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DETAILS OF REFRIGERATION SYSTEM
 
A. DESCRIPTION OF PLANT
 
7A1. Equipment on submarines. The cooling equipment of submarines consists of two separate systems, one for refrigeration proper, and the other for air-conditioning. The refrigeration plant is described here. The air-conditioning plant is described in Chapters 13 to 20 inclusive.

7A2. The refrigeration plant. The capacity of the refrigeration plant is one-half refrigeration ton when operating at 460 rpm with 5 gallons of water at 85 degrees F per minute circulating through the condenser, and a suction pressure corresponding to an evaporation temperature of -5 degrees F. The system consists of the main elements connected to a circuit by piping, with various valves, gages, and controls necessary for automatic operation. Each item is described in detail later, with illustrations showing construction or operation. In addition, Figure 7-1 shows the complete refrigeration system, with all piping connections, and the location of all elements, valves, and devices (this diagram is inserted at the

  end of the book). The main elements and accessories are as follows:

1. One compressor, York-Navy Freon 12, enclosed single-acting vertical, two cylinders, 2 5/8-inch bore x 2 1/2-inch stroke.

2. One condenser, York-Navy Freon 12, horizontal shell-and-tube 4-pass, 6 9/16 x 30 inches.

3. One receiver, York-Navy Freon 12, 6 x 36 inches.

4. One Kramer Trenton Model 71L ice cuber in a Victor insulated cabinet.

5. One water cooler. This is not an integral part of the refrigeration system. It consists of a pipe leading out of the water storage tank into the cool room where in a few coils it chills the water before it goes out to the scuttlebutts.

6. Two evaporators (see Figure 7-2). The evaporators consist of the main refrigerant piping coiled back and forth on the overhead of the insulated boxes to provide a large area of cooling surface. One evaporator is in the cool room and the other in the refrigeration room.

 
B. THE COMPRESSOR
 
7B1. General description. The compressor is of the vertical, single-acting, reciprocating, two-cylinder type.

1. Bore 2 5/8 inches; stroke, 2 1/2 inches.

2. Driven by three V-belts from a 1.75 hp electric motor, speed 1750 rpm, 250 (175-345) volts direct current (d.c.).

3. Lubricating oil charge, 5 pints of Navy Symbol No. 2135, or equivalent.

4. The suction, or intake, valve of each cylinder is located in the piston top. The discharge valves are located in the discharge valve plate at the top of the cylinders. These valves are of the flex-action diaphragm type and are easily accessible. The tops and upper portion of the sides of the cylinders are finned for air-cooling.

A sectional view of this compressor is shown in Figure 7-3 and an exploded view in Figure 7-4. In the following description, numbers in

  parentheses correspond to index numbers in these figures.

7B2. Crankcase. The crankcase (1, Figures 7-3 and 7-4) is a single cast-iron case, designed with smooth curved lines for strength and for elimination of unequal stresses. It has a large oil capacity to provide good lubrication and ample heat dissipation. The crankcase opens at only one end, for shaft removal, to keep the points of possible leakage at a minimum. The construction is especially rugged around the bearing areas. A drain for removing oil and a sight glass for checking the oil level in the crankcase are provided.

7B3. Crankshaft. The crankshaft (26) is made of die-forged open-hearth steel. It is short, has great rigidity, and is so designed that it needs no counterweights. The thrust face on the dead end of the shaft is centrifugally

 
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Figure 7-2. Refrigeration evaporator, typical layout.
Figure 7-2. Refrigeration evaporator, typical layout.
lubricated by oil that comes in through holes bored in the shaft. Note that endwise play of the crankshaft is controlled by the thickness of the gasket (39) between the bearing head and the crankcase, at the power end of the shaft. For repair, the entire crankshaft, with rods and pistons attached, is removed and replaced as a unit through the opening at the top of the crankcase, after the cylinder casing has been removed.

7B4. Crankshaft main bearings. The crank shaft main bearings (3) are die-cast sleeve type babbitt bearings, diamond bored to mirror finish, with ample oil-ways for lubrication. Note that these bearings are interchangeable. The bearings are inserted by a light press fit, and a lug on the bearing shell locks them, preventing rotation.

7B5. Bearing head to crankcase. The main bearing at the drive, or flywheel, end of the crankshaft is carried on a detachable bearing head (2) bolted to the crankcase. The bearing head may be removed by taking out the capscrews (47), after first removing the flywheel (34) and shaft seal assembly (31).

7B6. Connecting rods. The connecting rods (15) are made of malleable iron I-section, with full-floating piston pins (24). The piston pin bushings (20) are of bronze with oil holes. At the crank pin end, the connecting rod bearings are of centrifugally cast babbitt, diamond bored to mirror finish simultaneously with the

 
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Figure 7-3. Compressor, sectional view.
Figure 7-3. Compressor, sectional view.
bushing for good alignment. If damage occurs to the bearing at either end, the whole connecting rod must be replaced as a unit, as it is especially made.

