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Symbols used in Danfoss literature
WARNING may result in injury
Tip, helpful suggestion
CAUTION may result in damage to product or
property
Lubricate with hydraulic fluid
Reusable part
Apply grease / petroleum jelly
Non-reusable part, use a new part
Apply locking compound
Non-removable item
Inspect for wear or damage
Option - either part may exist
Clean area or part
Superseded - parts are not interchangeable
Be careful not to scratch or damage
Measurement required
Note correct orientation
Flatness specification
Mark orientation for reinstallation
Parallelism specification
Torque specification
External hex head
Press in - press fit
Internal hex head
Pull out with tool – press fit
Torx head
Cover splines with installation sleeve
O-ring boss port
Pressure measurement/gauge location or
specification
The symbols above appear in the illustrations and text of this manual. They are intended to communicate
helpful information at the point where it is most useful to the reader. In most instances, the appearance
of the symbol itself denotes its meaning. The legend above defines each symbol and explains its purpose.
Overview
This manual includes information for the installation, maintenance, and minor repair of Series 51
hydraulic proportional controls. It includes a description of the unit and its individual components, and
minor repair procedures.
Performing minor repairs may require removal of the unit from the vehicle/machine. Thoroughly clean
the unit before beginning maintenance, or repair activities. Since dirt and contamination are the greatest
enemies of any type of hydraulic equipment, follow cleanliness requirements strictly. This is especially
important when changing the system filter and when removing hoses or plumbing.
A worldwide network of Danfoss Global Service Partners is available for major repairs. Danfoss Global
Service Partners are trained by the factory and certified on a regular basis. You can locate your nearest
Global Service Partner using the distributor locator at www.powersolutions.danfoss.com. Click on the
Sales and Service
link.
Service Manual
Series 51 Hydraulic Proportional Controls Service Manual
Introduction
6
11009446 • Rev BA • July 2014