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13
MISCELLANEOUS SYSTEMS
 
A. ENGINE ORDER INDICATOR SYSTEM
 
13A1. Description. The engine order indicator system is composed of 4 rotary transmitter switches and 4 sets of indicating lights in the maneuvering room, and 2 rotary transmitter switches with 2 sets of indicator lights in each engine room. The purpose of the system is to transmit orders for engine operation between the maneuvering room and engine rooms.

The circuit designation is 3MB and it is energized from the ship's 120-volt d.c. supply taken either from the d.c. bus of the I.C. switch board, or directly from either the port or starboard lighting feeder, depending upon the type of installation.

13A2. Operation. The maneuvering room transmitter unit has a rotary selector switch for each main engine with positions marked STOP, START, OFF, CUT-IN, and CUT-OUT. The 4 indicator reply lights in the maneuvering room for each main engine are marked START, STOP, READY, CUT-OUT. A push button on the transmitter operates a bell in each engine room.

The double indicator in each engine room has 4 indicator reply lights for each engine. They are marked START, STOP, CUT-IN, CUT-OUT. The orders received from the maneuvering room are shown by this double indicator. In order that the maneuvering room may

  know that orders were correctly received, the rotary transmitter switch in the engine room is used to acknowledge orders. This switch is marked STOP, START, OFF, READY, and CUT-OUT.

Following is a normal sequence of signals transmitted in starting an engine:

1. The maneuvering room turns the rotary switch to START, thereby lighting the START lamp in the engine room indicator.

2. The engine room acknowledges by turning the rotary switch to START, thus lighting the START lamp in the maneuvering room indicator.

3. The engine room signals READY to the maneuvering room. This indicates that the engine is running and that they are ready to turn over governor control.

4. The maneuvering room signals CUT-IN, indicating that they are taking over governor control. If at any time during the engine's operation, the engine room signals CUT-OUT, it means that the engine room desires the load to be removed from the engine and wishes to have governor control. The maneuvering room acknowledges the order by signaling CUT-OUT.

 
B. LUBRICATING OIL AND ENGINE CIRCULATING
WATER ALARM SYSTEM
 
13B1. Description. The lubricating oil (low pressure) and engine circulating water (high temperature) alarm system is composed of pressurestatic and thermostatic contact makers which under certain conditions close a circuit and provide an indicating signal.

Pressurestatic contact makers are installed in the lubricating oil lines to all main engines and to the auxiliary engine, and in the

  lubricating oil supply between the reduction gears and main motor bearings.

A pressurestat is essentially an automatic contact maker consisting of a metal case in which the lower portion is sealed into an oil tight chamber by means of a diaphragm. The upper side of the diaphragm carries the movable portion of the contact maker. Oil from the line is led to the lower chamber under working

 
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Figure 13-1. Schematic diagram of engine order indicator system.
Figure 13-1. Schematic diagram of engine order indicator system.
 
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Figure 13-2. Engine order telegraph maneuvering
room transmitter.
Figure 13-2. Engine order telegraph maneuvering room transmitter.
  pressure, forcing the diaphragm upward against the tension of a coil spring and holding the contacts open. If the pressure drops below a set value, the diaphragm is forced downward by the spring tension and closes the contacts, energizing a light and bell circuit. The pressure at which the pressurestat functions may be varied by adjusting the spring tension. A pressurestat may be used either in oil or in water lines.

The thermostatic contact makers are installed in the circulating water lines leaving each main engine and the auxiliary engine. They perform the same function as the pressurestat, but their contacts are closed by the effect of heat on a bimetallic strip.

The pressurestatic and thermostatic contact makers for each main engine are connected in parallel so that the operation of either one closes the circuit to a red indicator lamp and a horn at the engine control station, thus giving an alarm of an abnormal condition.

The pressurestats installed in the lubricating oil line between the reduction gears and main

Figure 13-3. Engine order indicator installed on engine gage board.
Figure 13-3. Engine order indicator installed on engine gage board.
 
