Manual de Servicio Sauer Danfoss

Service Kit Instructions

Series 40 - M46 Servo piston installation 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 information. 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 adjustment 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.

Fig. 1 - Assemble Servo Piston (Pump)

NOTE: If the retaining ring cannot be installed, additionally 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

Fig. 2 - Adjust Centering Spring (Pump)

© Danfoss, 2013

It will be impossible to obtain pump neutral position if any axial looseness exists between the centering screw and the servo piston.

BLN-10018 • Rev AB • September 2013

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Piston Ring Grooves Seal Ring

O-Ring

Seal Ring

Bearing Ring Grooves

Bearing Ring

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.

O-Ring Bearing Ring

Fig. 3 - Assembled Servo Piston with Rings (Pump Shown) For variable pumps, tandem pumps, and variable motors, 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.

Fig. 4 - Bearing Rings, O-Rings, and Seal Ring Installed (Pump Shown) 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.

Fig. 4 - Install Second Seal Ring

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 necessary to compress the piston seal rings while installing the servo piston on these pumps.

© Danfoss, 2013

BLN-10018• Rev AB • September 2013

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