MPA Logo, San Francisco Maritime National Park Association, USS Pampanito, Historic Ships at Hyde Street Pier, Education Programs Maritime Park Association Home Page Maritime Park Association Home Page Events Maritime Park Association Home Page Maritime Park Association Home Page Maritime Park Association Home Page Volunteer Membership Donate Maritime Park Association Home Page USS Pampanito Submarine Historic Ships at Hyde Street Pier Education Programs About Maritime Park Association Home Page Directions to Maritime Jobs at Maritime Facility Rental at Maritime Trustees of the Association Calendar Press Room Store Maritime Map
9
CARE AND MAINTENANCE
OF THE MODEL X-1 DISTILLING UNIT
 
A. REPAIRS
 
9A1. Evaporator. Repairs to the shell sections and the head of the evaporator can be made only at locations where careful preheating can be done before brazing, and where facilities for annealing the entire section at about 750 degrees F. after brazing are available. Small cracks in a seam however, may be repaired by carefully heating and then covering the crack with soft solder.

Leaky tubes may be rolled with the expanders provided in the spare parts box, or the tubes may be driven out and replaced in the usual manner.

9A2. Heat exchanger. The heat exchanger is of special type construction with the tubes made tight by packing rings. The packing rings are of both metallic and fiber construction and the exchanger may leak a little if it has been standing a long time without use or if it has just been repaired with new packing. When this occurs the exchanger tubes should be filled with water and allowed to stand for 3 or 4 hours during which time the fiber material will swell and the exchanger will then be tight under test. The exchanger should not leak in service since the packing will always be wet.

9A3. Procedure for packing exchanger. The packing for the exchanger is shipped in packages, each package containing 120 each of the fiber and metallic rings for the 1 1/4-inch i.d. tubes and 120 each of the fiber and metallic rings for the 3/4-inch o.d. finned or wired tubes. Always use a fiber ring first and a metallic ring second when packing 3/4-inch tubes, and a metallic ring first and a fiber ring second when packing 1 1/4-inch tubes. Packing tools will be found in the spare parts boxes.

It will normally never be necessary to replace the 1 1/4-inch tubes, but should this have to be done, all the 3/4-inch tubes must be driven out and the plates removed before work may be done on the 1 1/4-inch tubes. The 3/4-inch tubes are

  easily removed so that the 1 1/4-inch tubes may be exposed in a relatively short period of time. Care should be taken in selecting the proper size metallic and fiber packing for each tube because the sizes are only slightly different.

To repack the 3/4-inch tubes proceed as follows:

a. Remove the nuts and covers from both ends of the exchanger.

b. Place the pipe sleeves over the studs and replace the nuts to hold the plates together.

c. Secure the guide pin tool for the 3/4-inch wired or finned tubes from the spare parts box. This is piece No. 811-1c:

d. Insert the guide pin tool in the 3/4-inch tube and drive the tube just through the plate, using the wooden mallet.

e. Drive out the 3/4-inch tubes which need repacking.

f. Remove the old packing rings, being careful not to scratch or score the packing box.

g. Remove all the packing rings from the drillings.

h. On the opposite end of the exchanger, push the tubes back into the tube sheet and drive through as in Step d. Remove the old packing rings as described in Steps f and g.

i. Place the tubes back into tube sheet about flush with the face.

j. Use the packing insertion tool, piece No. 811-1a, from the spare parts box.

k. Hold the tube with the piece of wood to prevent it from coming out of the sheet while the opposite end is being packed. (It may be necessary to secure the wood in place.)

l. Insert the guide pin tool for 3/4-inch tubes in the end of the tubes; place the fiber ring over the pin and press it into the tube plate, driving the packing firmly with the packing tool and a light tap of the wooden mallet or 3/4-pound hammer.

m. Insert the metallic ring and drive it in the same way as a fiber ring.

 
(59)

n. Pack the opposite ends, using the same procedure.

o. Remove nuts and sleeves, and clean the old gasket. Use new gaskets and bolt the plates in place.

NOTE. The packing must be installed with the fiber rings in contact with the distilled water or distillate, and the metallic packing away from it.

