Usage:
M312 (6TL),
M315 (7ML),
M318 (8AL) Excavators
The standard setting for the braking torque response for swing pumps on the listed models can be adjusted to the feel of the individual operators. The throttle spool pistons in the swing pump regulator can be changed to produce a softer or harder braking action.
This adjustment can be made for those swing pumps that are modified using the following rework kits that were installed during a recent product improvement program:
The modifications include a new regulator, 139-8929 Adjustment Group. In addition, the Swing Mode Pressure Specifications should be set for MODE 1 at 1000-1050 kPa (145-150 psi) and for MODE 2 at 1600-1650 kPa (230-240 psi).
In order to adjust the braking torque response, the throttle spool pistons in the regulator are replaced according to the type of response that is preferred. For the standard braking action, two 139-9222 Pistons are used. The standard piston is identified by a groove depth of 1.00 mm (.039 in). For maximum braking action, two 139-9224 Pistons are used. This piston is identified by a groove depth of 1.35 mm (.053 in). For minimum braking action, two 139-9223 Pistons are used. This piston is identified by a groove depth of 0.80 mm (.031 in).
NOTE: The depth of the groove is shown at the head end of the piston.
To change the braking action, follow this procedure.
1. Position the machine on a level surface and stop the engine.
2. Install a vacuum pump on the hydraulic tank.
3. Remove plugs (1) with a hex socket wrench.
4. Remove springs (2) and pistons (3) with a magnet.
5. Install the desired pistons and reassemble springs (2) that were removed.
6. Install plugs (1) to close the swing pump regulator.
Removal of throttle spool pistons from swing pump regulator.
(1) Plugs. (2) Springs. (3) Pistons.