20 |
MAINTENANCE |
|
A. PRELIMINARY INSTRUCTIONS |
|
20A1. General. Extreme vigilance and care
should be practiced in the inspection, cleaning, and repair of parts. Personnel performing repair work should use common sense
when judging whether or not a part should be
put back into service or discarded. If there is
any doubt, the part should be replaced. With
the exception of bearings and electrical equipment, corrosion should be removed from arts
by washing them in clean, fresh water. Dry
|
|
the parts thoroughly, and apply a light film
of gyro oil to prevent rusting or corrosion.
Use Navy-approved cleaning fluid to clean
grease and oil from the parts. Keep the bearings oiled and clean by wrapping them in wax
paper until needed for assembly. The area in
which the repair work is being performed
should be kept in a clean condition in order
to prevent dust from getting on the parts.
|
|
B. MAINTENANCE Of RODMETER |
|
1. STATIC VENT COCK
2. STATIC SHUT-OFF VALVE
3. BYPASS VALVE
4. DYNAMIC VENT COCK
5. DYNAMIC SHUT-OFF VALVE
Figure 20-1. Valves and vent cocks in position
to check for clogged rodmeter.
20B1. Testing for obstruction in the rodmeter. The rodmeter may become clogged
with jellyfish, mud, seaweed, or other foreign
matter. Consequently the pressure difference
will not be normal, and the mechanism will
not register correctly. The following test
must be performed when the ship is on the
surface. Position the valves and vent cocks as
|
|
shown in Figure 20-1. If a full stream of water
does not flow from both vent cocks, it is an
indication that the line not flowing is clogged.
20B2. Blowing out the rodmeter. This
operation should be performed with the rodmeter in its extended, or operating, position.
It is a good practice to blow out both lines
even if the tests for obstruction indicate only
one line clogged, as foreign matter has possibly entered both passages. Blow out the
rodmeter in the following manner: Disconnect the static hose from the static pressure
pipe nipple at the top of the manometer
piping. Pinch the end of the hose to prevent
leakage of water. If the line is completely
clogged, water will not leak from the hose.
Connect the low-pressure air line of the ship
to the static hose, and blow the obstruction
out of the hose and rodmeter into the water
outside the ship. Do not apply the low-pressure air hose to the piping that enters the
manometer as the air pressure will blow out
the mercury. When a full stream of water is
obtained from the static hose, place the end
of the static hose over the end of the hose
fitting at the upper end of the static piping
of the manometer, and install the hose clamp
securely. Blow out the dynamic line of the
rodmeter in the same manner. Go through the
venting routine after connecting the hoses
to the manometer. (See Section 19A3.)
|
|
227
|
20B3. Removing solid obstructions from the
rodmeter. If obstructions cannot be removed
by blowing out the rodmeter with compressed
air, the following operations are necessary.
Raise the rodmeter to its fully housed position. Close the sea valve. Unlatch the stop
bracket at the top of the hoist assembly by
opening and removing the lock that secures
the bracket in position above the rodmeter,
and swing it to one side. Remove the lower
end of the rodmeter from the sea valve extension by raising the rodmeter to the upper
sprockets. Using a soft brass wire, dig out the
obstructions from the orifices (openings) on
the lower end of rodmeter.
Do not use steel wire or a drill to clean
out the orifices as they may score the orifices
or break off in the openings.
Blow out the rodmeter (as described in
Section 20B2) while out of the valve extension. Have one crew member hold his hand
near the orifices to detect the flow of air which
indicates that the orifice and tubing are clear.
Repeat the operation until all passages are
|
|
clear. Align the lower end of the rodmeter
with the opening in the sea valve extension
and carefully lower the rodmeter to its fully
housed position.
Use care in placing the tip of the rodmeter in the packing gland so as not to
roughen or remove the packing.
At this point the tip of the rodmeter is
approximately 1-inch above the sea valve gate.
Connect the tubing from the rodmeter to the
manometer. Open the sea valve. Swing the
stop bracket to its normal position above the
rodmeter and secure it in place with the lock.
It is important that the stop bracket be in
position above the rodmeter at all times except during the above operation, or when the
rodmeter is being replaced.
