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6270A Pressure Control Module (PCM) Valve Inspection

More detailed instructions are in the 6270A Service Manual on page 59. Here is a link to that,
6270A Service Manual

This procedure is intended for Fluke Calibration Employees, Approved Service Providers, or other authorized personnel trained on service repairs of 6270A pressure controllers.

Leaking control valves can cause up or down pressure leaks or poor control. Valves can become contaminated with Teflon tape or other sealing compounds, particles from supply gas, contamination from test devices. Valves can also wear out with use.

This shows how to disassemble the PCM and check if there is wear or contamination on the sealing surfaces of the valves.

Before removing the PCM, vent the supply pressure.

1. Pull out the handle located directly below the numeric keypad. This unlocks the front panel.

2. Pull the handle to slide out front panel and access the Module Bay.

For safety, the 6270A automatically vents to atmosphere when the front panel is unlatched and opened. When the front panel is open, the system stays in the Vent mode until closed

3. Loosen the two hex bolts on the front of the PCM and slide the PCM out of the bay.

4. Turn the PCM over and remove the three screws. Take the cover off the PCM.

5. Remove the two nuts holding the coils onto the valves, and remove the white cable connector from the top of the circuit board.

6. Remove the coils and the wiring harness by sliding them up.

7. Remove the stem (also called tube) of the valve in question by unscrewing it from the sub base. Note that the plunger inside the stem will fall out if you don't hold it in.

8. Inspect the pad on the plunger and the sealing surface of the sub base that the pad contacts. Note that it is normal for the pad to have a dent in it but it should not be jagged and/or falling apart.

     

9. Remove the sub base by removing the four Phillips screws. Note the orientation of the sub base even though there is a guide pin for it. Inspect the sealing surfaces on the manifold that the valves attach to and inspect the bottom of the sub base.

10. If necessary clean the surfaces with a light solvent like glass cleaner or alcohol. Blow some clean dry air or nitrogen through the manifold.

11. Lubricate o-rings with Krytox GPL 205/6 lubricant. Fluke part number 2493420 for a 0.5 oz. tube.

12. Reassemble in reverse order with these torque values:
Sub base Phillips screws 
Stem / Tube
Coil nuts
Cover screws
PCM hex bolts 0.5 to 0.7 N∙m (4 to 6 lbf·in)<br /

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