Compact Blade Damper Valve

Retrofit work usually has no room. The BZ-DV is a wafer-pattern blade valve with a face-to-face dimension of 120 mm to 300 mm depending on size, so it can be dropped between two existing flanges where a conventional damper would need the duct cut back.

Construction

A single blade rotates on a through shaft inside a machined body. The blade has a chamfered edge that mates with a tapered seat, giving a line contact that stays tight as the seat wears. Bodies are cast or fabricated depending on size; both are pressure tested before despatch.

Shut-off performance

Standard seat is metal-to-metal for temperatures above 200 °C, and a PTFE or EPDM soft seat below that. Metal seated valves hold class IV leakage; soft seated valves hold class VI. Where the valve is used for isolation before maintenance we recommend the soft seat, because a class IV leak is enough to prevent a man entering the duct.

Actuation

Quarter-turn electric, pneumatic rack and pinion, or lever. A manual lever with a lockable detent is common on small sizes used for balancing. Positioners are available where the valve is used for modulating duty rather than isolation.

Limits

Sizes above 1,200 mm are better served by a louvre or double louvre gate: a single blade that large needs a heavy shaft and a large actuator, and the economics stop working. We will quote either way but we will also say which one we would fit.