CONDENSERS

CONDENSERS

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
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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.
Keep the exterior surface of the tubes and the fins on an air-cooled condenser free of dirt or any matter that might obstruct heat flow and air circulation. The finned surface should be brushed clean with a stiff bristle brush as often as necessary. Low-pressure air is very useful in removing dirt in hard-to-reach places on condensers. When installations are exposed to salt spray and rain through open doors or hatches, you should take steps to minimize corrosion of the exterior surfaces.

Testing For Leaks

To prevent serious loss of refrigerant through leaky condenser tubes, test the condenser for leakage by following the PMS.
To test for leaky condenser tubes, drain the waterside of the condenser. Then insert the exploring tube of the leak detector through one of the drain plug openings. If this test indicates that Freon gas is present, you can find the exact location of the leak by following these steps:
1. Remove the condenser heads.
2. Clean and dry the tube sheets and the ends of the tubes.
3. Check both ends of each tube with a leak detector. Mark any tubes that show leakage. If you cannot determine that a tube is leaking internally or around the tube sheet joint, plug the suspected tube and again check around the tube sheet joint. Mark the adjacent tube, if necessary, to isolate the suspected area.
4. To locate or isolate very small leaks in the condenser tubes, hold the exploring tube at one end of the condenser tube for about 10 seconds to draw fresh air through the tube. Repeat this procedure with all the tubes in the condenser. Allow the condenser tubes to remain plugged for 4 to 6 hours; then, remove the plugs one at a time and check each tube for leakage. If a leaky tube is detected, replace the plug immediately to reduce the amount of refrigerant escaping. Make appropriate repairs or mark and plug all leaky tubes for later repairs.

Plugging or Retubing Condensers

The general procedures for plugging or retubing condensers can be found in Naval Ship's Technical Manual (NSTM), Chapter 254, “Condensers, Heat Exchangers, and Air Ejectors.” When plugging or retubing a specific condenser, follow the procedures in the manufacturer’s technical manual.