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
5
CARE AND MAINTENANCE
OF THE MODEL S DISTILLING UNIT
 
A. RETARDING SCALE FORMATION
 
5A1. Scale formation. The coils of the distilling unit gradually become coated with scale, and if the operation is continued over too long a period the accumulation of scale will tend to make the tube cones stick together, and difficult to separate. Since the tubes are made of comparatively soft copper nickel, separating them cannot be accomplished without the certain danger of damaging the cones.

5A2. Flushing during operation to retard scale. After every 10 to 20 hours of continuous operation all heaters should be turned on and the unit operated about 3 hours with maximum feed allowing stable operation. If the compressor discharge pressure continues to increase and does not come down after flushing, more heaters should be used and the overflow rate increased for the remainder of the patrol or until such time as the flushing will reduce the compressor discharge pressure.

Operators should endeavor to keep the compressor discharge pressure as low as possible. When the pressure begins to increase and fails to return to the initial operating pressure after flushing, the overflow rate during operation should be gradually increased by using more heaters and increasing the feed rate. The unit should not be operated for more than 22 continuous hours between flushings.

The periodic flushings will retard the increase in operating pressure, but this will nevertheless

  gradually rise. A rise in pressure of approximately 2 1/4 pounds from the initial operating pressure of 3 1/2 pounds may be considered safe. That is, 5 3/4 pounds is the upper limit of compressor gage pressure, at a compressor speed of 1100 rpm. In an emergency, 6 1/4 pounds may be used as the upper gage pressure limit.

If the discharge pressure is allowed to increase much beyond the pressures indicated, cleaning by the acid method will be extremely difficult and the type of scale formation will make it necessary to disassemble and clean mechanically, which is always difficult.

Every effort should be made to return to the base or tender with distilling units operating at 5 3/4 pounds or less compressor discharge pressure. Under these conditions the stills may be easily and quickly cleaned by chemical methods without disassembly.

5A3. Flushing during shutdown period. The rate of scaling will be retarded if the distilling unit is operated at all times with a minimum of 20 gallons per hour overflow, and, after the unit is secured, flushed for a period of 1 1/2 to 2 hours with cold sea water at a rate of approximately 60 gallons per hour overflow, with the weir left filled with sea water. Under the above conditions the distilling unit should operate for a period of 350 to 400 hours.

 
B. THE TWO-LOBED ROOTS-CONNERSVILLE COMPRESSOR
 
5B1. Lubrication. The compressor is lubricated from two reservoirs, one at each end. Each oil reservoir is supplied with an oil level indicator which has previously had the proper oil level marked on the gage. The oil level should be checked every 24 hours and oil added as needed when the compressor is not running.

Two vertical 1/2-inch nipples with couplings closed with two 1/2-inch pipe plugs are provided

  for filling the oil compartment. The pipe plugs are removed and oil poured into the couplings until the proper level is reached. The oil may be drained from the compartment by opening the 1/2-inch petcocks. Oil is retained in the oil compartment by oil seal rings or packing glands.

The reservoir of oil at the pulley end of the compressor lubricates the ball bearings by a slinger ring attached to the drive shaft. The

 
(22)

reservoir of oil at the opposite end from the pulley lubricates the timing gears and ball bearings at that end of the compressor by the splashing of the gears. All the bearings and gears run at a high temperature, and no oil lighter than Navy Symbol 1150 (SAE 70) should be used in the Roots-Connersville compressor.

On the old type vapor compressors, steam seals were used and leakage was carried away through a drain pipe into the vapor separator and out through the vent pipe. These seals were a source of trouble and on the later type compressor they have been replaced by packing glands. Steam leakage is now prevented by the use of stuffing box glands. These glands should be adjusted so that they will be just tight enough to prevent leak age. Excessive tightness will damage the packing and shaft sleeves, causing excessive heating and the impellers will stick. The gland nuts must be tightened evenly. When steam leakage cannot be stopped by tightening the glands, new packing must be installed. This may be done without dismantling the compressor. The nuts are loosened first and then the gland is backed out.

