The Parshall flume is one of the most accurate, versatile flow measurement tools in the entire world. However, while the Parshall flume is accurate, you need to make sure that you are using it the right way, which means promoting the proper upstream conditions.
If your upstream conditions aren’t ideal, it will be very difficult for your operators to take the accurate readings that you need, potentially impacting the success of your system. Fortunately, maintaining upstream conditions is easier than you might think, particularly when you have the right tips at your disposal. Learn how you can ensure the right Parshall flume upstream conditions, and find out how you can get the highest quality Parshall flumes possible.
Basic Conditions
Measuring flow is extremely complicated, and requires several basic conditions. To get the accurate readings that you need, the flow entering your Parshall flume needs to be subcritical. This means that its velocity shouldn’t be too high, and its surface must be free from turbulence.
To prevent turbulence, you need to be sure that your flow is approaching your Parshall flume in a long, straight channel. Generally, this can be accomplished by having an approach that is ten to twenty times the width of your Parshall flume throat.
Similarly, your flow needs to be evenly distributed, meaning the surface of the flow is uniform. To ensure even distribution, the floor of the approach channel must be level. If the floor of your channel isn’t level, you will likely see surface turbulence.
Other Upstream Requirements
Once you’ve ensured the basic requirements for proper upstream conditions, there are a few other tasks you should complete to make sure the flow entering your flume is subcritical.
First, there should be no bends directly upstream of your flume. Any bend in the upstream channel can affect flow distribution and potential velocity. Second, you need to be certain that the flow smoothly transitions from the channel to your flume. The easiest way to do this is to install side wing walls that gradually converge. Finally, if you’re working with a natural upstream channel, you must maintain the banks and prevent vegetation to preserve your flow.
You also need to think about the likelihood that submergence will occur with your flume. While Parshall flumes can still function in submergence conditions, it makes things much more difficult. If submergence is a possibility, you can install your Parshall flume so that it is slightly above the floor of the channel. Following these guidelines will ensure that you’re able to take the accurate readings that you need.
Get Help with Parshall Flume Upstream Conditions
If you want to get the most out of your Parshall flume, then it is imperative you’re maintaining the right upstream conditions. Fortunately, as we have seen, preserving your upstream conditions is easy when you follow the right tips. After your Parshall flume upstream conditions are secure, you need to purchase your flume from a trusted manufacturer like Tracom, FRP.
Tracom offers a wide selection of fiberglass products including Parshall flumes, and we can provide you with the flow management tools that you need. Contact Tracom to get more information about our catalogue and to request a product quote.
