Diaphragm Vacuum Pump N 828 / N 838
Servicing
Translation of original Operating and Installation Instructions, english, KNF 121249-121517 09/19
45
b.) Remove pump head
1. Mark the position of the head plate (
3
), intermediate plate (
2
)
and housing (
1
) relative to each other by a drawing line with a
felt-tip marker (M, see Fig. 29). This helps avoid incorrect as-
sembly later.
2. Undo the 4 screws (
4
) in the head plate (
3
) and lift the head
plate with the intermediate plate off the pump housing.
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) (
8
) on the thread of the new dia-
phragm.
6. Turn the fan until the connecting rod (connecting part between
motor shaft and diaphragm) is at top dead centre.
7. Screw the new diaphragm (
7
), complete with diaphragm spac-
er(s) (
8
) into the connecting rod (clockwise) and tighten it by
hand.
d.) Change valve plates/sealings
1. Use a small screwdriver to remove the two screw caps (
10
) on
the pump head and then undo the screw(s) (
9
).
2. Separate the head plate (
3
) from intermediate plate (
2
).
3. Remove the valve plates/sealings (
6
) from the intermediate
plate.
4. Check that the valve seats in the head plate and intermediate
plate are clean; if scratches or distortion corrosion are evident
on these parts they should be replaced.
5. 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 valve plates/sealings.
6. Check that the valve plates/sealings are not deformed by mov-
ing them gently sideways in their recesses.
7. Place the head plate (
3
) on the intermediate plate (
2
), in the
position indicated by the marking (
M
).
8. Check that the head plate (
3
) is centered by moving it gently
sideways.
