Danfoss Incorporating welded piston assemblies Installation guide

Service Kit Instructions

Series 20

Incorporating welded piston assemblies

Certain models of 21 through 27 Series pumps and motors were originally produced with plastic ﬁlled cylinder block piston assemblies. Certain Series 20 back-to-back transmissions were produced with hollow cylinder block piston assemblies. Certain models of 21 through 23 Series pumps and ﬁxed motors are now being produced with solid cylinder block piston assemblies. To simplify spare parts inventory for these units, welded piston assemblies are provided as spare parts.

When replacing plastic ﬁlled, hollow, or solid pistons with welded pistons during overhaul or repair of a unit, it is mandatory that the welded pistons be incorporated symmetrically in multiples of three (3)[either three (3), six (6), or all nine (9)] in order to assure the block assembly remains in balance and speed capability is not adversely a ected.

Units originally equipped with welded piston assemblies MUST be repaired with welded piston assemblies.
Welded	Hollow
Piston	Piston
Assembly	Assembly

Solid				Plastic
Piston				Filled
Assembly	End View of Solid, Welded, Hollow, and Plastic Filled			Piston
	End View of Solid, Welded, Hollow, and Plastic Filled			Assembly
			Piston Assemblies
		W		O
	O	O	W	W
	O	O	W	W
			-OR-
	W	W	O	O
	O	O	W	W
			W = Welded
			O = Other

WARNING

Due to their higher mass, solid pistons reduce the speed capabilities of the pump or motor in which they areinstalledbyapproximately20%. SolidpistonsMUSTNOTbesoldassparepartsorbeinstalledinpumps or ﬁxed motors which were originally equipped with plastic ﬁlled, hollow, or welded pistons. Operating a hydrostatic pump or motor at speeds above its rated capability may cause loss of hydrostatic braking capacity.

BLN-9736 • Rev BA • September 2013