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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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.
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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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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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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
8. Place housing horizontally. Screw in the rest
of the screws on port ange.
Tighten screws to torque according to
exploded view..
10. Position port plate by using the two guide
pins. Do not use force for this operation.
9. Place pump vertically. Place 10.5 mm guide
pins in port ange.
11. Ensure port plate is tted tightly against the
bottom.
Important: Lubricate port plate with clean
ltered fresh water. If valve plate is
disassembled from cylinder barrel please
see section 5 before continuing.
12. Screw eye bolt in cylinder barrel.
13. Make sure there is enough free space for the
shaft beneath housing. Carefully lower
cylinder barrel into housing.
WARNING:
If cylinder barrel is dropped or lowered too
fast into housing, main bearing and shaft
bearing might be damaged. Replacement
can only be done at Danfoss, Nordborg.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
14. Unscrew M8 eye bolt. 15. Place the four springs and spring guide in
cylinder barrel. Springs must be positioned
in the holes.
Note: For APP S 38 and APP S 674 38 a
distance ring must be placed underneath
each spring.
16. Retaining guide, retaining ball and retaining
plate must be mounted as indicated in
below picture.
17. Ensure that retaining plate is oriented
correctly, i.e. with its slant surfaces pointing
downwards.
18. Place retaining guide, retaining ball and
retaining plate in cylinder barrel.
Note: If pistons are replaced, place new
pistons in clean ltered water for a couple
of minutes. Exercise piston shoes to make
them “run” smoother.
19. Place pistons in retaining plate and cylinder
barrel.
When pistons are placed, tilt retaining plate
for easier placement of swash plate.
If swash plate has been disassembled from
mounting ange, see page 14 for assembly
of swash plate.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
20. Lubricate piston shoes and swash plate with
clean ltered water.
22. Place three bolts in mounting ange.
Turn each bolt one round at a time to ensure
mounting ange is mounted as straight
downwards as possible. Be careful not to
squeeze O-ring.
24. Lubricate and press new ceramic ring into the
shaft seal cover by using the press bush tool.
21. Remember to place the guide pin in the
housing.
23. Screw in the rest of the bolts and tighten all
screws to torque according to exploded
viesw.
Note: Screws for lifting eye are shorter than
the rest.
25. Place the new O-ring on shaft seal cover.
WARNING:
Ensure that the face with rubber seal is
positioned against shoulder in shaft seal
ange.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
26. Place pump upside down to get access to
shaft. Position the distance ring.
28. The shaft seal consists of 3 parts.
27. Lubricate shaft and shaft seal with clean
ltered water.
29. Mount new shaft seal with the carbon seal
face pointing upwards and ensure, the
spring tap is placed in the hole.
30. Use the press bush tool to press the seal
down and at the same time turn the seal
clockwise until spring stops at distance ring.
31. Right position of the spring can be inspected
through inlet hole. The groove on shaft shall
also be above shaft seal.
Spring against distance ring
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
33. Position the shaft seal cover on shaft. Be
careful not to damage the ceramic ring.
WARNING!
Be careful, the shaft has sharp edges.
35. Lubricate the shaft with water before
mounting the stop bush.
34. Hold the cover down with one hand and
tighten the bolts with torque according to
exploded view.
36. Mount O-ring in the shaft groove.
37. Mount stop bush. Ensure the gap with
O-ring groove is pointing in correct
direction (towards pump).
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
38. Press stop bush in place by using the press
bush tool.
4. Disassembling and
assembling of the
swash plate
WARNING:
Make sure that the surface on the swash
plate does not get any marks.
1. Place the swash plate upside down.
Remove the 2 bolts holding the swash plate.
Remove the mounting ange from the
swash plate.
2. Check that the O-ring and pin are in good
condition (Provided with sealing set).
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
3. Change the O-ring on the mounting ange. 4. Mount the swash plate on the 2 guide pins.
Carefully by hand tilt the unit to horizontal
position and mount the 2 bolts which hold
the swash plate. Tighten the bolts with a
torque according to exploded view.
Finally check the surface on the swash plate
for any marks or foreign particles.
5. Mount the assembled part on the pump.
5. Disassembling and
assembling of cylinder
barrel-/ valve plate
1. Push a screwdriver into the hole between
cylinder barrel and valve plate.
Carefully push downward the screwdriver so
that it makes a gap between cylinder barrel
and valve plate. Use this gap to put in
another screwdriver and loosen the valve
plate from the cylinder barrel.
