General Pump MW Repair Manual

MW/S

8

Repair Manual

MWS45A-MWS50A-MWS55A

MW32A-MWS36A-MWS40A

General Pump
is a member of
the Interpump Group

Ref 300791 Rev.C

11-12

GENERAL PUMP

INDEX

1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2. REPAIR INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2.1 Repairing Mechanical Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 3

2.1.1 Disassembly of Mechanical Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 4

2.1.2 Assembly of Mechanical Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 15

2.1.3 Increase and Reduction Classes . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 27

2.2 Repairing Hydraulic Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 27

2.2.1 Dismantling the MW32A, MWS36A, MWS40A Head-Valve Units . . .Page 27

2.2.2 Assembling the MW32A, MWS36A, MWS40A -Valve Units . . . . . . . .Page 31

2.2.3 Dismantling the MWS45A, MWS506A, MWS55A Head-Valve Units .Page 37

2.2.4 Assembling the MWS45A, MWS506A, MWS55A Head-Valve Units .Page 40

2.2.5 Dismantling the Plunger Unit-Supports-Seals . . . . . . . . . . . . . . . . . . .Page 45

2.2.6 Assembling the Plunger Unit-Supports-Seals . . . . . . . . . . . . . . . . . . .Page 48

3. SCREW CALIBRATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 52

4. REPAIR TOOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 53

5. MAINTENANCE LOG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Page 54

A member of the Interpump Group

MW/S SERIES

Ref 300791 Rev.C

11-12

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GENERAL PUMP

A member of the Interpump Group

MW/S SERIES

1. INTRODUCTION

This manual describes the instructions for Repairing MW/S Series pumps, and must be carefully read and
understood before performing any repair intervention on the pump. Proper pump operation and longevity
depend on the correct use and maintenance. General Pump declines any responsibility for
damage caused by the misuse or the non-observance of the instructions described in this manual.

2. REPAIR INSTRUCTIONS

2.1 Repairing Mechanical Parts

Mechanical parts repair must be performed after removal of oil from the casing. To drain
the oil, remove the oil dipstick, (1, fig. 1) and then the draining plug (2, fig. 1).

The oil must be placed in a suitable container and disposed of in special centers.
It absolutely must not be discarded into the environment.

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GENERAL PUMP

2.1.1 Disassembly of Mechanical Parts

The correct sequence is the following:

Completely drain the oil from the pump, then disassemble the casing cover (and relative o-ring), unscrewing
the 6 M10 screws (1, fig. 2).

Remove the tab from the PTO shaft (2, fig. 3).

A member of the Interpump Group

MW/S SERIES

Unscrew the reduction gear cover fixing screws (1, fig. 4).

Ref 300791 Rev.C

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GENERAL PUMP

Position the 3 grub screws or M8 threaded screws (1, fig. 5) with the function of extractors in the holes and
two sufficiently long M10 screws with the function of supporting the cover (2, fig. 5).

Slowly screw in the 3 M8 screws (1, fig. 6) with the function of extractors to fully remove the cover unit
and pinion.

A member of the Interpump Group

MW/S SERIES

Complete disassembly of the reduction gear cover from the pinion is possible following these steps:
Remove the retaining ring Ø120 (1, fig. 7)

Ref 300791 Rev.C

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GENERAL PUMP

Separate the pinion from the cover, working with an extractor hammer on the pinion itself (1, fig. 8).

Remove the retaining ring Ø55 (1, fig. 9) and the bearing support ring (1, fig. 10) from the pinion.

A member of the Interpump Group

MW/S SERIES

Extract the seal ring from the reduction gear cover, working from the inner side of the cover (1, fig. 11).

Ref 300791 Rev.C

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GENERAL PUMP

Unscrew the screws holding in the ring gear (1, fig. 12) and remove it (1, fig. 13).

Remove the ring gear (1, fig. 14). Where necessary, it is possible to utilize an extractor hammer to be
applied on the 2 M8 holes (2, fig. 14).

A member of the Interpump Group

MW/S SERIES

Remove the key from the shaft (1, fig. 15).

Ref 300791 Rev.C

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GENERAL PUMP

Remove the ring gear support ring (1, fig. 16).

Unscrew the connecting rod screws (1, fig. 17).

A member of the Interpump Group

MW/S SERIES

Remove the connecting rod caps with the lower semi-bearings, taking special care of the disassembly
sequence during disassembly.

The con-rod caps and their relative half supports must be reassembled in exactly the same
order and coupling with which they were disassembled.

To avoid possible errors, caps and half-supports have been numbered on one side (1, fig. 18).

Ref 300791 Rev.C

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GENERAL PUMP

Advance the half supports completely in the direction of the pump head to allow the crankshaft to come
out. To facilitate this operation, use special tool (p/n F27566200) (1, fig. 19).

Remove the three upper half-bearings of the half supports (1, fig. 20).

A member of the Interpump Group

MW/S SERIES

Unscrew the reduction gear box fixing screws (1, fig. 22).