To repack the 1 1/4-inch tubes proceed as follows:

a. Drive out and remove all the 3/4-inch tubes and the old packing rings.

b. Block up the exchanger on wood.

c. Disconnect the pipes and remove the 3/4-inch tube plates.

d. Drive in the 1 1/4-inch tubes so they just clear the packing, using the tool provided, and remove the old packing rings.

e. Drive back the 1 1/4-inch tubes from the opposite end to just clear the packing and remove the packing material at that end.

f. Push the tubes back flush with the tube plate; hold the opposite end of the tube and pack the same as described for 3/4-inch tubes. (Insert the metallic ring first and the fiber rings second for the 1 1/4-inch tubes.)

g. Clean the tube plates, use new gaskets and assemble, packing the 3/4-inch tubes as previously described.

9A4. The vapor compressor. When a complete overhaul of the compressor is necessary, it must be removed from the distilling plant. Remove the belt guard, loosen the variable pitch drive and take off the belts. Disconnect the motor leads and take out the bolts holding the motor to the motor support on top of the compressor. Remove the motor from the compressor. Remove the insulating board. Remove the compressor lagging and take off all the oil piping after draining the oil from the compressor. Remove the pressure gage and piping where needed. It is advisable to mark the oil piping so that it may be put back in the exact location. Take off all the nuts and lockwashers, attaching the compressor to the distilling unit, and break the gasketed joint, using jack bolts if available, and lift off the compressor.

NOTE. It is very desirable that any repairs to a vapor compressor be done by a tender or a naval shipyard.

  9A5. Disassembly. (See Figure 9-1.) Remove the motor supporting plate (piece 13). Remove the cotter pin (piece 28), the nut (piece 27) and washer (piece 26), and remove the pulley (piece 83) using the puller. Remove the drive end cover (piece 14). Remove the gear housing (piece 15). Remove the cotter pins from the shaft nuts (piece 77), and remove the nuts. Remove the bolts (pieces 64 and 70), the dowel retainer and dowels from driven gear (piece 19) and remove the gear from the hub. Remove the bearing lockouts (piece 42) and the lockwashers (piece 44) from the rotor shafts. Using the gear puller provided in the spare parts box, remove the driven gear hub (piece 20) and the drive gear (piece 18) from the shafts and remove the keys.

NOTE. The driven gear must be loosened from the hub and removed first before attempting to remove the drive gear. If this is not done, the rotors will be damaged.

Match mark the bearing retainers with the end plates so that the parts may be reassembled in the same relationship. Remove the bolts (piece 62) from the bearing retainer plate (piece 46) and, by using the puller, pull out bearing retainers (piece 32). This will also bring out the bearings and oil slingers. Remove the shims (piece 43), carefully noting their number and position so that they may be reinstalled correctly.

On the drive end of the compressor, remove the bearing lockouts and lockwashers (pieces 42 and 44). Remove the oil slinger and spacer (piece 47) from the driven shaft. Remove the bolts (piece 63) from the bearing retainers (piece 32). By means of the puller, the bearing retainers with bearings and oil slingers may be pulled out. Remove the packing glands (piece 53) from the shafts. Remove the shaft sleeves (pieces 36 and 37).

Match mark the end plates with the cylinder so that the parts may be reassembled in the same relationship. Remove the bolts and lockwashers (pieces 61, 80, and 75) that hold the drive end plate (piece 10) to the cylinder. Remove the end plate from the cylinder. The dowels (piece 81) that position the end plate to the cylinder should remain in the cylinder. The end plate at the gear end of the compressor (piece 10) may be removed in the same manner after the

 
60

Figure 9-1. Vapor compressor, three lobe (exploded view).

shafts and rotors have been removed. Remove the packing (piece 51) from the end plates.

9A6. Assembly. (See Figure 9-1.) Before assembling the compressor, all parts should be thoroughly cleaned and inspected. Any slight burrs or rough edges on the cylinder or end plates should be removed with crocus cloth. Install the shaft sleeves (pieces 36 and 37), packing (piece 51), and packing glands (piece 53) in both end plates. The sleeves for the gear end (piece 36) have a smaller inside diameter than the sleeves for the drive end (piece 37).

Coat the face of the gear end plate (piece 10) and the cylinder (piece 1) with Perfect Seal No. 4, manufactured by the P. O. B. Manufacturing Co., Cincinnati, Ohio, or an equivalent seal. Place the end plate in position over the dowels in the cylinder. Install the bolts and lockwashers (pieces 80 and 75) and tighten them evenly. Place the cylinder upright on the end plate. Install the drive shaft and rotor into the cylinder with the gear end down. Turn the keyway in the shaft to the left (looking at the top of the compressor). Install the driven shift and rotor into the cylinder, gear end down and keyway in the shaft to the left (looking at the top of the compressor).