3. Lubricate the new O-rings/back-up rings
and the liners in the cylinder barrel with
clean ltered water. Lower the valve plate
upside down on the cylinder barrel. Place
the press bush for valve plate (provided in
tool set) like on the picture. Screw the bolt
into the shaft of the cylinder barrel.
Turn the nut slowly clockwise. The valve
plate must slide carefully into the cylinder
barrel. Stop when the gap between cylinder
barrel and valve plate is 1-2 mm.
2. Remove the O-rings and backup rings. If
they have been removed they can not be
reused.
Mount the new back-up rings on the valve
plate rst and then mount the O-rings.
Mount backup rings rst
Mount then
O-rings
4. Remove the press bush again by screwing
the nut counter-clockwise.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
6. Disassembling and
assembling of the
ush valve
1. Unscrew the ush valve counter-clockwise
by using the pin wrench.
3. Place a bit of grease on the thread on the
plug. Screw it into the port ange.
Tighten with torque according to exploded
view.
2. Remove the O-rings (green and black).
If necessary, change the valve cone, spring
and plug. It is important that if the spring is
changed it is located like on the picture.
The end of the spring must be against the
shoulder of the valve cone.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
7. Changing pistons Note : It is essential that the pump is serviced
in conditions of absolute cleanliness.
Tools needed:
• 13 mm combination wrench
• 6 mm allen key
• Tool set 180B4347
7.1. Disassembling
To understand the pump design better, please
also see the exploded view in item 8.
1. Disconnect the pump from the rest of the
system.
WARNING:
Never unscrew the 4 screws marked with
coloured sealer.
2. Loosen all screws on the pump except the
three screws as shown in the picture below.
Note: There is still water inside the pump.
3. Mount the guide bolt in the top hole. 4. Unscrew the remaining three screws by
using a combination wrench to turn each
screw a couple of rounds at a time so the
ange is removed as straight forward as
possible.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
5. If the ange does not move forward - loosen
the drain plug to empty the pump from
water by releasing vacuum.
Drain
plug
7. Carefully turn the ange and push it
backwards to make it rest on the housing
surface. Ensure not to scratch the swash
plate surface.
Swash
plate
surface
6. Remove the ange when the remaining
three screws have been loosened. The
guide bolt must remain mounted.
8. Adjust the retaining plate to be parallel to
the end ange.
9. Screw the stop for the retaining ring into the
centre to keep the retaining ball in place.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
10. Carefully remove the pistons one by one. WARNING:
11.
Ensure that the piston shoes and the
piston surfaces are not damaged during
removal. It is recommended to place the
pistons upside down on an even and clean
base/surface.
12. Remove the retaining ring by sliding it
across the stop for the retaining ball. If
necessary, tilt the ange.
13. Inspect the piston liners.
14. Replace any worn parts.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
7.2. Assembling
1. Carefully push the retaining ring in place. 2. Insert the pistons randomly.
3. Remove the stop for retaining ball. 4. Place the retaining ring in an odd angle
corresponding to the orientation of the
swash plate.
5. Tilt the ange and replace the ange O-ring. 6. Turn the ange and gently push it into the
housing.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
7. Mount the three screws as shown below.
Tighten them to torque acc. to exploded
view.
9. Mount the remaining screws and cross
tighten them to torque accroding to
exploded view.
11. Bleed the pump.
8. Remove the guide bolt.
10. Connect the pump to the rest of the system.
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
8. Exploded view
APP S (674) 21-38
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Service guide | Disassembling and assembling APP S 21-38 / APP S 674 21-38
9. When should the
pistons be replaced
This section provides guidance on, how to
determine whether the parts of the pump are
worn and should be replaced. In case of doubt
- the pistons must be replaced. The pictures
below are meant as a guideline for evaluating
the wear of the sliding surface.
Picture 1:
No wear or cavitation of the piston shoe.
New inspection is required in 4,000 hours.
Note: If the pistons break down, the pump will
suer a disastrous breakdown.
Picture 2:
Cavitation of the piston shoes.
New inspection is required in 2,000 hours.
Picture 3:
Cavitation of the piston shoes.
All pistons must be replaced within the next
1,000 hours.
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Danfoss A/S
High Pressure Pumps
DK-6430 Nordborg
Denmark
© Danfoss | DCS (im) | 2016.05
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