Lower the rodmeter to its normal housed
position or to the fully extended position as
desired. Place the hoist crank in the brackets
provided, and replace the deck plate over the
sea valve. Vent the system in accordance with
the instructions outlined in Section 19A3.
|
|
C. REPLACING A DAMAGED RODMETER |
|
20C1. General instructions. If the rodmeter
is bent so that it cannot be drawn up into the
ship, it is necessary to install a spare rodmeter. Do not attempt to force the damaged
rodmeter up into the ship, as the hoist mechanism may be damaged. The removal and installation operations should be carried out
only when the ship is surfaced. If the damaged rodmeter is to, be salvaged, it may be
accomplished if a diver is available. Lower
the diver over the side of the ship so that he
can rig a line around the damaged rodmeter.
Secure the other end of the line to the ship
so that the rodmeter can be pulled out of the
water after it is pushed out of the sea valve.
20C2. Breaking out spare rodmeter. (See
Figure 20-2.) Break out the spare rodmeter
and place it alongside the hoist mechanism
so that it will be immediately available when
needed.
20C3. Removing the clamp and guard assembly. (See Figure 20-2.) From 1/2-inch
|
|
diameter dowel pin stock, make up two
tapered wooden plugs 1-inch long tapering to
3/8-inch diameter at one end. Loosen the hose
clamps and remove the two lengths of hose
from the nipples on the upper end of the rodmeter. Unscrew the longest (after) nipple
and plug the hole in the rodmeter with a plug.
Remove the forward nipple in the same
manner, and plug the hole. Remove the two
nuts and bolts that secure the clamps and
guard to the rodmeter, and remove the clamp
and guard assembly. Raise the guard by means
of the hoist up against the stop bracket above
the rodmeter. Knock out one of the stop pins
in the rodmeter.
20C4. Installing the clamp and guard assembly. (See Figure 20-2.) The two clamps
and the guard are marked to facilitate reassembly. These marks should be adjacent to
one another when the pieces are assembled on
the rodmeter. Place the two clamps around
the upper end of the spare rodmeter so that
|
|
228
|
Figure 20-2. Rodmeter.
the clamps are over the stop pins provided at
the top of the rodmeter. Place the guard between the clamps. Align the mounting holes
in the three pieces, and install the two bronze
bolts and nuts that secure the clamp and guard
assembly to the rodmeter. Tighten the nuts
securely.
|
|
20C5. Installing the spare rodmeter. (See
Figure 20-2.) If the damaged rodmeter is
partially raised, push it downward until the
remaining stop pin rests on top of the packing
gland in the sea valve extension. It may sometimes be necessary to drive the rodmeter
downward with a sledge and wooden block.
Place the tip of the spare rodmeter on top of
the damaged rodmeter, making certain that
the dynamic orifice in its leading edge is
facing forward. Note the arrow stamped on
the rodmeter for facing the spare rodmeter
in the proper direction. Remove the cotter
pin and clevis pin that secure the old guard
to the lifting bar on the hoist chain, and remove the old guard. Align the opening in the
lifting bar with the opening provided in the
guard on the spare rodmeter, and install the
clevis pin and cotter pin that secure the lifting bar to the guard assembly. Place the loose
end of the dynamic hose over the nipple provided on the dynamic (short) nipple on the
top of the rodmeter. The opposite end of this
hose is attached to the lower pipe at the top of
the manometer. Secure the hose to the nipple
with a hose clamp. Place the end of the static
hose on the long nipple on the top of the rodmeter. The opposite end of the static hose is
attached to the top pipe fitting at the top of
the manometer. Secure the hose to the nipple
with a hose clamp. It is a good practice to
wire the two hose clamps together with soft
brass wire to prevent the hoses from slipping
off the nipples at deep submergence pressures.
Knock out the pin from the damaged rodmeter and push downward on the spare rodmeter to drive the damaged rodmeter downward and out of the ship. Vent the system in
accordance with the instructions given in
Sections 19A3.
|
|
D. MAINTENANCE OF MANOMETER |
|
20D1. General instructions. Valves and
vent cocks should be kept clean and lubricated
with a good grade of waterproof grease. Keep
the hose securely clamped to the nipples of
the piping of the manometer. The gland on
the manometer shaft in the gear chamber is not
adjustable and should be kept clean and well
|
|
greased by tightening the grease cup on the
front of the gear chamber (Figure 20-3). Friction in this shaft is usually due to hardened
deposits of salt and grease in the gland. Remove the hardened grease, and clear the gear,
roller, and float rack. Fill the gland with
fresh grease.
|
|
229
|
1. GREASE CUP AND TUBE
2. GEAR CHAMBER
3. DRIVING ARM PIN
4. DRAIN SHIELD AND TUBE
5. GEAR SHAFT DRIVING ARM
Figure 20-3. Front view of gear chamber.