The connecting rod is replaced as follows After the connecting rod bearing is cast, the babbitt is split, and the cap is attached at a predetermined bolt tension. Each bolt is marked by reference to its own hole. The diamond boring is then done. The bolts, Therefore, must be replaced in the exact holes for which they are marked, otherwise distortion of the bearing results. The bolts are not inter changeable. The cap is positioned by means of a dowel that must be removed before the cap is detached.

7B7. Pistons. The pistons (21) are of cast nickel-iron alloy, of double-trunk type providing cross-head effect for even distribution of pressure on cylinder walls, with large bearing surface. There is one compression ring (22) in the top bearing section, and two ventilated oil rings (23) in the bottom bearing section. The full floating hollow piston pin (24) has soft metal end plugs to prevent possible scuffing of cylinder walls. When the vapor enters through the intake port, it passes around the middle section where the piston body is narrowed. The suction or inlet valve is in the piston top and is discussed later.

7B8. Cylinder. The cylinder (6) is a one piece casting with cooling fins around the upper part. It is bolted to the crankcase. The intake and outlet ports are located on opposite sides of the cylinder between the two cylinders. Locating dowel pins are provided for placing the cylinder accurately on the crankcase. The gasket (38) between these two parts is of lead coated copper.

7B9. Discharge valve plate. The discharge valve plate (8) that carries the two discharge valves, has holes coinciding with bolt holes in the cylinder head. The same bolts fasten both parts to the cylinder. In addition, this plate has two capscrews (48) that attach it to the interior cylinder wall.

7B10. Cylinder head. The cylinder head (7) has a high-domed construction to provide a cushioning effect in reducing pressure pulsations.

  The outside of this cylinder head is finned for cooling reinforcement. Dowels are used for accurately locating the head on the cylinder.

7B11. Discharge valves. The discharge valves (13) are simple and effective. They are, made of highest grade specially processed valve steel, with low lift, quiet and positive flexure action, and large vapor passages.

Their construction is as follows: Three disks of spring metal, nearly the same diameter as the piston, lie assembled on the discharge valve plate. The valve plate and the disks have rings of small holes for the vapor to pass, but the holes in the valve plate and the holes in the disks do not coincide, so that when the disks are down tight on the discharge valve plate, all passage is completely closed. The three disks are slightly dished in section and placed thus bottom disk concave downward; small spacer; middle disk concave upward; top disk concave downward. A hold-down screw passes through the center of this assembly into the discharge valve plate, with pressure enough to flatten the disks. The two upper disks serve as a spring to back up the bottom disk.

On the compression stroke of the piston, these disks yield, permitting vapor to pass up ward only. They close down tight on the reverse flow. When the disks lift, the vapor can flow not only through the holes, but also around between the disks. This is a precaution against slugging or violent pulsations. In assembling the discharge valve, the small holes in the disks must be aligned.

7B2. Suction valves. The suction valves (13A) are located at the top of the pistons. The suction valve diaphragms are similar in action to the discharge valve diaphragms, but the size of the holes and their distances from the center are different; hence, the suction and discharge diaphragms are not interchangeable. (In the 4-inch bore x 4-inch stroke air-conditioning compressor, the two sets of diaphragms are alike and therefore interchangeable.) In assembling the suction valve, the holes in the diaphragms must be aligned. A Dardellet self locking screw (25) is used for the center hold down. This requires a special screwdriver and valve hold-down bushing for installation.

 
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Figure 7-4. Compressor, exploded view.
Figure 7-4. Compressor, exploded view.
 
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An additional safety feature is a small hole through the side of the piston near the top. When starting the compressor, this hole permits Freon 12 under excessive pressure to flow through. In normal operation, at designated pressure, this small hole is kept sealed by lubricating oil.

7B13. Gaskets. Lead-coated copper is used for gaskets, and no special materials are required. However, at three points it is most important that the correct specified thickness be used. These points are:

1. Between discharge valve plate and cylinder. This gasket (40) determines the clearance between the piston top and the cylinder head; this clearance is only a few thousandths of an inch.

2. Between crankshaft main bearing head and crankcase. This gasket (39) determines the thrust collar clearance and the endwise play of the shaft.

3. Between bearing head and shaft seal ring cover plate. This gasket (37) controls the seal tension diaphragm tension.

7B14. Crankshaft seal. The crankshaft seal assembly (31) is the patented York Balanseal construction, one of the salient features of the York-Navy compressor, It has few parts and no springs, and is easily serviced.

The seal between the shaft and the crankcase is made by the shaft seal collar (30). Around the shaft and rotating with it, is a fixed collar held in place by a steel ball (29), the seal face of which is lapped to a fine finish. Against the rotating seal face of this shaft collar, another seal collar, or seal ring, presses. This collar has a similarly lapped face and is held stationary by a spring diaphragm attached to the crankcase. The diaphragm is under tension in the assembly and holds the two sealing faces together at a definite pressure.

