How a Pneumatic Liquid Level Switch Operates

The pneumatic liquid level switch is a dependable, easy-to-operate solution for level control of your oil and gas production vessel. A pneumatic level switch is used to maintain desired level in separators, scrubbers, treaters, and other vessels. Here’s how it works:


Supply Pressure Coming Through Filter of Liquid Level Switch

Supply pressure comes in through the filter, into the pilot body, creating a force on the stem, keeping it closed.

The float lever is magnetically opposed to the magnet in the shuttle which has a check ball on the top and bottom to seal off the flow in either direction. In the closed position it repels the shuttle downward, blocking the flow of supply gas to the diaphragm.

Diaphragm Creating Seal to Block Vent Path in Liquid Level Switch

As the liquid level rises and the float moves up, the float lever pivots down, repelling the shuttle up. Therefore, the channel for the supply pressure to contact the diaphragm opens. This creates enough force to push the stem outward so that the supply pressure can flow to output. The diaphragm also creates a seal, which blocks the vent path.

The pneumatic dump valve receives an output signal telling it to open, dumping liquid from the vessel.

As the liquid level and float move down, the lever pivots upward, repelling the shuttle back down. This blocks the pressure to the diaphragm, which allows the stem to close with the O-ring sealing on the beveled surface.

With pressure no longer on the supply side of the diaphragm, the pressure from the output port pushes the diaphragm to flow out to vent.

For manual actuation of the switch, after being installed in the vessel, there’s a manual override button on the top.

The level switch comes direct-acting. If you need to switch it to indirect, simply rotate the pilot body 180 degrees.

Other Options

Kimray's Liquid Level Switch Extension Options

If you need an extension to give the float more clearance, we offer a 3” extended version. We also offer an electric version of the level switch. If you need to control the level from outside of the vessel, we offer a compact, external float cage that works with both the pneumatic and electric level switch.


If you have questions about this or any other Kimray product, contact your local store or authorized distributor.