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PART II - CHAP. V O.P. NO. 747

INSPECTION AND TESTING GENERAL INSTRUCTIONS

1. Depth charge components procured by the Bureau of Ordnance are delivered to Naval Mine Depot, Yorktown, Virginia ; Naval Ammunition Depot, Hawthorne, Nevada and Naval Ammunition Depot, Crane, Indiana. Material is distributed from these principal sources to activities ashore and afloat.

2. In order to insure that pistol and booster extender parts are in proper working order when issued, certain functional tests, described below, should be performed on each. Other functional tests should be applied only to a certain percentage of each lot issued. A depot inspector's tag should be secured to each of the components. This procedure will insure the parts to be in working order and they may be assembled with other components, without further test, to make up the complete depth charge. The depot inspection tag should be removed when each component is installed in a depth charge case.

3. The depots should not break down and inspect new material received from contractors. Any components which fail to meet the required functional test should be set aside. The responsible contractor should be notified through the cognizant Naval Inspector of Material of the defects found and the number of units involved. Copy of this notification should be forwarded to the Bureau of Ordnance. The contractor supplying the defective material should be given the option of sending his representatives to

 

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INSTRUCTIONS FOR MAINTENANCE TESTING AND REPAIR

the depot to correct the faults noted or have the material returned to his plant for reconditioning.

TESTING SETS

4. Two types of testing sets are available for issue to depots, tenders and shore activities authorized to overhaul pistol and booster extender components.

(a) Test set Mark 2 Mod. 1 contains all the necessary tools for disassembly and assembly of Mark 6 and Mark 6 Mod. 1 pistol and booster extender components. In addition apparatus for applying air pressure test up to 60 psi is included in the test set.

(b) Test Set Mark 3 consists of air and water tanks and necessary fixtures, valves, and gauges for testing and calibrating the Mark 6 Mod. 1 pistol. The essential parts of this test set are packed in one box. A compressed air supply of about 300 psi will be required for use of this equipment.

TESTING PISTOLS

5. Depth charge pistols should be tested only as necessary to insure their satisfactory operation because continued working of these mechanisms will distort the bellows and cause unnecessary wear on the plunger releasing mechanisms. A pistol to be used only for instruction and drill should be provided where necessary.

 

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ASSEMBLY OF PISTOL TESTING SET
ASSEMBLY OF PISTOL TESTING SET

 

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TESTS OF MARK 6 AND MARK 6 MOD, 1 PISTOLS
(MARK 2 MOD. 1 SET)

6. The standard functional test procedure for these pistols using the Mark 2 Mod. 1 test set is as follows:

(a) Remove detonator and safety cover if attached. See that the detonator collar and detonator holder are in place.

Cocking Tool

(b) Cock the pistol. Use the cocking tool provided in the Mark 2 Mod. 1 test set for this purpose. In the cocking operation push inward on the cocking tool until its shoulder contacts the detonator holder. Repeat the operation several times to insure that the firing plunger lock balls are firmly seated on the beveled edge of the guide tube bushing. Although the premature firing of an improperly cocked pistol in the test set, without attached detonator, will not have harmful results, accidental firing of detonator from this cause has resulted in serious injury to personnel. THEREFORE THE COCKING OPERATION SHOULD ALWAYS BE PERFORMED WITH CARE.

(c) Turn the index pointer back and forth several times through the full range from "safe" to "30." See note Chapter IV paragraph 19(b).

(d) Set the index pointer at "100." Set the pointer in deep firing mechanism of Mark 6 Mod. 1 pistol at "0-300."

(e) Clamp the testing set holder in a vise with the larger opening up. Assemble the parts in the holder as follows:

 

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TESTING SET MARK 2
TESTING SET MARK 2

 

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TESTING SET MARK 2, MOD. 1
TESTING SET MARK 2, MOD. 1

 

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(1) Rubber washer (largest outside diameter.)
(2) Depth charge pistol.
(3) Rubber washer (smallest outside diameter.)
(4) Cover.
(5) Clamping piece.