NOTE. The drive shaft is on the right when assembling the compressor in this manner. The keyways in both shafts must be to the left or to the right (looking at the top of the compressor).

Coat the faces of the drive endplate (piece 10) and the cylinder with Perfect Seal No. 4 or equivalent. Install the drive end plate over the shafts and over the dowels in the cylinder. Install the bolts and lockwashers (pieces 80 and 75) and tighten evenly. Install the bearing retainers (piece 32) with the oil slingers (piece 34) and bearings (piece 35). Make certain that the oil seals (piece 54) are in place in the grooves in the retainers. It will be necessary to press the bearings on to the shafts by using special tools. Make certain that the pilot hole in the bearing retainer lines up with the dowel in the end plate.

NOTE: If the bearings and oil slingers have been removed from the bearing retainer, they should be reassembled before installing them over the shafts. The oil slinger is installed with the large diameter toward the inside of the retainer

  away from the bearing. The bearing is installed with the smooth side next to the oil slinger.

Make certain that the shims (piece 43) are installed between the bearing retainers and the end plate at the gear end of the compressor. Install the bearing retainer plates (piece 46) at the gear end and install and tighten the bolts. Install the lockwashers (piece 44) and locknuts (piece 42) in the gear end of both shafts. Tighten the locknuts and turn down the tang of the lockwashers into the slot of the locknut.

NOTE. The gear end locknuts and bolts must be tightened first to prevent pulling the shafts in the rotors.

Check the rotor end clearance which should be 0.009 to 0.011 inch at each end. If necessary, add or remove shims until the proper clearance is obtained. Install and tighten the bolts holding the bearing retainers at the drive end. Install the lock wire. Install the spacer (piece 48) and oil slinger (piece 47) on the drive end of the driven shaft. Install lockwashers (piece 44) on the drive end of each shaft and install and tighten the locknut (piece 42). Insert the key (piece 25) in the driven shaft (piece 21) and press the driven gear hub (piece 20) into place. Insert the key (piece 25) in the drive shaft (piece 22) and press the drive gear (piece 18) into place using the special tool. With the keyways in both shafts to the right (facing the gear end of the compressor), and with the marked tooth space on the driven gear (piece 19) meshed with the marked tooth on the drive gear, push the driven gear into position over the hub using the special tool. Install the dowels (piece 59), dowel retainer plate (piece 58) and bolts (pieces 64 and 70). Tighten the bolts and install the lock wire. Install and tighten the shaft nuts (piece 23) on both shafts. Insert the cotter pins.

9A7. Clearances. Check the rotor clearances to see that they are within the following limits:

Rotor to rotor0.014-in. to 0.018-in.
Rotor to end plate-drive end0.009-in. to 0.011-in.
Rotor to end plate-gear end0.009-in. to 0.011-in.
Rotor to cylinder0.006-in. to 0.009-in.

The rotor end clearances can be adjusted by varying the thickness of the shims between the bearing carrier and the end plate at the gear end.

 
61

If the rotor to rotor or rotor to cylinder clearances are incorrect, the gears and bearings should be checked for wear.

CAUTION. Do not drive against the shaft or any part mounted on the shaft after the thrust bearings (piece 35) have been clamped in place by the retainer plate (piece 46). Cover the sealing faces of the motor supporting plate (piece 13) and the cylinder with Perfect Seal No. 4 or equivalent. Install the plate on the cylinder, insert and tighten the bolts securely. Shellac a new gasket (piece 55) to the drive end cover (piece 14), grease the gasket and the face of the end plate and install the cover. Shellac a new gasket (piece 56) to the gear housing (piece 15), grease the gasket and face of the end plate and install the gear housing. Install the pulley (piece 83), washer (piece 26), and nut (piece 27) on the drive shaft. Tighten the nut and install a cotter pin (piece 28).

9A8. Mounting the compressor on the unit. Place a new gasket from the spare parts box on the top head of the distilling unit and then place the compressor over the stud bolts. Replace the lock

  washers and nuts and draw down the nuts uniformly. After mounting the compressor make certain that it may be easily turned by hand and that it does not bind or strike anywhere. Replace all of the oil piping around the compressor and install the lagging. Replace the insulating board. Replace the motor on top of the compressor and bolt it securely to the motor supporting plate attached to the top of the compressor. Replace the pulley on the compressor and attach the belts, tightening the belts by means of the variable pitch drive. Replace the pulley guard. Connect up the motor leads. Place the proper amount of Navy Symbol 9370 (SAE 40) oil in the compressor.

