Compressor gets hot and blows line

[Joe Ross]

Originally Posted by matthewdenny

So when we enable the robot the compressor kicks on, the pressure builds in our high pressure tanks, gets to 65 psi, holds there for ~20 seconds,

You're missing a few important pieces of information. How long is the compressor on when it's building pressure in your high pressure tanks? What gets to 65PSI, low pressure gauge or high pressure gauge? How much air storage do you have on the high pressure side?

I suspect you've mis-plumbed something or have a leak somewhere, causing the compressor to be on much longer then expected.

[Al Skierkiewicz]

Mark I think has the solution. I did not consider the regulator in backward. It is designed to vent to atmosphere any excess pressure on the output port.

[matthewdenny]

Originally Posted by Joe Ross

You're missing a few important pieces of information. How long is the compressor on when it's building pressure in your high pressure tanks? What gets to 65PSI, low pressure gauge or high pressure gauge? How much air storage do you have on the high pressure side?

I suspect you've mis-plumbed something or have a leak somewhere, causing the compressor to be on much longer then expected.

The high pressure side gets to 65 psi.

The compressor is on a minute or so, and gets to 65 psi, stays there, and half a min later or so blows the line.

~120 in^3 of air stored on te high side. No tanks after the main regulator.

[matthewdenny]

It turns out that the main regulator was tuned backwards. I'd like to blame the freshman that put it in, but I may have told him to so it that way in reflection. Chalk it up to last minute oversight.

[matthewdenny]

Al, I don't think I have posted in the lab view forum. We did have a java issue with motors recently that was resolved by calibrating the talons.

[Chris Fultz]

you might want to have fewer things cantilevered off of the compressor exit port. The material on the compressor is cast, and can crack at the seam of the casting. It looks like you have several heavy components attached.

We usually just have the fitting out of the compressor, the relief valve, and then a tube connector and everything else is mounted to a mounting board.

[PAR_WIG1350]

Originally Posted by Chris Fultz

you might want to have fewer things cantilevered off of the compressor exit port. The material on the compressor is cast, and can crack at the seam of the casting. It looks like you have several heavy components attached.

We usually just have the fitting out of the compressor, the relief valve, and then a tube connector and everything else is mounted to a mounting board.

Alternatively, you could pass the fittings through panels to support them.

[Al Skierkiewicz]

Matthew,
So everything is OK now? When the line blew after only a minute, had the compressor been running for a long time before that? I am asking because one minute is much less than I would consider for the output temp to be so high. For all teams, this little compressor has a duty cycle spec. It really only expects to be run for a short time with a long off time in between so that it can cool down.

[JamesCH95]

Originally Posted by Chris Fultz

you might want to have fewer things cantilevered off of the compressor exit port. The material on the compressor is cast, and can crack at the seam of the casting. It looks like you have several heavy components attached.

We usually just have the fitting out of the compressor, the relief valve, and then a tube connector and everything else is mounted to a mounting board.

While I do not disagree with you in principle, in practice we have run several robots like this without any failures.

[cbale2000]

We had a similar problem to this one with our 2011 robot where the tubing would overheat and fail. We found this only occurred during demos following that competition season (it never actually happened at a competition), but nonetheless it got to be quite annoying to have to put a new piece of tubing on every few minutes.

Eventually we mounted one of the kit computer fans so it blew across the compressor, and the change in temperature was drastic.

We did tests and generated a chart based on the results:
https://docs.google.com/spreadsheet/ccc?key=0AqQx991m_YKGdEc3OV9NbG10YmluNjM2UFRhYV9Gb lE&usp=sharing


Long story short, if you can use a fan to cool your compressor, do it.

[MechEng83]

We had an interesting related failure last night while we were practicing for the upcoming CAGE Match off-season event.

The students were practicing a maneuver where the intake comes in and out, which means air was constantly being used for 15+ minutes. As I was shouting across the field for them to let the robot rest and have the compressor cool off, I hear a loud pop and the sound of uncapped compressor running. Turns out, the elbow fitting we use to come out of the t-fitting attached to the compressor failed, blowing off the ferrule assembly the tubing plugs into. The compressor was too hot to touch and I suspect the plastic on the 90 degree elbow got warm enough that the metal bit was able to slip past its molded grip.

It was a good reminder for my students why safety glasses are important while working near the robot, and that the Viair compressors shouldn't be run continuously. Because of space constraints, we can't really put a fan on the compressor the way it's mounted right now, but it's definitely something the students will remember next year (if we have pneumatics)

[notmattlythgoe]

Originally Posted by MechEng83

We had an interesting related failure last night while we were practicing for the upcoming CAGE Match off-season event.

The students were practicing a maneuver where the intake comes in and out, which means air was constantly being used for 15+ minutes. As I was shouting across the field for them to let the robot rest and have the compressor cool off, I hear a loud pop and the sound of uncapped compressor running. Turns out, the elbow fitting we use to come out of the t-fitting attached to the compressor failed, blowing off the ferrule assembly the tubing plugs into. The compressor was too hot to touch and I suspect the plastic on the 90 degree elbow got warm enough that the metal bit was able to slip past its molded grip.

It was a good reminder for my students why safety glasses are important while working near the robot, and that the Viair compressors shouldn't be run continuously. Because of space constraints, we can't really put a fan on the compressor the way it's mounted right now, but it's definitely something the students will remember next year (if we have pneumatics)

We found that even air blowing across the compressor works wonders. Almost everything on our robot this year was run by pneumatics so our compressor did a lot of work. Even after running through several batteries from practicing our compressor never got hot to the touch.