KNF N85.3 - Page 30

Servicing Diaphragm pump N85, N86
30 Translation of original Operating and Installation Instructions, english, KNF 121258-121528 01/20
c) Changing the diaphragm
1. Turn the fan to bring the diaphragm (9) to top dead centre.
2. Lift the edge of the diaphragm, and gripping it on opposite
sides, unscrew it by turning anti-clock-wise. Please take care
that the disc spring (12) and diaphragm spacers (11) on the
threaded portion of the diaphragm do not fall into the housing.
3. Take the disc spring (12), diaphragm spacer(s) (11), and the
washer (15) off the threaded portion of the diaphragm and re-
tain them.
4. Check that all parts are free from dirt and clean them if neces-
sary (see Chapter 9.2. Cleaning).
5. Put the washer, diaphragm spacer(s), and disc spring, in that
order, on the thread of the new diaphragm.
 The concave side of the disc spring must be towards the
diaphragm.
6. Turn the fan until the connecting rod (13) is at top dead centre.
7. Screw the new diaphragm, complete with washer, diaphragm
spacer(s), and disc spring, into the connecting rod (clockwise)
and tighten it by hand.
d) Changing the valve plates
1. Separate the head plate (3) from intermediate plate (2).
2. Remove the valve plates/sealings (7) from the intermediate
plate.
3. Check that the valve seats in the head plate and intermediate
plate are clean. If scratches, distortion, or corrosion are evident
on these parts they should be replaced.
4. Lay the new valve plates/sealings in the recesses in the inter-
mediate plate. The valve plates/sealings for suction and pres-
sure sides are identical, as are upper and lower sides of the
valve plates/sealings
5. Check that the valve plates/sealings are not deformed by mov-
ing them gently sideways in their recesses.
e) Refitting the pump head
1. Turn the fan to bring the diaphragm to top dead centre.
2. Place the intermediate plate (2) with valve plates/sealings (7)
and head plate (3) on the housing, in the position indicated by
the marking (M).
3. Check that the head plate is centred by moving it gently side-
ways.
4. Gently tighten the screws (4), evenly and diagonally.
5. Turn the fan to check that the pump rotates freely.
6. Turn the fan again to bring the diaphragm to top dead centre.