Needle valves

Needle valves are among the simplest types of flow control valves, offering precise and stepless adjustment from fully closed to fully open positions. Because the needle valve is symmetrical, it provides the same throttling and flow resistance regardless of flow direction. The flow is regulated through a finely adjustable needle-shaped orifice, enabling accurate control of flow rate. Needle valves are commonly used to adjust the speed of hydraulic actuators such as cylinder strokes or hydraulic motors, where precise control of movement speed is essential.

Applications

Needle valves can be positioned in various ways depending on the application: either to restrict the inflow to the consumer or between the pressure line and the tank to divert excess flow, a process known as bleeding. Unlike check valves with throttling, which restrict flow in one direction while allowing free flow in the other, needle valves function as symmetrical throttling valves, restricting flow equally in both directions. This makes them particularly useful when precise flow control is required regardless of the flow direction.

Sizes

The size of needle valves is specified by the orifice diameter, and Sun Hydraulics offers sizes ranging from 0.9 mm up to 21.6 mm in opening. The orifice diameter is critical to the valve’s ability to regulate flow and determines how much oil can pass through the valve at various settings. Sun Hydraulics’ data sheets include detailed flow curves that clearly show the relationship between flow rate and pressure drop across the valve, facilitating proper selection and sizing for different applications.