Your instrument is fitted with either a Brass or Stainless Steel Control Valve. The procedure to make this adjustment is similar but requires a different tool. Examine the lock nut underneath the control valve handle. If it is brass, – click here for the brass control valve tutorial.
The Control Valve is the valve that directs the flow of nitrogen from CHAMBER / OFF / EXHAUST. This valve will require periodic adjustment. If a leak is in the control valve, the symptoms are generally a continual flow of gas into the chamber even while the instrument is in the “OFF” position. To correct this, follow the instructions below:
With the Stainless Steel valve you will need two tools to make the adjustment. These tools were provided originally with your instrument. If you have misplaced it you can purchase a replacement from PMS Instrument. The top is a 11/32 inch Combination Wrench and the bottom is a 3/32 inch Allen Key.
1. Connect instrument to a supply tank. Remove lid of chamber and turn valve to the “OFF” or “EXHAUST” position. Listen for gas leak. (Make sure that you are in a quiet environment that allows you to detect when the gas hiss stops).
2. Use the allen key to loosen the set screw in black handle of the control valve. Lift the handle straight up to remove.
3. Using the box end of the combination wrench, slowly tighten the packing gland nut.
Do not over tighten the valve packing, as permanent damage will result. Over tightening can additionally make the valve too tight to function normally.
4. Rotate wrench clockwise until the gas leak can no longer be heard. Remove wrench and reinstall the black handle. Note: If the instrument is used over a wide range of temperatures, some adjustment may be needed due to thermal expansion within the valve; this is normal.