Replacing The Metering Diaphragm - ProMinent Beta BT4b Operating Instructions Manual

12.2

Replacing the metering diaphragm

WARNING!
A few cubic centimetres of feed chemical may have accumu‐
lated behind the metering diaphragm in the backplate fol‐
lowing a leak - depending on the design!
– Take this feed chemical into consideration when you are
planning a repair - especially if it is hazardous!
Personnel:
n
If necessary take protective measures.
n
Observe the safety data sheet for the feed chemical.
n
Depressurise the system.
n
1. Empty the liquid end (turn the liquid end upside down and allow the
feed chemical to run out; flush out with a suitable medium; flush the
liquid end thoroughly when using hazardous feed chemicals!)
2. Turn the stroke adjustment dial until the stop at 0 % stroke length if
the pump is running (the drive axle is then difficult to turn).
3. Switch off the pump.
4. Unscrew the hydraulic connectors on the discharge and suction
side.
5. With PP types with bleed valve: Firstly remove the bleed valve (star
handle), then lift off the cover of the liquid end with a screw driver.
6. Remove the screws (1).
7. Loosen the dosing head (2) and the backplate (4) from the pump
housing (6) - but only loosen!
8. Hold the pump housing (6) with one hand and clamp the diaphragm
(3) with the other hand between the dosing head (2) and the back‐
plate (4).
9. Loosen the diaphragm (3) from the drive axle with a gentle back‐
wards turn of the dosing head (2), diaphragm (3) and backplate (4)
in an anticlockwise direction.
10. Unscrew the diaphragm (3) completely from the drive axle.
11. Remove the backplate (4) from the pump housing (6).
12. Check the condition of the safety diaphragm (5) and replace if nec‐
essary.
13. Push the safety diaphragm (5) onto the drive axle only until it lies
flush with the pump housing (6) and no further!
14. Tentatively screw the new diaphragm (3) onto the drive axle until its
stop position.
ð The diaphragm (3) is now sitting at the stop of the thread.
15. Should this not work, remove dirt or swarf out of the threads and
screw the diaphragm (3) onto the drive axle correctly this time.
The diaphragm must be screwed exactly onto the
drive axle otherwise the pump will subsequently not
meter correctly!
16. Unscrew the diaphragm (3) again.
17. Place the backplate (4) onto the pump housing (6).
Technical personnel
Repairs
39