New Energy Saving Counterbalance Valve 2015-01-2858
Counterbalance valves are used in hydraulic circuits to avoid uncontrolled movements of cylinders and Motors. They are often installed in the return line of the cylinder or motor. The flow control valve on the meter in side then sees a positive load regardless of external forces on the cylinder. The counterbalance valve can be seen as a relief valve with a setting high enough to support the highest expected load. The setting of the counterbalance valves is reduced when the cylinder or motor moves. Usually the inlet pressure of the cylinder is used as a Pilot Pressure for the counterbalance in the return line. The so called Pilot Ratio describes how much the setting of the CB valve is reduced per increase in Pilot Pressure. A high Pilot Ratio of 10 e.g. reduces the setting by 100 bar when the Pilot Pressure increases by 10 bar. The selection of the Pilot Ratio is a compromise between stability (low Pilot Ratio) and efficiency (a high Pilot Ratio allows to move the cylinder with lower pressures). The application engineer must select the counterbalance valve with a Pilot Ratio low enough to ensure stable movement although that may lead to higher inlet pressures to drive the cylinder. The new ‘triple ratio counterbalance’ valves allows lower inlet pressures and offers the same stability since it uses the low Pilot Ratio (that leads to lower efficiency) only when it is required for stability. It has a higher Pilot Ratio when the cylinder doesn't move yet (Pilot Pressure reduces the setting but the cylinder doesn't move yet) and when there is no overrunning load that could cause instability. A comparison shows that the new valve allows the same cylinder/motor speed with inlet / Pilot Pressures that are 15% to 40% below the ones required for a standard counterbalance valve.