Danfoss APP 21 User manual

Service guide
APP pumps
APP 21 - 46 and APP W HC 15 - 30
Disassembling and assembling
hpp.danfoss.com

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
2 | 180R9406 | AX274339308034en-000302
This document covers the instructions for disassembling and assembling the axial piston pumps
APP 21-46 and APP W HC 15-30
Tools provided with toolset 180B4172:
• 10 mm combination wrench
• 13 mm combination wrench
• 6 mm allen key
• Adjustable pin wrench
• Stop for retainer plate
• Press bush for valve plate
• Shaft seal extractor ø45
• M8 allen screw (20 mm and 140 mm)
• Press bush ø45 (Plastic)
• M8 mm eye bolt
• M8 mm nut
• M8 x 70 mm screw
1. Introduction
Table of Contents Contents
1. Introduction..............................................................................................................................................................2
2. Disassembling the pump..................................................................................................................................... 3
3. Assembling the pump .......................................................................................................................................... 6
4. Disassembling and assembling of the swash plate..................................................................................10
5. Disassembling andassembling of cylinder barrel and valve plate......................................................11
6. Disassembling and assembling of the ush valve....................................................................................11
7. Changing pistons..................................................................................................................................................12
8. When should the pistons be replaced...........................................................................................................17
9. Exploded view APP 21-26 , APP 30/1500 and APP W HC 15-24 ..........................................................18
10. Exploded view APP 30/1200, APP 38/1500, APP 46/1780 and APP W HC 30..................................19
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 on page 18 and 19.
WARNING:
Do not reuse disassembled O-rings or shaft
seal as they might be damaged. Always use
new O-rings.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 3
2. Disassembling the
pump
2. Using a 10 mm combination wrench,
unscrew the four bolts from shaft seal
ange.
If shaft seal ange is stuck, screw in two
bolts in holes in the ange to remove it.
1. Disconnect the pump and motor from the
system. Remove non-return valve and
connector from the pump.
4. Mount the M8 allen screw from the tool
set in the top of the shaft.
5. Wet the shaft and shaft seal with clean
ltered water.
3. Remove ceramic ring from ange by
gently pushing it from the back of the
sealing ring.
6. Carefully remove the shaft seal assembly
using the shaft seal extractor supplied in
the toolset. The extractor must t
underneath the shaft seal. Press the arms
of the extractor together when turning the
bolt.
7. Turn pump into vertical position with shaft
pointing downwards.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
4 | 180R9406 | AX274339308034en-000302
9. 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.
11. Swash plate must be placed so that its
surface is not scratched. For further
disassembling of swash plate, see page 10.
10. Screw the eye bolt in the M8 hole in the
middle of the ange. Pull it straight
upwards.
8. Using a 13 mm combination wrench,
remove all the bolts on the mounting
ange except the three shown in the next
picture.
WARNING:
Do not loosen the two screws keeping
swash plate in place.
12. Remove by hand the pistons one by one.
Be careful not to scratch the pistons. Tilt
the retainer plate to horizontal position for
easy removal of pistons, if required.
WARNING:
Do not use any tools.
13. Remove the retainer plate and the retainer
ball.
Warning: So not loosen the three screws
in the retainer plate.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 5
14. Remove the retainer guide, the 4 springs
and the spring guide.
15. Mount a 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. It is not replaceable.
17. Remove the port plate by hand.
16. Place cylinder barrel upside down.
For further disassembling of cylinder
barrel and valve plate see page 11.
18. Remove, by hand, the two pins.
Note: The following operation is only
necessary if O-ring on port ange is to
be changed.
19. Place the pump horizontally.
20. Remove the remaining screws in port
ange by using a 13 mm combination
wrench. Carefully separate house and port
ange. Ensure that pin for the positioning
house is not lost.
21. For further disassembling of ush valve,
see page 11.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
6 | 180R9406 | AX274339308034en-000302
3. Assembling the pump
5. Position housing aligning pin hole
over guide pin.
6. Gently 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.
3. Mount O-ring.
4. Insert pin for positioning housing
on port ange.
Ensure that two screw holes can be
reached from below.
Note:
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.
1. Lubrication:
• To prevent seizing-up, lubricate all
threads with PTFE lubrication type.
• O-rings inside pump may 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.
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.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 7
9. Place pump vertically. Place 10.5 mm pins
in port ange.
10. Position port plate by using the two pins.
Do not use force for this operation.
8. Place housing horizontally. Screw in the
rest of the screws on port ange. Tighten
screws to a torque according to exploded
view.
12. Screw eye bolt in cylinder barrel.
13. Make sure there is enough free space for
the shaft beneath the housing. Gently
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.
14. Unscrew M8 eye bolt.
15. Place the four springs and spring guide in
cylinder barrel. Springs must be
positioned in the holes.
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 page 11
before continuing.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
8 | 180R9406 | AX274339308034en-000302
17. Place retainer 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 retainer plate and
cylinder barrel.
When pistons are placed, tilt retainer
plate for easier placement of swash plate.
If swash plate has been disassembled from
mounting ange, see page 10 for assembly
of swash plate.
20. Lubricate piston shoes and swash plate
with clean ltered water. Remember to
place the pins in housing.
21. Place the pins in the housing.
16. Retainer guide, retainer ball and
retainer plate must be mounted as
indicated in below picture.
22. Place the mounting ange.
Remember to place the guide pin in the
housing.
. 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.
23. Screw in the rest of the bolts and cross
tighten all screws to a torque according to
exploded view.
24. Place pump horizontally to get access to
shaft.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 9
25. Lubricate shaft with clean ltered water.
26. Place stop for shaft seal on shaft.
WARNING:
Ensure that carbon ring is pointing
outwards.
28. Press new ceramic ring into retainer ring
by using plastic tool provided.
WARNING:
Ensure that the face with rubber seal is
positioned against shoulder in shaft
seal ange.
27. Use plastic assembly tool provided with
large diameter pointing downwards, to
press seal home against shoulder of stop
for shaft seal.
30. Place shaft seal ange on shaft. Tighten
the bolts with a torque according to
exploded view.
29. Remove old O-ring and t new one on
shaft seal ange.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
10 | 180R9406 | AX274339308034en-000302
1. Place the swash plate upside down.
Remove the 2 bolts holding the swash
plate. Remove the mounting ange from
the swash plate.
3. Change the O-ring on the mounting
ange.
2. Check that the O-ring and pin are in good
condition (provided with seal set).
4. Mount the swash plate on the 2 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 torqueaccording 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.
4. Disassembling and
assembling of the
swash plate
WARNING:
Make sure that the surface on the swash
plate does not get any marks.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 11
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.
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.
4. Remove the press bush again by screwing
the nut counter-clockwise.
Turn the nut slowly clockwise. The valve
plate must slide gently into the cylinder
barrel. Stop when the gap between
cylinder barrel and valve plate is 1–2 mm.
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.
5. Disassembling and
assembling of cylinder
barrel and valve plate
6. Disassembling and
assembling of the
ush valve
Mount then
O-rings
Mount
backup
rings rst
1. Unscrew the ush valve counter-clockwise
by using a pin wrench.
2. Remove the O-rings (green and black). If
necessary, change the valve cone, spring
and plug. If the spring is changed it is
important that it is located like on the
picture. The end of the spring must be
against the shoulder of the valve cone.
3. Put a little amount of grease on the thread
on the plug. Screw it into the port ange.
Tighten with a torque according to
exploded view.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
12 | 180R9406 | AX274339308034en-000302
7. Changing pistons Tools needed are:
• 13 mm combination wrench
• 6 mm allen key:
•
• Service kit - see parts list 521B0941
7.1 Disassembling
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 above.
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 the combination wrench to turn
each screw a couple of rounds at a time so
the ange is removed as straight forward
as possible..

