A rotary valve is used in bulk material handling technology for discharging and metering bulk materials. The functionality and design of rotary valves are similar to those of pumps and compressors. While the fluid in pumps is liquid and in compressors gaseous, rotary valves transport bulk materials and other solids.

The rotary valve is used for the metered conveyance of bulk materials. It transports materials such as powder, granules, grain, or pellets between two areas, even with different pressure conditions.

Rotary valves are used in many industries, for example, in food technology, plastics processing, the chemical industry, the cement industry, and biomass conveying. They are used for metering, discharge, and pressure relief and are often part of pneumatic conveying systems. Rotary valves are often installed under silos and bunkers to relieve the silo pressure on the bulk material.

Dry and free-flowing bulk materials such as road salt, animal feed and feed pellets, plastic granules, or wood pellets are conveyed.

Abrasive or sensitive materials can also be processed with special designs. It is crucial that the material flows freely and does not tend to stick together.

Inside the rotary valve, a cell wheel or rotor rotates with several chambers – called cells or chambers. These collect the bulk material at the inlet and convey it to the outlet. The gap between the rotary valve and the housing ensures that the system remains pressure-tight to a certain degree, which is especially crucial for pneumatic conveying.

Rotary valves can handle pressure differences of up to 3.5 bar. Simple rotary valves with 8 chambers can be used for pressure differences of up to 0.5 bar. Medium-pressure rotary valves up to 1.5 bar or high-pressure rotary valves up to 3.5 bar are then equipped with cell wheels with up to 18 chambers.

Yes, there are many variants. Depending on the application and demands, a distinction is made between standard rotary valves, blow-through valves for pneumatic conveying, rotary valves, and tangential valves.

There are different versions for each type of rotary valve, such as temperature-resistant, hygienic, or explosion-proof models.

The material design also varies – for example, stainless steel versions for food or wear-resistant coatings for abrasive media.
The selection of the right material, bearings, or sealing system always depends heavily on the material being conveyed and the ambient conditions.

Rotary valves are nowadays frequently used as protective systems in many potentially explosive atmospheres under the EU Directive 2014/34/EU.

In general, the directive distinguishes between devices that are designed to be free of ignition sources or pressure shock-resistant and autonomous protective systems.

Autonomous protective systems are flameproof and serve for explosion isolation or as safety devices for burn-back protection. These are very often also referred to as flameproof devices.

Rotary valves can reduce the ingress of air or gases into sealed systems or piping networks. Rotary valves with a very small gap between the rotor and the housing of up to 0.1 mm are often used for so called gas tide rotary valves. Rotary valves with up to 18 chambers, resulting in a very large sealing surface, minimize the air penetration. Additionally, rotary valves can be equipped with leakage air connections or a separate leakage air collector.

The correct design of a rotary valve depends on factors such as flow rate, material and material properties, type of bulk material, ambient temperature, pressure conditions, installation location, and environmental conditions. Hygiene requirements or the use of rotary valves in ATEX areas also play an important role. A customized design ensures optimal function and a long service life of the system.

Modern rotary valves are low-maintenance but should be inspected regularly. Seals and bearings, in particular, are wear parts that should be replaced as needed. Many models offer easy access for cleaning and maintenance, which minimizes downtime.