Interchanging and Intermixing Tube Fittings

Posted by John Comi | 7/28/14 7:30 AM 0 Comments

Intermixing Tube Fittings

This is the first of a two articles focused on interchanging tube fittings and intermixing tube fitting components.  Part one deals with interchanging tube fittings. Part two will take up the issues in intermixing tube fitting components.

The Problem

Creating leak-tight systems is important to most manufacturing process.  The integrity of instrumentation and control systems have significant impact on:

  • Safety and the environment

  • Product quality

  • Productivity and costs

When tube fittings leak, it is usually due to improper installation, tubing quality, or product selection. Other times leaks are caused when the components of tube fittings are mixed when making up a fitting.  This is called intermixing tube fittings.  We will talk about this in my next blog.

Interchanging tube fittings is when one tube fitting brand is substituted for another.  While this usually happens during maintenance, especially when OEM equipment or original system installation need updates or replacement.  It can also occur when an individual maintenance worker or contractor substitutes the brand specified by the system designer with another brand. This usually happens because:

  1. The current or specified brand is not available at the time of installation

  2. The installer or owner company prefers a different tube fitting brand based on cost and/or experience with the brands.

Some Considerations

Installers and desigers can be confident when interchanging tube fittings if:2leakfreevertical

  • They know the replacement brand is a “drop-in” replacement in terms of both size and performance for the current component. 

  • Installers are familiar with assembly and installation practices. 

  • The fittings have the necessary approvals and meet the performance standards for the application and for material traceability.

And Some Guidelines

Therefore, when choosing a substitute tube fitting brand, installers and purchasing agents should choose brands that:

  1. Are drop-in substitutes for the current brand in terms of size and installation practices.  This means that the distance between the points where tubing seats into the tube fitting are identical. 

  2. Have documented performance demonstrating that the tubei fittings meets or exceed the performance of the current tube fitting brand.

  3. Offer documentation and certification that meet material and traceability requirements for the industry and application.


Designers, installers and OEMs having service issues or are who simply looking for a replacement or backup for their current tube fitting brand can save a lot of engineering and maintenance time, installation problems, and dead inventory by following a few simple guidelines. 

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As usual, we invite your comments about this topic and invite your suggestions for future blog topics.

Topics: Tubing, Tube Fittings