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9
CARE AND MAINTENANCE
 
A. GENERAL INFORMATION
 
9A1. Checking the system. A regular routine of checking a refrigeration system, or systems, should be established to insure proper care and operation. Make a systematic check every two weeks of all pressures and temperatures throughout the system. Such a check determines the need for any, corrective measures before the condition becomes acute.

9A2. Opening a charged system. Whenever it is necessary to open a fully charged system for investigation or repair, the final evacuation should be to a pressure slightly above atmospheric pressure (1 to 2 pounds' gage) to prevent air from entering the system. If the final pressure should reach a point lower than zero pounds' gage, sufficient refrigerant should be admitted to the evacuated part to raise the pressure to between 1 and 2 pounds' gage. Connections may then be broken, and the necessary investigation or repairs made. If more than a few minutes must elapse after breaking the connections, the open ends of the system should be plugged.

When connecting the part to the system again, make one joint first and blow out the part under investigation with gas from the system, then quickly finish making up the other joint.

Refrigerant charging lines, although of small size and short length, should be purged with refrigerant gas immediately before actual charging is started.

9A3. Purging air from system. After a system has been open for repair, it is advisable to check for air in the system before proceeding with regular operation. Either of two methods may be used for checking for air. The preferred method is as follows:

1. Close the liquid king valve from the receiver.

2. Pump down the system to 5 inches of vacuum.

NOTE. While pumping down, open the

  circulating water valves wide in order to run with the lowest possible head pressure and to condense all condensable vapors.

3. Shut down the compressor.

4. Close the discharge valve on the compressor.

5. Close the stop valve from the condenser to the receiver.

6. Attach a small hose to the air purge valve on the condenser.

7. Insert the other end of the hose in a glass jar or vessel filled with water or light Freon oil.

8. Crack the purge valve on the condenser. If air is in the system, large air bubbles will show in the water. When all the air is out, small bubbles will show in the water, and a sharp cracking sound will be heard. These small bubbles are Freon. The purge valve should now be closed, and the system put into normal operation.

The other method of testing for air in the system is by observation of temperatures as follows:

1. Operate the system for 30 minutes. Observe the pressure and temperature as indicated on the high-pressure Freon 12 gage.

2. Compare the temperature corresponding to the discharge pressure, as noted in red figures on the dial of the pressure gage, with that shown on the liquid. If it is more than 5 degrees lower than the temperature corresponding to the discharge pressure, the system should be purged.

3. While the system is operating, purge air by cracking the purge valve on the condenser. Purge at intervals until the air is expelled from the system. This is indicated by a temperature difference of about 5 degrees.

9A4. Testing far leaks. If leakage is suspected in any of the joints or other parts, use the testing procedure detailed in Section 11F.

 
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B. EVAPORATOR
 
9C1. Cleaning evaporator coils. The evaporator coils of the refrigeration system should   be cleaned only with a clean dry cloth each time the coils are defrosted.
 
C. COMPRESSOR
 
9C1. Starting the compressor after a prolonged shutdown. IMPORTANT. Before starting a Freon 12 compressor that has been idle for some time, observe the height of the oil level in the compressor crankcase. If the oil level is above the oil sight bull's eye, a considerable quantity of Freon 12 has been condensed in the crankcase and absorbed by the oil. The amount of Freon 12 mixed with the oil depends upon the temperature of the oil and the length of the shutdown period. The oil and Freon 12 solution may entirely fill the compressor crankcase. If the compressor is started under such conditions, the shaft seal diaphragm may be broken or the seal assembly distorted. Excess oil and Freon 12 solution may be drained from the crankcase by the following procedure:

1. Temporarily connect a 3/8-inch line from the compressor oil drain valve to the suction pressure gage valve.

2. Close the suction stop valve.

3. Open the oil drain valve and the suction pressure gage valve; then slowly rotate the compressor by hand. Do not start the compressor motor. Continue rotating the compressor by hand until the oil level can be seen in the oil sight glass.

It is expected that oil which leaves the compressor crankcase will return to the compressor during normal operation. However, after the system has been placed in operation, check the oil level over a period of several hours. Do not allow the compressor to operate with a low oil level in the crankcase.

