Rotary Valve Specifications: Rotor Type, Bore Size, and Capacity Sizing

A rotary valve looks like a simple component — a rotor spinning inside a housing, metering material through while maintaining a pressure seal. In practice, getting the spec wrong (rotor type, bore, pressure rating) is one of the more common causes of poor conveying performance and premature wear. Here's what actually needs checking before you order one.

Rotor Type Is Matched to Material Behaviour, Not Guessed

ENZAC's rotary valve range offers 8 rotor configurations, each solving a specific material handling problem:

• Open Fixed Vane — the standard configuration for most free-flowing powders and granules
• Open Fixed Chamfered — for smearing materials that tend to pack into standard vane pockets
• Reduced Capacity — for applications needing a lower, controlled throughput without changing bore size
• Reduced Capacity Multi-Vane — combines reduced capacity with finer metering resolution
• Replaceable Blade — for abrasive materials, where vane wear is expected and cost-effective replacement matters more than a longer-life fixed rotor
• Closed Rotor — for materials with poor flow characteristics that need better sealing between pockets
• Staggered Pockets — twin-outlet configuration for specific discharge geometries
• Helical — reduces pulse discharge, useful where downstream equipment is sensitive to surge feeding

Specifying "a rotary valve" without naming a rotor type is specifying an unfinished RFQ — the wrong rotor on an abrasive or cohesive material shows up as premature wear or poor sealing within months, not years.

Valve Types and Pressure Rating

Beyond rotor geometry, ENZAC's rotary valves come in several valve types matched to the conveying method downstream: Discharging & Metering (general purpose), Blow-Through (in-line with a pneumatic conveying pipe), Sanitary Quick-Clean (food/pharma, fast teardown for cleaning), and Granule Discharge. Maximum pressure rating reaches up to 21 PSI for blow-through and pipeline-integrated types — a detail that matters if your system runs positive-pressure pneumatic conveying rather than simple gravity metering.

Bore and Configuration Range

Standard bore range runs 150–600mm; custom non-standard bores are available with an 8-week delivery lead time (against a 12-week standard market lead time for custom sizing).

Capacity Is a Formula, Not a Catalogue Lookup

The volume-per-revolution figures above are only half the sizing equation. Actual throughput depends on:

T = 0.06 × V × N × Y × R

Where T = throughput (t/hr), V = volume per revolution (L/rev), N = rotor speed (RPM), Y = fill efficiency (typically 0.7–0.9, material-dependent), and R = bulk density of the material (t/m³).

This is why two plants running the same 300mm-bore valve on different materials will see meaningfully different real-world throughput — a low-density, poor-flowing powder fills the rotor pockets less efficiently (lower Y) than a dense, free-flowing granule. ENZAC calculates this per material rather than quoting off the catalogue's volume-per-revolution number alone.

Construction and Coating Options

Interior coatings — tungsten, Teflon, ceramic powder, or hard chrome — extend service life against abrasive materials and reduce product sticking on cohesive ones. Shaft sealing is available as packing gland or air purge, with air purge generally preferred where product contamination from seal wear is a concern. Construction spans mild steel, SS304, and SS316 (sanitary grade) depending on the application.

What to Send With Your Enquiry

To get an accurate rotary valve spec rather than a generic catalogue quote, provide: material bulk density and flow characteristics (abrasive, cohesive, free-flowing), required throughput in t/hr, system pressure differential, and whether the valve sits in a blow-through pneumatic line or a simple gravity-metering position. Review the Rotary Valve equipment page for the full range and rotor selection detail.