Each gland is packed thus: one ring of Johns-Manville No. 360, three rings of Johns-Manville No. 610, one ring of Johns-Manville No. 360.

Remove the first ring of No. 360 packing, using the packing hook found in the spare parts box, and one ring of No. 610. Insert two new rings of No. 610 and one ring of No. 360. Insert the gland and tighten carefully. This should make the stuffing box tight. However, if this is not satisfactory, remove all five rings from the stuffing box and insert one ring of No. 360, three rings of No. 610 and one ring of No. 360. Tighten gradually and evenly as recommended. The packing gland which is split may be removed from the shaft during the packing operation if found necessary.

When a complete overhaul of the compressor is necessary it must be removed from the distilling unit.

5B2. Keeping oil out of the compressor. Should oil for any reason get into the steam compressor it will be left inside the 1/4-inch tubes of the heat exchanger coils, causing the pressure to go up and the heat transfer rate to fall off, besides contaminating the distillate with oil. A thin film of oil may be noticed on the surface of the condensate. To remove oil from the tubes, shut the unit down

  and flush with feed water until the overflow feed runs cool. Shut off the feed. Disconnect the condensate piping and make a connection to the condensate header with hose or piping, running the open end to just below the compressor. Add about two or three gallons of any pure oil solvent such as naphtha, to this open end, completely filling the tube bundle. Drain and repeat with the same solvent. Reconnect the unit and continue operation.

5B3. Removing compressor from the unit. In removing the compressor, proceed as follows;

a. Remove the belt guard, loosen the variable pitch drive, and take off the belts.

b. Disconnect the motor leads and take out the bolts holding the motor support on top of the compressor.

c. Remove the compressor lagging and after draining the oil from the compressor take off all the oil piping.

d. Remove the pressure gage and piping where needed.

e. It is advisable to mark the oil piping so that it may be put back in the exact location.

f. Take off all the nuts and lock washers attaching the compressor to the distilling unit, breaking the gasketed joint by 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.

5B4. Disassembling compressor (new type). Figure 5-1 shows an exploded view of the two-lobed compressor. Remove the motor-supporting base. Remove the drive and cover, and then remove the gear house cover. Mark each gear hub and each shaft to be certain that the assembly of the timing gears will be exactly in the same position as before. Also mark a gear tooth and its mating groove to insure proper location of the impellers and gears. Remove the taper pin on the timing gear which is pinned, using the taper pin punch in the compressor spare parts box.

CAUTION. Care should be exercised to avoid bending the shaft by placing a heavy iron against the hub of the gear when driving out the pin.

Remove the gears by means of the gear puller provided in the compressor spare parts box. Remove the cap screws, and insert the 1/4-inch cap screws provided in the spare parts box into the

 
23

bearing carrier. With the aid of these screws, take out the bearing carrier. The carrier will contain the bearings and oil slingers.

On the drive end of the compressor the bearing lock nuts and then the cap screws must be removed. Remove the oil slinger. By means of the 1/4-inch cap screws the bearing carriers may be pulled out. Remove the shims carefully.

Drive out the taper pins that locate the gear-end head plate and remove all cap screws and lock washers. By means of wedges, force the head plate from the cylinder. The drive-end head plate need not be removed.

Remove the glands from the shafts and take out all the packing.

Pull the impellers and shafts from the drive-end head plate.

Should it be necessary to replace the impellers or gears in the compressor, a complete new assembly must be used because gears and impellers are matched and cannot be used interchangeably. A complete set is provided in the spare parts box.

5B5. Assembling the compressor. Push the shafts with the impellers through the drive-end head plates and then place the gear-end head plate over the shafts and against the cylinders. Insert the taper pins to locate the head plate correctly in the original position. Insert the cap screws and draw them up uniformly tight. Do not insert and tighten one cap screw without installing and tightening the other simultaneously.

Insert the bearing carriers with the oil slingers and drive on the oil slingers using the drive tube provided in the compressor spare parts box.