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Figure 13-4. Schematic diagram of lubricating oil
flow pressure) and engine circulating water
(high temperature) alarm system.
Figure 13-4. Schematic diagram of lubricating oil flow pressure) and engine circulating water (high temperature) alarm system.
 
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Figure 13-5. Elementary wiring diagram of engine
lubricating oil flow pressure) and circulating water
high temperature alarm system for one engine.
Figure 13-5. Elementary wiring diagram of engine lubricating oil flow pressure) and circulating water high temperature alarm system for one engine.
Figure 13-6. Lubricating oil (low pressure) and engine
circulating water (high temperature) alarm panel.
Figure 13-6. Lubricating oil (low pressure) and engine circulating water (high temperature) alarm panel.
  motor bearings operate red indicator lamps and a horn in the maneuvering room.

A blue lamp at all indicator stations shows that the circuit is energized. Test cutout switches are also provided, by means of which the operation of the light and horn circuit may be tested.

Power for this system is taken either from the a.c. or d.c. bus (depending upon the type of installation) of the I.C. switchboard through a fused switch. The circuit designation is EC.

 
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C. HULL OPENING AND MAIN BALLAST TANK INDICATOR SYSTEMS
 
13C1. Description. The hull opening and main ballast tank indicator systems are used to indicate, by means of lamps, the open or closed state of the openings in the hull.

Mechanically operated contact makers are used to operate a group of lamps located on a panel at the control stations. There are also mechanical indicators on the outside of the electrical contact box which provide a local indication of the position of a valve.

The group of panel lamps has colored glass covers of red or green mounted over each lamp. The lighting of these lamps indicates the dangerous position of the particular hull opening in red, and the safe position in green, both conditions being for the submerged condition. A dimmer for all lights is mounted on the after end of the indicator panel.

13C2. Hull opening indicator system (circuit TR). The hull opening indicator system has contact makers, including mechanical indicators, installed on the operating mechanism of each hatch, outboard ventilation, engine induction and exhaust valve. Each of these contact makers is connected through a separate 3-ampere fuse to operate the 2 lamps (in parallel) for each of the indicator openings.

An additional 10-dial indicator in each engine room is connected to show the position of the engine exhaust valves and the ventilation valves.

On all indicators, red lights show hatches, doors, engine valves, and hull ventilation valves not completely closed. Green lights show hatches actually dogged tight.

Power for the hull opening indicator system is obtained from the 8-volt secondary of either of two 120/8-volt transformers, depending on the position of the unfused switch on the I.C. switchboard. The common terminals of this switch feed the circuit through a set of 15-ampere fuses.

Lamps and their fuses in the control room and engine rooms may be identified by numbers engraved on the panels.

  13C3. Main ballast tank indicator system (circuit TP). The main ballast tank indicator system has contact makers, including mechanical indicators, installed on the operating mechanism of each main ballast, safety, negative, and bow buoyancy tank vent valves. All flood valves and flood valve contact makers are omitted except those for the safety and negative tanks. Each contact maker is connected through a separate 3-ampere fuse to operate the 2 lamps in parallel for each of the indicator openings.

Red lights show flood valves actually closed tight and vent valves not completely closed. Green lights show vent valves that are actually closed tight and flood valves completely open.

Power for the main ballast indicator system is obtained from the 8-volt secondary of either of two 120/8-volt transformers, depending upon the position of the fused primary switches for each transformer and the position of an unfused switch connected to the secondaries of the transformers. Power is taken from this switch through a pair of 10-ampere fuses on the I.C. switchboard.

13C4. Maintenance. Lamps and fuses may be tested by means of a jumper wire with one end connected to the circuit terminal screw provided near the bottom of the fuse panel. The other end of the wire must be touched to the top of the fuse for the lamp being tested. If both lamps for that circuit light, the fuse may be tested by touching the jumper wire to the bottom of the fuse clip.

A check for the proper operation of all hull opening contactors and indicators, followed by any necessary adjustments, should be made at the end of every overhaul or upkeep period and every 2 weeks thereafter.