(f) See that all the parts are centered relative to each other and that the cover is flat on its washer. Clamp the parts together by rotating the clamping piece to the right until it is tight.

(g) Attach the pump to the valve in the cover and pump air into the mechanism until the gauge shows a pressure of 30 psi.

(h) Watch the pressure gauge. If the pressure loss in the system is not more than five pounds in one minute, the pistol is sufficiently tight.

(i) If the system fails to hold the pressure, check the testing equipment for leaks. Be sure that this assembly is tight and that the valve is not leaking.

(j) If the leak persists, tag the pistol to indicate the fault and set it aside for reconditioning at an overhaul station.

(k) If the pistol proves to be sufficiently air-tight, determine its firing depth as follows:

(1) Pump air slowly into the testing set until the pistol fires. This is indicated by the click of the firing plunger striking the detonator holder collar.

(2) Note the pressure when the pistol fires. A pressure of 44.4 pounds per square inch is equivalent to 100 feet of sea water, and a pressure of not less than 40 pounds and not more than 49 pounds when the pistol fires indicates a satisfactory pistol. To get the exact reading at the instant the pistol fires,

 

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watch the gauge closely. It may be difficult to stop pumping immediately, especially if the pistol fires at the beginning of a down stroke of the pump.

(3) Also check pressure required to fire at 30 foot setting. Firing should occur between 10 and 15 psi.

(l) Disconnect the pump and depress the plunger in the valve to allow the air to escape.

(m) Remove the pistol from the testing set. Release entrapped air in hydrostatic chamber of Mark 6, Mod. 1 pistol by pressing down on ball valve with a tool provided for this purpose. Cock the firing plunger and replace the inlet valve cover.

NOTE: High firing pressures recorded for Mark 6 Mod. 1 pistol may be caused by closed ball valve in deep firing mechanism. This valve should be open to pressure flow when pointer is set at "0-300."

(n) If the firing pressure is within the limits specified above, the pistol is satisfactory for service. If it is not within these limits, tag the pistol to indicate the fault and set it aside for calibration or reconditioning.

NOTE: If the readings taken on a series of tests are consistently high or low, check the gauge on the testing set for accuracy.
 

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TESTING FIXTURE
TESTING FIXTURE

 

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TESTS OF MARK 6 AND MARK 6 MOD, 1 PISTOLS
(Pistol Testing Fixture) Test Set Mark 3

7. The standard functional test procedure for these pistols using pistol testing fixture of the Test Set Mark 3, is as follows:

(a) Remove the detonator and safety cover if attached.

DO NOT replace the detonator collar and detonator holder.

(b) Cock the pistol. Use the cocking tool provided in the Mark 2 Mod. 1 test set for this purpose. In the cocking operation push inward on the cocking tool until its shoulder contacts the detonator holder. Repeat the operation several times to insure that the firing plunger lock balls are firmly seated on the beveled edge of the guide tube bushing. Although the premature firing of an improperly cocked pistol in the test set, without attached detonator, will not have harmful results, accidental firing of detonator from this cause has resulted in serious injury to personnel. THEREFORE THE COCKING OPERATION SHOULD ALWAYS BE PERFORMED WITH CARE.

(c) Turn the index pointer back and forth several times through the full range from "safe" to "30." See note Chapter IV paragraph 19(b.)

(d) Set the index pointer at "100." Set the pointer in deep firing mechanism of Mark 6 Mod. 1 pistol at "0-300."

(e) Draw up fixture head by turning handle of holding down screw. Unhook carrier latch and swing carrier to one side.

(f) Place pistol in fixture and swing carrier back into place with latch secured under fixture top plate.

 

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PISTOL TESTING FIXTURE
PISTOL TESTING FIXTURE

(g) Clamp head in place on flange of pistol by turning handle of holding down screw. A piece of tubing may be used on this handle to tighten the screw securely.

