Servicing
Swing Piston Pumps NPK 09
8
2. Re-assemble the "piston assembly":
Lay the new piston seal (
13
) on the retainer plate (
11
) with
the sealing lip towards the free surface of the retainer
plate.
Lay the support (
12
) on the retainer plate/piston seal
assembly.
Push the new countersunk flat head screw (
14
) through the
assembly, and fit the same number of washers as previ-
ously used.
3. Insert the piston assembly (retainer plate, support, piston seal
and washer(s) with their screw) into the cylinder from above,
on to the connecting rod.
The piston seal must not be distorted during assembly. It must
make contact with the cylinder all round its circumference.
4. Fasten the "piston assembly" by tightening the screw (
14
).
5. Reassemble the "head assembly": stack the following parts on
top of each other in the order given: ribbed head (
3
), gasket
(
6
), valve plate (
7
), intermediate plate (
2
), and valve plate (
8
).
Fig. 6 shows the correct orientation of the parts, particularly the
valve plates, in relation to the compression symbol on the head
plate. Both valve plates are identical, and they can be fitted
either way up. The intermediate plate can also be fitted either
way up.
6. Place the "head assembly" on the pump housing (
1
) - as a
guide to orientation see fig. 3 (single head models) or fig. 4
(twin head models). Reference point is the compression
symbol (indicated with a
K
in the diagrams), or the mark (
M
).
7. Tighten the screws (
4
) at first lightly, then firmly by hand, in a
diagonal pattern (max. tightening torque 1.5 Nm).
8. Rotate the fan by hand to check that pump turns easily.
9. Pump model NPK 09 DC only: refit cover (
18
) to the housing.
For twin head pumps, repeat the operations described for the
second head, and replace the connections between the two heads.
If, after changing the piston seal, the specified vacuum is not
reached, check the following:
pneumatic connections for tightness
for twin head models that the head connections are
gas-tight
if the washer(s) under the support has/have been
assembled.
If, after changing the piston seal, the pump produces no flow,
check the position and orientation of gasket (
6
), valve plate (
7
),
intermediate plate (
2
) and valve plate (
8
). See fig. 3,4 and 6.
5.2. Changing the valve plates
Spare part*
Quantity
Valve plates
2 (twin head pumps: 4)
Parts required
