Maintenance
Clean suction and discharge valves
35
Subject to technical changes.
Stepper motor-driven diaphragm dosing pump NXP-M and NXP-P
Operating instructions
12.3 Change the diaphragm
d
e
c
b
a
Fig. 33: Exploded view of the diaphragm and dosing head
12.3.1 Remove the old diaphragm
Precondition for action:
ü
You have disconnected the dosing pump from the mains supply.
ü
You have depressurised the hydraulic sections of the plant.
ü
You have rinsed the dosing pump using a safe medium (e.g. water).
Perform the following working steps:
1.
Screw out the four screws (5) on the dosing head using a suitable tool
(SW 3 Allen key) and take off the dosing head (4).
2.
Use pliers to bend the edge of the diaphragm (3) slightly upwards and
screw it out counter-clockwise.
12.3.2 Install a new diaphragm
Precondition for action:
ü
You have thoroughly cleaned the diaphragm rod (2) and the
diaphragm flange (1) so that the new diaphragm is not affected by
dosing medium residues.
ü
The diaphragm (3) thread was lightly greased (e.g. Molycote
Longterm W2).
1.
Screw the diaphragm manually in the clockwise direction until it
safely contacts into the diaphragm rod.
2.
Bring the dosing head into position and insert the screws. First
tighten the screws finger-tight. After this, tighten the bolts on the
diagonal, e.g. top left – bottom right – top right – bottom left.
NOTE
Damage to the dosing head/diaphragm leaks
If you tighten the screws too much, this can lead to the dosing head
being damaged. However, not tightening the screws enough leads to
the diaphragm being leaky and correct functioning being affected.
ð
Tighten the screws to a torque of 16 Ibf in.
ü
Diaphragm change finished.
i
It may be necessary to gauge the delivery capacity after
replacing the diaphragm or other dosing pump spare parts.
12.4 Clean suction and discharge valves
Contaminated valves affect the dosing preceision and this means that
you should clean the valves on a regular basis.
With dosing heads made of plastic, when replacing a valve you must
replace the complete dosing head (see chapter 14 “Spare parts“ on page
39).