Drive the bearings on the shafts and into the carriers against the oil slingers. On the gear end, follow with the spacer collar.

Heat the drive shaft gear in an oil bath to a temperature of about 250 degrees F. and quickly place it over the shaft and press in the key. Set the impeller shaft in the correct timing position, using the gear spanner wrench from the spare parts box to turn the gear. Heat the driven shaft gear to about 250 degrees F. in an oil bath, then quickly place it on the shaft and press in the taper pin. Check to be sure that the taper pin is in the proper location and will enter 80 percent of the distance by hand and then drive it in firmly, placing a heavy iron against the gear hub to prevent the bending of the shaft while driving the pin.

  On the drive end, after installing the carriers, oil slingers, and bearings on both of the shafts, and placing the collar and slinger plate on the short shaft, tighten the lock nuts. By the use of laminated shims the axial position of the impellers must be adjusted to divide the total end clearance of .012 inches as nearly equally as possible between each end of the impeller and its head plate. The laminated shims are .002 inches thick. Any extra clearance should be left at the gear end when it is not possible to set the impellers exactly in the central position.

The clearance on the driving face of the lobe of the impeller on the drive shaft should be .016 inch and on the back of the lobe .006 inch. If the impellers strike after being set for these clearances, look for burrs, roughness, or particles of metal imbedded in the impeller.

If the impellers are not timed correctly with the taper pin driven firmly into the driven shaft, loosen the thrust bearing clamping plate and drive out the taper pin. Place a thin strip of metal of the proper thickness between the close impeller lobes and, by use of the gear spanner wrench (from the compressor spare parts box) placed on the gears, turn the impellers in the proper direction to cause the gear on the driven shaft to turn to the correct location. The gear fit is too tight on the shaft to permit movement with the spanner wrench. Put pressure on the gear with the spanner wrench and strike the hub of the gear, causing it to jump to a new position. The taper-pin hale in the gear shaft may be reamed and the taper pin driven in a little deeper. Tighten the thrust bearing clamping plate.

The impellers when correctly turned and located maybe revolved easily by hand or spanner wrench.

The proper impeller clearances are:

Between tip and case top0.004 in. to 0.006 in.
Between tip and case bottom 0.004 in. to 0.006 in.
End clearance (gear end) 0.004 in. to 0.006 in.
End clearance (drive end) 0.004 in. to 0.008 in.
Total end clearance 0.012 in.
Tips and back of case 0.004 in. to 0.006 in.
Open or front contour 0.008 in. to 0.010 in. clearance.
Closed or back contour 0.005 in. to 0.006 in. clearance.
Total impeller contour 0.016 in.
 
24

Figure 5-1. Vapor compressor, two lobe (exploded view).

CAUTION. Do not drive against the shaft or any part mounted on the shaft after the thrust bearing has been clamped in place by the clamping plate.

Place safety wiring on the clamping plate cap screws. Reinstall the gear housing and drive-end housing, together with the drive shaft end cover and oil slinger.

  Repack all packing glands with the proper packing, install the packing glands, and tighten them carefully.

Shellac the joint surfaces on the compressor and motor-supporting plate, and then insert and tighten the bolts uniformly.

 
C. CLEANING THE MODEL S DISTILLING UNIT
 
5C1. Methods of cleaning. The distilling surfaces of the unit are cleaned by either of two methods:

(a) by using a muriatic acid (HCL) solution; or

(b) by scraping and wire brushing.

The approved method of cleaning is the acid method. The acid method should be used only at a base or alongside a tender, as it requires special apparatus and an experienced crew. However, in case the acid method is not available, or if the unit is allowed to get too dirty for the acid method to be effective, the unit must be disassembled and cleaned mechanically.

5C2. Routine for acid cleaning. The Model S distilling unit may normally be cleaned by circulating a solution of 6.8 percent by weight of muriatic acid (HCL) in water through the still.

A 6.8 percent by weight muriatic acid solution is made up by adding 2 gallons of concentrated commercial muriatic acid (20 degrees Baume) to 10 galIons of fresh water.

