Blog

Over the years, there are have been a number of developments to the thin-plate weir – expanding weirs beyond the V-notch and Rectangular styles commonly used. Each special weir type is an attempt to overcome very specific limitations of the thin-plate weirs in general.

The usual method of dissipating the energy of a weir's nappe is by a hydraulic jump downstream of the weir. In an earthen channel, if the is no provision for this dissipation of energy, there will be a tendency to sour the downstream channel. This scour and erosion of the channel…

In selecting a site to install a staff gauge for surface water monitoring, there are several factors to consider:

The common sources of errors for weir installations can be broken down into four categories: Flow approaching a weir installation should be no more than 0.5 fps and the upstream channel (weir pool) should be straight and of uniform cross-section for 20 times the maximum…

Since its introduction in the 1930’s, the Palmer Bowlus Flume has grown to be the second most common flume for measuring sanitary flows. There are, however, several distinct disadvantages in using Palmer Bowlus flumes. Unlike other styles of flumes that have strictly defined…

The Palmer Bowlus flume was designed for installation in existing manholes and in line with sewer piping / channels. These sorts of installations normally see nice average to upper range flows.

Like H flumes, on free-spilling discharges from pipe where more accuracy (+/- 3-5%) is needed that the California Pipe Method can supply (+/-10%), Montana flumes can be used to for accurate flow measurement.

On free-spilling discharges from pipe where more accuracy (+/- 3-5%) is needed that the California Pipe Method can supply (+/-10%), it is common to see H flumes used.

Free-spilling discharge offers challenges in how to best measure the flow. Unlike piped or channeled flow, free-spilling discharge means that many of the flumes and weirs that could otherwise don’t adapt well. However, the California Pipe Method is one approach that requires…

Automatic Samplers (also called autosamplers or simply samplers) collect and store water samples for laboratory analysis without the need for operator intervention. When used in conjunction with a flume or weir, automatic samplers can collect samples that are truly representative…

As winter approaches, the problem of how to continue accurate flow measurement raises its ugly head. The flumes most affected by cold weather are those that are measuring runoff flows. These are typically H Flumes mounted at or above grade and usually don’t see continuous…

The buildup of solids can wreak havoc on otherwise good flume applications if the style of flume isn’t well chosen.

Many times, customers who opt to use a fiberglass Packaged Metering Manholes want to a have a full composite installation. For traffic applications this means that composite grade rings are needed to set the frame / cover over the manhole. To assist you in tracking down suppliers…

The Parshall flume is the most widely used flume for measuring the flow of water in open channels and non-full pipes. The flumes have a number of distinct operational advantages, including:

The accuracy of the depth-discharge relations for Palmer Bowlus flumes in not considered to be constant over the full range of flows. The decrease in accuracy reflects the increased importance (and uncertainty) of the Coefficient of Discharge (Cd) at low flows.

While weirs can be useful in a measuring flow in surface water applications, there are distinct disadvantages to using them. For a weir to develop the necessary upstream velocity profile, the channel upstream of the weir must conform to certain specific requirements:

For a flume to operate correctly the flow approaching it must be sub-critical and under open channel (non-full pipe) flow conditions. Sometimes, however, the space available at a site means that where the flume has to be situated clashes with the ability to properly condition the…

The Parshall flume is widely used to measure open channel flows both above and below grade. Above grade the flume is typically cast into a long, straight concrete channel or is free-standing with inlet / outlet end adapters and pipe stubs to connect the flume to piping. Below…

Parshall flumes are restrictions in a flow stream that raise the upstream level as flow is restricted before passing through the flume. This backwater extends upstream of the flume, into the approach channel. The difference in the water surface elevation upstream of the…

The way to pick the right point of measurement in a Parshall flume is…not to pick at all!