Leaking air

[Yuan Xue Lim]

We are having problem with our pneumatics system. We are trying to have our system to stay at 60psi for the working pressure. However, it is gradually leaking air. It used to be slower but right now it is at a faster rate.

We try check it using soapy water but we didn't see any leaks(bubbly).

Is it possible that it leaks because we don't have the storage tanks?

[Matt Howard]

A leak is a leak, no matter how the system is plumbed. Check the Regulator, we've had one fail on us every season.

[Daniel_LaFleur]

Check both ports on the compressor. For the last few years the screw in there has not had any threadlocker/teflon tape and the casting has leaked a little.

[TubaMorg]

Without storage tanks, your 120psi volume is very small. With such a system even very small leaks will run you out of air fairly quickly. That being said, there is no reason why you shouldn't have a tight pneumatic system. Check everything that sees pressure. Not just the joints. The gages can leak, the relief valve can leak, the regulator can leak, the fittings can leak, the solenoids can leak. Systematically and throughly check one component at a time with soap bubbles, because you surely have a leak. While in the Navy, we had an apparent leak in one of our systems and it took me 7 months to track it down. Just because you haven't found it, doesn't mean it doesn't exist.

[AustinSchuh]

Also, make sure the ends of the pneumatic tube were cut square. I've caught a couple leaks because someone cut the end at an angle and it could not go into the fitting far enough to make a good seal.

[apalrd]

Are you being generous enough with the teflon tape at the thread sealings? We taped the crap out of our pneumatic system, and combined with checking for flat cuts, our simple pneumatic system with a compressor, 1 air tank, and 2 solenoids with 3 pistons (kicker clutch and shifters) can hold the tank above 100psi overnight.

[jspatz1]

No storage volume (tanks) is your primary problem. Without more volume, almost no system could hold full pressure for long even if well assembled. The smallest leak will cause pressure loss fairly quickly. If your robot can accomodate tanks, add them. They are a common component of a system for good reason.

[ttldomination]

You wanna check your tubing first. I would recommend using smoke over water.

If it continues to leak, I recommend having some fun with duct tape, which is legal this year.

[Kevin Sevcik]

Originally Posted by apalrd

Are you being generous enough with the teflon tape at the thread sealings? We taped the crap out of our pneumatic system, and combined with checking for flat cuts, our simple pneumatic system with a compressor, 1 air tank, and 2 solenoids with 3 pistons (kicker clutch and shifters) can hold the tank above 100psi overnight.

There's still the whole "Too much of a good thing" problem. It's conceivable to put so much teflon on a fitting that you can't even thread it. It also makes it harder to tighten up fittings and increases the risk of getting shreds of teflon in your system. Not to mention the nightmare of having to clean it off the fitting if you ever have to disassemble things.

We usually don't bother with more than 2-3 wraps of teflon on my team or at my company for these reasons. If you properly tighten the fittings, this is more than enough to get a good seal, and little enough to not cause you problems.

[jspatz1]

Too much tape can also cause problems with fragments getting into the air flow and reaching the solenoid valve spools, where they can jam spools and cause a failure. A couple of wraps is sufficient. Just assemble your system tightly and with care.

[apalrd]

by "tape the crap out of it" I mean "tape the crap out of it until there is plenty but not too much". We don't have more than 3 wraps on any one fitting.