(h) Close valves D, E, F, G, and N and open valves H and K in testing fixture piping system.

(i) Apply air to test fixture by operating valve C and note pressure at firing on 60 lb. gauge adjacent to fixture. Close valves C and K when the gauge shows a pressure of 30 psi.

 

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Watch the pressure gauge. If the pressure loss in the system is not more than five pounds in one minute, the pistol is sufficiently tight.

(i) If the gauge shows falling pressure check for leaks. Be sure that the holding down screw is pulled down tightly to press the head gaskets on pistol flange and inlet and outlet connections. (1) If the leak persists, tag the pistol to indicate the fault and set it aside for reconditioning at an overhaul station.

(m) If the pistol proves to be sufficiently air-tight, determine its firing depth as follows:

(1) Open valve "C" slowly until pistol fires. Although detonator collar and detonator holder have been removed from the pistol and the firing plunger strikes against the rubber buffer in the test fixture pistol cocking pin, an audible click when the pistol fires will be heard.

(2) Note the pressure when the pistol fires. A pressure of 44.4 psi is equivalent to 100 foot depth of sea water, and a pressure of not less than 40 psi and not more than 49 psi when the pistol fires indicates a satisfactory pistol. To get the exact reading at the instant the pistol fires, watch the gauge closely. Close valve "C" immediately after the pistol fires.

(3) Also check pressure required to fire at 30 foot setting. Firing should occur between 10 and 15 psi.

(n) Open valve "N" to relieve the pressure in fixture. Raise up on pistol cocking lever to recock the Mark 6 pistol. Repeat this operation several times to insure proper seating of firing plunger lock balls on beveled edge of pistol central tube bushing.

 

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NOTE. This recocking operation cannot be performed on the Mark 6 Mod. 1 pistol because the ball valve in the deep firing mechanism is forced against its seat by the air retained in the pistol hydrostatic chamber.

To recock the Mark 6 Mod. 1 pistol after test, release entrapped air in pistol hydrostatic chamber by pressing down on ball valve with a tool provided for this purpose.

(o) Back off head holding down screw by turning handle. Unlatch carrier and swing it to one side. Remove pistol from the fixture.

(p) Replace detonator collar, detonator holder and locking spring. Recock the Mark 6 Mod. 1 pistol as noted in paragraph 7(n) above.

MARK 6 MOD, 1 PISTOL DEEP-FIRING TEST

8. The standard deep firing functional test procedure for completely assembled pistols using hydrostatic pressure in pistol testing fixture is described below. This test is not advisable for testing more than one percent of a lot. See note in paragraph 8(m). The procedure of chapter VI paragraph 16 should be followed to test the deep firing feature of each Mark 6 Model 1 pistol tested.

(a) Remove the detonator and safety cover if attached.

DO NOT replace the detonator collar and detonator holder.

(b) Cock the pistol. Use the cocking tool provided in the Mark 2 Mod. 1 test set for this purpose. In the cocking operation push inward on the cocking tool until its shoulder contacts the detonator holder. Repeat the operation several times to insure that the firing plunger lock balls are

 

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firmly seated on the beveled edge of the guide tube bushing. Although the premature firing of an improperly cocked pistol in the test set, without attached detonator, will not have harmful results, accidental firing of detonator from this cause has resulted in serious injury to personnel. THEREFORE THE COCKING OPERATION SHOULD ALWAYS BE PERFORMED WITH CARE.

(c) Turn the index pointer back and forth several times through the full range from "safe" to "30." See note Chapter IV paragraph 19(b).

(d) Set the index pointer at "100." Set the pointer on deep firing mechanism at "500."

(e) Draw up fixture head by turning handle of holding down screw. Unhook carrier latch and swing carrier to one side.

(f) Place pistol in fixture and swing carrier back into place with latch secured under fixture top plate.

(g) Clamp head in place on flange of pistol by turning handle of holding down screw. A piece of tubing may be used on this handle to tighten the screw securely.