The construction, operation, and adjustment of this seal are described in Sections 10K1 to 10K7.

Seals are designed for either clockwise or counterclockwise operation and are not inter changeable. Submarine installations are counterclockwise seals.

The rubbing faces of the two seal collars

  are lubricated by means of small holes in the seal face, carrying oil across the contact surfaces. This seal is below the oil level in the crankcase and oil flows by gravity into the seal from the shaft bearing. Therefore, a slight seepage of oil always appears on the outside of the seal.

7B15. Lubrication. The main shaft bearings and seal are flooded. The thrust bearings, receive a constant stream of oil from the centriforce oiler. The piston pin bearings and cylinder walls are lubricated by the usual splash-vapor method. The seal collar face is kept oiled by the rotation of the shaft. A number of pin-point depressions are arranged in a spiral path on the seal collar face, and oil working into these depressions provides uniform lubrication across the face.

7B6. Miscibility of oil and Freon 12 vapor. Freon 12 mixes readily with oil. However, no chemical reaction takes place, so that no harm is done to either. This mixing has a definite pressure-temperature relationship. For example, with an oil temperature of 60 degrees F and a pressure of 40 pounds gage, DTE heavy medium oil absorbs Freon 12 vapor to about 60 percent by weight.

The absorption increases with elevation in pressure, lowering of temperature, and length of compressor shutdown. Therefore, if there is a long shutdown, the oil absorbs so much Freon 12 that a high oil level appears in the sight glass. Actually the amount of oil may be below normal.

CAUTION. It is possible that even after a prolonged shutdown this oil and Freon 12 mixture may fill the crankcase. If the compressor is started under such conditions, damage to some part or parts is probable. Even if the oil-Freon 12 mixture does not fill the crankcase, starting may cause a sudden lowering of pressure in the crankcase, producing a violent boiling and foaming of the oil as the Freon 12 vapor leaves. This in turn would result in a loss of oil from the crankcase. Special care should be taken to check this matter after any shutdown. Moreover, gathering of frost on the crankcase indicates

 
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a lowering of temperature within, caused by too low pressure or some other possible cause, in which case the same troubles might arise. Frost should not be permitted to form on the compressor crankcase, and in the event that   it does, the system should be checked immediately.

NOTE. Because of the ready mixing of oil and Freon 12, oil must never be used in testing for Freon 12 leaks (see also Section 11F3).

 
C. CONDENSER AND PUMP
 
7C1. The condenser. The condenser is a four-pass water-cooled condenser of conventional shell-and-tube construction. The shell is made of brass, 30 inches long and 6 9/16 inches in diameter (see Figure 7-5). The condensing water enters and leaves at the same end in four sets of six tubes each, the tube ends being belled for better entrance. The heads are semispherical with baffle-plates cast enbloc to return the water flow. The water enters the lower-left set of tubes, returns through the lower-right set, goes back again through the upper-right set, and flows out finally through the upper-left set. The Freon 12 vapor enters the condenser shell at the top, flows around these water tubes, condenses, and drips to the bottom where the liquid Freon 12 exists. Vents and drains are provided.

The condenser is of such size that when the refrigerating system is operating at -5 degrees F evaporation temperature and is supplied with 10 gallons per minute of 85 degrees F water, for each refrigeration ton, the head pressure does not exceed 125 pounds gage. The condensing water enters at 85 degrees F and leaves at 88 degrees F, with a velocity of 73.5 feet per minute through tubes. The flow of water through the condenser should be controlled by regulating the opening of the discharge valve on the condenser. The desired temperature can be maintained by controlling the flow of water through the condenser. If water at too low a temperature is allowed to flow through the condenser, it may be impossible to maintain the desired discharge pressure of the refrigerant at the compressor.

Never attempt to control the flow of water or regulate the temperature of the water through the condenser by the inlet valve. The inlet valve should be kept fully open at all times. The water side of the condenser is tested to 236 psi. Therefore, the suction to sea, through which cooling water is supplied to the condenser, can be left open until the

  vessel submerges to a depth at which sea pressure is greater than the test pressure of the water side of the condenser. This depth is approximately 500 feet.

It is good practice to secure the plant and sea valves when submerging below 300 feet or when expecting a depth charge attack, and to open the vent on the water side of the condenser. This aids in preventing damage to the condenser during depth charging. At both ends of the condenser, two zinc fingers, or rods, extend into the water side. They are screwed in securely from the outside so that they may be removed easily and inspected without having to remove the heads. These zinc fingers act as protectors, that is, they tend to protect the other metal parts from the corrosive action of the water caused by electrolytic action induced by stray electric currents in the metal parts. These zinc fingers should be inspected at least once a month and replaced when deterioration reaches 50 percent. A zinc finger when new and at four stages of increasing deterioration is illustrated in Figure 7-6.