9A9. Preparation of the compressor for service. Start the distilling unit and observe the compressor while the unit is starting up; observe its operation carefully for a period of 2 hours after distillation has started. If the compressor shows no signs of sticking during this period, it will give satisfactory service. Should the compressor stop or bind during this operation, stop the compressor and allow it to cool until it turns freely by hand and then start the unit again.

 
B. CLEANING
 
9B1. Cleaning. At present (Jan. 1955) the acid cleaning method has almost entirely replaced the mechanical method, however, the mechanical cleaning equipment is carried on board tenders and could be used if acid cleaning equipment or material was unavailable. Both methods of cleaning are described in the following sections.

When mechanical cleaning was the only method used, the evaporator could be operated for 400 hours before cleaning. The absolute operating limit was 500 hours.

The heat exchanger was cleaned after 200 hours of operation and the operating limit was 250 hours.

Rotameters, manometers and flow-control valves were cleaned each time the evaporator was cleaned, or more often if necessary.

With the acid cleaning method, the cleaning interval is every 250 hours of operation. Less time is consumed and less work necessary to acid clean the distillers than to mechanically clean them. The heat exchanger requires cleaning at least each 250 hours of operation and, since the

  acid method cleans the heat exchanger, evaporator and all the connecting piping at the same time, the whole unit is cleaned with the heat exchanger.

A description of the mechanical method will be found in the following sections.

9B2. Cleaning crew. Two men comprise a cleaning crew. Unless a foot switch is provided, one man should operate the motor and one man should clean the tubes. The motor is turned on or off at the direction of the man cleaning the tubes. Make certain that the belt has sufficient slack so that it will slip if the bit becomes jammed in the tube.

9B3. Shear coupling assembly. (See Figure 9-2.) To provide protection for the small flexible shaft against excessive torque loads, a shear coupling assembly is attached to the cutter bit end of the flexible shaft. The feature of this assembly is a hexagonally shaped shear pin so constructed that it will break under excessive loads. The ends of the pin fit into hexagonally shaped housings, which in turn are enclosed in a common casing

 
62

Figure 9-2. Shear coupling assembly.
Figure 9-2. Shear coupling assembly.
which screws on to the cutter bit end of the flexible shaft casing. (This easing has a left-hand thread.) When the pin breaks, its broken ends can be easily removed from their housings and a new pin inserted.

9B4. Cleaning the evaporator. The following procedure should be observed in cleaning the evaporator:

a. Remove the section of insulation over the manhole.

b. Remove the manhole with the wrench provided in the spare parts box.

NOTE. If necessary, rig up a platform at about the level of the bottom of the evaporator.

c. Open the drain valve at the bottom and drain the evaporator (use wire if the line clogs).

d. Remove the bottom circular insulation.

e. Disconnect and remove the eight immersion heaters with the wrench from the spare parts box. Plug the heater connections with the 3/4-inch pipe plugs from the tube cleaner box.

f. Clean the scale from the heaters while they are still wet.

g. Disconnect the overflow piping from the handhole at the bottom of the evaporator and plug the connection with a 1-inch or 1 1/2-inch pipe plug from the tube cleaner box.

h. Start the feed pump. Open the feed valve and fill the evaporator so that the water level is about 1/8 inch below the tops of the tubes. Secure the feed valve and pump.

  i. Place a light inside the evaporator.

j. Disconnect the feed line from the inside shell of the evaporator at the union and lift out the pipe.

k. Using the special wrench from the spare parts box, unscrew the overflow funnel pipe and remove it.

l. Chip the scale from the compressor discharge pipe and underside of the baffle. Chip the scale from the shell of the evaporator about 4 inches above the tube plate. It is advisable to cover the tube plate to prevent big chips from falling into the tubes.

m. Remove the motor and flexible shafts from the tube cleaner box and connect them as follows Couple the large flexible shaft and casing to the driving unit by inserting the coupling attached to the flexible shaft into the keyed hole in the countershaft spindle. Screw the casing coupling nut tightly to the threaded hub of the eccentric.

The 1/2-horsepower motor speed is 1,725 rpm. Lift the belt guard and place the belt on the large motor pulley, and the small countershaft pulley. This setting of the belt will produce 3,450 rpm speed at the countershaft.