Ballast tank contactors and indicators on flood and vent valve operating gear should be checked at intervals not to exceed 6 weeks and preferably at the end of the upkeep period. All mechanical indicators on hull opening valves should be checked at the same time the electrical contactors are checked.

 
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Figure 13-7. Schematic diagram of hull opening
indicator system.
Figure 13-7. Schematic diagram of hull opening indicator system.
 
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Figure 13-8. On board view of hull opening and main ballast tank indicators.
Figure 13-8. On board view of hull opening and main ballast tank indicators.
 
Figure 13-9. Simplified wiring diagram for one unit of
hull opening and main ballast tank opening
indicator systems.
Figure 13-9. Simplified wiring diagram for one unit of hull opening and main ballast tank opening indicator systems.
 
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Figure 13-10. Schematic diagram of main ballast tank
indicator system.
Figure 13-10. Schematic diagram of main ballast tank indicator system.
 
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Figure 13-11. Main ballast tank indicator
with cover open.
Figure 13-11. Main ballast tank indicator with cover open.

If contactors contain microswitches, check the switch pins for freedom of operation. Contactor rotating parts and contacts should be inspected for loose electrical connections and fittings, dirt, burrs, and presence of any foreign matter. Mechanical linkages should be inspected for freedom of action, adjustment, and presence of rust, corrosion, or any foreign material that might cause faulty operation. Special attention

  should be given to checking for poorly fitting linkage pins, loose or missing cotter pins, and proper installation of linkages. When there is backlash in gears or wear in worms, readjustment is necessary.

The most serious results can be expected from improper operation either of the contactors on the hull openings which cannot be sight checked at rig for diving or of those valves that normally are not closed until after the first blast of the diving alarm. These valves include the hull ventilation valves, the main engine air induction valves, and the engine outboard exhaust valves.

13C6. Illumination of hull opening and main ballast tank indicators. The light from the indicators installed in the control room is reduced to a level satisfactory for preserving dark adaptation by means of rheostats installed in each system's supply lead. To prevent reduction of illumination in the instruments installed in the engine room, which are always under normal lighting, it has been necessary to install 2-contact split microswitches on openings whose position must be indicated in the control room. This results in full illumination of these indicators at all times. The power supply for the engine room indicators is not connected through the rheostats mentioned above. In other respects, the circuits resemble the simplified diagram shown in Figure 13-9.

 
D. RESISTANCE THERMOMETER AND PYROMETER SYSTEMS
 
13D1. Resistance thermometer systems. a. Electrical distant reading thermometers are installed to read the temperatures of various parts of the propulsion system and auxiliary generator. They are of two different types: the Brown Instrument Company type, used to measure temperatures of the lubricating oil and bearing, and air temperatures of the propulsion motors and reduction gears; and the Weston continuous reading duplex type, used to measure the temperatures of the bearings and air in the generators and the lubricating oil and circulating water in the engines.

b. Brown resistance thermometer. The resistance thermometer is based on the principle

  that the electrical resistance of a metal changes with the temperature. In the Brown thermometer used on submarines the system consists of small coils of resistance wire called bulbs, located at the points to be measured, and an indicating unit. The indicating unit contains a selector switch, a power supply, fixed resistor units, and a galvanometer calibrated in degrees Fahrenheit.

The resistors in the instrument are arranged to form 3 sides of a Wheatstone bridge circuit with one of the bulbs selected by the switch forming the fourth side. Thus a change in resistance of the bulb causes an unbalance of the bridge and changes the reading of the galvanometer (see Figure 13-16).

 
189

Figure 13-12. Schematic diagram of distant reading thermometer system.
Figure 13-12. Schematic diagram of distant reading thermometer system.
 
