Fluid Controls Ltd is one of the UK’s leading distributors for pressure control

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Flow Switches, Flow Meters and Excess Flow Valves

What is a flow switch?

A flow switch can perform a range of functions across a variety of applications. Designed to control the flow of liquid or gas through a designated channel, flow switches are used to monitor flow rates of liquids, protect pumps and trigger alarms if the flow is too high or low. Here, Fluid Controls explains everything you ever needed to know about flow switches.

What does a flow switch do?

To understand what a flow switch does in practice, it’s important to understand its inner workings. Many – but not all – types of flow switches comprise a paddle or some sort of magnetic trigger that connects to a circuit. The flow switch is installed in the channel through which the relevant gas or liquid passes. This media causes the paddle to rotate or else be displaced, which subsequently sends an electronic signal to a transducer.

The transducer converts this signal into a reading that is then sent to a transmitter. The transmitter measures the reading against predefined parameters and performs the necessary action required. This action could be the sounding of an alarm, shutting off elements of the system or diverting flow. As such, a flow switch can monitor and control flow either in a designated section of piping or right across an entire system. 

As we touched upon briefly earlier, some flow switches don’t have a physical paddle, such as ultrasonic flow switches. Instead, this type of flow switch bounces a signal off the monitored medium. This is especially useful in applications that require no moving parts for hygienic or low-maintenance purposes, or for use with contaminated or hazardous media. If in doubt, Fluid Controls’ experts can guide your selection process.

Where do you put a flow switch?

Where you put a flow switch largely depends on the type of switch and your specific application. However, there are some common considerations to bear in mind when installing a flow switch. It is important to install your flow switch on a straight section of pipe, ideally with the equivalent of ten times the pipe’s diameter in front and behind the switch. Try to avoid bends and any other fittings that could cause flow rate fluctuations.

How do you test a flow switch?

Again, the testing methodology for testing a flow switch hinges on the type of switch and where it is installed. But, as a general rule of thumb, you should be able to distinguish if your flow switch has been set up correctly and is working effectively by either observing it in action or by testing its electronics with an ohmmeter to ensure you have a completed circuit. If neither approach yields results, then it is time for a replacement.

Source flow switches from Fluid Controls

Fluid Controls has been supplying high-quality pressure control equipment since 1988. We can supply a range of UL, ATEX, IECEx and CE compliant flow switches from Malema. As a fully accredited ISO9001:2015 company, we provide a full installation and service facility for many of the products we supply. We also offer full pressure testing and repairs, as well as in-house or on-site training to optimise your user experience.

Interested in finding out more? You might enjoy our article about the difference between flow switches and flow meters. For more information about our full range of flow switches, or to discuss your application requirements in more detail, please contact Fluid Controls today on +44 (0)118 970 2060 or email fluid@fluidcontrols.co.uk

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