NOTE. To set the speeds or adjust belt tension, pull out the small handle and turn the eccentric to loosen the belt. Place the belt on the desired pulleys, turn the eccentric in the opposite direction to tighten the belt, and replace the handle in a locking position. Do not adjust the belt tension too tightly, but allow slack so that the

 
63
338450 O-55-6

belt will slip in the event that the cleaning tool becomes jammed in a tube. Be sure to replace the belt guard.

Couple the 9-foot long 0.615-inch o.d. casing assembly by threading the shaft coupling to the end of the large shafting. Put grease in the bronze casing coupling, slide it over the joint, and secure the thumb nut to the section near the end of the large shaft.

The 9-foot extension cable for the tube cleaning equipment consists of an 1 1/32-inch o.d. flexible shaft inside a heavy 0.615-inch o.d. double interlock casing. The assembly has a hexagon shear shaft coupling in the thrust end housing of the casing assembly (cutter bit end). This shear coupling may be replaced by unscrewing the end fitting of the casing. This fitting has a left-hand thread. (See Figure 9-2.)

Three accessories are provided for cleaning the 3/4-inch tubes, the choice of which is dictated by the nature of the deposit in the tubes. The accessories are the following:

1. Carbide tipped cutter bit. The cutter bit is the best and quickest method of removing hard scale formed by normal operation using untreated sea water feed. When using this bit, the tubes must be full of water. It should be used at 3,450 rpm and will clean about three tubes per minute.

2. Expanding wire brush. The expanding wire brush will readily remove soft scale usually formed from treated sea water feed. It will also remove hard scale if worked up and down in the tube for a long enough period. The tubes must be full of water or a stream of water must be flowing down the tubes when the expanding brush is used. It should be used at 3,450 rpm and will clean about three tubes per minute if the scale is soft. It may take 45 seconds or longer per tube if the scale is hard.

3. Vibrating head. The vibrating head must always be attached to a flexible holder. It will remove any type of deposit. It may be used with the tubes full of water or completely dry. It must be used when it is impossible to clean the tubes in the presence of water. The vibrating head should be used at 3,450 rpm and will take 30 seconds to 2 minutes per tube, depending on the type of scale. After using the vibrating head, the tubes must be polished with the expanding brush.

  n. Place the heavy shaft so that the smaller shaft will lie in a straight line with no short bends. Grease the large cable by means of the grease cup (about 8 to 10 shots) and connect by plugging the tube cleaner motor cord to the lighting circuit. Add more grease to the large cable about every 15 minutes.

NOTE. The motor is for 110 volts d.c. on d.c. voltage vessels.

o. Examine the scale, select the proper cleaning tool from the small toolbox, and proceed as follows:

1. Cleaning 3/4-inch tubes with the cutter bit (Figure 9-3). The tubes must be full of water.

(a) Attach the cutter bit to the end of the small shafting.

CAUTION. The cutting edges of the tool are tipped with tungsten carbide which is quite brittle. Do not drop the bit or strike the cutting edges on metal surfaces.

(b) Start the motor and proceed to clean the tubes by passing the bit through each tube once.

NOTE. Unless a foot switch is provided, one man should operate the motor and one man should clean the tubes. The motor is turned on or off at the direction of the man cleaning the tubes.

CAUTION. With the motor off, place the end of the bit gently in the top of a tube. Hold the cable about 6 inches back and line it up exactly with the tube. Start the motor and let the bit feed itself into the tube until the entire bit is in the tube. Now exert pressure and pass the bit through the tube. (The tubes are 16-14 inches long. The fixed sleeve on the cable indicates when the bit is completely through.) Pull the bit out of the tube, stopping the motor just before the bit is withdrawn, then go on to the next one, and so forth. One bit should clean the evaporator several times. As the cutting edges become dull, more pressure will be required to force the bit through the tube. When the pressure is too great or the bit begins to jam, the cutting edges should be lightly honed. When honing is no longer possible, the cutting edges should be reground. Should the cleaning tool fail to turn while the motor is running, the small hexagon shear coupling is probably broken. Remove the housing from the end of the casing (left-hand thread) and replace the shear coupling (Figure 9-2).

 
64

Figure 9-3. Cleaning gear with a cutter bit.
Figure 9-3. Cleaning gear with a cutter bit.
CAUTION. If the bit jams, secure the motor immediately and free the bit. Try cautiously again. If the bit continues to jam, mark the tube and go on to the next one. After the remainder of the tubes have been cleaned with the cutter bit, clean the marked tubes with the expanding brush or vibrating head, as directed in Step 2 or 3 following. The thin film of scale left by the bit in the expanded portion of the tubes will cause no trouble or loss of efficiency and need not be removed.

