Figure 4-11. Test of pressure control switch

TM 5-4120-356-14

TS5-4120-35614/411

TEST

1. REFER TO PARAGRAPH 4-13c FOR PRELIMINARY STEPS IN MAINTENANCE OF THE PRESSURE CONTROL SWITCH

2. CONNECT A CIRCUIT TESTER ACROSS THE ELECTRICAL CONTACTS OF THE PRESSURE CONTROL SWITCH.

SET THE CIRCUIT TESTER FOR CONTINUITY TESTING.

4. CONNECT A SOURCE OF VAPORIZED NITROGEN TO THE CAPILLARY TUBE FITTING OF THE PRESSURE CON-

TROL SWITCH. NITROGEN SOURCE MUST BE EQUIPPED WITH A GAGE CALIBRATED FROM 0 TO 500 PSIG

(0 TO 35 ks/cm2).

5. WHILE OBSERVING THE CIRCUIT TESTER, APPLY 350 PSIG (24.5 ks/cm2) NITROGEN PRESSURE TO THE

SWITCH. CIRCUIT TESTER SHOULD SHOW NO CONTINUITY BETWEEN THE ELECTRICAL CONTACTS.

WHILE OBSERVING THE CIRCUIT TESTER, SLOWLY INCREASE NITROGEN PRESSURE TO THE SWITCH. SWITCH

SHOULD TRIP(CIRCUIT TESTER SHOW CONTINUITY) WHEN NITROGEN PRESSURE IS INCREASED TO BETWEEN

384 AND 416 PSIG (27 TO 29 ks/cm2).

IF SWITCH DOES NOT TRIP AT ANY PRESSURE UP TO 500 PSIG (35 ks/cm2), REPLACE SWITCH.

IF SWITCH TRIPS BELOW 384 PSIG (27 ks/cm2) OR ABOVE 416 PSIG (29 ks/cm2), THE SWITCH MUST

BE CALIBRATED. TURNING THE CALIBRATION SCREW CLOCKWISE INCREASES THE PRESSURE AT WHICH THE

SWITCH WILL TRIP. TURNING THE CALIBRATION SCREW COUNTER-CLOCKWISE DECREASES THE PRESSURE AT

WHICH THE SWITCH WILL TRIP. CALIBRATE THE SWITCH TO TRIP AT 400 PSIG (28 ks/cm2).

IF SWITCH CAN NOT BE CALIBRATED AS OUTLINED IN STEP 8, REPLACE THE SWITCH.

IF SWITCH TRIPS BETWEEN 384 AND 416 PSIG (27 AND 29 ks/cm2), DECREASE NITROGEN PRESSURE

10.

SLOWLY. SWITCH SHOULD AUTOMATICALLY RESET (CIRCUIT TESTER SHOW A BREAK IN CONTINUITY) WHEN

NITROGEN PRESSURE HAS BEEN DECREASED TO BETWEEN 334 AND 366 PSIG (23 AND 26 ks/cm

IF SWITCH DOES NOT AUTOMATICALLY RESET WHEN THE NITROGEN PRESSURE HAS BEEN DECREASED TO

11.

BETWEEN 334 AND 366 PSIG (23 AND 26 ks/cm2), REPLACE THE SWITCH.

DISCONNECT THE CIRCUIT TESTER LEADS FROM THE SWITCH CONTACTS AND DISCONNECT THE NITROGEN

12.

SOURCE FROM THE SWITCH.

REFER TO PARAGRAPH 4-13c FOR FINAL STEPS IN MAINTENANCE OF THE PRESSURE CONTROL SWITCH.

13.

Figure 4-11. Test of pressure control switch