Danfoss S40 M Installation guide

Brand: Danfoss

Model: S40 M

Type: Installation guide

This manual is also suitable for

S40 P

Installation Information for Series 40 - M46

Servo Piston

Always install a servo piston which includes bearing and

seal rings when reassembling the Series 40 - M46

Variable Pump, Tandem Pump, or Variable Motor. Refer

to the appropriate Service Parts Manual for more in-

formation.

For variable pumps and tandem pumps, assemble the

centering mechanism as follows:

Install the inner spring guide, servo spring, servo stop

sleeve, and outer spring guide onto the centering adjust-

ment screw. Install the plain nut and half nut onto the

centering screw.

NOTE: Pumps built prior to date code 87-14 use a self

locking nut in this location. The self locking nut

should be replaced with the plain nut and half nut

when repairing. Refer to the appropriate Service

Parts Manual for more information.

Hold the centering screw from turning and tighten the

plain nut to compress the servo piston spring.

Slide the centering spring assembly into the servo piston.

Install the retaining ring into the piston to retain the spring

assembly.

NOTE: If the retaining ring cannot be installed, addi-

tionally compress the spring by tightening the

plain nut on the centering screw.

WARNING

The retaining ring MUST be securely seated in its

groove. Personal injury can result if the retaining

ring is forced from its groove by centering spring

force.

Loosen the nut on the

centering screw to seat the

retaining ring, then tighten the nut until all axial looseness

between the screw and the servo piston is eliminated. If

the nut is too tight, the spring assembly will be loose in the

servo piston. If the nut is too loose, the centering screw

will be loose in the spring guides.

CAUTION

It will be impossible to obtain pump neutral position

if any axial looseness exists between the centering

screw and the servo piston.

Fig. 2 - Adjust Centering Spring (Pump)

Fig. 1 - Assemble Servo Piston (Pump)

BLN-10018 • Rev AB • September 2013

Service Kit Instructions

Series 40 - M46

Servo piston installation

Lock the adjustment by tightening the half nut to 18 to 27

ft.lbsf. (24 to 37 Nm) while holding the plain nut from

turning. Recheck to be certain there is no looseness

between the screw and spring or spring and piston.

Fig. 3 - Assembled Servo Piston with Rings

(Pump Shown)

Fig. 4 - Bearing Rings, O-Rings, and Seal Ring

Installed (Pump Shown)

Fig. 4 - Install Second Seal Ring

Lubricate the bearing and seal rings and carefully slide

the piston assembly (end without a seal ring first) into the

servo bore in the top of the housing. Slide the piston

through the housing until the piston groove without a seal

ring is just exposed.

CAUTION

Do not slide the piston through the housing farther

than necessary to install the second seal ring. Sharp

edges on the servo bore, inside the housing, can

damage the first seal ring. Do not damage the

bearing ring when sliding the servo piston back into

the housing.

Lubricate and install the second piston seal ring and slide

the servo piston back into the housing.

NOTE: Units built prior to date code 86-22 do not have a

lead-in chamfer on the servo piston bore. A tool,

such as a piston ring compressor, will be neces-

sary to compress the piston seal rings while

installing the servo piston on these pumps.

For

variable pumps, tandem pumps, and variable mo-

tors, install the piston bearing rings in the second set of

grooves from the ends of the servo piston. Install the

piston seal expander O-rings in the grooves closest to the

ends of the servo piston. Install a piston seal ring over the

O-ring in the groove at the top end of the piston.

Do not stretch the seal ring any more than necessary

when installing.

Piston Ring Grooves

Bearing Ring Grooves

Seal RingSeal Ring

Bearing Ring Bearing Ring

O-Ring

BLN-10018• Rev AB • September 2013

Danfoss S40 M Installation guide

Brand: Danfoss

Model: S40 M

Type: Installation guide

This manual is also suitable for

S40 P

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Danfoss S40 M Installation guide

This manual is also suitable for

Danfoss S40 M Installation guide

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