(h) Close valves D, E, F, H, K and N and open valve G in testing fixture piping system.

(i) Open valve C to allow hydrostatic pressure to build up in fixture to about 10 psi on 0-300 lb. gauge. Open valve N to purge entrapped air in test fixture. Close valve N.

 

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(j) By use of valve C admit pressure to test fixture. Control the valve so that the gauge pressure rises at the rate of approximately 6.5 pounds per second.

(k) Watch the gauge closely during the pressure rise. A slight flicker of the gauge needle denotes the opening of the valve in the deep firing mechanism. Firing of the pistol takes place immediately thereafter. Note the pressure when the valve opens. A pressure of 222 psi is equivalent to 500 foot depth of sea water and a pressure of not less than 197 psi and not more than 247 psi when the valve opens indicates a satisfactory pistol. Close valve C immediately after the pistol fires.

(l) Open valve N to drain the fixture. Back off head holding down screw by turning handle. Unlatch carrier and swing it to one side. Remove pistol from the fixture.

(m) Pistols subjected to this test must be disassembled, blown out with air and then placed in an oven at 220°F for at least 4 hours to remove all traces of moisture from the mechanism. Reassembled pistols with damaged parts replaced may be issued to service after calibration and test as noted in Chapter VI.

NOTE: Because of the reconditioning necessary after this test it is not advisable to test more than one per cent of a lot. In the early stages of manufacture attempts were made to use air for this test so that it would not be necessary to break down the pistol for drying. However, it was found that the deep firing mechanism valve would not function properly under air pressure.
 

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TESTING BOOSTER EXTENDERS

9. The standard functional test procedure for Booster Extender Mechanisms using the Mark 2 Mod. 1 test set is as follows:

(a) Place the extender mechanism in the holder of the testing set. Pull off the safety fork. The hook on the extender testing tool may be used to pull off the plain type safety fork. When the safety fork is removed the extender spindle should move in approximately one quarter of an inch and open a passage for the entrance of air around the end of the spindle.

NOTE: Failure of the Mark 6 extender mechanism to meet this requirement should be rarely encountered. However, the Mark 6 Mod. 1 extender mechanism is equipped with a seal housed in the spindle bushing and failure of the spindle to move inward due to tightness of this seal will sometimes be encountered. See instructions noted in paragraph 19(a) of Chapter IV.

(b) Place hook of extender testing tool in the hole at the end of the spindle and pull the spindle out. Secure the extender stop on the end of the spindle and allow the spindle to slip back into the hole in the spindle bushing carrying the extender stop with it. See that the extender stop is centrally located with respect to the spindle so that this can take place.

NOTE: It will be necessary to drill a one eighth inch diameter hole in the extender stop for use with the Mark 6 Mod. 1 extender mechanism. Such a hole is necessary to insure the passage of air by the seal around the spindle. This
 

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hole should be centrally located on the flanged head of the extender stop and terminate in the cavity provided for the end of the spindle.

(c) Make up the test fixture with rubber washer, cover and clamping piece, as when testing a pistol.

(d) Pump air into the system until the booster spindle extends to the full travel permitted by the extender stop. This should occur at a, pressure of 4 to 10 pounds per square inch to be satisfactory. If it does not, tag the mechanism to indicate the fault and set it aside for reconditioning.

(e) If the mechanism operates within the limits specified, continue to pump air into the system until a pressure of 30 pounds per square inch is obtained. If the indicated pressure on the gauge does not drop more than 5 pounds in one minute, the mechanism is satisfactory. If the test indicates that the mechanism leaks, tag it to indicate this fact and set it aside for reconditioning at an overhaul station.

NOTE: When leaks are observed while making tests, be sure the leak is not in the testing set.

Check all extender mechanisms to insure that they are fitted with bellows retainer.

 

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Pistol Testing Fixture
Pistol Testing Fixture

(f) The standard functional tests of booster extender noted in this paragraph may be performed with the use of pistol testing fixture, the operation of which is described in paragraph (7) of this chapter.