7C2. Condenser water pump. The cooling water that condenses the Freon 12 vapor is supplied by a volute type of centrifugal pump. In the centrifugal pump, the intake water enters into the center, of the impeller on the axis of the pump. This impeller is carried on a shaft, both bearings of which are on one side, opposite the inlet. The impeller lies in a plane perpendicular to the axis. An exploded view of the pump is shown in Figure 7-7.

The impeller is of the enclosed type, that is, the water flows in passages inside the impeller (see Figure 7-7). The shaft is directly connected to a motor and turns at high speed. This speed imposes a centrifugal force on the water in the impeller passages. This centrifugal force causes the water to flow at high velocity from the eye, or inlet, of the impeller

 
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outward toward the periphery. This outward flow under centrifugal force creates a "suction" at the eye which pulls the feed water into the pump.

The inner surface of the case that surrounds the impeller has a volute, or spiral-shaped section, that is, an increasing radius around the

  circumference. The small inset in Figure 7-7 shows a sectional view of the case and volute interior. The volute case is designed to produce an even flow of water around the periphery and to reduce the velocity of flow gradually as the water flows from the impeller to the discharge outlet of the pump. This reduction
Figure 7-5. Condenser.
Figure 7-5. Condenser.
 
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in velocity changes the velocity head into pressure head.

The advantages of the centrifugal type pump are: 1) the flow from it is continuous; 2) the flow can be throttled without building up an excessive pressure, or overloading the motor; and 3) it operates at speeds normal to an electric motor; hence, it may be directly connected.

In the refrigeration system, one pump is used. It runs normally at 3,500 rpm, with a discharge pressure of 25 psi, and has a capacity of 5 gallons per minute (gpm).

In the air-conditioning system, two pumps are used, one for each condenser. Each pump runs normally at 2,600 rpm, with a discharge pressure of 25 psi, and a capacity of 40 gpm.

7C3. Circulating water systems. Figure 7-8 (inserted as a foldout at the back of the book) is a diagram of the circulating water supplying the condensers of the refrigeration and air-conditioning systems.

One pump supplies 5 gpm of cooling water at 25 psi discharge pressure to the refrigerating condenser. Two pumps, one for each condenser, supply 40 gpm of cooling water at 25 psi discharge pressure to the two air-conditioning condensers. All three pumps take their suction from the same sea chest and

  strainer through pipes (1) and (2). In pipe (2) a hose valve (10) is connected for emergency water feed to the system through the inlet side of the strainer. This connection normally is used to supply water to the system while the vessel is in dry dock.

Two separate suction lines lead from the basket-type strainer: pipe (3) supplying the refrigerating condenser pump and pipe (6) supplying the two air-conditioning condenser pumps. All pipes to the three pumps are provided with stop valves so that any one of the pumps may be shut off without halting the operation of the others.

The discharge from the refrigeration condenser pump goes directly to the condenser through pipe (4). From the refrigeration condenser, the circulating water goes through pipe (5) to a connection into the overboard discharge pipe (9).

The discharge from the two air-conditioning condenser pumps goes directly through pipes (7) to the two condensers. From the air-conditioning condensers, the circulating water goes through pipes (8) to a common two-valve manifold, and then into the overboard discharge pipe (9).

Any of the condensers may be cut out for cleaning or repair by closing the stop valve

Figure 7-6. Zinc fingers for condenser, showing stages of deterioration.
Figure 7-6. Zinc fingers for condenser, showing stages of deterioration.
 
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Figure 7-7. Condenser water pump, exploded view.
Figure 7-7. Condenser water pump, exploded view.
 
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in the discharge line of the condenser and the stop valve in the suction, line of the pump supplying it. If one of the air-conditioning condensers is to be cut out, its respective valve in the two-valve manifold of the discharge line must be closed.

The suction pressure of all three pumps is indicated by the pressure gage (A) connected to the common strainer. The discharge pressure of the pumps is indicated by the three gages (B) and (C).

The temperature of the incoming sea water is indicated by a thermometer located at the strainer inlet connection. The temperature of the water coming out of the condensers is indicated by a thermometer located at the condenser outlets.

Two drains lead from each pump. Drains also are provided on condensers. Vents are provided on the condensers and the strainer.

D. RECEIVER

7D1. Receiver. The receiver (see Figure 7-9) is a plain cylindrical tank, with dished heads made of brass. It is 3 feet long and 6 inches in diameter. The liquid inlet is at the top, near one end. The liquid outlet is near the other end and extends down as an extension of the outlet piping line into the receiver. It is brazed to the receiver shell at its entrance point. There is a 1/2-inch free space between the end of the outlet tube and the bottom of the receiver, where the liquid enters the tube.

  Figure 7-9. Receiver.
Figure 7-9. Receiver.