A charge of 30 gallons of the 6.8 percent muriatic acid solution is required for each still. It should be circulated at a rate of about 60 gallons per hour through the still.

The following is a list of the equipment needed for acid cleaning both stills:

1 battery jar-about 45-gallon capacity
1 rubber container-about 5-gallon capacity
1 rubber measuring bucket
2 40- to 50-foot lengths of hose
4 4-foot lengths of hose
2 6-foot lengths of hose
2 6-inch lengths of hose
1 10-foot length of hose
1 12-foot length of hose
2 acid pumps

Miscellaneous brass pipe, fittings and valves, several Stillson and monkey wrenches, hose clamps, screwdriver, and pliers. Fresh water connection to deck of ship or dock.

  12 gallons of HCL. (20 degrees Baume) Proceed as follows:

a. Drain the unit and disconnect all piping at the base comprising the feed, condensate, vent and overflow.

b. Connect a short length of pipe and a valve to each feed connection (valves 3 and 4, Figure 5-2).

c. Connect the two feed connections together into a T, using two 4-foot lengths of hose (1 and 2).

d. Connect two 4-foot long hoses (3 and 4) to the overflow connection and place the open ends in the 5-gallon rubber container.

e. Connect acid pump 2 as shown using the two 6-foot lengths of hose (5 and 7) and the 6-inch piece of hose (6) and a T with valve 2.

f. Run the two 40- or 50-foot lengths of hose (8 and 9) to the topside as shown.

g. Connect acid pump 1 using the two lengths of hose, 10 feet and 12 feet (11 and 12), and the 6-inch length (10) connected to a T and valve 1 as shown.

h. Measure 30 gallons of fresh water into the battery jar and mark the level.

i. Shut valves 3 and 4, open valve 1, prime acid pump 1 with fresh water and start pump 1.

j. Open valves 3 and 4 until the water runs from the overflow hose and nearly fills the 5-gallon rubber container.

NOTE. A man on topside should keep the water up to the mark in the battery jar as the units are being filled. Each unit holds approximately 16 gallons when full to the operating level.

k. Shut valves 3 and 4.

l. Prime acid pump 2 and start with valve 2 open.

m. Open valves 3 and 4.

n. Adjust valve 2 so that the level in the 5-gallon container is about constant. If pump 1 does not

 
25

Figure 5-2. Acid cleaning piping arrangement.
Figure 5-2. Acid cleaning piping arrangement.
give sufficient water through the units with valve 1 wide open it may be partially closed.

CAUTION. Do not shut valves 3 and 4 until valve 1 has been opened. The open end of hose 1 must not be below the level of the liquids in the battery jar.

  o. When water has been circulating freely about 15 minutes and all valves are adjusted, slowly add 12 gallons of 20 degrees Baume muriac acid to the battery jar. After all the acid has been added circulate the acid solution through the units for 2 hours.
 
26

p. At the end of 2 hours of acid circulation, place hose 8 overboard. When the level in the battery jar is near bottom, fill the jar with fresh water and keep it filled.

q. Circulate fresh water through the unit for an hour. Secure the pumps, disconnect the hoses, and drain the unit.

r. After every sixth acid cleaning, the shells of the unit should be removed and the coils inspected for scale. Until experience indicates otherwise, the outer two or three coils should be removed and inspected occasionally.

s. Reassemble the unit and fill with sea water.

NOTE. As the periodic inspections indicate, the units should be completely disassembled and the acid cleaning followed by a mechanical cleaning.

5C3. Routine for mechanical cleaning. When cleaning the Model S distilling unit by scraping and wire brushing, it is necessary to disassemble the unit. Use the following routine, taking particular care in handling the coils.

CAUTION. When disassembling the coils do not lay the coils on their sides. Stack the coils on a form, with the large ends down so as to prevent the union ends from touching the floor or deck.