9C2. Stop valves. If the stop valves on the compressor are of the double packed type, the valve stem is packed with a conventional stuffing box and a steel cap is provided to screw over the stem as a second seal against leakage around the stem. This seal cap seats on the top face of the valve body with a copper ring gasket or fiber gasket between.

9C3. Operation of stop valves. In order to manipulate the stop valves, it is necessary to

  remove the seal cap. To permit the valve stem to operate freely, loosen the valve stem packing gland. When opening or closing the valve by means of a wrench on the valve stem, or when tightening the internal packing gland with a wrench, it is essential to exercise every precaution not to scratch or otherwise mar the gasket seat which is the top edge of the valve body. Remember that valves made of brass are soft as compared to the steel used in the wrenches. Any scratches or burrs raised on this gasket seat by careless operation of the wrench are certain to impair the efficiency of the gasket joint.

If a valve of this type is manipulated frequently, the gasket should be inspected occasionally to see that it is in good condition.

If this gasket shows signs of flattening or of being scored, it should be renewed. The seal cap over the valve stem should provide an absolute seal against leakage, providing the gasket surface is not damaged and providing the gasket is in first-class condition.

IMPORTANT. Each time the valve is manipulated, the packing gland should be tightened, the seal cap drawn tight, and the gasket joint tested for leakage.

CAUTION. If the internal packing gland on the stop valve stems is not kept properly tightened, it is possible in opening the valve to back out the stem far enough to compress this packing from the inside and thus raise the valve stem higher than the normal full open position. The seal cap might then bear hard against the valve stem where the valve is open farther than normal, before it would seat properly on the gasket. Therefore, care should be taken to see that the internal packing gland is tight, and that the valve is not open farther than its normal full open position.

9C4. Difficulty of checking the oil level. As stated in Section 7B16, the greater the amount of Freon 12 absorbed by the oil, the higher the apparent oil level. The amount of refrigerant in the mixture is greater after a prolonged

 
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shutdown period. Therefore, a check of the oil level immediately after a prolonged shutdown is worthless for determining the actual working oil level.

9C6. Best time to check the oil level. The best time to check the oil level is after a prolonged period of operation, because then there is the least amount of refrigerant mixed with the oil. During the period of operation, the refrigerant is pumped out of the oil until only the normal quantity remains in solution. This check should be made with the compressor stopped.

9C6. Checking the oil level after a prolonged shutdown. If the apparent oil level is observed after a prolonged shutdown period and is above the sight glass in the side of the compressor, it is a good indication that a considerable amount of Freon 12 has been absorbed by the oil while the compressor has not been running. If this is the case, start the compressor as described in Section 8B4. If the oil level is lower than 1/4 up on the glass, it is almost certain that the actual working oil level is far too low. Add sufficient oil to raise the oil level to 3/4 up on the glass in the side of the crankcase. The compressor should now be started and checked as described in Section 9C7.

9C7. Checking the oil level when running. To check the oil level when the compressor has been running on its normal cycle with no prolonged shutdown:

1. Wait until the end of a period of operation, or if the operation is continuous, wait until it has operated at least half an hour.

2. As soon as the compressor stops, turn the flywheel until the two tapped holes for the flywheel puller are in a vertical line and observe the oil level in the bull's-eye sight glass. It nay be necessary to wait a few minutes until the oil settles in the crankcase.

The ideal oil level is from 1/2 to 3/4 up in the glass, checked as outlined above.

CAUTION. Do not remove oil from the crankcase because of an apparent high level unless it is known that too much oil has been added previously. If the oil level, checked as above, is lower than 1/4 up the glass, add oil.

  In adding oil, it is recommended that the level be raised only 3/4 up the glass.

9C8. Adding oil. To add oil to the compressor crankcase, use the small oil pump designed for this purpose and proceed as follows:

1. Remove the protector cap from the end of the oil pump and wipe the pump cylinder clean.

2. Insert the oil pump into the can of oil to be used.

3. Connect the pump discharge hose to the compressor crankcase oil charging valve, but do not tighten.

4. Hold the pump firmly, being careful not to strike the bottom of the oil can hard enough to puncture it. Displace the air in the oil pump connections by several strokes of the pump handle until oil appears at the oil charging valve. Then tighten the flare nut attaching the oil hose to the charging valve and open the valve.