20D2. Testing for loss of mercury. With the
bypass valve open, it should be possible to
turn the transmitter speed dial approximately
1/4-inch beyond the zero mark on the dial, and
when the dial is released it should read zero.
If it does not return to zero, it is an indication
|
|
that the mercury level is low, and that the
float is hitting the bottom of the float chamber.
20D3. Adding mercury to the float chamber.
Add mercury to the float chamber in the-following manner. Close the static and dynamic
shut-off valves. Disconnect the three connections on the manometer Y-pressure piping,
and remove the piping. Remove the back plate
from the gear chamber. Siphon off all the
water from the center and side tubes of the
manometer. Add mercury to one of the side
tubes until the float rises approximately 1/2-inch from the bottom of the float chamber.
This is determined by manually pushing the
rack and float downward until the float strikes
the bottom of the float chamber, then releasing
it and noting its rise. When measuring the
float rise in this manner be sure that the float
hits the bottom of the float chamber, and is not
prevented from doing so by the driving arm
pin (Figure 20-3) striking the front bracket
of the gear chamber. It will be necessary to
loosen the drawing arm clamping screw if the
pin hits the bracket. Connect the piping to
the manometer. Replace the gear chamber
cover. Vent the system until all the air is
removed from the hydraulic system as described in Section 19A3. Reset the speed dial
to zero. (See Section 20E1.)
|
|
E. MAINTENANCE OF TRANSMITTER |
|
20E1 Setting the speed dial to the zero
position. Thoroughly vent the hydraulic
system, (See Section 19A3.) House the rodmeter. Open the bypass valve. If the driving
arm pin has been loosened (see Section 20D3),
tighten it while holding the transmitter speed
dial on zero. Be sure that the driving arm is
so located on the gear wheel shaft that it will
not rub on the front bracket, or on the front
cover of the gear chamber. Slightly rotate
the transmitter speed dial backward and forward from the zero position, pushing the adjusting fork (Figure 20-4). The dial should
return to the zero position. If not, set the dial
to zero by means of the adjusting screw on
the adjusting fork (Figure 20-4).
|
|
20E2. Checking integrator timer. There are
two types of integrator timing mechanisms
used with the mercury manometer log. They
are the synchronous motor integrator timer
(known as the a.c. clock type), illustrated in
Figure 18-5, and the d.c. clock integrator
timer, known as the d.c. clock type (Figure
20-5). In the 18- and 20-knot logs, the d.c.
clock is used and the integrator operating
arm makes 180 strokes per hour. In the 22-knot logs, some having d.c. clocks and some
having a.c. clocks, the operating arm makes
240 strokes per hour. The number of strokes
per hour for each particular unit is indicated
on a marker plate which is mounted over the
|
|
230
|
1. TRANSMITTER CASE
2. CASE MOUNTING STUD
3. GEAR SHAFT DRIVING ARM
4. MAINSHAFT
5. GEAR WHEEL SHAFT
6. ADJUSTING FORK
7. ADJUSTING SCREW
8. DRIVING ARM PIN
9. GEAR CHAMBER
Figure 20-4. Adjusting fork.
timing counter window. Check the integrator
timer in the following manner:
Using an accurate stop watch, start the
watch and record the indication on the timing
counter when the counter number begins to
change. Stop the watch and record the
counter reading at the exact termination of
1-hour. The timing counter should read the
number of strokes indicated on the marker
|
|
Figure 20-5. Direct current clock integrator timer.
Figure 20-6. Distance repeater contacts adjustment.
|
|
231
|
plate for that particular unit. If the timing
of the a.c. unit indicates that the number of
strokes per hour is in error, check the constant
frequency supply to be sure it is exactly 60
cycles. Also check the gearing for deposits of
grease which may prevent the constant speed
motor from running at synchronous speed.
Clean and lubricate the gear mechanism. On
the d.c. clock integrator timer, any error in
the clock may be corrected by means of the
regulator lever on the escapement (Figure
20-5). Moving the lever down one division on
the scale will cause the clock to gain about
half a minute per day. Moving the regulator
up one division on the scale will cause the
clock to lose approximately half a minute per
day.
