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Pressure Tube Seals:
Front vs Back

Ace Glass uses two types of seals for our line of pressure tubes: front and back seals. Why are there two different types, and which one should you consider using for your application?

The back seal plug (Figure 1, above), which is pretty much an industry standard, was developed first. That style is still offered by virtually all lab supply companies, and by Ace Glass as well. The front seal (Figure 2, below) came later, around 1989, and Ace remains (to the best of our knowledge) the only manufacturer that makes this style seal.

While Ace still sells the back seal, it's a simple fact of life that we do so only to be compatible with what the rest of the market offers. In every case, we will recommend our front seal for your application. Here's why:

The front seal style provides a better, more consistent seal. This is critical for pressure applications -- Ace pressure tubes are rated 150 psig at 120 degrees C, while our Hydrogenation bottles are rated at 60 psig at room temperature. Our new line of Round Bottom Pressure Flasks, great for use with heating mantles, are rated @60 psig up to 120 degrees C.

Also, there are the threads to consider. Do you think it's possible that, on a back-seal plug, your viscous materials might well migrate up into the threads on the plug?

Yep, you're darned right it's possible!

But the front seal design easily eliminates that issue, as the O-Ring seal is located BELOW the threads (see Figure 2 again). This revolutionary design from Ace makes sure that your work is kept free of contaminants.

For great chemical compatibility and resistance, greater temperature range, and better value, Ace uses and recommends FETFE O-Rings on all our pressure vessel plugs.