5C4. Disassembling the Model S distilling unit. The disassembly procedure is as follows:

a. Drain. Drain unit completely of water.

b. Braces. Remove the braces at the bottom of the unit.

c. Connections. Remove the thermometer bulb and disconnect and remove all piping, comprising the feed, condensate, vent and overflow pipe with overflow cup.

d. Insulation. Remove the insulation from the shell and keep it in a dry place.

e. Heaters. Disconnect the electric heater plugs (heater plugs are the locking type and must be turned about a quarter turn before disconnecting). It is not recommended that the heaters be removed at this time.

f. Glands. Remove the packing glands on the vent and condensate pipes.

g. Flanges. Remove the small flange from the bottom of the lower shell section, using the jack bolts to break the gasketed joint. Take the two large nits from the middle flange section and put over the shorter studs on opposite sides of the

  bottom flange; replace the two small flange nuts and tighten to hold the cone sections together.

h. Lower shell. Remove all nuts from the middle flange of the shell and break the gasketed joint. with the jack bolts provided. Take off the lower part of the shell.

i. Upper shell. Remove the nuts from the top flange and remove the upper half of the shell.

j. Conical shells. Remove the heaters and separate the two conical shells which make up the overflow heat exchanger.

5C5. Cleaning the surfaces. a. Shells. Clean the surfaces of both shells and inner cone by wire brushing and scraping with soft copper scrapers and wire brushes.

b. Coils. Insert the pins (found in the spare parts box) into the clips, on each side at the top of the vapor separator to support it, and to remove its weight from the coils.

Clean as much of the outer surface of the lower coil as possible with the coil in place. Surfaces of coils must be kept wet, otherwise the scale will be hard to remove and the coils may not come apart without damage. Disconnect the eight unions at the top of the lower coil and one union at the bottom. Remove the coil and its three spacing cones, tapping with a wooden mallet if necessary. (A union wrench and wooden mallet will be found in the spare parts box.)

CAUTION. Great care must be taken not to let the coils drop. Handle them carefully so that the ends of the coils will not be damaged. A stand should be available for holding the coils. If none is available they may be placed in the lower shell for protection.

Clean the inner surface and complete the cleaning of the outer surface.

Clean each succeeding coil in the same way.

c. Vapor separator. Remove the pins from the vapor separator and wire brush the eight upper headers and the inner cylinder of the vapor separator.

(CAUTION. Never attempt to remove more than one coil at a time from the distilling unit. If a coil sticks, light tapping around the top third of the coil with a wooden mallet will eventually loosen it. Do not hit the coil too hard as this may deform the copper nickel tubes or shape of the coil.

 
27
338450 O-55-3

5C6. Assembling and testing the Model S distilling unit. Proceed as follows:

a. Vapor separator. Place the vapor separator in place and insert the pins to hold it.

b. First operation in replacing coils. Place back into position the last coil removed.

NOTE. A small arrow stamped on the tab of all coils aligns with the arrow stamped on the upper head plate, below the pulley.

c. Upper and lower headers. Connect all the unions of this coil to the upper headers. Connect the lower discharge header to the small coil header, positioning the discharge header as nearly vertical as possible.

d. Routine for replacing coils. Plug up the open unions on the lower discharge header. Connect a rubber hose to the outlet of the discharge header and fill the tubes with fresh water until water runs out of the open top unions. Inspect the bottom union and small coil header for leaks. If any union leaks, it may be corrected by lapping its two contacting faces with the opposing parts of a spare union; or by applying a film of white lead on the union. In this operation it is possible to check only the lower connections for leaks.

Remove the hose and top plug in the lower header so that the next coil can be set in place.

Place the three spacer cones inside the next coil and stand the small end of the coil in the steel coil assembly cone which should be placed directly below the unit.

Align the arrow on the coil in the assembly cone with the arrow on the top flange, raising the coil into position. Two men should lift the coil and assembly cone, keeping the part unions on the upper headers from striking the part unions on the coils as the coil is raised. A third man should guide the lower end of the coil and assembly; as it is raised and place a small hydraulic or screw jack under the assembly cone, using a small piece of wood between the bottom of the assembly cone and the top of the jack. Raise the coil with the jack until the union on the small coil header aligns with the union on the discharge header. The coil must be jacked up so that the bottom union makes up exactly. The union should be started by hand, making sure that the threads are not crossed. Guide the coil so that the top unions do not strike the headers.