(c) After all the tubes have been cleaned, secure the motor, unscrew the bit (wrenches will be found in the tube cleaner box), dry, oil, and replace the bit in the box.

NOTE. If the small cable runs hot in cleaning the tubes, it should be greased. In any event, this cable should be greased at least once every hour of continual use. To grease the smaller cable, remove the flexible shafting from the inside casing and wipe with grease as it is reassembled. If the large cable runs hot, add more grease to the grease cup.

2. Cleaning 3/4-inch tubes with the expanding wire brush. The tubes must be full of water.

(a) Attach the expanding brush to the end of the small shafting.

  (b) Start the motor and work the expanding brush up and down the tube. Make certain that the brush goes entirely through each tube. The operator can tell by the vibrations of the brush when all the scale is removed. If the scale is soft it should be possible to clean two or three tubes per minute. A minute or more per tube may be required to remove the hard scale.

(c) Remove the expanding brush, dry, oil, and replace in the box.

3. Cleaning 3/4-inch tubes with the vibrating head. The tubes may be full of water or dry.

(a) Attach the flexible holder and vibrating head to the end of the small shafting.

(b) Start the motor and work the vibrating head slowly up and down the tube. Keep the vibrating head in motion. Do not permit it to remain at one spot in the tube for any length of time. The operator can tell by the vibrations of the brush where patches of scale remain and when it has all been removed. Clean each tube completely before proceeding to the next one. A minute or more may be required per tube, depending on the hardness and type of scale.

 
65

NOTE. After using the vibrating head, the tubes must be polished with the expanding brush.

(c) Disassemble the overflow piping between the evaporator and the heat exchanger. Straight sections of 1-inch or 1 1/2-inch I.P.S. (Iron Pipe Size) may be cleaned with the vibrating head for the 1-3/4-inch o.d. tubes attached directly on the small shafting (Figure 9-4). Elbows or bends in 1-inch I.P.S. pipe and sections of 3/4-inch I.P.S. pipe may be cleaned with the 3/4-inch vibrating head. A stream of water must be flowing through the section of pipe being cleaned, otherwise the head will become clogged with scale.

(d) Remove the vibrating head and flexible holder, dry, oil, and replace in the box.

9B5. Cleaning the 1 3/4-inch o.d. heater tubes and inside of overflow pipe. The scale should be removed in the presence of water (Figure 9-3).

a. Select the vibrating head and flexible holder for the 1 3/4-inch o.d. tubes and attach it to the end of the small shafting. Use a cleaner shaft speed of 3,450 rpm.

b. Start the motor and work the vibrating head slowly up and down the heater tubes until all the scale is removed.

  NOTE. Place a clamp on the large shafting to serve as a guide to indicate when the vibrating head is entirely through the 16 1/4-inch long tubes.

c. Clean the inside of the overflow pipe in the same manner as the heater tubes were cleaned.

d. Remove the vibrating head, flexible holder, and small shafting. Dry, oil, and replace the vibrating head and flexible holder in the box.

e. Attach the 1 3/4-inch o.d. expanding brush directly to the end of the large shafting, and polish the heater tubes.

f. Remove the 1 3/4-inch o.d. expanding brush, dry, oil, and replace in the bag.

9B6. Cleaning 4-inch o.d. tube located in the center of the evaporator.

a. Drain the water from the unit. Should the flow stop before draining is complete, insert a wire in the drain line to start the flow.

b. Connect a hose to the ship's water supply and place the end inside the evaporator. Direct a small stream of water down the sides of the 4-inch tube.

CAUTION. Do not clean the 4-inch tube when it is full of water.

c. Select the large expanding brush and attach it to the end of the large shafting.

Figure 9-4. Cleaning gear with a vibrating head and expanding wire brush.
Figure 9-4. Cleaning gear with a vibrating head and expanding wire brush.
 
66

Figure 9-5. Water nozzle.
Figure 9-5. Water nozzle.
d. Remove the belt guard and place the belt on the sit all pulley and the large countershaft pulley to give the lowest shaft speed, approximately 1,725 rpm.