Ref 300791 Rev.C

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GENERAL PUMP

Position the 3 grub screws or M8 threaded screws (1, fig. 23) with the function of extractors in the holes and
two sufficiently long M10 screws with the function of supporting the reduction gear box (2, fig. 23).

Slowly screw in the 3 M8 screws (1, fig. 24) to prevent the box from tilting too far and getting locking in the
housing. Remove the box while supporting the shaft to prevent damage (1, fig. 25)

A member of the Interpump Group

MW/S SERIES

Unscrew the bearing cover fixing screws from the opposite side (1, fig. 26 and fig. 27).

Ref 300791 Rev.C

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GENERAL PUMP

Position the 3 grub screws or M8 threaded screws (1, fig. 28) with the function of extractors in the holes.

Slowly screw in the 3 M8 screws (1, fig. 29) to prevent the cover from tilting too far and getting locked in the
housing. Remove the bearing cover while supporting the shaft to prevent damage (1, fig. 30).

A member of the Interpump Group

MW/S SERIES

Remove the crankshaft from the PTO side (1, fig. 31)

Ref 300791 Rev.C

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GENERAL PUMP

In the event that it is necessary to replace one or more con-rods or plunger guides, operate as follows:
Unscrew the screws with tool #F27566200 to unlock the con-rods (1, fig. 32) and then extract the con-rod
plunger guide units from the back casing opening (1, fig. 33).

It is now possible to disassemble the plunger guide seal rings, taking care to not damage the plunger guide
sliding rod.

A member of the Interpump Group

MW/S SERIES

Whenever it becomes necessary to replace the plunger guide seal rings without
dismantling the entire mechanical part, it is possible to extract the seal rings with the
use of tool #F27644300 operating as follows:

Insert the tool between the rod and the seal ring (1, fig. 34) and, with the extractor hammer, complete
insertion of the tapered section inside the seal ring (1, fig. 35).

Ref 300791 Rev.C

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GENERAL PUMP

Extract the seal ring using the tool extractor hammer (1, fig. 36).

Remove the two spindle locking retaining rings Ø120 (1, fig. 37).

A member of the Interpump Group

MW/S SERIES

Remove the spindle (1, fig. 38 and extract the con-rod (1, fig. 39).

Ref 300791 Rev.C

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GENERAL PUMP

Couple the half supports to the previously disassembled caps, referring to the numbering (1, fig. 40).

To separate the rod from the plunger guide, unscrew the hexagonal head M10 screws with a 17mm socket
wrench (1, fig. 41), blocking the rod with the 36mm fork spanner.

A member of the Interpump Group

MW/S SERIES

Ref 300791 Rev.C

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GENERAL PUMP

2.1.2 Assembly of Mechanical Parts

Proceed with assembly following the reverse order indicated in point 2.1.1. The proper sequence is as
follows:

Assemble the rod to the plunger guide. Insert the elastic pin Ø5 in its hole on the plunger guide (1, fig. 42)
and join the rod to the plunger guide by means of M20 x 35 screws (1, fig. 43).

Lock in the rod in correspondence with the two planes with a 36mm fork spanner (1, fig. 44) and proceed with
calibration with a torque wrench (1, fig. 45) as indicated in paragraph 3 “Screw Tightening Calibration”.

A member of the Interpump Group

MW/S SERIES

Insert the con-rod in the plunger guide (1, fig. 39) and then insert the spindle (1, fig. 38). Apply the two
shoulder retaining rings (1, fig. 37).

Assembly has been carried out properly if the con-rod foot, plunger guide and
spindle rotate freely.

Separate the caps from the half supports. Proper coupling can be verified by the numbering on the side
(1, fig. 40).

After having checked casing cleaning, proceed with assembly of half support-plunger guide unit inside
casing rods (1, fig. 33).

Insertion of the half support-plunger guide unit in the casing must be made with the
half bearings set in the direction in which numbers are visible from above.

Ref 300791 Rev.C

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GENERAL PUMP

Block the three units with the use of special tool #F27566200 (1, fig. 32).

Pre-assemble the ring inside the crankshaft bearings (on both sides of the shaft down to the stroke) using
special tool #F27604700 (1, fig. 47).

The inner and outer rings of the bearings must be reassembled keeping the same
coupling with which they were disassembled.

A member of the Interpump Group

MW/S SERIES

Insert the shaft from the PTO side, taking care not to hit the previously assembled con-rod shanks (1, fig. 48)
and (1, fig. 49).

The crankshaft must always be assembled with the PTO on the opposite side with
respect to the 1/2” NPT holes for the oil discharge plugs on the pump casing
(1, fig. 51).

Ref 300791 Rev.C

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GENERAL PUMP

Fully insert the shaft in the casing (1, fig. 50 and fig. 51).

Pre-assemble the outer ring of the pinion bearing on the reduction gear with the aid of special tool
#F27604900 (1, fig. 52), inserting fully down to end stroke (1, fig. 53).

A member of the Interpump Group

MW/S SERIES

From the opposite side of the reduction gear box, pre-assemble the external ring of the crankshaft bearing
with the use of tool #F27605000 (1, fig. 54), inserting fully down to end stroke (1, fig. 55).

Ref 300791 Rev.C

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