20E3. Installing and adjusting distance repeater contacts. (See Figure 20-6.) Remove
the old contact assembly as a unit from the
transmitter case bracket. Resolder the wires
to the new contact assembly lugs, replace the
insulating sleeves on the lugs, and mount the
|
|
new assembly on the bracket with the holding
screws. Center the contact springs on the star
wheel, and tighten the holding screws. If
either contact spring does not press against
the star wheel in the open position, increase
its tension by bending the spring as shown in
Figure 20-6. Heavy spring tension is more
desirable than light tension. Rotate the star
wheel until the upper (longer) contact spring
just drops clear of the tooth. At this instant
the upper contact should rest squarely on the
lower contact, but the upper contact spring
should not touch the star wheel until the
lower contact spring drops to the next tooth.
This is important for proper, quick, make and
break operation. If necessary, bend the tip of
the upper contact spring to provide the correct clearance as shown in Figure 20-6. When
the contacts are clean and properly adjusted,
there should never be excessive sparking. The
tungsten contacts must be absolutely free of
oil or grease. If the contacts are pitted, they
may be cleaned with fine sandpaper or a contact stone. Do not oil the star wheel.
|
|
F. MAINTENANCE OF MASTER SPEED REPEATER |
|
20F1. Follow-up motor. The follow-up motor used in the master speed repeater is the
same as the lead screw drive motor used in
the master speed indicator of the Pitometer
rotary balance type log. Test, removal, and
installation operations are covered in Sections
5M3, 5M4, and 5M6.
20F2. Calibrating the master speed repeater.
(See Figure 20-7.) In order to make the speed
indication of the master speed repeater agree
with the speed indication of the transmitter
speed dial, calibrate the master speed repeater
in the following manner: Remove the interior
mechanism from its case and place it on a
convenient surface. Connect the jack of the
case to the plug on the back of the mounting
plate by means of the plug-jack cord furnished for this purpose. Do not energize any
circuits. Remove the pointer and dial from
the master speed repeater. Manually turn the
gearing of the follow-up motor until the cam
and roller are within approximately 0.005
|
|
inch of seating in the hollow of the pointer
cam as shown in Figure 20-7. Use care in turning the gears as excess motion may bend the
supporting arm of the cam roller.
At this point, the limit switch which prevents over-travel of the follow-up motor
should operate. If necessary, reset the limit
switch operating screw. Replace the dial and
pointer without the pointer hub cap, and set
the pointer at exactly 22 knots by loosening
the three screws clamping the pointer to the
hub; then replace the pointer hub cap. The
speed pointer is now in correct relation to
the cam (Figure 20-7). Now rotate the followup gearing by hand until the master speed
repeater indicates about 5 knots. Energize
the 1Y circuit. If the master speed repeater
speed indications do not agree with those of
the transmitter, it will be necessary to align
the self-synchronous repeater with the self-synchronous transmitter.
This is accomplished in the following
|
|
232
|
Figure 20-7. Cam positioned for setting pointer at 22 knots.
|
|
manner: Close the dynamic and static shutoff
valves and open the bypass valve. Loosen the clamping
screw of the gear shaft driving arm (Figure 20-4). Slowly turn the dial in
the transmitter to 15 knots and secure the dial
in this position to the fixed pointer with a
small C-clamp. Loosen the clamps that secure
the self-synchronous repeater to the mounting
plate of the master speed repeater, and
shift this repeater until the speed pointer
reads 15 knots as indicated on the master
speed repeater dial. Tighten the clamps to
secure the repeater in this position on the
mounting plate. Remove the C-clamp from
the transmitter dial. Slowly turn the speed
dial of the transmitter back to the exact zero. If
the master speed repeater does not indicate
zero, or approximately zero, clamp the transmitter
dial at zero and make further very slight
adjustments of the self-synchronous
repeater in the master speed repeater. Tighten the clamping screw of the driving arm (Figure 20-4), and remove the C-clamp.
|
|
G. SYNCHRONIZING SPEED AND DISTANCE REPEATER |
|
20G1. Resetting the speed pointer of the speed and distance repeater.
If the speed indications of the speed and distance repeater
do not agree with the speed indications of the
master speed repeater, shift the repeater of
the former in the following manner: Remove
the speed and distance interior mechanism
from its case. Connect the plug jack cord to
|
|
the case and interior mechanism. Loosen the
clamps that secure the repeater to the mounting
plate. Shift the repeater from until the
speed indications agree with those of the master speed
repeater, then tighten the clamps to secure
the repeater in position. Install the
speed and distance interior mechanism in its case.
|
|
233
|