About 3 inches on each side of this interior outlet tube is a baffle-plate, reaching halfway up the shell and with a 1/2-inch free space at the bottom. These baffles prevent the liquid from surging from end to end of the receiver as a result of the motion of the vessel. Such surges would periodically prevent the liquid refrigerant from entering the liquid outlet connection. The receiver has a drain valve in the bottom. It is about one-third filled when the system is in operation.

 
E. AUTOMATIC CONTROL DEVICES
 
7E1. Thermostatic expansion valve, internal equalizer. The remote bulb, often called the thermo-, or thermal bulb, contains Freon 12, and is attached to the suction line at the exit of the evaporator coil (see Figure 7-10). Since Freon 12 has an exact temperature-pressure relationship, any variation of temperature within the remote bulb, caused by temperature variation in the suction line at the point of attachment, produces a corresponding variation of pressure within the bulb. This pressure is communicated to the upper side of the diaphragm in the expansion valve. The other side of the diaphragm (with airtight separation from the first) is part of the regular refrigeration fluid circuit. Therefore, a   pressure difference between the two sides causes the diaphragm to move. This in turn moves the valve stem, permitting more or less liquid Freon 12 to flow through.

The thermostatic expansion valve thus controls the quantity of liquid refrigerant that is admitted to the evaporator. It is designed to maintain the refrigerant vapor leaving the cooling coils at a constant degree of super heat, regardless of suction pressure. Hence its function is twofold: 1) it acts as automatic expansion control, and 2) it prevents the liquid refrigerant from surging back to the compressor.

The piping connections include a liquid strainer and a solenoid valve, with shutoff

 
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Figure 7-10. Thermostatic expansion valve, internal equalizer.
Figure 7-10. Thermostatic expansion valve, internal equalizer.
valves used in servicing the strainer, solenoid valve, and thermostatic expansion valve; and manually operated valves for use if it is desired to examine the thermostatic expansion valve or solenoid valve, or to clean the strainer.

a. Adjusting the thermostatic expansion valve. Some thermostatic expansion valves are set in the factory at 5 degrees F superheat. Navy specifications call for 10 degrees F superheat, and expansion valves for submarines are factory set at this amount. To change the superheat setting, remove the seal nut and manipulate the adjusting stem. Turning this stem clock wise (tightening the spring) increases the superheat and reduces the flow of liquid through the valves. Turning the stem counter clockwise reduces the superheat and increases the flow through the valve. After this final setting, it is seldom necessary to readjust it. These valves are made to control accurately the amount of superheat in the suction vapor. They will not withstand rough usage; After they are once adjusted, they must not be played with or readjusted, unless there is distinct evidence that they are not functioning properly.

b. Thermostatic expansion valve trouble. The thermostatic expansion valve should

  function without any difficulty if the system is free of dirt or foreign matter and contains no moisture. However, dirt or foreign matter may get in between the seat and the valve, and prevent the valve from closing tight. The presence of moisture in the system causes a freeze-up at the valve port and prevents the passage of Freon 12.

If it is evident that Freon 12 is not passing through the expansion valve, the valve should be disassembled by removing the capscrews connecting the power assembly to the body. This permits the valve cage assembly to be examined for the presence of such things as frost, ice, or dirt.

Care should be taken in reassembling the thermostatic expansion valve to see that all gaskets are properly placed, and that the valve cage assembly is properly aligned.

7E2. Solenoid valve. The solenoid valve (see Figure 7-11) is an important control device in the system, since it is the valve that halts the operation automatically in response to operating conditions. It is located in the liquid refrigerant line ahead of the thermostatic expansion valve. When the current is on, the magnetic coil of the valve is energized, causing the plunger to retract and lift the

 
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Figure 7-10a. Typical refrigeration control devices.
NavPers 17130, E-40, E-135
Figure 7-10a. Typical refrigeration control devices.
valve off its seat, thus permitting the refrigerant to flow through. When the space that the thermostat controls reaches the desired temperature, the thermostatic control device breaks the electrical circuit, and the magnetic coil releases the plunger, instantly closing the valve and completely stopping the flow of refrigerant.

A breakaway pin under spring pressure acts as a kickoff when the electrical circuit is interrupted, assuring positive closing of the valve.

The valve-closing part is a small piston, separate from the valve stem. This piston has a loose fit, so that when it is closed, the high-pressure liquid may flow up between it and the body wall, exerting this pressure downward on the piston top to maintain a complete and tight closure.

The valve stem also is separate from the plunger. When the magnetic coil is energized, the plunger snaps up, striking a hammer blow against the upper flange of the stem to insure

  positive opening. The stem, thus lifted off the secondary seat in the piston, enables the high pressure above the piston to flow out through the piston opening. Since the closing pressure on the piston is thus removed, the incoming liquid flow causes the piston to rise, fully opening the valve.