IMPORTANT. Use Navy Oil, Symbol No. 2135, or equivalent.

5. Pump oil into the compressor crankcase until the oil covers 4 of the bull's-eye sight glass.

6. Close the charging valve tightly, replace the valve seal cap, and disconnect the pump hose, taking care not to spill oil on the deck. Replace the flare seal cap on the oil charging valve outlet.

7. Place the protector cap on the oil charging pump when the pump is not in use.

NOTE. When steel or iron pipes and fittings are used for Freon 12 mains, condenser, or evaporator, a sample of oil from the crankcase should be taken at least every six months, and if it proves to be contaminated with scale or foreign matter, all the oil must be removed. If clean copper tubing is used for the Freon 12 mains, condenser, and evaporator, and reasonable care has been exercised against dirt entering the system during its installation, the oil in the compressor crankcase probably is not contaminated sufficiently to require renewal between overhaul periods; but if the compressor is ever disassembled and left open to the atmosphere longer than six hours, the oil must be renewed, since it will have absorbed sufficient water from the atmosphere to make

 
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renewal necessary. The cleanness of used oil is easily determined by observation. Pour a sample of oil into a glass and allow it to stand for a few minutes until the oil foam has dissolved.   If particles of scale or foreign matter are visible either on the surface or in suspension, the oil is dirty and should not be used, Drain the crankcase and add new oil.
 
D. CONDENSER
 
9D1. Condenser shutdown. If there is a possibility of obtaining a freezing temperature in the condenser compartment during the shutdown period of any condenser, it is necessary that the condenser be thoroughly drained of water, to prevent a freeze-up that would damage the condenser tubes.

9D2. Cleaning the condenser. The condenser tubes should be inspected every three months, to determine whether or not cleaning is required.

All condensers should be cleaned before the vessel leaves the harbor for war patrol.

To clean the condenser tubes, shut off the water supply and discharge valves and drain the tubes; then remove the heads.

Use a water lance and soft rubber plugs to clean the condenser tubes. Care must be taken that the protective film of corrosion-resisting preparation on the inner surfaces of the tubes is not destroyed during the cleaning process. Inspect the zinc fingers at regular monthly intervals. Renew the fingers when they show 30 percent deterioration.

These instructions have been taken from the York instruction book, but in actual operation it has been found that the condenser gives very little trouble, and if the system has not been operated in shallow waters, there is little chance of the condenser becoming dirty. The operating temperatures are low enough so that scale does not form in the tubes. Unless there is a definite indication that the condenser is plugged up, it is opened only for inspection at regular overhaul periods.

9D3. Defecting condenser leaks. In order to prevent serious loss of refrigerant through leaky tubes, it is advisable to test the condensers for leakage once every two weeks. The test should always be conducted on a condenser that has not been in use for at least 12 hours. There is always a small air pocket in the top of the heads. Slowly open the vent valves on the water side, one at a time, and

  insert the exploring tube of a leak detector. If this simple test shows the presence of Freon 12 gas, the exact location of the leak or leaks may be determined as follows:

1. Remove the water heads and listen at each section for the hissing sound that indicates gas leakage. This assists in locating the section of tubes to be further investigated. If the location is not definite, all the tubes must be investigated. If the probable location of the leaky tubes is determined, treat that section in the following manner

2. Wash the tube heads, and with a cloth or a ball of cotton, clean all the tubes (while wet) until the inner walls are dry and shining; then hold the exploring tube in one end of each condenser tube long enough (about 10 seconds) to draw in fresh air. As soon as fresh air is drawn into the tube, drive a cork into each end of the tube. Repeat this with all the other tubes in the suspected section, or if necessary, with all the tubes in the condenser. Then let the condenser remain in this condition for 48 hours before doing anything further.

NOTE. It is against submarine instructions to have carbon tetrachloride on board. However, the condenser may be overhauled or tested outside the submarine. If the condenser is being tested for leaks outside the submarine, carbon tetrachloride should not be used in cleaning the tube heads or tubes, as its fumes give the same flame discoloration as Freon 12, and serve only to confuse the investigation.