CAUTION. The 4-inch brush must be used only at low speed. The operator at the motor should keep his hand on the switch so that he can secure it instantly at the direction of the operator cleaning the tube.

e. Place a stop on the sleeve of the large cable that the whole brush will not go entirely through the 16 1/4-inch long, 4-inch o.d. tube.

f. With the motor off, place the brush in the large tube. Start the motor and work the brush up and down the tube, taking care that the brush does not come out of the tube while the motor is running. Secure the motor before removing the brush from the tube.

g. Remove the large brush, dry, oil, and replace in the box. Disconnect the large shafting, dry, oil, and replace in tube cleaner box. Do not

  attempt to coil the shafting too tightly. Utilize the full width of the tube cleaner box. Replace the motor and other parts.

h. Remove the 4-inch handhole. Remove the scale accumulation by hand and flush out the scale with a water hose from the bottom head of the evaporator.

i. Replace the handhole, the overflow tube with funnel, the inside feed connection and the manhole cover.

j. Clean the rotameters, manometer and flow control valve.

k. Reassemble the overflow piping.

9B7. Cleaning the heat exchanger. The heat exchanger using 3/4-inch o.d. finned tubes should be cleaned as follows:

a. Remove the covers from both ends.

NOTE. Remove the nuts from every stud before attempting to remove the covers. However, it is not necessary to break the gasket joint

 
67

between the small plate and the inlet end cover. Do not remove the small plate from the inlet end cover except after about 4,000 hours.

b. Connect the tube cleaning motor and flexible shafts as for cleaning the 3/4-inch o.d. tubes of the evaporator. (See Figures 9-3 and 9-4.) Connect the water hose with nozzle for the 3/4-inch o.d. tubes attached. (See Figure 9-5.)

c. Examine the scaled tubes and select the proper tool.

NOTE. The lower three or four rows of tubes in the exchanger will usually have a hard scale similar to that found in the evaporator tubes. The carbide tipped cutter bit is the best and quickest tool to remove a hard scale and should be used in these tubes.

The upper five or six rows of tubes in the exchanger will usually have a soft slime-like scale. The expanding wire brush will remove this type of scale quite effectively and should be used in these tubes. Both of these attachments should be used at 3,450 rpm. One man should stand by the motor to operate the switch, a second man should clean the tubes, and a third man should handle the water hose.

d. Insert the hose nozzle in the end of heat exchanger tube at the less accessible end and run a small stream of water through the tube. With the proper tool attached, mark off a point on the cable about 49 inches from the end. Start the tube cleaner motor and pass the cleaner through the tube, withdrawing the hose nozzle just before the cleaner reaches the nozzle. Care should be taken to line up the cable with the tube when starting the cleaner tool into the tube.

NOTE. A stream of water must always be flowing through the tubes while cleaning.

CAUTION. Should the bit jam, secure the motor immediately and free the bit. Try cautiously again. If the bit continues to jam, mark the tube and go on to the next one. Clean the marked tubes with the vibrating head or expanding wire brush. Should the cleaning tool fail to turn while the motor is running, the small hexagonal shear coupling is probably broken. Remove the housing from the end of the casing (left-hand thread) and replace the shear coupling (Figure 9-2).

e. Dry, oil, and replace the tube cleaning gear in box.

  NOTE. Be certain to disassemble and grease the 9-foot shafting before replacing in the box.

f. Remove the 3/4-inch brine overflow pipe connection at the bottom of the exchanger and clean the pipe. Connect to the heat exchanger after cleaning.

g. Clean the end covers of the exchanger and replace, using new gaskets.

9B8. Instructions for resharpening cutter bits. A hone is provided in the tube cleaning box for sharpening the tungsten carbide cutting edge. When the bit cannot be sharpened by the hone, it must be ground. A diamond impregnated or silicon carbide wheel should be used.

a. Each flute of the cutter bits must be ground separately.

b. Grind only on the cutting edges, never on the diameter, noting particularly-that the 15 degrees relief angle is maintained.

c. If a wheel is used:

1. Never permit the wheel to become loaded. Keep it clean.

2. Keep the bits in motion while passing the wheel, avoiding any stationary contact.

d. Be certain that the cutting edge of each tungsten carbide bit is indexed and ground identically so that each flute does the same amount of cutting.

9B9. Acid cleaning. Naval vessels employing vapor compression distilling units, particularly submarines, maintain a very limited reserve of distillate. It is therefore important to maintain distiller efficiency at the highest possible level and to assure a minimum of lay-up time for removing the scale deposits from the heat transfer surfaces.

