Servicing
Diaphragm Vacuum Pump N 828 / N 838
42
Translation of original Operating and Installation Instructions, english, KNF 121249-121517 09/19
c.) Change diaphragm
1. Turn the fan to bring the diaphragm (
7
) to top dead centre.
2. Lift the edge of the diaphragm and, gripping it on opposite
sides, unscrew it by turning anti-clockwise.
3. Take the diaphragm spacer(s) (
8
) off the threaded portion of
the diaphragm and retain it/them.
4. Check that all parts are free from dirt and clean them if neces-
sary (see Chapter 8.2. Cleaning).
5. Put the diaphragm spacer(s) rod (
8
) in the thread of the new
diaphragm.
6. Turn the fan until the connecting rod (
9
) is at top dead centre.
7. Screw the new diaphragm (
7
), complete with diaphragm spac-
er(s) (
8
) into the connecting rod (
9
) (clockwise) and tighten it
by hand.
d.) Change valve plates/sealings
1. Separate the head plate (
3
) from intermediate plate (
2
).
2. Remove the valve plates/sealings (
6
) 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 (
6
) in the recesses in the
intermediate plate (
2
). The valve plates/sealings for suction
and pressure sides are identical, as are upper and lower sides
of the plates.
5. Check that the valve plates/sealings are not deformed by mov-
ing them gently sideways in their recesses.
e.) Refit pump head
1. Turn the fan to bring the diaphragm (
7
) to top dead centre.
2. Place the intermediate plate (
2
) with valve plates/sealings (
6
),
and head plate (
3
) on the housing, in the position indicated by
the marking (
M
).
3. Check that the head plate (
3
) is centred by moving it gently
sideways.
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 structured diaphragm (
7
) to top
dead centre.
7. Now tighten screws (
4
) firmly diagonally
(tightening-torque: 3.5 Nm).
