Weirs and Flumes


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The most commonly used technique of measuring the rate of flow to BS3680 is to use a hydraulic structure inverted into an open channel which acts to restrict the flow of liquid in the channel. These Hydraulic Structures are known as primary devices.

Primary devices can be divided into two broad categories: weirs and flumes. The type of primary device depends on the application; flow rate, channel shape and the presence of debris in the channel. It is important that the correct primary device is chosen to ensure reilable measurements of flow.

A weir is essentially a dam built across an open channel over which the liquid flows through a specially shaped opening or notch. The restriction of the flow through the opening means the level in the approach channel will rise and fall proportional to the flow enteing the channel. This level is converted to a flow figure through a set of BS standard equations.

The most common types are the rectangular weir and the V-notch weir.

In general the V-notch is prefered as it gives higher acuracy (1-2%) although where large debris is present the rectangular weir ismore suitable although it is slightly less accurate (1-4%).
V-notch Weir
Rectangular Weir
A flume usually consists of a converging section, a throat and a diverging section. It is a specially shaped open channel flow section with an areas and/or slope that is different from that of the channel.

The most common type is the rectangular flume although several other types are available. although flumes are less acurate than weirs (2-5%), they are useful when large volumes are being measured and debris is present. Flumes also have the advantage that they are largely self cleaning, thus requiring less maintenance.

Pulsonic Technologies flumes have been developed to ensure a high level of accuracy with long term durability and ease of installation. They can be supplied with an integeral approach section or without (conventional flume) and manufactured in GRP (304 as standard – 316 optional) or stainless steel.
Price on application
Pulsonic Technologies

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Greetland, Halifax, West Yorkshire, HX4 8LR

Tel: 01422 363462

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