VWR VP 820 Manuel D'instructions page 10

English
Removing pump head
1. On the pneumatic head connection (3), loosen the union nuts (2) by
hand. Then slightly loosen the angle-fitting (1) in the pump head (4)
by turning it anticlockwise, so that the connecting tube can be pulled
out.
2. Mark the position of top plate (fig. 7/5), head plate (fig. 7/6),
intermediate plate (fig. 7/8) and adapter relatively to each other by a
drawing line (for two-headed pumps: at both pump heads) with a felt-
tip pen. This helps to avoid incorrect assembly later.
3. Loosen the outer screws (fig. 4/5) on the pump head/pump heads.
4. Carefully remove pump head / pump heads.
Change diaphragm
Replace the diaphragms of both pump heads consecutively in order
to ensure that the same number of diaphragm spacers is used.
1. Push down one diaphragm until other diaphragm is pushed upwards
to its highest position.
2. Carefully unscrew this diaphragm (1) anti-clockwise using both
hands.
3. Replace spacer thick (2) and spacers thin (3) onto the screw thread
of the new diaphragm (same number and order).
4. Screw in the new diaphragm and tighten it by hand.
5. Complete steps 1 through 4 for the second pump head.
Change valve plates/sealings
Replacing the valve plates/sealings of both pump heads consecu-
tively.
1. At one pump head: Loosen screw(s) (1) in the center of the top plate
(2).
2. Remove top plate (2) and head plate (3) from intermediate plate (5).
Valve plates/sealings (4) are visible
3. Remove old valve plate/sealings.
4. Clean intermediate plate (5) carefully (if there should be deposits in
the recesses in the intermediate plate).
5. Insert new valve plates/sealings (4) in the recesses in the
intermediate plate (5).
6. Carry out the steps 1 to 5 for the second pump head.
7. Dispose of the old diaphragms and valve plates/sealings properly.
Refitting pump head
1. At one pump head: Apply pressure all around the edge of the
diaphragm.
2. Place the intermediate plate (8) with valve plates/sealings on the
adapter in accordance with the felt-tip pen marking.
3. Place the head plate (6) on the intermediate plate (8) in the position
indicated by the guide pin (7).
4. Place the top plate (5) on the head plate (6) in accordance with the
felt-tip pen marking.
5. Gently tighten screws (4) in diagonal order.
10
Fig. 4: Removing pump head
Fig. 5: Change diaphragm
Fig. 6: Change valve plates/sea-
lings