Manual for submarine mining

by United States. War Department

However, each mine should be tested separately, as follows:

With the D. C. on the D. C. busses of the power panel, close switch 7 up, open the power switch on the mine block of the mine circuit to be tested, and put the M-AM “plug” on the upper point of the power switch. If the automatic switch falls, adjust the solenoid or hold the switch up while testing the circuit, otherwise the reading obtained will be that of the red lamp and bell circuit. These operations put the mil-ammeter and its protective lamp in series with the mine circuit.

The circuit is as follows: From the negative D. C. bus on the power panel, to switch 7 closed up, through the mil-ammeter and its protective lamp, to the terminal bar, to the M-AM lead, to the plug, to the upper point of the power switch P, through the solenoid, to the middle of the testing switch T, to the upper point of same, to the upper point of the automatic switch, to the middle of same, to the mine switch, through same, to the terminal bar, through the 19-conductor and the single-conductor cables, to the mine transformer primary, to the mine case, to ground, to the D. C. “earth” terminal on the power panel, to switch 7, and to the positive D. C. bus on the power panel.

With from 80 to 110 volts these readings should normally be between 30 and 40 mil-amperes. A mine may be fired if the reading with 80 volts is between 14 and 120 mil-amperes. These limits increase with the testing voltage. If the mine tests within the firing limits, the solenoid should be adjusted if the current is above its normal setting (0.075 amperes). If the test indicates that the mine can not be fired, the mine switch should be opened.

4. Test of the automatic switch, red lamp, and bell.—Throw the D. C. power on the busses of the operating board by closing switch 3 up. Open the bell switch. Next close the testing switch down on the mine block under test. The red lamp should glow and the corresponding automatic switch trip. (For circuit see fig. 18.) Now close the bell switch, throwing the bell in parallel with the red lamp; the bell should ring. Next open the bell switch and repeat the test for each mine block in turn.

5. Test of the alternating circuit.—This circuit is tested with D. C., as follows: Connect the A. C. and D. C. jaws on the master block with a jumper, open the power switches, close switches 3, 8, and 9 up on the power panel. The green and white lamps of the operating board under test should glow. A break or an excessive resistance in the casemate grounds, or elsewhere in the circuit, will be indicated by the lamps not glowing, or glowing dimly.

The circuit is as follows: From the negative D. C. bus on the power panel, to switch 3, to the “operating board” terminal, to the D. C. lead, to the D. C. post on the signal block, through the green lamp, to the D. C. jaw on the master block, through the jumper, to the A. C. jaw on the master block, through the white lamp and resistance in parallel, to the A. C. post on the signal block, to the A. C. lead, to the A. C. “operating board” terminal, to switch 8, to the A. C. bus, to switch 9, to the casemate transformer secondary, back to switch 9, to the other A. C. bus, back to switch 8, to the A. C. earth, through ground, to the D. C. earth, to switch 3, and to the positive D. C. bus on the power panel. With this circuit on, remove the 90-ohm resistance in parallel with the white lamp; the white lamp should glow more brightly, indicating continuity of circuit through the resistance as well as the white lamp.

It will be observed that the above test is for only a part of the A. C. circuit. To test the firing switch and the lower contact of the automatic switch, open switches 3, 8, and 9, close 7 up, remove the jumper, put the M-AM “plug” on the A. C. jaw on the master block, close the firing switch, and trip in turn each automatic switch by raising the corresponding knob on the solenoid and observe the reading of the mil-ammeter. Close each automatic switch up before tripping the next one.

The mil-ammeter reading should be from 30 to 40 mil-amperes, indicating a circuit through the firing switch and the automatic switch. The circuit is as follows: From the negative D. C. bus on the power panel, to switch 7 closed up, through the mil-ammeter and its protective lamp, to the operating board terminal, to the M-AM lead, to the “plug,” to the A. C. jaw on the master block, through the firing switch F. S., to the A. C. bus on the operating board, to the lower point of the automatic switch which was tripped, to the middle of same, to the mine switch, through the same, to the terminal bar, through the 19-conductor and the single-conductor cables, to the mine transformer primary, to the mine case, to ground, to the D. C. “earth” post on the power panel, to switch 7, to the positive D. C. bus on the power panel.

6. Test of the delivery of the A. C. power to the operating board.—See that all the automatic switches of the operating boards are up and all the firing switches of the master blocks open. Close switches 4 and 9 up (or down) and 8 down; close the testing switch T. S. on the master block. The white lamp should glow and the A. C. bus-bar voltage should drop appreciably.