Both an iris valve and a pinch valve are chosen for the same job — controlling how much powder leaves a hopper, silo or bag. Neither has a disc or a gate in the flow path, and both are far better suited to bulk solids than a ball or gate valve. But they achieve control in completely different ways, and the difference decides which one works on a given line.

An iris valve uses a set of blades arranged around the bore. As the ring is turned, every blade rotates inward at once, and the opening contracts concentrically — it stays a circle, just a smaller one, until it closes completely.

A pinch valve uses a flexible elastomer sleeve. Air pressure (or a handwheel) squeezes the sleeve from two sides until the walls meet. The opening goes from a full circle to a slit, then to nothing.

This is the practical difference. An iris valve keeps a circular aperture at every position, so material flowing through it sees a smooth converging passage with no corners. A pinch valve at part-closure forms an elongated slot, and the sides of the sleeve bulge outward.

For free-flowing powders and granules, the concentric aperture is a real advantage: powder cannot lodge in a corner that does not exist. For material that tends to arch, a circular aperture of a given width passes more reliably than a slot of the same area.

The AD, IR and KD series cover general powder duty: see the AD iris valve, the IR iris valve and the KD iris valve. The AD series is the usual choice as a powder choke valve — see the AD series iris valve article for application detail.

See the VMP pneumatic pinch valve for standard air-operated duty and the PVE heavy duty pinch valve for mining and slurry service.

Neither type is a compromise version of the other — they solve different problems. Tell us the medium, the aperture you need and whether the duty is shut-off or control, and we will point you at the right one. Compare all types in the bulk solids valve selection guide or browse the full range.