CONFIDENTIAL TIBU3340-02

Damage to the bucket cylinder can result from excessive hydraulic pressure that builds up in the cylinder due to incorrect operation or abuse of the bucket or the work tool that is being used. Two examples are cited below:

1. During bucket operation, hydraulic pressure can build up to excessive levels in the bucket cylinder and lines when the blade is allowed to maintain contact with a fixed object.
2. If the bucket cylinder is not fully retracted (as advised in the Operation and Maintenance Manual) and the hammer is used in a non-vertical trajectory, it is possible to either bend or fracture the rod of the cylinder due to the occurrence of high pressure spikes, when operating the hydraulic hammer.

SOLUTION:

The installation of a relief valve in the control valve for the bucket cylinder can help prevent the bucket cylinder from being damaged due to excessive pressure. The relief valve is installed in the head end line of the valve section of the main valve block for the bucket cylinder. See Illustration 1.

NOTE: All 303.5 (DCH1-Up) Machines should have factory fitted relief valves.

NOTE: The 304.5 (WAK) Machines were produced for a short period without the relief valve as standard. After reviewing the following text check for specific valve arrangement on your machine.

The following relief valves have been released into the parts system for field installation:

NOTE: THE INSTALLATION OF A RELIEF VALVE IN THE BUCKET CYLINDER DOES NOT PRECLUDE THE REQUIREMENT FOR CORRECT OPERATION OF THE BUCKET AND/OR WORK TOOL.

Illustration 1. Top View of the Main Control Valve showing the Bucket Cylinder Control Valve (A). The relief valve is to be installed in the top port of the Bucket Cylinder Control Valve that is towards the outside of the machine. The "X" in the drawing indicates the side of the valve that is towards the outside of the machine next to the frame skirting.

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