The magnetic coil is extra powerful and does not need Fusetron protection on alternating current. A surge protector is included for direct current in excess of 50 volts. The coil does not overheat or burn out under normal service.

The coil and leads are waterproof, which prevents failure caused by condensation of moisture in low-temperature or high-humidity compartments.

The solenoid valve should be located in a horizontal line, with the direction of refrigerant flow corresponding to the arrow on the valve body, and the coil in a vertical lane above the valve.

Liquid Freon 12 should never be permitted

Figure 7-11. Solenoid valve.
Figure 7-11. Solenoid valve.
 
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Figure 7-12. Thermostat.
Figure 7-12. Thermostat.
to remain trapped in the valve after the shut off valves ahead of and behind it have been closed. When pumping down for examination or removal of the solenoid valve, always close the hand valve on the inlet side first; later close the hand valve on the outlet side.

7E3. Thermostat. A thermostat (see Figure 7-12) is an electrical switching device (wired into the solenoid circuit) for automatic control of refrigeration or air-conditioning. It is controlled by temperature changes at a remote point by means of a long flexible tubing with an end bulb that may be placed at any desired location. The thermostat mechanism contains a flexible metal bellows, one side of which communicates with the remote bulb tubing in which is a volatile liquid similar to Freon 12. Remote bulbs for air contact operation are finned. Bulbs for surface contact operation are bare of fins so that they may be clamped firmly against a pipe or other surface (see Figure 7-13).

As the temperature at the remote location drops to a desired point as a result of the refrigeration action, the corresponding pressure of the liquid within the tubing moves

  the bellows to degrees (its set operating position, so that it causes a spring-and-magnet-controlled contact to snap off, breaking the electric circuit and closing the solenoid. The snap action is rapid, thus preventing excessive arcing and

Figure 7-13. Thermo-bulbs.
Figure 7-13. Thermo-bulbs.

insuring long life of the contact points. Refrigeration therefore stops in the section controlled by this solenoid valve.

When the temperature at the same remote location rises above the desired point, the

 
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reverse action takes place. The switch snaps on, closing the electric circuit, thus opening the solenoid valve and starting refrigeration again. By this means, the refrigeration is maintained economically at a desired temperature. When all solenoid valves are closed, the compressor is stopped by the low-pressure cutout switch.

On some installations, the thermostats used on the refrigerating boxes have two contact points. One contact point controls the solenoid valve on the meat or vegetable room, and the other is connected to the solenoid valve on the ice cuber. The ice cuber does not have a thermostat, and the solenoid is wired in parallel with the meat and vegetable room thermostats. If the contact points on either the meat or vegetable room thermostats are closed, the ice cuber solenoid valve is open.

a. Temperature adjustment. To dower the temperature at which the thermostat breaks the circuit, causing the solenoid valve to close, turn the spring cap (see Figure 7-12) counterclockwise. This decreases the tension on the spring. To raise the temperature at which the thermostat breaks the circuit, turn the spring cap clockwise.

b. Differential adjustment. The thermostat cannot, of course, keep the temperature at one absolutely exact degree. It keeps it within a certain limited range of temperatures. The range is called a differential. The holes (A, B, C, and D in Figure 7-12) in the arm permit variation of the differential. Minimum differential is secured by attaching the connector rod hook in hole A. Moving the hook to the holes B, C, or D increases the differential by approximately 20 degrees F for each hole.

7E4. Liquid strainer. Because of the solvent quality of Freon 12, any particles of grit, scale, and so forth that the system may contain are readily dislodged from the piping and fittings.

Strainers (see Figure 7-14) are provided in the liquid line branches to each evaporating surface, to protect the thermostatic expansion valve and the solenoid valve. If a liquid line strainer becomes clogged to the extent that it should be cleaned, this condition is evidenced by a loss of refrigerating effect in the room or surface on the line that it protects.

  The liquid strainer can be tested by placing the hand alternately on the strainer and on its inlet line. If the strainer feels distinctly colder than the line, it is a sign of partial clogging and the screen probably needs to be cleaned. All pressures should be checked. If frost gathers on the strainer shell, it is a sign of bad clogging, and the screen should be cleaned immediately.

To clean a liquid line strainer, shut off the manually operated stop valves ahead of and behind it and open the manual bypass valve a slight amount in order not to interrupt refrigeration. Loosen the cap, or cover plate, which is bolted to one end of the liquid strainer and remove the internal screen. Dip the screen in an approved cleansing solvent and blow it out with air. Also blow out the inside of the strainer body with air.

IMPORTANT. When placing the strainer back in the line, blow a little Freon 12 vapor through it to remove the air before closing the cover plate joint.

7E5. Dehydrator. A dehydrator (see Figure 7-15) is inserted in the liquid line between the receiver and the evaporator. The piping connection includes a three-valve bypass, so that it can be isolated when not in use.

