Danfoss PAHT and PAHT G 50-90 Hydraulic Pump Service Guide: Disassembling and Assembling

Introduction

This guide provides detailed instructions for the disassembly, inspection, and assembly of Danfoss PAHT and PAHT G 50-90 hydraulic pumps. It also includes spare parts lists and information on required tools.

Tools required for dismantling the pump: (Refer to Section 9 for specific tool sets)

Disassembling the Pump

Follow these steps carefully to disassemble the pump:

1. Loosen and remove 4 screws.
2. Remove mounting flange.
3. Remove spring.
4. Remove shaft sealing. ⚠️ Caution: Avoid scratching the sealing surface on the shaft.
5. Remove 2 guide pins.
6. Remove O-ring.
7. Turn pump upside down.
8. Loosen and remove 10 screws.
9. Remove cover.
10. Remove pistons and retainer plate.
11. Remove retainer ball.
12. Remove retainer.
13. Remove spring.
14. Remove cylinder barrel.
15. Remove port plate.
16. Remove 1 guide pin.
17. Turn pump upside down and remove 2 washers.
18. Loosen and remove 6 screws.
19. Remove port flange.
20. Remove 1 guide pin.
21. Remove O-ring from port flange.
22. Loosen thrust plate from cylinder barrel.
23. Remove thrust plate.
24. Remove O-rings from thrust plate.
25. Remove backup rings from thrust plate.
26. Remove 1 guide pin from end cover plate.
27. Loosen and remove screw from swash plate.
28. Remove swash plate.
29. Remove 2 guide pins from end cover plate.
30. Remove O-ring from end cover plate.
31. Remove shaft sealing from mounting flange.

The pump is now disassembled.

Inspection

Valve and Thrust Plate

1. Neither the valve plate nor the thrust plate must show any sign of wear.
2. Hold a ruler against the surface of the plate and check tightness against a light source.
3. Check that both O-rings and back-up rings are not broken and do not show severe wear.

Swash Plate

1. Check that the surface of the swash plate is smooth and without any large scratches (depth more than 0.1 mm).
2. Play in the ball and socket joint must not exceed 0.1 mm.

Pistons

1. Thickness of piston shoes must be at least 4.4 mm.
2. Hold a ruler against the surfaces of the piston shoes to check that the surfaces are even and smooth and without any scratches. It is acceptable that the (black) treated surfaces of the pistons are partly worn.
3. Check bushes in the cylinder barrel for wear and scratches.
4. Check the main bearing for wear and scratches.

Assembly

⚠️ 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 absolutely clean before mounting.

Lubrication:

• To prevent seizing-up, lubricate all threads with PTFE lubrication type.
• O-rings inside the pump may be lubricated only with clean filtered water.
• O-rings for the port flange, mounting flange, and flushing valve must be lubricated.
• It is important to lubricate ALL parts to be assembled with clean filtered water (Especially all PEEK parts).

Follow these steps carefully for assembly:

1. Tools required for assembly of the pump. (Refer to Section 9)
2. Parts needed for assembly of the pump. (Refer to Sections 5 & 7)
3. Mount 1 guide pin in housing.
4. Mount O-ring in port flange.
5. Mount port flange on housing. Use pin as guide.
6. Mount 6 screws (M8x55).
7. Tighten screws to 30 Nm.
8. Turn pump upside down.
9. Mount 1 guide pin inside the housing on the back side of the port plate.
10. Mount port plate. Be aware of orientation/guide pin.
11. Mount backup rings on the thrust plate.
12. Mount O-rings on the thrust plate.
13. Spray with water on cylinder barrel and thrust plate.
14. Mount thrust plate on cylinder barrel.
15. Press thrust plate into cylinder barrel.
16. Mount cylinder barrel in housing.
17. Mount spring.
18. Mount retainer on top of the spring.
19. Spray with water and mount retainer ball.
20. Place retainer plate on top of retainer ball.
21. Spray with water and mount pistons.
22. Spray with water and mount O-ring on end cover.
23. Mount 2 guide pins on end cover.
24. Mount swash plate.
25. Mount screw (M8x20).
26. Tighten screw to 30 Nm.
27. Mount 1 guide pin on housing.
28. Spray piston shoes with water.
29. Mount end cover on the housing.
30. Mount 10 screws (M8x20).
31. Tighten 10 screws to 30 Nm.
32. Turn pump upside down and mount 2 guide pins.
33. Spray with water and mount O-ring.
34. Spray shaft sealing with water before mounting.
35. Mount shaft sealing.
36. Use tool and press shaft sealing into place.
37. Mount transparent ring.
38. Mount metal ring.
39. Mount spring.
40. Mount special tool on shaft.
41. Spray with water.
42. Mount sealing (smallest diameter pointing down).
43. Mount mounting flange.
44. Mount 4 screws.
45. Tighten screws to 30 Nm.
46. Finished.

Spare Parts List for PAHT 50-90

Key Spare Parts:

• 180B4196 - Seal set (PAHT 50-90)
• 180B4195 - Cylinder barrel set (PAHT 50-90)
• 180B4192 - Valve plate set (PAHT 50-70)
• 180B4193 - Valve plate set (PAHT 80-90)
• 180B4194 - Piston set (PAHT 50-90)
• 180B4252 - Swash plate set (PAHT 50)
• 180B4255 - Swash plate set (PAHT 63)
• 180B4258 - Swash plate set (PAHT 70)
• 180B4253 - Swash plate set (PAHT 80)
• 180B4256 - Swash plate set (PAHT 90)

Exploded View for PAHT G 50-90

This diagram illustrates the exploded view of the PAHT G 50-90 hydraulic pump. It details the assembly sequence and placement of parts including the housing, pins, screws, O-rings, end cover, swash plate, cylinder barrel, spring, retainer ball, retainer plate, pistons, key, washer, retainer, port plate, valve plate, backup rings, port flange, shaft sealing, and mounting flange.

Tool Sets

The following tool sets are recommended for servicing the PAH, PAHT, and PAHT G 50-90 pumps:

• 180Z0237 - Tool set (PAH / PAHT / PAHT G 50-90)
• Shaft bush, torpedo
• Press tool 1
• Press tool 2