Pnuematic fittings

[IndySam]

Originally Posted by Daniel_LaFleur

If you use push-to-fit fittings, I suggest getting a tubing cutter and ensuring that you cut the tubes square. Angle cuts cause so many leaks ...

Excellent point, that one tool will save you hours of leak fixing and should be in the toolbox of anyone using pneumatics.

[Tristan Lall]

I endorse the comments about cutting the tubing properly. Impress upon everyone who works with pneumatics that this is critical.

As for the pneumatics rules...hopefully there will be some further improvements, but as they stood in 2011, the rules were very strict, but relatively straightforward. It's easier for you to just refer to the rules than for me to reiterate everything, but here are some highlights.

Tubing is restricted by inside diameter: only Ø0.160 in ID is allowed. Since the Princess Auto tubing doesn't seem to indicate the ID, you'd have to demonstrate to the inspector that the tubing was the right size. Ø0.250 in OD tubing is often found with this ID, but there are variations.

The vendor rates the tubing for 125 psi working pressure; that's sufficient, so bring a printout of that web page to inspection. (Allowing tubing documentation in lieu of factory-printed markings was a great change.)

As for the ¹/₈ in NPT restriction, it's a bit non-obvious. By supplying and allowing parts that don't use NPT fittings (e.g. the Festo valves), FIRST is endorsing the interpretation that it's based on size rather than the presence of NPT threads. This effectively means that the port diameter may not be larger than that of a ¹/₈ in NPT port, whatever the actual method of connection. Notably, that's different from the orifice diameter, which happens to be around Ø0.125 in on a lot of ¹/₈ in NPT hardware. In fact, the maximum port diameter that would engage a ¹/₈ in NPT fitting is about Ø0.37 in, but because the depth of the tapered port is unknown, the maximum diameter is not precisely defined. (This is therefore an area for improvement in the rules.)

Originally Posted by George C

We had an issue this past season with some Festo solenoids that had been anodized after threading so that the push fittings wouldn't thread in. We had to re-cut the threads with a 1/8 NPT tap.

Given <R67B>, I'd try to avoid this in the future. (That's arguably a prohibited modification to a pneumatic component. You're not supposed to perform machining operations on valves.)

[jspatz1]

McMaster has push fittings.