190

Figure 13-13. Schematic diagram of Brown distant
reading thermometer system for
main motors and reduction gears.
Figure 13-13. Schematic diagram of Brown distant reading thermometer system for main motors and reduction gears.
The power supply consists of a transformer and rectifier for the later vessels and a resistor and rheostat for dropping the voltage from the 115-volt d.c. lighting system for earlier vessels. In both types the final input to the instrument is approximately 8 volts d.c.

c. Weston duplex continuous reading thermometers. The Weston resistance thermometers used on submarines depend on the same principle as the Brown type, with one major difference: Instead of a simple Wheatstone bridge and galvanometer, a modified bridge and an instrument known as a ratiometer are used. The circuit is shown in Figure. 13-17. R3 is made equal to R4. Hence it can be seen that the current in the 2 coils C1 and C2 of the instrument

  will be the same when the resistance of R1 equals the resistance of R5. For any other resistance of R1, more current will flow in one coil than in the other. In the instrument, the 2 coils are mounted on opposite sides of the pivot. A soft iron circular core threads through the coils. A permanent magnet yoke with 2 semicircular pole pieces almost surrounds the moving coils and core but it is slightly eccentric with respect to the pivot. This causes the air gap to be smaller at one side than the other. As currents flow in the 2 coils connected to produce torque in opposite directions, they move to such a position that their torques are equal. Since torque is determined by the product of the current in the coil and the magnetic flux across the air gap, the coil carrying the least current moves to a
 
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point in the air gap having greater flux density, that is, toward the narrow gap. Since the position of the pointer depends on the ratio between 2 currents rather than on their absolute value, voltage fluctuations have no effect on the accuracy of the instruments. In the Weston thermometers, a separate movement is furnished for each temperature point, 2 being combined into a single duplex instrument.

As with the Brown type instruments, the Weston type also may be either d.c. or a.c., and the series resistor or transformer and rectifier are incorporated in the instrument case.

13D2. Brown indicating pyrometers. The temperature of the exhaust gas from a cylinder of any diesel engine is a reliable indication of the load on that particular cylinder.

The exhaust gas temperatures of each cylinder are obtained with a Brown indicating pyrometer which makes use of the thermoelectric principle of dissimilar metals: An electromotive force is generated in a circuit of 2 wires of different metals when the 2 junctions of those wires are at different temperatures. This electromotive force varies in magnitude with the difference in temperature between the 2 junctions. The hot junction is exposed to the temperature of the exhaust gas, and the cold junction is located at a galvanometer through which the circuit is closed. This galvanometer is the indicator and is graduated in degrees of temperature corresponding to the voltage generated. Because the generated electromotive force is zero when the 2 junctions are at the same temperature, the galvanometer is adjusted to indicate its own, or cold junction, temperature when the circuit is open, or in the OFF position. The galvanometer automatically varies its pointer position with changes in the temperature at the hot junction.

One of the 2 thermocouple wires is made of pure iron; the other is made of constanten, a nickel-copper alloy. The wires are welded at the tip of the thermocouple and mounted in a closed-end protecting tube of pure nickel. The protecting tube is fitted with a terminal head in which the connections are made between the extension leads and the thermocouple wires.

  Figure 13-14. Brown distant reading resistance
thermometer indicator and switch panel.
Figure 13-14. Brown distant reading resistance thermometer indicator and switch panel.

Figure 13-15. Weston resistance thermometer bulbs.
Figure 13-15. Weston resistance thermometer bulbs.

Figure 13-16. Brown resistance thermometer bulb.
Figure 13-16. Brown resistance thermometer bulb.

 
192

Figure 13-17. Electrical resistance thermometers.
Figure 13-17. Electrical resistance thermometers.
 
193

Figure 13-18. Duplex constant reading resistance
thermometer gage.
Figure 13-18. Duplex constant reading resistance thermometer gage.

Figure 13-19. Brown pyrometer indicator and rotary
switch for main engine exhaust temperatures.
Figure 13-19. Brown pyrometer indicator and rotary switch for main engine exhaust temperatures.

The indicating mechanism is essentially a millivoltmeter, calibrated in degrees of temperature corresponding to the temperature-emf relationship of the iron-constanten thermocouple. The galvanometer is, and functions as, a common direct current instrument except for the fact that the adjusting screw is used for ambient temperature setting instead of zero setting.

To obtain the best indication of diesel engine temperatures, it is necessary to place a thermocouple tip in the exhaust port of each cylinder. Some engines also use a thermocouple at a point in the exhaust pipe system where the

  temperature of the combined exhaust gas from all cylinders can be measured. This point is called the common temperature.

