The first step in installing a Parshall flume is finding the right spot. Quite a few factors go into site selection, so this isn’t a decision to be taken lightly. Proper site selection is key to getting successful flow rate measurements with your flume. Fortunately, there are a few tips you can keep in mind to make sure you’ve got the right spot. Learn how to find the right site for a Parshall flume.
Consider the Channel Dimensions
It’s no accident that site selection tends to revolve around the dimensions of the flume and the channel. The relationship between the two is essential to the proper function of the flume itself. Generally speaking, a Parshall flume should be about a third to a half of the width of the channel’s water surface under normal flow conditions. With this kind of balance, the flume can accommodate increased flows without being so big that it inflates the cost. Because of this, you’ll need to find a site that works well with the size of flume you have in mind for your unique flow conditions.
Optimize Upstream Conditions
Upstream conditions are key to a well-functioning Parshall flume. When you’re picking the proper installation site, it must be free of any dips, elbows and bends immediately upstream that could cause the flow to not have a uniform velocity upon entering the flume. If these conditions are present in your flow channel, you’ll want to make sure the flume is situated sufficiently downstream from them to give the flow a chance to even out.
Space From Pipes Appropriately
When installing a flume in a pipe system or with a metering manhole, it must be spaced properly away from pipes. For example, the flume shouldn’t be situated right up against an incoming pipe. This is because a Parshall flume is a rectangular channel while the pipe is round. The flow needs time to transition from one to the other, and that requires extra space. Without this space, the flow will become turbulent, which throws off the accuracy of flow rate measurements. End adapters are useful in ensuring that the proper spacing is maintained between pipes and flumes.
Consider Elevation Needs
The inherent design of a Parshall flume requires a drop in elevation throughout the flume. Because of this, the downstream channel will need to be lower than the upstream channel. While finding a site with these conditions will solve all elevation concerns, it’s not always possible. Additionally, it’s not always possible to modify the downstream conditions accordingly. In these cases, you’ll have to elevate the flume itself. When elevating the flume, the upstream channel walls will need to be high enough to contain the increased elevation in water level. If that’s not possible, you’ll need to find another site.
Parshall Flumes From Tracom
Now that you know how to find the right site for a Parshall flume, you can get one of your own. Tracom is happy to help with a team of expert designers who can plan the right design for your unique flow channel conditions. Contact us today to get started!