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 13
5. If the ange does not move forward -
loosen the drain plug to empty the pump
from water by releasing vacuum.
6. Remove the ange when the remaining
three screws have been loosened. The
guide bolt must remain mounted.
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.
8. Adjust the retainer plate to be parrallel to
the end ange.
9. Screw the stop for the retainer plate into
the centre to keep retainer plate/retainer
ball assembly in place.
10. Carefully remove the pistons one by one.
Drain plug
Swash plate
surface

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
14 | 180R9406 | AX274339308034en-000302
11. Warning:
Ensure that the piston shoes and the
pistonsurfacesarenotdamagedduring
removal.Itisrecommendedtoplacethe
pistons upside down on an even and
clean base/surface.
12. Inspect the piston liners.
Replace any worn parts.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 15
7.2 Assembling
1. Lubricate pistons with clean ltered water.
Insert the pistons arbitrarily. 2. Remove the stop for retainer plate.
4. Place the retainer plate in an 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. 7. Mount the three screws as shown above. Tighten them to a torque according to
exploded view.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.0316 | 180R9406 | AX274339308034en-000302
8. Remove the guide bolt.
Mount the remaining screws and
cross tighten them to a torque according
to exploded view.
9. Connect the pump to the rest of the
system and bleed the pump.

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 17
8. When should the
pistons be replaced
1. No wear or cavitation of the piston shoe.
New inspection is required in 4,000 hours. 2. Cavitation of the piston shoes. New inspection is required in 2,000 hours.
3. Cavitation of the piston shoes.
All pistons must be replaced within the
next 1,000 hours.
This section provides guidance on, how to deter-
mine whether the parts of APP 21-43 are worn
and should be replaced. In case of doubt - the
pistons must be replaced. The pictures below are
ment as a guideline for evaluating the wear of
the sliding surface.
Note:
If the pistons break down, the pump will
suer a disastrous breakdown.

Service guide |Disassembling and Assembling, APP 21 - 46 and APP W HC 15 -30
© Danfoss | 2023.03
18 | 180R9406 | AX274339308034en-000302
9. Exploded view
APP 21-26 , APP 30/1500 and APP W HC 15-24

Service guide | Disassembling and Assembling, APP 21 - 46 and APP W HC 15 - 30
© Danfoss | 2023.03 180R9406 | AX274339308034en-000302 | 19
10. Exploded view
APP 30/1200, APP 38/1500, APP 46/1780 and APP W HC 30

© Danfoss | DCS-SGDPT/SI | 2023.03 180R9406 | AX274339308034en-000302 | 20