  NOTE. If no jacking cone is available, pressure may be applied to the thick circular bottom header portion of the coil (3/8-inch diameter) using wood to cushion the force of the jack.

CAUTION. Great care must be taken not to put any pressure on the 1/4-inch tube that leads from the 3/8-inch header at the bottom of the coils. In most of the union nut wrenches a small slot has been cut in the end. If absolutely necessary, fit this slot over the back part of the union and align the two parts of the unions before starting the union nut by hand.

After the bottom union is tightened firmly, the jack should be lowered. With no tension on the bottom of coil it is now possible to rotate the large (top) end of the coil so that the top unions will make up. The coil should now be jacked up a second time so that the top unions make up squarely with no bending of the tubes. Tighten the top unions and remove the jack.

e. Replacing remaining coils. Repeat the operations described in Section 5C6 on each of the remaining coils and spacer cones in sequence.

f. Pins. Remove the pins from the top of the vapor separator and allow the outer section of the separator to rest in the first coil.

g. Testing the coil assembly. Test the coil assembly for tightness by connecting a rubber tube to the outlet of the lower discharge header and filling the entire bundle with distilled water (about 2 gallons). Elevate the open end of the rubber tube above the upper unions on the coils so that the tube assembly may be filled completely with water. Leaks in the upper unions can be found and corrected without removing the coils. Leaks in lower unions will be indicated by water dripping but this cannot be corrected without removing the coils. For this reason, the lower unions and the 1/4-inch tubes, to which the lower unions are attached and brazed to the 3/8-inch bottom header rings, should be tested as installed.

h. Gaskets. Use new flange gaskets where needed. Extra gaskets are provided in the spare parts box.

i. Upper shell. Place the upper half of the shell in position, matching the arrows on the flanges. Screw all nuts halfway onto the studs.

j. Lower shell. Place the lower cones in position with the proper gaskets and install the heaters.

 
28

Align with the arrows on the flanges and raise the conical shells into position. Install the middle flange nuts and tighten by hand.

k. Packing gland. Renew the packing in the condensate manifold packing gland, using a piece of 3/8-inch pipe instead of condensate pipe. Screw the packing down hard and then back off on the packing gland nut; leave the nut installed loosely in the plate.

l. Pipes. Center the vent and condensate pipes in their respective holes in the bottom cover plate. Place the cover plate and supporting ring for the lagging over the studs and secure with the proper nuts, tightening firmly.

m. Shell flanges. Tighten the nuts on the upper and middle shell flanges.

n. Packing. Install packing in the vent pipe packing gland and tighten both the vent pipe and condensate pipe packing glands.

CAUTION. The nut on the vent pipe has a dual purpose: it acts as a packing gland nut, and it insures a tight nesting of the ten coils. For this reason, the vent pipe nut must be pulled up tightly. A loosely nesting set of coils will cause too great a difference between the condensate and feed temperatures, allowing excessive heat loss in the

  condensate, and making it impossible to operate with the proper amount of overflow.

o. Heaters. Install heater connections.

p. Braces. Install the braces at the bottom of the unit.

q. Connections. Connect all piping.

5C7. Final testing of reassembled unit. The final testing is done as follows:

a. Test for leaks. Start the feed pump and fill the unit with water until it appears at the overflow cup. Check the center and lower flanges for leaks, also the packing gland nuts and the bottom of the unit and threads where electric heaters are inserted. Test the heaters to determine whether or not all are working, by noting the readings on the ammeter.

NOTE. Do not install lagging until the unit operates without leaking.

b. Insulation. Install insulation and check heaters again to insure that all are connected properly.

5C8. Repairing coils. Any possible damage to the coils will require the use of silver solder. Cracks occasionally are found in the brazing. Proper brazing equipment and an expert mechanic are required for this work.

 
29
338450 O-55-4

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