3. After the tubes have been corked up for 48 hours, get three men on the job, one to remove corks at one end, one to remove corks at the other end and handle the exploring tube, and the third man to watch the color of the flame in, the lamp. Start with the top row of tubes in the section being investigated, remove the corks simultaneously at each end of the tube, and insert the exploring tube for 5 seconds; this is long enough to draw into the lamp any Freon 12 gas that is bottled up in the tube.

 
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4. Mark any leaky tubes for later identification.

5. Leakage of any of the tube joints is indicated by the presence of oil at the joint after tire 48-hour period.

  The procedure described is a laborious one, but it is the only method found to date that can give conclusive evidence, and it has given satisfactory results in most cases in which it has been used.
 
E. THERMOSTATIC EXPANSION VALVE
 
9E1. Indications of need of cleaning. When the thermostatic expansion valve is working properly, the temperature of the pipe on the outlet side of the valve is much lower than the temperature of the pipe on the inlet side. if this temperature difference does not exist when the plant is in operation, it is an indication that the valve seat is dirty and clogged with foreign matter.

9E2. Cleaning. If the valve seat is dirty or clogged, the best remedy is to close the stop valves on each side of the thermostatic expansion valve and remove the valve bonnet assembly from the valve body to obtain access to the internal parts. Do not pinch the small remote bulb tubing.

Use the manually operated bypass valve to

  admit liquid to the evaporator coils during the period required for repairs, being careful not to open the bypass wide enough to allow liquid Freon 12 to carry over to the compressor.

After the necessary repairs have been made, be sure that all internal parts are thoroughly clean and dry. Place the valve bonnet assembly on the valve body and pull up the bolts hand tight. Open slightly the stop valves on each side of the thermostatic expansion valve long enough to expel the air from the line, and bolt the valve together securely.

After all connections have been made and tested for leakage, close the manually operated bypass valve tightly. Open the stop valves on each side of the thermostatic expansion valve and operate as usual through the thermostatic expansion valve.

 
F. SUCTION LINE STRAINER
 
9F1. Cleaning the suction strainer. The suction vapor strainer in the suction line at the compressor serves to prevent scale or foreign matter from entering the compressor. To clean the strainer screen proceed as follows:

1. Pump out the compressor.

CAUTION. Before the strainer is opened, be sure the gage shows slightly above atmospheric pressure. Use accurate gages.

2. Mark the strainer body cover so that it can be replaced in its original position. The gasket should also be replaced in its original position.

3 Remove the strainer body cover, with draw the strainer, and immediately replace the cover on the strainer body to prevent foreign matter or moisture from the air from getting into the system.

  4. Clean the strainer and spring by washing them in approved cleaning solvent; dry them in the air.

5. Clean the strainer seat inside the strainer body, being careful to wipe out any particles that may drop down into the strainer body. Use only chamois or lint-free cloth. If this strainer seat is dirty, the screen does not seat properly and dirt may pass through into the compressor.

6. Reassemble the strainer in the body with the spring in place.

7. See that the cover gasket is in good condition.

8. Bolt the cover on the body, drawing up the capscrews evenly.

 
G. CARE OF V-BELTS
 
9G1. Alignment and tension. To insure long life and satisfactory operation of the V-belts, the motor pulley and flywheel must be in exact alignment and the belts must be under proper tension.   The main steps used to align and apply the V-belts are as follows:

1. Preparatory to aligning the drive, find the magnetic center of the rotor. This may be done by running the motor idle and measuring

 
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from the inside face of the motor pulley to some fixed point on the motor frame. This distance must be maintained during the alignment procedure.

2. Loosen the bolts that hold the motor to the base.

3. Move the motor on the rail base forward far enough for the belts to slip over the pulley and flywheel without stretching.

4. Proceed with the alignment, keeping in mind that the face of the motor pulley must be parallel with the face of the flywheel, that

  the belt grooves must be in alignment, and that the rotor must be on its magnetic center.

5. By means of the adjusting screws on the motor base, move the motor back until the belts are reasonably tight. To have the proper tension, a belt should have about a 1-inch sag when applying thumb pressure halfway between the pulley and the flywheel. When this condition is obtained, tighten the bolts holding the motor to the base. Belt dressing should not be used on the belts and the belts should never be cut and spliced.

 
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