2-Way and 3-Way Pressure Compensated Flow Control Valves

How does a compensated valve hold speed constant?

A plain orifice gives a constant flow only at a constant pressure difference. When the load rises, the flow drops and the cylinder slows down. A pressure compensated flow control valve adds a pressure balance (spool) to the metering orifice that keeps the pressure drop across the orifice constant regardless of load. The speed stays stable whether the cylinder runs free or works at full load.

2-way or 3-way - which design fits?

Both designs meter the flow independently of load, but they differ in how they handle the excess oil. The 2-way valve sits in series and throttles the surplus into heat; it suits a fixed-displacement pump. The 3-way valve returns the surplus through a third port to tank or a bypass and therefore runs more efficiently.

Meter-in or meter-out - where do you throttle?

The placement decides whether the inlet or the outlet is throttled. Meter-in controls the supply and suits pushing loads. Meter-out controls the return, holds the cylinder against overrunning loads and prevents run-away. For overrunning or changing loads, metering on the outlet is almost always the safe choice.

• Meter-in: throttles the supply, ideal for purely pushing loads with low waste heat.
• Meter-out: throttles the return, stabilizes overrunning loads and prevents cavitation in the cylinder.
• Bypass (meter-out with 3-way): bleeds off surplus oil and lowers the energy loss.

What about viscosity, temperature and filtration?

Temperature and viscosity affect the flow across the metering orifice. A temperature compensated valve keeps the speed constant even as oil temperature changes. Watch the allowed viscosity range, clean filtration and a compensation pressure that sits above the maximum load pressure drop, otherwise the valve stops regulating.

Frequently asked questions