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A problem with the application of thin-plate weirs in the field is the lack of proper conditioning of the flow before it reaches the weir crest. Baffles, placed upstream of the point of measurement, can be used to correct both poor approach velocity profiles and surface…

Freestanding staff gauges are a good solution to the need to measure level in a flume, weir, or channel.  They are also useful in stream gauging or as replacements for other gauges that are damaged or no longer readable. Openchannelflow fiberglass freestanding staff gauges…

Reinforced weir boxes are a convenient way of measuring seepage flows out of a dam when the pipe is just below grade.  Reinforcing the sidewalls of a weir box can allow the structure to withstand the pressures exerted by the soil in shallow burial applications. In these…

Feedlots are an economical way to feed and raise a variety of livestock, but they generate large quantities of runoff, which can impact ground and surface water supplies.  Accurate flow measurement is important as part of a BMP approach to the problem and both flumes and…

A common problem we encounter in talking to customers about using weirs is lack of understanding of where the correct point of measurement is. Unlike a flume, where the point of measurement is integral or fixed in the structure, for a weir, the point of measurement is upstream of…

In selecting a material of construction for a flume or a weir, it is not uncommon for the decision to be made “go with stainless” without a consideration of the grade of stainless that best fits the application.  Both T-304 and T-316 stainless steels are…

Fiberglass packaged metering manholes are an innovative solution to the problem of needing to measure piped flow below grade. Packaged metering manholes factory integrate a flow element (usually a flume, but weirs and magnetic flow meters can also be integrated) directly into a…

Investigations by researchers have shown that in sharp-crested weirs even very slight rounding or dulling of the square upstream edge of the weir crest has a measureable effect on discharge. The effect of weir crest rounding on discharge is most evident on well rounded weirs with…

To accurate measure flow, thin-plate weirs are intended to operate under free-flow conditions with the nappe freely spilling over the weir’s crest.  However, there may be occasions when a weir becomes submerged – either through changes or mismanagement of the…

There is a lot of confusion as to what materials are suitable for making a thin-plate weir from.  Some installations use plywood, some stainless steel, some painted steel, and other fiberglass or aluminum. In making a weir plate the most important consideration is the weir…

In our series on Selecting a Primary Device we looked at:  Choosing Between a Weir and a Flume and Choosing a Weir or Flume Style.  In this closing article we now look at sizing a weir or flume. The basic consideration in sizing a particular style of weir or flume…

In the first article of this series on Selecting a Primary Device we discussed criteria that can be used to select between a weir and a flume.  Now our attention turns to selecting a particular style of weir or flume. The choice of device style is normally dictated by the…