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| Illustration 1 | g00816269 |
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| Illustration 2 | g00816349 |
The drift reduction valves for the VA boom cylinder head end and for the stick cylinder rod end are pilot controlled valves. The drift reduction valve will prevent circuit leakage in the main control valve when the implement control valve is in the NEUTRAL position.
While the implement in the NEUTRAL position and a load is raised, the static pressure from the load goes into the drift reduction valve. This forces the load check valve against the seat. This blocks the oil return flow. Now, the cylinder position will be maintained.
The load check valve is opened by pilot controlled pressure in order to permit the oil in the spring chamber behind the load check valve to return to the tank. The pressure in the spring chamber decreases and the double check valve opens in order to return the cylinder oil to the tank. The effective area at the load check valve cylinder port and the static pressure from the cylinder is now able to open the load check valve. The oil is now able to drain through the control valve.
When the main control valve is activated to the STICK OUT position or to the VA BOOM RAISE position, the pump pressure is applied against the bottom end of the load check valve. When the pump pressure increases beyond the force of the load check valve spring, the load check valve opens in order to provide pressure to the cylinder.
The drift reduction relief valve opens when the circuit pressure between the cylinder and the load check valve exceeds the relief valve setting. When the relief valve opens, oil is sent to the opposite end of the cylinder in order to lower the load.
The VA boom or the stick can be lowered manually if pilot pressure is lost. The manual lowering screw moves the pilot piston downward in order to lower the implement without pilot pressure.