Solenoid Valves

Solenoid and other Valves for thick liquids

Thick viscous liquids such as Heavy oils, Greases, Syrups and other Glutinous media cannot be controlled by standard or general purpose solenoid valves as these solenoid valves will not operate with fluids with a viscosity over 40 or 50 CST (Centistokes), ie, air, water, light oils etc. For thick liquids you will require a more specialist coaxial valve or air operated angle seat piston valves that can handle thick liquids up to 500 or 600 Centistokes.

Basically standard solenoid valves have thin flexible diaphragms with pilot holes that are easily blocked, even using a direct acting solenoid valve may cause operational issues.

There are 2 main solutions available depending on operational conditions and the availability of compressed air. In essence if you have a compressed air line then this can be used to control an angle seat piston valve. Read more about valves for thick media here...

Here we have a basic angle seat piston valve.

Inlet and outlet ports at the base directly opposite each other with an almost clear flow path through the valve.

The valve is controlled by compressed air at the actuator head usually by a 3/2-way solenoid valve and small control electrical supply. So for a normally closed angle seat piston valve when compressed air is applied the internal actuator lift the piston allowing flow, when compressed air is vented by the 3/2 control solenoid (pilot solenoid) the actuator closes and in turn closes the valve preventing flow. Sizes typically 3/8 to 3" BSP Temp 200C max, pressure 0 to 16 Bar.

Unlike a general purpose solenoid valve on the right where by typically the flow very arduous. then up through 90 degrees over the orifice then back down 180 degrees under the seal then 90 degrees and back out. 

This design if fine for water, air and other inert gases but for thick liquids would prove useless in most cases. In fact the valve would probably open and fail to close regardless. Then there are the issues of the pilot holes blocking.

So do not use general purpose solenoid valves for thick liquids.

Here we have a 2/2-way coaxial solenoid valve.

Inlet and outlet ports are directly opposite each other and the flow is almost perfectly linear. Due to the unique design of coax valves these are an ideal solution for glutinous and contaminated media even at high pressures or high temperatures. You can see from the cutaway drawing on the right that the flow path left to right is far better than any basic solenoid valve and with these design features and the added benefits of high flow, options for open and closed position switches, ATEX rated coils, 3/2 way function and manifold systems to suit most applications.

Port sizes 1/8 to 2" BSP or flange; pressure 0 to 300 bar, temperatures -30C to +200C max.

Here we have a 3/2 way air operated coaxial valve, also available in 2/2 way. All coax valves can be mounted in any direction, offering bi-directional flow control and are available in normally closed or normally open. Again clean filtered compressed air is used to control the valve, but unlike an angle seat piston valve these can be modular in design and handle pressure exceeding 100 bar.

Port sizes from 1/4 to 2", Pressures from 0 to 120 bar.

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