destroy the thin
protective coating on the inner surfaces of the tubes. If
the tubes become badly corroded, replace them.
Replacement avoids the possibility of losing the charge
and admitting salt water to the system.
Cleaning Air-Cooled Condensers
Although the large plants are equipped with
water-cooled condensers, auxiliary units are commonly
provided with air-cooled condensers. The use of
air-cooled condensers eliminates the necessity for
circulating water pumps and piping.