Edwards Vapour Diffusion Vacuum Pump Diffstak 250/2000P

Disconnect the pneumatic pipelines from the Diffstak

Remove the socket-head screws securing the valve-plate to the shaft

Remove the valve-shaft for Diffstak 63/150P and 100/300P pumps

Detach the red safety cover from the pneumatic actuator

Remove the three screws retaining the actuator to the boss on the valve-body

Carefully withdraw the valve-shaft (complete with actuator) from the valve-body

Remove the valve-shaft for Diffstak 160/700P pumps

WARNING: Remove all traces of the cleaning solution before you operate the pump.

Select the cleaning solution suitable for the type of pump fluid used

Ensure the jet assembly is vapour de-greased

Pump Interior Inspection and Cleaning

Inspect the pump interior for solid deposits of pump fluid

Is there a solid deposit of pump fluid around the base?

Use an ultrasonic cleaning bath to remove deposits if present

Wash the interior of the pump and components with the selected cleaning solution

Adjust Valve Closed Position Indicator

Loosen the clamp screw (7) on the valve closed position indicator (1)

Slide the position indicator in the dovetail groove (3) until the gap (2) is correct

Apply a suitable thread sealant to the clamp screw (7)

Tighten the clamp screw to a torque of 0.4 Nm

Adjust Valve Open Position Indicator

Repeat Steps 1 to 3 for the valve open position indicator (6)

Adjust the gap (5) between the valve open position indicator and the end of the pneumatic actuator

Allow the Diffstak pump to cool and open it to atmospheric pressure.

Switch on the pump heater for a maximum time of two minutes to warm the pump fluid.

Ensure the pump fluid is not vaporised.

Disconnect the Diffstak from the electrical supplies.

Detach the Diffstak from your vacuum system.

Remove the drain-plug and allow the fluid to drain from the pump.

Removal of Damaged Position Indicators

Refer to Figure 27 and loosen the clamp screw on the valve open position indicator.

Slide the valve open position indicator down the dovetail groove and out of the cylinder.

Loosen the clamp screw on the valve closed position indicator.

Slide the valve closed position indicator down the dovetail groove and out of the cylinder.

Installation of New Position Indicators

Ensure the dovetail groove is clean.

Slide the new valve closed position indicator into the dovetail groove, ensuring correct orientation as shown in Figure 27.

Adjust the position indicator until the gap between the position indicator and the valve actuator is correct.