- Load Haul Dump:
- R2900G (S/N: GLK1-UP; JLK1-UP)
The following information is additional information for the above listed machines.
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| Illustration 1 | g01251194 |
Schematic for dual pilot check valve, the steering control valve and the steering neutralizer valves (1) Purge orifice (2) Spring (3) Valve spool (4) Steering control valve (5) Left neutralizer valve (6) Right neutralizer valve (7) Dual pilot check valve (8) Check valve (9) Check valve | |
Dual pilot check valve (7) allows valve spool (3) to shift if purge orifice (1) becomes plugged. Oil flows from the STIC steering pilot valve, through check valve (8) or check valve (9), through neutralizer valve (5) or neutralizer valve (6) and into the pilot chamber on steering control valve (4). This moves valve spool (3) against return spring (2). If oil flow from the STIC steering pilot valve is stopped, check valve (8) or check valve (9) will close. This prevents flow back to the STIC steering pilot valve. This also traps oil in the pilot chamber of steering control valve (4). As return spring (2) pushes valve spool (3) to the HOLD position, the oil that is trapped in the pilot chamber is forced back to the hydraulic tank through purge orifice (1). This allows the valve spool (3) to smoothly return to the HOLD position.
If purge orifice (1) is plugged, oil will be trapped in the pilot chamber of steering control valve (4), and valve spool (3) will remain in the LEFT TURN position or the RIGHT TURN position. In order to overcome this problem, pilot oil opens check valve (8) or check valve (9) when the pressure in the pilot chamber is increased. The pressure in the pilot chamber also increases when the STIC steering control lever is moved to the LEFT TURN position or the RIGHT TURN position. Oil then flows from the pilot chamber, through neutralizer valve (5) or neutralizer valve (6), dual pilot check valve (7) and STIC steering pilot valve to the hydraulic tank.