The mechanical method of cleaning is inefficient, time consuming and somewhat damaging to the heat transfer surfaces. As a result, distilling units were generally operated to the point of lowest tolerable capacity, necessitating long and expensive overhaul periods. In consideration of the foregoing, an acid cleaning method has been adapted for submarine usage.

9B10. Intervals of cleaning. Clean distilling plants with the sodium acid sulphate solution, normally after each 250 hours of operation, or when the steam chest pressure reaches 6 psi.

 
68

FIGURE 9-6 TYPICAL ARRANGEMENT OF PORTABLE ACID CLEANING TANK AND CONNECTIONS TO DISTILLING PLANT

FIGURE 9-7 ACID CLEANING PIPING ARRANGEMENT FROM HEAT EXCHANGER TO BRINE TANK.

9B11. Cleaning crew required. One man can efficiently clean one distilling plant in 2 hours time if equipment is kept available and in a good state of readiness.

9B12. Equipment required.

a. One copper or nonferrous metal container of 25-35 gallons capacity, fitted with a bottom discharge line and suitable strainers, valves and a fine mesh screen cover.

b. Suitable hoses for connecting the brine tank to the acid tank and the acid tank to the feed pump. It is suggested that all hose couplings be numbered to insure tight make-up.

c. 50 pounds of sodium acid sulphate (niter cake) for each distilling plant to be cleaned.

9B13. Preparations for cleaning.

a. Fill evaporator as for normal operation, and turn on all heaters.

b. While waiting for unit to heat up, carry out normal prestarting routine, checking

1. Tightness of belts.

2. Compressor oil level.

3. Bypass valve open.

4. Motor rheostat turned down.

5. On converted units, while cleaning, check open evaporator level safety line stop valve.

c. Make up mixture of sodium acid sulphate and water (salt or fresh), following formula:

Sodium acid sulphate (lbs.) =capacity of unit (gph) X 4/5

This makes a mixture of about 12 percent strength.

d. Make necessary connections, with hoses to feed pump from acid tank, and from brine tank to acid tank. (See Figure 9-6.)

NOTE. Be sure that the hose from the acid tank to the feed pump is filled with the acid solution and free of air.

e. Line up condensate and brine systems as in Figure 9-7.

9B14. Procedure for cleaning.

a. When unit is ready to start, follow normal starting procedures.

b. When balanced, cut feed rate to about 50 percent normal flow. To maintain distillate balance this will require cutting off heaters.

  c. Shift feed pump suction from normal source to acid tank suction line. Secure the normal source.

d. Blow or drain first 20 gallons of brine-condensate mixture to bilge. Afterwards blow all acid-brine-condensate mixture to acid tank. This keeps acid solution at full strength.

e. Maintain steam chest pressure at four psi, using bypass valve.

f. Continue circulating acid-brine-condensate mixture through the unit for 1 1/2 hours.

g. Shift the feed pump suction to the normal source after cleaning period is completed, and discharge all distillate to the bilge, making frequent Kleinschimdt conductivity tests until distillate is acceptable for regular use. One hour's operation should restore maximum purity.

NOTE. If need for distillate is critical, it can be run to the regular storage throughout the cleaning process, provided the Kleinschmidt conductivity tests taken on the distillate is within the specified limits. This will require that the same amount of water (salt or fresh) be added to the mixture to keep it to the correct strength.

NOTE. Should the steam chest pressure remain high after returning to normal operation, the distilling unit has not been properly descaled. In such a case, repeat the cleaning process, using a fresh charge of sodium acid sulphate mixture.

h. Shift the distillate to its regular storage and continue normal operation.

i. When secured, rinse all equipment with fresh water and stow away for future use.

9B15. Safety precautions.

a. Sodium acid sulphate is inert in the dry state. Store in moistureproof containers.

b. It is only mildly acidic when in use and will not harm the skin or clothing. Normal safety precautions should be followed to prevent contact with the eyes or with skin for prolonged periods. Mild irritations will result.

c. Insure that all equipment is kept clean, and if acid container is used as a rag or waste container, clean thoroughly of all oil and waste before using again.

d. Keep valves in systems in good condition, to insure there is no possible contamination of distillate when in normal use.

 
69

Previous chapter
Previous Chapter
Sub Refrig. Home Page
Sub Distilling Home Page
Next chapter
Next chapter


Copyright © 2013, Maritime Park Association
All Rights Reserved
Legal Notices and Privacy Policy
Version 1.10, 22 Oct 04