Sun Hydraulics Pilot-to-Open Check Valve

Sun Hydraulics pilot-to-open check valves are non-modulating, on/off devices used for holding a load or actuator in position. They allow free flow from the valve port to the load port and block reverse flow until pilot pressure opens the valve, giving positive load locking and protection against hose failure. They can be built directly into an actuator or applied through manifolds with a wide range of mounting options, and are directly interchangeable with counterbalance cartridges of the same port count, cavity and flow path for a given frame size.

The standard pilot ratio is 3:1, meaning pilot pressure needed to open the valve is directly proportional to load pressure; a 5:1 ratio version is also available where a lower pilot pressure is preferred. Pilot type is either standard (non-sealed) or sealed, and valves are offered non-vented or vented. On vented models, the spring chamber is referenced away from the outlet port, either to a dedicated fourth port or, on atmospherically-referenced models, out the back of the valve body or through an external SAE vent port, so the valve remains unaffected by outlet pressure.

A bypass-orifice version is also available, allowing a customer-specified restricted flow in the reverse direction rather than a hard block. Manual load release is available on many models, including a tamper-resistant version, to allow a load to be lowered by hand. External pilot or vent port threads are available in BSPP, SAE and NPTF, useful where a remote pilot signal or vent line is needed. A flush-mount body style is also available on the smallest cavity size.

Maximum operating pressure across the range is 5000 psi (345 bar), with maximum valve leakage typically 1 drop per minute at 110 SUS (24 cSt). Standard seals are Buna-N, with EPDM and Viton available on most models and polyurethane seal kits offered for most configurations. Corrosion-resistant stainless steel bodies (suffix /AP) and mild steel, zinc-nickel-plated bodies (suffix /LH) are available on selected models.

Sun Hydraulics Pilot-to-Open Check Valves: Key Specifications

• Maximum operating pressure: 5000 psi (350 bar)
• Pilot ratio: 3:1 standard, 5:1 available on selected models
• Maximum valve leakage: 1 drop/min at 110 SUS (24 cSt)
• Cracking pressure options: typically 4–150 psi (0.3–10.5 bar), with a low-pressure 1 psi option on the 5:1 ratio model
• Bypass orifice range (where fitted): customer-specified, typically .016–.218 in depending on cavity size

Configuration Options

• Pilot type: standard (non-sealed) or sealed pilot
• Venting: non-vented, vented with a dedicated vent port, or vented and atmospherically referenced (external SAE vent port also available)
• Bypass orifice: available on selected models for a controlled, customer-specified rate of reverse flow
• Manual load release: standard or tamper-resistant version, for manually lowering a load
• External pilot/vent port: BSPP, SAE or NPTF threads available on selected models
• Seal material: Buna-N, EPDM, Viton, Polyurethane
• Material/coating: standard, stainless steel passivated (/AP), mild steel zinc-nickel (/LH)

Features and Benefits

• Positive load locking with protection against hose-burst failure
• Directly interchangeable with counterbalance cartridges of the same frame size, port count and flow path
• Vented options remain unaffected by outlet pressure, giving more predictable pilot control
• Bypass orifice option allows controlled reverse flow rather than a hard block
• Manual load release, including a tamper-resistant version, allows safe manual lowering of a suspended load
• Available across Series P to Series 4, covering a wide range of flow capacities and cavity sizes

Downloads

The following download is available from Sun Hydraulics:

• Sun Hydraulics Pilot-to-Open Check Valve Catalogue