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Parker’s piloted load holding/counterbalance valves are a combination of a relief, sequence, and flow control valve that can handle pressures up to 420 bar (6000 psi) and flows up to 350 lpm (90 gpm). These robust valves allow the operator to maintain control of the load by preventing it from overrunning the pump while also protecting against thermal expansion. The wide selection of pilot ratios enables the valve to open based off a given backpressure specific to the application, which could be much lower than the spring pressure setting. This feature allows predictable and consistent control of a load throughout its lowering cycle.
Markets:
• Aerial
• Construction Equipment
• Material Handling Equipment
• Miscellaneous Industrial
• Miscellaneous Mobile
Features/Benefits:
• Hardened, precision ground parts for durability
• Poppet style construction with minimal leakage
• Tamperproof versions available
• Single cartridge valve with integral reverse flow check valve
• Available pilot ratios 8:1 to 1.5:1
• All external parts zinc plated
Applications:
• Load holding
• Position holding
Additional Technical Insight:
The load control valves are load assisted i.e the pilot pressure acts on the difference between the setting and the load at the pilot ratio.
It should always be set at a minimum of 30% higher than the maximum load induced pressure to ensure the valve closes correctly.
Sizing a counterbalance valve needs care in that the flow required is usually higher than system pump flow, as in the case with a cylinder application (retract flow could be twice the system flow) though oversizing the valve could cause instability.
Because of dynamic load variations in many applications, it may be necessary to use a lower pilot ratio or fit an orifice in the pilot line in order to gain stability. The valve will be affected by backpressure and care must be taked with proportional and closed center systems.
