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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

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.

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

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

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.

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

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

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.

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

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

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.

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.

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.

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

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

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.