FAQ

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.

A blow-through valve, also known as a blow-through rotary valve, is used to convey bulk materials in pneumatic conveying systems. Bulk materials are often transported throughout the entire industrial processing process via pneumatic conveying systems.

The rotor of the blow-through valve feeds the product directly into a pneumatic conveying line. This often involves fine-grained or powdery media such as milk powder, starch, or grains, which are processed in the food industry. The rotor of a blow-through rotary valve are always open at the front to allow the product to be transported through the conveying line.

Open rotary rotors without side plates are used in blow-through valves. The conveyed medium is feed directly into the pneumatic conveying line. These rotors have very narrow gaps, both vertically and horizontally, to keep leakage rates low and increase the efficiency of the blow-through valve and the entire pneumatic conveying system.

As an alternative to blow-through rotary valves, standard rotary valves with a closed rotor can also be used in conjunction with a feed shoe. Neue JÄGER feed shoes are typically equipped with a Venturi nozzle. The narrowing of the cross-section in the feed shoe’s connecting line causes an increase in velocity and thus a pressure drop in the pneumatic conveying line. This pressure drop subsequently leads to very low leak rates and efficient emptying of the individual chambers of the rotary valve.

In pneumatic conveying systems, pressure differentials often occur between the pneumatic conveying line and the inlet above the rotary valve. Blow-through rotary valves from Neue JÄGER can be used for pressure differentials of up to 3.5 bar. Rotary valves for medium-pressure or high-pressure blow-through valves have rotors with up to 18 chambers, depending on the pressure differential. The high number of chambers increases the sealing surface between the housing and the rotary valve, allowing pressure differentials of up to 3.5 bar to be bridged.

A self-cleaning rotary valve is used to convey slightly sticky, caking, or firmly adhering bulk materials. The individual chambers are emptied by forced evacuation using a separate rotor which is placed below the main rotor.

Self-cleaning rotary valves are typically equipped with rounded chambers. This facilitates chamber cleaning and emptying, and the cleaning-rotor, which is located below the main motor, always follows a circular path. Rotary vane feeders can be made from all available materials. The range extends from mild steel 1.0577 and stainless steel 1.4301 to high-alloy steels such as 1.4571, 1.4539, and 1.4828.

The scraper wheel and main rotor must be synchronized to prevent collision between the rotors. In all Neue JÄGER self-cleaning rotary valves, both rotor shafts are connected via two gear wheels, which enable precise synchronization of the two rotors to avoid safely any kind of collision.

Self-cleaning rotary valves can be equipped with a cleaning hatch below the cleaning rotor. Removing the cleaning hatch allows easy access to the rotor of the self-cleaning rotary valve, thus allowing for quick and easy cleaning. The cleaning hatch can also be made of a transparent material upon request to check the degree of population.

Commercially available helical gear drives are typically used to drive also self- cleaning rotary feeders. The geared motor can be connected to either the main rotor or to the cleaning wheel, for example, via a motor lantern. The motor mount is usually attached directly to the cleaning-wheel; the spur gear then transfers power to the main rotor.

A tangential rotary valve, also known as a offset rotary valve, is used for the gentle conveyance of bulk materials. The inlet and outlet of the rotary valve are tangentially offset. Tangential rotary valves are typically equipped with a pre-scraper to prevent overfilling of the chambers.

The pre-scraper at the inlet of the tangential airlock prevents the chambers from overfilling. The rotor rotates in the direction of the pre-scraper. This prevents the chambers from overfilling and pushes excess material into the next chamber.

The pre-scraper on Neue JÄGER tangential rotary valves can be adjusted. This allows the flow rate at the inlet of the rotary valve to be regulated. Additionally, the pre-scraper can be equipped with adjustable and replaceable sealing strips. A special cleaning flap in the inlet allows for easy replacement of the adjustment strips without dismantling the entire tangential valve from the piping system.

Tangential rotary valves are generally used for coarse-grained bulk materials and granules. Bulk materials containing particles up to 70 mm in size can also be gently conveyed with tangential valves. The pre-scraper of the tangential valve pushes the bulk material back into the next chamber when the chambers are overfilled. This largely prevents damage to the media between the rotary valve and the housing.