This article was originally published on June 6, 2022, and was updated on March 5, 2025.
In water and wastewater applications, corrosive substances or blockages from sludge or slurries can compromise your pressure and temperature instruments. How can you safeguard these instruments and maintain operational efficiency? A diaphragm seal offers protection, but not just any seal will suffice. You'll want a diaphragm seal with a flushing connection that can simplify the seal's cleaning process and prevent clogging.
I've been working with Ashcroft - a leader in pressure and temperature instrumentation - for the better part of 33 years. Initially, I was the branch manager at an Ashcroft distributor, and for the past 10 years, I have been the Northwest territory manager. In both roles, I have helped customers understand the features and benefits of water and wastewater instrumentation.
Read this article to learn what a flushing connection is, how it can help a diaphragm seal be more effective in harsh applications and when it's most advantageous to put one to work for you.
What is a flushing connection on a diaphragm seal?
In some situations, diaphragm seals that are meant to protect your instrument also need protection from process media that is clogging the seal. A flushing connection like those offered on many Ashcroft® diaphragm seals allows an operator to flush debris from the surface of the diaphragm to prevent it from becoming clogged during an application.
The connection is typically a threaded auxiliary that is machined into the lower housing of a diaphragm seal.
Figure 1. Flushing port threaded to lower housing of diaphragm seal
The diaphragm seal types available with a flushing connection are threaded or flanged. Flushing connections are available in 1/8 in., 1/4 in. and 1/2 in. sizes. Typically, a single flushing connection is used but dual flushing connections in either 1/4 in. or 1/2 in. are available.
Storing the flushing connection
When the flushing connection is not in use, it is important to use a flushing plug or a valve to prevent process media from leaking. The flushing plug should be of the same material as the lower housing to ensure compatibility with the process. If a valve is used, you also want to be sure the wetted parts are compatible with the process media.
When to use a flushing connection on your diaphragm seal
There are many instances where you might use a flushing connection on your diaphragm seal, including those featured in the table below.
The flushing connection is an option you should always consider when any of the above situations may come into play in your application. However, there is an additional cost for flush port options, so if you do not require any of the above capabilities, we do not recommend using this option.
What kinds of diaphragm seals offer flushing connections?
Ashcroft manufactures many types of diaphragm seals equipped with integral flushing connections, including the 101 Threaded Diaphragm Seal (see Figure 1). When a flanged seal like the DF seal is used (see Figure 2), the flushing ring is a standalone accessory mounted between a flanged seal and the mating flange in your system (see Figure 3).
Figure 1: Ashcroft® 101/201 Threaded Diaphragm Seal
Figure 2: Ashcroft® DF Flushed Flanged Diaphragm Seal
Figure 3: Ashcroft® FR Flush Rings
Ready to learn more?
Now that you know more about flushing connections for diaphragm seals, you can help protect your instruments from clogging and corrosion. If you want more information on mounting accessories and assemblies, here are a few additional resources that can help:
- When to Use a Welded Instrument Assembly
- Best Practices for Installing Flanged Diaphragm Seals
- What’s the Right Pressure Instrument Mounting Assembly for Me?
- Accurate and Reliable Isolation Ring Assemblies for Water/Wastewater Applications
- The Expert Guide to Instrument Assembly [Webinar]
Feel free to contact us with any questions or concerns. Our industry experts can help address any issues you have. In the meantime, download our Complete Guide to Pressure Instrument Assembly.