The dehydrator is intended to be used only in charging the system with Freon 12, when adding refrigerant to compensate for loss through leaks, or when the presence of moisture in the system is suspected, as would be evidenced, for example, by a freeze-up at one of the expansion valves.

The dehydrator drying element is a cartridge filled with activated alumina or silica gel, which absorbs any moisture in the liquid refrigerant that is passed through it.

There is no definite rule governing the length of time that the drier charge remains effective, but it is generally considered advisable to renew or reactivate it after it has been used for 12 to 15 hours.

After the dehydrator has been in use for a while, its cartridge also gathers some sediment, thus restricting the passage of liquid through it. If the outlet end of the dehydrator shell feels cold to the hand, this indicates partial clogging. If this coldness increases, the cartridge should be replaced. If frost

 
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gathers on the shell, it is a sign of bad clogging and the cartridge should be replaced at once.

Reactivation of a used cartridge is accomplished by subjecting it to heat (300 degrees F) in a ventilated oven for 12 hours; then sealing the ends of the cartridge, and allowing it to cool.

IMPORTANT. After placing the cartridge back in the shell, blow a little Freon 12 vapor through it from the inlet side, to free the shell of air; then tighten the end cap.

7E6. Low-pressure cutout. The low-pressure cutout and high-pressure cutout switches are similar in mechanism to the thermostat.

The low-pressure cutout, or suction pressure, switch (see Figure 7-17) is located on the compressor base or on a panel adjacent to it. The tubing leading to its bellows is connected into the suction line at the intake port. Its wiring is connected into the pilot circuit of the compressor motor starter. When all the solenoid valves have closed, thus halting the refrigerant flow, the suction pressure drops until it reaches the setting of the low-pressure cutout, which is about 2 psi. When the suction pressure reaches this point, the switch opens, thus stopping the compressor.

If, for any other reason, the pressure in the low-pressure line should drop, the cutout switch stops the compressor at 2 psi. When one or more of the solenoid valves open, the suction pressure will rise, causing the switch to close and start the compressor. This switch has a differential of about 18 psi. That is, it stops the compressor when the low pressure drops to 2 psi, and snaps on at about 20 psi, restarting the compressor. The low-pressure cutout provides automatic control of the system. It halts the system when the desired degree of coolness in all spaces has been reached, thus making possible economical operation, and it prevents the rooms from getting too cold.

a. Pressure adjustment. To raise the low-pressure cutout point, turn the spring cap to increase the compression of the spring. To lower the low-pressure cutout point, turn the spring cap to decrease the compression of the spring.

In some cases it may be desirable to increase the differential between the cutin and cutout

  points to prevent short cycling of the compressor.

Where solenoid valves controlled by thermostats are used in multiple evaporator installations, set the suction pressure switch to stop the compressor after the last solenoid valve has closed, and to start the compressor again when one or more of the solenoid valves have opened.

7E7. High-pressure cutout. The high-pressure cutout switch (see Figure 7-18) also is located on the compressor base or on a panel adjacent to it. The tubing leading to its bet lows is connected to the high-pressure line at the discharge port. Its wiring is connected to the pilot circuit of the compressor motor starter. This switch serves as a safety device to prevent dangerously high pressure from developing within the system. When the discharge pressure rises to the setting of this

Figure 7-14. Liquid strainer.
Figure 7-14. Liquid strainer.

 
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Figure 7-14a. Dehydrator and liquid trainer, York ice machine.
NavPers 17022, Amphib 104
Figure 7-14a. Dehydrator and liquid trainer, York ice machine.
 
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switch, which is usually 150 psi, the switch opens, stopping the compressor and shutting down the system. This switch has a differential of about 25 psi. When the high pressure falls to 125 psi, the switch closes, automatically starting the compressor again.

a. Pressure adjustment. To raise the high-pressure cutout point, turn the spring cap to increase the compression of the spring. To lower the high-pressure cutout point, turn the spring cap to decrease the tension of the spring.

  7E8. Relief valve. The relief valve is of the conventional positive self-seating type, located on the discharge line from the compressor. It is furnished with interconnecting piping, and serves to vent excessively high discharge pressure to the suction, or low-pressure, side of the compressor. The relief valve acts as a safety device, and in the event that the high-pressure cutout switch should fail to stop the compressor, it comes into operation at 200 psi, preventing any further rise in pressure and bypassing this back to the low-pressure side.
Figure 7-15. Dehydrator.
Figure 7-15. Dehydrator.
 
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Figure 7-16. Low- and high-pressure control switch, York ice machine.
NavPers 17022, Amphib 106
Figure 7-16. Low- and high-pressure control switch, York ice machine.
 
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7E9. Packless valves. A number of packless stop valves (two-way and angle types) are inserted in the refrigerating circuit at various places. A two-way valve is illustrated in Figure 7-19. This type is of the packless design and contains a puncture- and blowout-proof diaphragm that seals off the fluid flow chamber from the outside handle stem space. The lower stem is separate and is kept in contact with the upper stem, or handle part, by a   spring; the sealing diaphragm is located between the two parts.

