CONVERTER ASSEMBLY PURGE

As we mentioned before, the converter should be purged before any test. This purging is the key to a trouble-free operating converter. Only dry, oil-free nitrogen, Type I, Class 1, Grade A (FED SPEC BB-N-411) is to be used for purging converters. While operating purging unit, you have to wear protective gloves. The discharge fittings can reach temperatures that will cause severe burns if grasped with bare hands.

Before starting to purge the unit, empty it of LOX and allow it to warm to room temperature. Then proceed as follows:

1. Cap the converter quick-disconnect coupling assembly and attach a drain line to the quick-disconnect coupling assembly.

2. Ensure the purge unit power switch is OFF. Connect the purging unit electrical power cable to a suitable electrical power source.

3. Open the Npurge unit inlet valves. 2 supply cylinder valve and the

4. Turn the purge unit power switch ON, and allow the unit to warm up approximately 10 minutes.

5. Measure the outlet temperature of the purge unit using a thermometer, GG-T-336, Type 2, Class D or equivalent. Temperature should be between 200 F (93 C) and 250F (121 C) prior to connecting the purge unit to converter.

6. Connect the purging unit to the fill, buildup, and vent valve of converter.

7. Purge the converter assembly. The maximum inlet pressure and temperature should be 55 psig and 250 F, respectively. The purge time for 10-liter LOX converters which are at ambient temperature is from 45 to 75 minutes.

8. When purging is completed, turn the purge unit power switch OFF, secure the N2 supply cylinder valve and the purge unit inlet valves. Disconnect the purge unit from the converter.

NOTE: Should the unit fail a test, the first step of the repair action is to repurge the unit.

INSULATION RESISTANCE TEST (EMPTY)

To perform the insulation resistance test, proceed as follows:

1. Secure the empty converter in the rack provided on the test stand countertop.

2. Using the test stand cable assembly, connect the upper terminals of the high capacitance cable assembly to terminals A and B of the liquid oxygen quantity gauge capacitance type tester.

3. Turn the power switch ON and allow the tester to warmup 10 minutes prior to proceeding.

4. Turn the MEGOHMMETER RANGE SELECTOR to its X-1 position.

5. Turn the FUNCTION SELECTOR knob to the A AND B position. Record the reading on the meter in the space provided on the Performance Test Sheet. Reading should not be less than 2.0 megohms.

6. Turn the FUNCTION SELECTOR knob to A TO GROUND and B TO GROUND positions respectively. Record the readings in spaces provided on the Performance Test Sheet. Readings should not be less than 1.0 megohm in either position.

7. If insulation resistance readings are less than allowed, connect the cable assembly to the lower probe terminals, and repeat steps 5 and 6.

8. If readings are acceptable, replace the high capacitance cable with the low capacitance assembly. Repeat steps 5 and 6. If readings are acceptable, proceed to step 11.

9. If readings continue to be less than acceptable, moisture may still be present in the sphere assembly. Purge the converter and repeat the test.

10. Converter assemblies that fail the insulation resistance test, and cannot be corrected by replacing the low or the high capacitance cable assembly or by purging, are condemned.

11. Leave all connections unchanged and start the capacitance test (empty).

CAPACITANCE TEST (EMPTY)

To perform the capacitance test, proceed as follows:

1. Turn the CAPACITANCE RANGE SELECTOR knob to the X-10 position.

2. Turn the FUNCTION SELECTOR knob to its CAPACITANCE (UUF) position.

3. Record the meter reading in the space provided on the Performance Test Sheet. Reading should be 121.5 to 125.5 micro-microfarads (UUF).

4. If this reading is not within these limits, moisture may still be present in the sphere. Purge converter again and repeat the capacitance test.

5. Converter assemblies that fail the capacitance test and cannot be corrected by purging are condemned.

6. Turn the power switch off and disconnect the test stand cable assembly.