The Brown pyrometer system includes a multipoint switch through which the individual thermocouples are connected to the indicator.

All connections between thermocouples and the instrument are made with the wires supplied for this purpose: the iron wire being used for the positive lead, and constanten wire for the negative lead. These 2 wires are of the same material as the thermocouple and cause the cold junction to be extended from the thermocouple terminals back to the indicator. No other types of wire are used for this purpose.

Resistors are provided in the system and are used for adjusting the resistance of the external leads to a standard value. The galvanometer of this instrument is calibrated for a 15ohm external resistance. The resistor connections simply increase the total resistance of the extension leads to 15 ohms, and this amount should not be exceeded.

The resistors do not compensate for ambient temperature changes.

Figure 13-20 Pyrometer unit as installed in engine.
Figure 13-20 Pyrometer unit as installed in engine.

 
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13D3. Maintenance. Frequent inspections must be made to insure that all connections are tight and free from corrosion. As small voltage values are used in these circuits, the accuracy of the instrument depends on perfect contact.   Thermocouples and thermometers usually cannot be repaired if faulty, but must be replaced. It is essential, therefore, that a full allowance of spare thermocouples and thermometers be carried aboard at all times.
 
E. HYDROGEN DETECTOR SYSTEM
 
13E1. Description. There are two types of hydrogen detectors in service: type N.H.D., manufactured by the Cities Service Company, and type M.S.A., manufactured by the Mine Safety Appliance Company. The function of the detectors is to take a sample of exhaust air continuously from the batteries and indicate the percentage of hydrogen concentration in the battery ventilation ducts.

The operation of both types of detectors is based on the principle of a balanced Wheatstone bridge circuit. The air sample is drawn, by means of a motor-driven pump, across one leg of the balanced circuit where it is caused to burn with an intensity dependent upon the amount of hydrogen present. The heat created heats that leg and increases its resistance, thereby creating an electrical unbalance in the entire circuit. The meter connected across the bridge circuit then shows a deflection, on a properly divided scale, that is directly proportional to the percentage of hydrogen present in the air sample.

  In addition to the meter indication, the M.S.A. type contains a white light connected in the circuit, indicating normal operation as long as the hydrogen content is below 3 percent. When the motor pointer indicates 3 percent on the scale, a circuit to a red warning light is closed. This red warning light will remain ON until it is manually reset. Both meter and light indications are transmitted to repeater instruments in the maneuvering room.

The type N.H.D. detector is supplied with 115-volt to 120-volt alternating current directly from the a.c. bus of the I.C. switchboard. This system uses a rectifier to convert the alternating current into direct current for the bridge circuit.

The M.S.A. type detector is supplied with 120-volt direct current from the lighting feeder.

Detailed descriptions of these systems and specific instructions for maintenance, repair, and adjustments may be found in the manufacturer's instruction book pertaining to the particular type of installation.

 
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Figure 13-21. Schematic diagram of hydrogen detector system.
Figure 13-21. Schematic diagram of hydrogen detector system.
 
196

Figure 13-22. Schematic diagram of Cities Service type hydrogen defector.
Figure 13-22. Schematic diagram of Cities Service type hydrogen defector.
 
197

Figure 13-23. Arrangement of units in Cities Service type hydrogen detector.
Figure 13-23. Arrangement of units in Cities Service type hydrogen detector.
 
Figure 13-24. Cities Service type hydrogen detector system, master indicator and remote indicator.
Figure 13-24. Cities Service type hydrogen detector system, master indicator and remote indicator.
 
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Figure 13-25. M.S.A. type hydrogen detector
remote indicator.
Figure 13-25. M.S.A. type hydrogen detector remote indicator.

Figure 13-26. M.S.A. type hydrogen detector
with door open.
Figure 13-26. M.S.A. type hydrogen detector with door open.

  Figure 13-27. M.S.A. type hydrogen detector.
Figure 13-27. M.S.A. type hydrogen detector.
 
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