The combination bypass and check valve incorporated in the lower stem provides automatic opening under any pressure regardless of spring tension or spring size. This feature eliminates the necessity of applying pressure on the lower end of the stem seat and consequently makes this valve a multidirection universal packless valve.

Figure 7-17. Low-pressure cutout switch.
Figure 7-17. Low-pressure cutout switch.
 
Figure 7-18. High-pressure cutout switch.
Figure 7-18. High-pressure cutout switch.
 
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Figure 7-19. Packlass valve.
Figure 7-19. Packlass valve.
 
Figure 7-20. Type Q Navy manifold, exterior.
Figure 7-20. Type Q Navy manifold, exterior.
 
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Figure 7-21. Type Q Navy manifold, cutaway.
Figure 7-21. Type Q Navy manifold, cutaway.
 
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In the closed position of the valve, the diaphragm and the check valve seal the bypass and prevent leakage to the auxiliary valve chamber. In the open position of the valve, the check valve seals the bypass, with a positive metal-to-metal back seat, and permits the removal of the diaphragms for inspection or replacement under full pressure.

7E10. Type Q Navy manifold. The Type Q Navy manifold (see Figure 7-20) is a new development in which several of the separate control valves are contained in a single compact casing. These include the thermostatic expansion valve, solenoid, strainer, hand expansion valve, shutoff valves, and flanged line connections. Taking the place of assemblies of the separate items, it eliminates 20 joints, which are always potential refrigerant leakage points.

There are two types of Type Q Navy manifolds, one with an internal equalizer on the expansion valve for the refrigeration system, the other with an external equalizer on the expansion valve for the air-conditioning system. Figure 7-21 shows cutaway views of interior construction and flow path through the manifold.

7E11. Gages and thermometers. The refrigeration system also includes the necessary pressure gages and thermometers for observing the pressures and temperatures at various places in the circuit.

Figure 7-22 illustrates the dial of a Freon 12 gage. The pressure and vacuum scale is printed in black, and the corresponding temperature scale in red. The short pointer, red in color, is an extra nonworking, or stationary, pointer that may be set manually to indicate the maximum working pressure. The gage for the suction, or low-pressure, side reads to 150

  psi. The gage for the discharge, or high-pressure, side (and the separate testing gage) reads to 300 psi. Both read to 30 inches of vacuum.

NOTE. The temperature scale on this gage indicates temperatures of Freon 12 corresponding only to the pressures measured. The gage cannot measure temperatures directly.

7E12. Suction strainer. The suction vapor strainer is similar to the liquid strainer and is located near the compressor, connected to the suction inlet line. Its purpose is to prevent scale, dirt, or foreign matter from entering the compressor, where they might injure the finely finished surfaces of the valves or cylinder walls. The strainer body can be opened by unbolting its cap and the strainer screen can be removed for cleaning (see Section 9F1 for directions on care and cleaning).

Figure 7-22. Freon Gage.
Figure 7-22. Freon Gage.

 
F. ACCESSORIES
 
7F1. Ice cube maker. The ice cube maker is of a commercial type (see Figure 7-23). On submarines it is usually a seven-tray cuber, and has a rated capacity of 15 pounds of ice in six hours or sixty pounds per day. This capacity is based on using water at 100 degrees F to fill the trays and subcooling the ice 15 degrees. The capacity can be increased by staggering the filling of the trays, that is, instead of filling   all seven trays at one time, fill two of them at a time at about one-hour intervals. Empty the trays as soon as they are frozen and put the ice in the storage tray in the bottom of the ice cube maker or in the meat compartment of the icebox. Thus a supply of ice can be kept on hand at all times.

The ice cube maker is a part of the refrigerating system and has its own solenoid and

 
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expansion valve (see Figure 7-1). The solenoid valve is wired into the electrical circuits of the solenoid valves of the cool room and refrigerating room in such a way that if either one of these two solenoid valves remains energized, the ice cube solenoid valve also remains energized. If both of these solenoid valves shut down, halting the refrigeration system, the ice cuber also stops operation.

7E2. Wardroom refrigerator. The wardroom refrigerator is designed especially for submarine

Figure 7-23. Ice cube maker.
Figure 7-23. Ice cube maker.

  installation and is built into the vessel. The refrigerating unit is located to the left of the box under the sink. The outstanding feature of this machine is that the condenser is air-cooled (see Figure 7-24). The refrigerator is for daily preservation of food used in the wardroom.

Figure 7-24. Wardroom refrigerator unit.
Figure 7-24. Wardroom refrigerator unit.

7F3. Scuttlebutt. A water coil in the cool room supplies cold water for the wardroom scuttlebutt. Care should be taken to keep the temperature of the cool room above freezing in order not to freeze the water in the coil.

 
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