In chemical test rigs or precision injection systems, a needle valve alone often delivers erratic flow at very low rates – surging or even stopping. This happens because at openings below 5%, the tiny annulus between cone and seat is easily blocked by micro‑bubbles or particles.The main Needle Valve product names of China Needle Valve Network include:J29 Angle Pressure Gage Needle Valve,J49 Flange Pressure Gage Needle Valve,JJM1 Pressure Gage Needle Valve,JJM8 Pressure Gage Needle Valve,JJY1 Ferrule Needle Valve,J24W Angle Type Globe Needle Valve,J19 Pressure Gage Needle Valve,J23 SA Flowmeter Three-way Valve, Needle Valve,J13W 3-type Internal Thread Needle Valve

How the combination works

Install a restriction orifice downstream of the needle valve. The orifice provides a fixed resistance, while the needle valve creates an adjustable pressure drop upstream. Together, the needle valve operates at a larger opening (15–30%), avoiding the unstable micro‑open zone, while total flow remains finely adjustable.

Sizing tips

Orifice diameter: calculated from the minimum required flow, typically 1–3 mm.

Needle valve full‑open Cv should be 3–5 times the orifice Cv.

For dirty fluids, add a strainer upstream of the needle valve.

Field example

A catalyst injection pump had flow jumping between 0.5 and 2 L/h with only a needle valve. Adding a 1.5 mm orifice stabilised flow, and the needle valve operated smoothly at 1/4 turn, achieving stable 0.3 L/h.

Bottom line: When low‑flow control is unstable, do not just replace the needle valve – add a restriction orifice. It keeps the needle valve away from the micro‑open zone, delivering stable and reliable regulation.

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