SHAPA – A Practical Guide to Rotary Valves

LEVCentral Expert Commentary

Rotary valves are often overlooked because of their apparent simplicity. Yet they are among the most critical components in many pneumatic conveying, dust collection and bulk solids handling systems. A poorly selected rotary valve can restrict product flow, increase air leakage, reduce system efficiency and even compromise explosion protection.

This excellent SHAPA Technical Bulletin explains the engineering principles behind rotary valves and demonstrates that selecting the correct valve is far from straightforward. Although the valve itself contains only a single moving part—a multi-vane rotor—its performance is influenced by numerous factors including product characteristics, pressure differential, rotor speed, operating clearances and the overall design of the conveying system.

The guide also dispels a number of common misconceptions. Rotary valves do not create product flow—they simply meter material that can already flow into them under gravity or controlled feeding conditions. Likewise, all rotary valves leak air to some extent, and understanding this inevitable leakage is essential when designing pneumatic conveying or dust collection systems.

For LEV professionals, rotary valves are encountered most commonly beneath cyclones, baghouses and cartridge dust collectors, where they discharge collected dust while maintaining the pressure differential within the extraction system. Selecting the correct valve therefore has a direct influence on collector performance, airflow stability and, in some applications, explosion isolation.

View SHAPA Technical Bulletin

Key Learning Points

The guide explains:

• The purpose and operating principles of rotary valves.
• The different functions performed by rotary valves, including:
  • Product metering.
  • Airlock duties.
  • Pressure isolation.
  • Process isolation.
  • Explosion and flame barrier applications.
• Why rotary valves do not generate product flow.
• The effects of:
  • Rotor speed.
  • Pressure differential.
  • Air leakage.
  • Filling efficiency.
  • Product flow characteristics.
• The influence of product properties such as:
  • Abrasiveness.
  • Cohesiveness.
  • Moisture content.
  • Particle size.
  • Temperature.
• Valve construction features and design options.
• Materials of construction.
• Rotor clearances and wear considerations.
• Typical installation issues and common causes of poor performance.

Source Document Information

Organisation: SHAPA (Solids Handling & Processing Association)

Document: Technical Bulletin No. 13 – A Practical Guide to Rotary Valves

Authors: Ian Blackmore (Rota Val Ltd) and Professor Mike Bradley (The Wolfson Centre, University of Greenwich)

Document Type: Technical Guidance

Primary Topics: Rotary Valves, Airlocks, Pneumatic Conveying, Dust Collection, Bulk Solids Handling

Audience: LEV Designers, Dust Collection Engineers, Pneumatic Conveying Engineers, Commissioning Engineers, Mechanical Engineers and Process Engineers.

LEVCentral Perspective

Whilst rotary valves are seldom considered part of the LEV system itself, they are often critical to the reliable operation of dust extraction plant.

Every cartridge collector, baghouse or cyclone relies upon the collected material being discharged continuously without allowing excessive air leakage back into the collector. If the rotary valve is undersized, incorrectly selected or excessively worn, the resulting leakage can reduce collector efficiency, disturb airflow within the system and adversely affect pneumatic conveying performance.

The bulletin also illustrates an important systems engineering principle: individual components cannot be selected in isolation. Rotary valve performance depends upon the pressure differential, conveying system, product characteristics and downstream equipment. This reinforces the need to view dust collection systems as integrated engineering solutions rather than collections of individual components.

Further Resources

• SHAPA – Dust Hood Selection
• SHAPA – Cartridge Filter Technology
• ACGIH – Industrial Ventilation: A Manual of Recommended Practice for Design
• HSG258 – Controlling Airborne Contaminants at Work

Recommended Learning

• M505 Control of Hazardous Substances
• P600 Methods for Testing Performance of LEV
• P601 LEV Thorough Examination & Testing
• P602 LEV Basic Design Principles
• P604 LEV Commissioning & Performance Evaluation

Thought Leadership

Rotary valves demonstrate that even the simplest-looking components can have a disproportionate influence on system performance. Because they perform several functions simultaneously—metering product, maintaining pressure differentials, controlling air leakage and, in some designs, contributing to explosion isolation—they must be selected with the same level of engineering care as fans, filters and ductwork.

For LEV professionals, the message is clear: dust collection performance depends not only on efficient contaminant capture but also on the reliable handling of the material once it has been collected.

Understanding the role of rotary valves helps engineers appreciate the complete journey of the contaminant—from source capture, through transport and filtration, to safe discharge from the collection system.