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Caps and Plugs: When to Use Which One?

by Luke Wurban, on Fri, Sep 06, 2019 @ 11:09 AM

They both block off parts of a fluid system and still fully pressurize it - so what's the difference?

Watch this Tech Tip video where we explain the difference between caps and plugs, and when to use each one for your applications.

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A cap is used to block off a piece of tubing at the end. With a cap installed, you can fully pressurize your system. 

The cap is a complete Swagelok assembly, with a nut, a front ferrule, a back ferrule, and a fitting body. The difference is that the fitting body is blank rather than open. This allows you to install the nuts and ferrules onto the tubing and pre-swage them. As with a regular tube fitting, it takes only one and 1/4 turns to pull it up into place. 

Later, when you want to switch out the cap, you simply remove the blank fitting body and follow standard Swagelok reassembly instructions to install the tubing into the rest of your fluid system.


A plug is used to close off a port. If you have a tee, for instance, and want to use only two of the three ends, use a plug. You simply remove the nuts, ferrules and tubing, take the plug, and tighten it on the end you want to close off. The plug already has machined ferrules inside, so you don't need to pull it up 1 and 1/4 turns after it's finger tight. You tighten it only 1/4 turn, and the job is done.

As with the cap, a plug allows you to fully pressurize your system.

Edmonton Valve & Fitting has all the caps and plugs you need, along with a full range of other fluid system components. Call us at 780-437-0640 or contact us through our website.

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Central & Northern Alberta’s leading fluid handling components supplier.

For 50 years we have provided professional support and an extensive local inventory of Swagelok products. We offer custom solutions, applications support, training, equipment, and tools to help ensure safe and reliable operations.

CONTACT US 780-437-0640

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Edmonton Valve & Fitting Inc.
4503-93 Street NW
Edmonton AB T6E 5S9
PH: 780.437.0640

Drayton Valve & Fitting Ltd.
5614 - 55 Street
Drayton Valley AB T7A 1S9
PH: 780.542.7988

Fort McMurray Valve & Fitting Ltd. 266 MacKay Crescent
Fort McMurray AB T9H 5C6
PH: 780.790.0640

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