Short answer: no. Parker and Swagelok tube fittings can look almost the same, but they are designed and made to different tolerances. You should not mix their parts. This article explains why, what can go wrong, and what to do when you need a replacement fitting.
Why Parker and Swagelok Parts Should Not Be Mixed
A compression tube fitting seals by deforming ferrules between the nut, the body and the tube. For this to work, the angles and dimensions of the nut, the ferrules and the body must match exactly. Each manufacturer designs these parts as one system. Swagelok tube fittings are made to close tolerances, because without them the interaction of the nut, two ferrules and the body would not be successful.
Parts from two manufacturers may thread together, and may even feel tight. But a connection that is tight is not necessarily a connection that seals or that will hold under pressure and vibration. Manufacturers warn against interchanging components from different brands, and a mixed fitting is outside the manufacturer’s design and warranty.
What Can Go Wrong
- Leaks at low or high pressure, sometimes only after thermal cycling or vibration.
- Poor tube grip, so the tube can be pushed out under pressure.
- Damaged tube or parts, because ferrules bite or seat in the wrong place.
- Hard-to-find faults, since a mixed fitting may pass a quick hand check but fail later.
In a wellsite sampling or test line, a leak can mean lost samples, bad data, or a hazardous release of hydrocarbons or gas.
Comparison at a Glance
| Question | Answer |
|---|---|
| Do the nuts and bodies look similar? | Often yes |
| Are the ferrule shapes and tolerances the same? | No, each manufacturer has its own design |
| Can I mix parts of the two brands? | No |
| What should I do when replacing a fitting? | Use the same manufacturer’s complete fitting |
What to Do Instead
- Identify the brand of the existing fitting before you replace or extend a line.
- Replace complete assemblies (body, nut and ferrules) from the same manufacturer.
- Use a fitting of one brand on both sides of a union, or use a proper adaptor made for the two thread standards.
- Use good-quality tubing with the correct outside diameter, and cut it square and clean.
- Follow the installation instructions. For Swagelok, scribe the nut and tighten it as described in the Swagelok and Parker fittings article and the fitting instructions for other connection types.
- Check the connection for leaks before the line is pressurized, for example before a flow test or when taking samples.
Frequently Asked Questions
Are Parker and Swagelok fittings interchangeable?
No. They may look alike, but they are designed to different tolerances and should not be mixed. Use complete fittings of one manufacturer.
Can I use a Parker nut on a Swagelok body?
No. Do not mix nuts, ferrules and bodies from different manufacturers, even if the thread seems to fit.
What if I only have a Parker fitting on one end of a line?
Use a fitting of the same brand on that end, or use an adaptor intended for that connection. Do not force a different brand’s parts together.
How do I check that a Swagelok fitting is tight enough?
Follow the tightening turns for the fitting size, and use gap inspection gauges where they apply.
Key Takeaways
- Parker and Swagelok fittings are not interchangeable.
- Never mix nuts, ferrules and bodies from different brands.
- Replace complete fittings, follow the installation instructions, and check for leaks before pressurizing.
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