INSPECTION OF CASES

10. Inspect a depth charge case as follows:

(a) Remove the metal shipping covers.

(b) Inspect the case and central tube for TNT exudate leaks. Exudate is a dark brown oily liquid which separates out from cast TNT and may exude from the cases after a period of storage. While modern methods of refining and loading TNT virtually eliminate any possibility that such exudate will be found, it must be remembered that this exudate is highly inflammable and must be handled accordingly. If any traces of exudate are found on depth charges, wipe them off with waste (or similar material), using carbon tetrachloride as a solvent if necessary. Alkali and all soap type cleaners should not be used. Dispose of the waste with due regard for the inflammability of the exudate.

 

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Cross section of case.

Blue Indicates Exterior Red Indicates Interior

 

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(c) Check the diameter and length of the case to see that they are with in the specified tolerances.

NOTE: Each Mark 6 and Mark 6 Mod. 1 case shall pass through a ring gauge having an internal diameter of 17.70 inches, plus or minus .010, and a length of not less than 4.0 inches. Activities undertaking to gauge depth charge cases should use a gauge having an internal diameter conforming as closely as possible with the maximum limiting dimension.

Metal procurement difficulties have made it necessary to allow some manufacturers more liberal tolerance on the length of the case. It will be found that the length of some cases are 3 /16 inch short of the required nominal dimension of 27.625 inches.

(d) Check to insure that the ends of the cases are not deformed so as to prevent rolling in depth charge release tracks. Manufacturing specifications require that each case shall roll evenly and smoothly upon a gauge consisting of a pair of parallel rails, each rail having a horizontal bearing face width of not less than 3.0 inches and a vertical guide face not less than 3.0 inches high. These horizontal and vertical faces should form an angle of 90' and meet in a sharp corner. The distance between the inside faces of the two vertical guides shall be 27.70 inches, plus or minus .020 inches. Test rails shall be level in a crosswise direction, and inclined along their length at an angle of between three and five degrees. Test rails shall be not less than six feet long to allow for at least one complete revolution of the case during its passage along the test rails unassisted.

 

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(e) Cases in service which have slight exterior deformations may be used provided the functioning of the case in release tracks, roller loaders and projectors is not impaired. Badly deformed or leaky cases should be returned to depots for reconditioning or disposed of as circumstances require. The charge must be removed from damaged loaded cases before attempting extensive repairs.

(f) Inspect the central tube and see that it has no projections or deformations which will interfere with motion of the booster can or proper assembly of the pistol or booster extender. Check the dimensions of the tube with a cylindrical plug gauge having a diameter of 4.160 inches (plus .003, minus .000) and a length of 8.75 inches (plus or minus .030.) This gauge should enter and pass freely through the length of the central tube.

(g) Inspect the tapped holes in the flanges at the end of the central tube.

(h) Inspect and clean the gasket seats on both ends of the case to be sure that the assembly can be made watertight.

(i) Inspect the gaskets and see that they are in good condition.

(j) Inspect empty cases for leaks. Cases must hold an internal air pressure of 20 pounds per square inch without leaking. If welding is required, check dimensions after completing the welding.

 

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INSPECTION OF BOOSTER CANS

11. Inspect booster cans as follows:

(a) Inspect cans for leaks, holes, or any evidence that the TNT charge is wet.

(b) Examine the booster for deformations which might interfere with its movement inside the depth charge central tube. See that the joint between the can and head is tight and in good condition.

(c) Use a ring gauge with an inside diameter of 4.145 inches (plus 0.000, minus 0.003) and a length of 1.0 inch (plus or minus 0.030) to check the diameter of booster cans. The booster cans should pass freely through this gauge.

(d) Inspect the detonator envelope and see that it is in good condition and securely soldered in the booster can.

(e) If there is any indication that the booster is defective, set the unit aside for repairs or, if aboard ship, return it to a depot for replacement.

Booster can cross section.

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