[Mr. Lim]

We installed fittings on these tanks yesterday, and I can absolutely see how this happened.

As a student and I were tightening the NPT fittings, we wondered "when should we stop?"

The plastic ports didn't offer increasing resistance as you tightened fittings into them, like metal ports do. They just spun and spun and spun with the exact same resistance as we went.

We stopped when we still saw 1-2 threads exposed on the fittings.

They still felt loose in comparison to when you put fittings on metal components, but they did not leak.

WE VERY EASILY could have tightened them so much that the fitting bottomed out, and only then would it feel like the turning resistance increased. By then, you're pre-loading the thread, and could fracture the end of the cylinder...

This is speculation of course, but for any teams using these tanks:

Tighten your fittings until you see 1-2 threads exposed. That is tight enough to NOT LEAK, given you've properly applied teflon tape/have sealant already applied to the fitting. Most fittings in the pneumatic KoP bag have white sealant already applied to the threads.

Don't risk tightening them any more, if this is "tight enough."