KNF SC 920 G Mode D'emploi page 78

Servicing
Fig. 15: Position of valve plates (12)
Fig. 16: Position and orientation of
disk spring (7) and washer (8) at
34
Change valve plates
1. Mark the position of head plate (9) and intermediate plate (10)
relative to each other by a drawing line with a felt-tip pen. This
helps avoid incorrect assembly later.
2. Mark the position of head plate (9) and intermediate plate (13)
relative to each other by two drawing lines with a felt-tip pen.
3. Mark the position of head plate (9) and intermediate plate (14)
relative to each other by three drawing lines with a felt-tip pen.
4. Undo the three screws (6) in head plate (9) and remove head
plate from intermediate plates (10), (13) and (14).
5. Remove valve plates (12) and O-rings (11) from intermediate
plates (10), (13) and (14).
Instead of lying on intermediate plate, O-rings could stick to
head plate (9).
6. Lay the new valve plates (12) and the new O-rings (11) on the
intermediate plates (10), (13) and (14).
Upper and lower sides of the valve plates are identical. For
correct position see fig. 17.
7. Dispose of the old diaphragms and valve plates/sealings
properly.
Mount pump head
1. Place head plate (9) on intermediate plates (10), (13) and (14)
in the position indicated by the drawing lines.
At the front edge the three intermediate plates must lie in a line
on which head plate is placed flushly.
2. Tighten the three screws (6) of head plate (9) carefully slightly
hand-tight (tightening torque: 0.6 Nm).
For position and orientation of disk spring (7) and washer (8) of
screw (6) see fig. 18.
screw (6)
3. Place head cover (3) on pump housing (17).
4. Tighten the nine screws (2) of head cover (3) slightly in the
first instance. Start with the screws of medium pump stage,
then tighten the screws on the right, and finally on the left.
5. Now, tighten the screws (2) firmly (tightening torque: 6 Nm);
tighten the center screws first, then continue outward.
If the screws are stiff to turn, the intermediate plates do not lie
in a line at front edge, or intermediate plates and head plate
are not placed flushly (see step 1).
6. Remount the covers (4).
7. Tighten the two screws (1) on the head cover (tightening
torque: 5 Nm).
Translation of original Operating Instructions, English, KNF 334631-334633 07/21
Vacuum Pump System SC 920G