Danfoss APP S 21-38, APP S 674 21-38 Service guide
Service guide
Instruction
APP S / APP S 674 pumps
Disassembling and assembling
APP S 21-38 / APP S 674 21-38
Disassembling and assembling
APP S 674 21-38
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
Table of Contents
1. Disassembling ..........................................................................2
2. Disassembling the pump ................................................................3
3. Assembling the pump...................................................................8
4. Disassembling and assembling of the swash plate ......................................14
5. Disassembling and assembling of cylinder barrel-/ valve plate ..........................15
6. Disassembling and assembling of the ush valve .......................................16
7. Changing pistons ......................................................................17
7.1. Disassembling .........................................................................17
7.2. Assembling ............................................................................20
8. Exploded view APP S (674) 21-38........................................................22
9. When should the pistons be replaced...................................................23
This document covers the instructions for
disassembling and assembling the axial piston
pumps APP S (674) 21-38.
Tools provided with toolset 180B4347:
• Adjustable pin wrench
• Stop for retainer plate
• Press bush for valve plate
• Press bush ø 45 (Plastic)
• M8 mm eye bolt
• M8 mm nut
• M8 x 70 mm screw
• M8 allen screw (20 mm and 140 mm)
1. Disassembling
Important: It is essential that the pump is
serviced in conditions of absolute cleanliness.
Place the pump on a pallet or other stable
surface above the ground. Ensure that the pump
cannot roll. It must be possible to place the
pump vertically with the shaft pointing downwards. This can be done between two pallets or
between two boards on a pallet provided that
the distance is minimum 50 mm.
For a better understanding of the pump, please
see the exploded view in item 8.
WARNING:
Do not reuse disassembled O-rings or shaft
seal as they might be damaged. Always use
new O-rings.
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180R9278 | 521B1306 | DKCFN.PI.013.D3.02 | 05.2016
Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
2. Disassembling the
pump
1. Disconnect the pump from the rest of the
system.
3. Carefully remove the stop bush ring and the
O-ring with a screw driver.
2. Lubricate shaft with clean ltered water.
4. Using a 10 mm combination wrench,
unscrew the four bolts from shaft seal
ange.
WARNING!
Place the shaft seal press bush tool to
ensure the ange does not pop out and
damage the ceramic ring.
5. Place two bolts in screw holes in the ange.
180R9278 | 521B1306 | DKCFN.PI.013.D3.02 | 05.2016
6. Remove ange slowly.
WARNING!
Be careful, the shaft has sharp edges.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
7. Remove O-ring. Remove ceramic ring from
ange by carefully pushing it from the back
of the sealing ring.
9. Place the press bush tool over the shaft seal
again. Through the inlet port lift the shaft
seal with a screwdriver between shaft seal
and spring.
WARNING!
Be careful not to scratch the shaft.
8. Wet the shaft and shaft seal with clean
ltered water.
10. Carefully remove the shaft seal and ring.
11. Carefully remove the spring by lifting it with
a screwdriver.
12. Turn pump into vertical position with shaft
pointing downwards and remove the shaft
seal distance ring.
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180R9278 | 521B1306 | DKCFN.PI.013.D3.02 | 05.2016
Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
13. Using the 13 mm combination wrench,
remove all the bolts on the mounting ange
except the three shown in the picture under
item 14.
WARNING:
Do not loosen the two screws keeping
swash plate in place.
15. Screw the eye bolt in the M8 hole in the
middle of the ange. Pull it straight upwards.
14. Unscrew the remaining three bolts. Turn
each bolt one round at the time to make
sure that the ange is removed as straight
forward as possible.
16. Swash plate must be placed so that its
surface is not scratched. For further
disassembling of swash plate, see page 14.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
17. Remove by hand the pistons one by one.
Be careful not to scratch the pistons.
If required, tilt the retainer plate to horizontal position for easy removal of pistons.
WARNING:
Do not use any tools.
19. Remove the retaining guide, the 4 springs
and the spring guide.
18. Remove the retaining plate and the
retaining ball.
Note: As the retaining ball is not attached
to the retaining plate, it might fall out.
20. Mount the 8 mm eye bolt in the cylinder
barrel. Pull straight upwards. A continuous
lift will elevate the cylinder barrel out of
housing. This can only be done if shaft seal
is removed.
WARNING:
If the cylinder barrel is dropped or lowered
too fast into housing, the main bearing/
shaft bearing might be damaged.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
21. Place cylinder barrel upside down. For
further disassembling of cylinder barrel and
valve plate see page 15.
23. Remove, by hand, the two guide pins.
Note: The following operation is only
necessary if O-ring on port ange is to be
changed.
22. Remove the port plate by hand.
24. Place the pump horizontally.
25. Remove the remaining screws in port ange
by using a 13 mm combination wrench.
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26. Carefully separate house and port ange.
Ensure that guide pin for the positioning
house is not lost. For further disassembling
of ush valve, see page 16.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
3. Assembling the pump
WARNING:
Do not use silicone when assembling the
pump. Do not reuse disassembled O-rings;
they might be damaged. Always use new
O-rings.
Important:
It is essential that the pump is serviced in
conditions of absolute cleanliness. All parts
must be absolute clean before mounting.
1. Lubrication:
• To prevent seizing-up, lubricate all threads
with PTFE lubrication type.
• O-rings inside pump must be lubricated only
with clean ltered water.
• O-rings for port ange, mounting ange and
ushing valve must be lubricated.
• It is important to lubricate ALL parts to be
assembled with clean ltered water
(Especially all PEEK parts).
2. Place port ange with O-ring pointing
upwards.
3. Insert guide pin for positioning housing on
port ange.
Ensure that two screw holes can be reached
from below.
4. Mount O-ring.
5. Position housing aligning pin hole over
guide pin.
6. Carefully press downwards. Be careful not to
squeeze O-ring. If O-ring is damaged, the
pump will leak.
7. Screw in at least two screws.
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180R9278 | 521B1306 | DKCFN.PI.013.D3.02 | 05.2016
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