Using Tube Fittings from Different Manufacturers May Lead to Leaks

Single sourcing tube fitting components will significantly reduce the risk of costly leaks.

By Jon Kestner, Senior Product Line Manager — Swagelok Company

Using quality components is vital to keeping industrial fluid and analytical instrumentation operating at peak performance. If even one component fails, costly leaks can result, leading to potential system and employee safety concerns. Intermixing and interchanging tube fittings from different manufacturers can sometimes cause these problems.

Plant operators should strongly consider obtaining all their tube fittings from a single, trusted partner to prevent operational lapses. Although some manufacturers claim their tube fitting components are interchangeable with their competitors, taking this risk is significant. No manager wants to compromise worker safety and place their colleagues in danger (Figure 1).

If intermixing and interchanging tube fitting components are standard practices at a facility, it is time for the facility manager to reconsider this process. Poor system performance will be of lower concern if tube fittings fail.

The Basics of Tube Fitting Intermix and Interchange

Intermix and interchange, despite the similarity in names, do not represent the same practice (Figure 2):

• Intermix: Tube fitting components, including the nuts, ferrules, and bodies from two or more manufacturers are mixed and then assembled to make a completed fitting.
• Interchange: A tube fitting from one manufacturer that has been installed on a piece of tubing is disassembled, and the tubing, nut, and ferrules are then reassembled into a tube fitting body from another manufacturer.

The Problems Caused by Intermixing or Interchanging Components

Intermixing or interchanging components should be discouraged because tube fittings are not standardized industrywide. Variances in standards from manufacturer to manufacturer mean differences will exist. Sometimes the issues are incidental, but the variances can lead to substantial and significant problems.

It is not hard to understand why intermixing or interchanging tube fittings may be an appealing proposition for facility managers. If manufacturers insist there are no consequences for using their products in conjunction with other brands, some managers may begin using tube fittings from different manufacturers to save money.

Intellectual property constraints prevent manufacturers from accurately reproducing their competitors’ tube fittings. If the tube fittings are not exactly the same, costly leaks are possible, eliminating whatever cost savings might have come from the less expensive fittings. It cannot be stressed enough: If tube fitting components are not specifically designed to work together, they may fail catastrophically, putting employees at risk and leading to unplanned downtime for the facility’s fluid systems.

Some of the potential problems with interchanged or intermixed fittings include:

• Inconsistent sealing surfaces due to design, construction, and torque value differences
• Sealing surface incompatibilities due to geometry, tolerances, and metallurgic properties
• Compromised function and leaks caused by overtightening the nut
• Fatigue failure as a result of cyclic loading that permanently deforms the fitting components
• Ineffective sealing surfaces resulting from different swaging mechanisms, material hardness, and tolerance variations

With all the potential problems that interchanging or intermixing tube fitting components can cause, including unpredictable performance, increased costs, and potential safety hazards, it is clear neither one should be a standard operating procedure in a facility. Additionally, the equipment’s warranty may be voided if components are mixed with those from another manufacturer. Higher-than-expected costs may result in the event of a significant failure. (Figure 3).

Never Intermix or Interchange Tube Fittings

Most fluid system standards agencies specify that facilities should never practice intermixing or interchanging tube fitting components. Some agencies have even gone so far as to criticize those who encourage the practice, suggesting that anyone who would propose intermixing or interchanging tube fitting components is not following engineering best practices.

The clearest way to keep tube fitting components from failing is to ensure they are all sourced from the same reliable manufacturer. Doing so will prevent employees from accidentally intermixing or interchanging components and preserve industrial fluid systems over their lifetime.