Different Rotor Options Inside Rotary Valves

Published - 6th Nov 2023

Rotary valves & airlocks are the most popular product we manufacture here at Rotolok. They are what the company has been built on. There are various rotor types because we handle so many different products in so many applications.

Rotor General Functions

There are three basic functions and the main two are ‘feeding product at a set rate’ and ‘feed product at the rate on input’. A typical application is where they sit under a silo and for function one the product falls into the valve and is then dropped out the bottom at a rate depending on the size and speed of the valve. The second function is where the valve just keeps going so product falls out the bottom at the same flow rate as it enters. The rotors are mainly to provide an airlock to stop air going back up into the silo and pressurising it.

Rotor General Functions

Fixed Open
This is the simplest to make and fits the majority of applications. It is sealed around the three edges of the blade creating the most restriction of airflow back up the system. It is also the most economical to manufacture.

Fixed Open Rotor

Open Adjustable
This performs in the same way as the three edges mentioned before but the blades are adjustable. This is mainly used for abrasive products as the blades can be a/r steel or flexible (polyurethane) and easily replaced rather than replacing the rotor.

Open Adjustable Rotor

Closed Fixed
The pockets in these valves are the same but they now have a disc or shroud at each end to close the ends of each pocket off. It creates a gap between the end cover and the shroud. This would be for abrasive products that you don’t want rubbing on the end covers. It basically protects the end covers more.

Closed Fixed Rotor

Closed Tipped
This would be used for the same reasons as the other tipped rotors.

Closed Tipped Rotor

This puts a radius in the bottom of each pocket to minimise clumping, which can stop the product falling out.

A chamfer is made on the trailing edge of each vane, blade, or tip, which allows product particles to fall away from the edges.

This solves the problem of air leakage on a closed rotor. It is a bit more expensive to make than standard and can cause the product to get in the mini pockets and not get out again.

Reduced Capacity
This allows for a smaller volume of product in each pocket, reducing the throughput of a larger valve when a smaller valve would be a restriction for the particle size of the product. It also helps against clumping.

As the name suggests this scrapes the bore clean of a product that tends to smear. There are two opposing blades slightly offset from each other.


By putting in a mid-disc we create a staggered pocket construction giving half a pocket volume discharge at the outlet, smoothing the output.

This helps stop all the product falling out of each pocket in one go by allowing it to fall out gradually. The scissor also reduces shock loading of harder particles caught in the nip point of the inlet.

This is an extreme version of an open adjustable style. The deep flexible blades can bend around larger, unbreakable product lumps.

Quick Release
The end cover unbolts and pulls out easily with the rotor meaning it can be cleaned. Useful when the product passing through the valve is changed.


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