Compressor gets hot and blows line

[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, then the line coming out of the compressor blows out. The line and compressor are very hot when this happens. Any ideas?

[Nirvash]

How much air storage to do have? And does the compressor have a fan on it? The VIAIR really needs one if it is going to be running for any extended period of time.

[IndySam]

Compressors create heat when they compress air. In normal usage the heat is dissipated and doesn't cause a problem. If however the compressor is on for a long period of time, like in practice, there can be enough heat generated to soften the hose and create failure.

In good practice to connect the pressure relief valve and pressure switch directly to the compressor with brass fittings. This helps isolate the hose from the heat. The more metal between the hose and the compressor the better.

[JamesCH95]

How many tanks, of what size, are you trying to fill?

Originally Posted by IndySam

Compressors create heat when they compress air. In normal usage the heat is dissipated and doesn't cause a problem. If however the compressor is on for a long period of time, like in practice, there can be enough heat generated to soften the hose and create failure.

In good practice to connect the pressure relief valve and pressure switch directly to the compressor with brass fittings. This helps isolate the hose from the heat. The more metal between the hose and the compressor the better.

To that end, note the compressor in the lower left-hand corner of the robot: coupler, tee to relief valve, couple, tee to pressure switch, couple, tee to pressure gauge, then the quick-disconnect to a hose.

We also added the medium-sized muffin fan from the KOP blowing across the compressor and fittings, which helps a lot.

[Jarren Harkema]

We found that this happens as well. Mounting a 12V server fan pointed right at it keeps it as cool as a cucumber... or at least one that has been sitting on the counter. We had to run without the fan last night, and remembered just how hot it got.

[FrankJ]

Originally Posted by IndySam

In good practice to connect the pressure relief valve and pressure switch directly to the compressor with brass fittings. This helps isolate the hose from the heat. The more metal between the hose and the compressor the better.

Not only is it good practice, but the relief valve is required to be teed to the compressor with a metal fitting by rule.

[Al Skierkiewicz]

Does the tubing pull out of the compressor or does the line fail by producing a bubble and then blow out at the soft spot?
If it produces the bubble then the compressor is likely running continuous for several minutes (~10 or longer). It sounds like the high pressure relief valve is not calibrated. This is supplied uncalibrated and needs to be adjusted by the team to release at 125 psi. A compressor that runs for an extended period will blow out the line. It does this by heating the tubing to a temperature where it fails under pressure. To calibrate, loosen the locking ring on the valve, it is the lower hex hardware on the valve. Then power the robot and enable, short the pressure switch which should run the compressor continuously. With an accurate pressure gauge on the high pressure side, watch for the pressure to rise to 125 psi and listen and feel for air escaping the top of the valve. If it does not, turn the top counter clockwise until air is vented from the valve. If air is released at a lower pressure, then turn the top clockwise until 125 psi is reached when it vents. Tighten the locking ring without letting the top of the valve rotate. Remove the short across the pressure switch and see if the compressor shuts off when the pressure reaches ~120 psi.

If it simply pulls out of the fitting, one of two things are occurring. Your gauge is not accurate and you are exceeding 150 psi and failing at the fitting. Or the fitting could be bad and not securing the tubing. Once inserted you should not be able to pull out the tubing without pressing the release ring first.

[Mark McLeod]

Originally Posted by matthewdenny

... the pressure builds in our high pressure tanks, gets to 65 psi, holds there for ~20 seconds ...

That sounds like your main regulator is not plumbed correctly.
On the regulator there is an arrow on one of the ports. The high pressure tubing must go into the port that is at the tail end of the arrow, and only that port. The other three ports are kept at working pressure ~60psi.

[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]

We are pressurizing 3 of the 41in^3 tanks.

The setup

VI Compressor-->Tanks (with pressure switch, and pressure gauge installed on the tanks -->Regulator (60 psi) ----Splits to two paths

Path A: ---> 30 psi regulator -->solenoids
Path B: ----> Solenoids

[matthewdenny]

Let me check the regulators, and get back to you.

[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.

[Kyler Hagler]

Like many have said, we always use lots of brass fittings at the beginning of the line from the compressor and put the required fittings on there as well, this helps because the brass dissipates the heat before it reaches the tubing.

[Nate Laverdure]

Reverse the polarity to the compressor?

Originally Posted by Al Skierkiewicz

The compressor runs in either direction. It is more efficient in the proper direction so the opposite polarity gets it a little hotter than normal.

Originally Posted by Don Rotolo

Temporarily disconnect the compressor and use a voltmeter for testing. reverse polarity may make the compressor supremely unhappy.