pneumatic tubing swelling

[Batterink]

http://imgur.com/MLbRg18

We have this piece of tubing going from the compressor to a T-fitting. We noticed last night that it had swollen and had it replaced. The new one has now swollen. Our system isn't going above 115 psi, so I don't think the pressure is an issue.

Does anyone have any ideas, or experience with a similar problem?

[notmattlythgoe]

Originally Posted by Batterink

http://imgur.com/MLbRg18

We have this piece of tubing going from the compressor to a T-fitting. We noticed last night that it had swollen and had it replaced. The new one has now swollen. Our system isn't going above 115 psi, so I don't think the pressure is an issue.

Does anyone have any ideas, or experience with a similar problem?

Could the compressor be getting hot and melting the tubing?

[Batterink]

Originally Posted by notmattlythgoe

Could the compressor be getting hot and melting the tubing?

I suppose. If the tubing is touching the compressor anywhere it would be on the opposite side of where the heatsink is. I didn't think that part of the compressor got very hot, but I could be wrong.

[notmattlythgoe]

Originally Posted by Batterink

I suppose. If the tubing is touching the compressor anywhere it would be on the opposite side of where the heatsink is. I didn't think that part of the compressor got very hot, but I could be wrong.

We used a computer fan to blow air across our compressor last year and it kept it nice and cool all season. Before this it was getting extremely hot.

[Chris_Ely]

Originally Posted by Batterink

I suppose. If the tubing is touching the compressor anywhere it would be on the opposite side of where the heatsink is. I didn't think that part of the compressor got very hot, but I could be wrong.

Is this tubing being connected directly to the compressor output?
If so, I would recommend adding some metal fittings before the plastic tubing to dissipate heat from the hot air coming out of the compressor. Placing one of the large fans from the KoP next to the compressor will also help.

[MrForbes]

I'll confirm the suggestion to add a fan, blowing across the compressor, to solve this problem. The duty cycle of the compressor is only 9%, which means you need to let it cool for eleven times as long as you run it. This time of year, we typically are working on the robot, and testing stuff...running it for five minutes at a time is typical, and doing this will over heat the compressor, unless you add active cooling. It doesn't take much to keep it cool, one of those square fans at least 100mm across should do it.

[notmattlythgoe]

Originally Posted by MrForbes

I'll confirm the suggestion to add a fan, blowing across the compressor, to solve this problem. The duty cycle of the compressor is only 9%, which means you need to let it cool for eleven times as long as you run it. This time of year, we typically are working on the robot, and testing stuff...running it for five minutes at a time is typical, and doing this will over heat the compressor, unless you add active cooling. It doesn't take much to keep it cool, one of those square fans at least 100mm across should do it.

I was amazed last year at how cool the fan kept it, especially with how hot it was getting prior to adding it. I don't think the compressor ever got hotter than warm to the touch.

[pribusin]

Not only does the compressor get hot from the friction of the piston but the Ideal Gas Law states that increasing the pressure of a gas increases its temperature. The compressed air from the compressor is actually hotter than ambient. If you run it for a long time it would be conceivable that the tube gets heated by the compressed air to a point where it can no longer withstand its designed working pressure and you see the bubbling that you showed.

A short metal pipe attached to the compressor would help to dissipate this heat.

Or let your system coll a bit in between runs.

EDIT: looks like John beat me to it

[Batterink]

There are a few metal fitting before the tubing is attached. We'll see about mounting a fan to cool it this evening.

Thanks everyone.

[MrForbes]

Originally Posted by Batterink

We'll see about mounting a fan to cool it this evening.

Thanks everyone.

You're welcome!

You don't need to attach the fan to the compressor itself. It would be better to mount the fan next to, or over, the compressor so it blows air across the compressor head (the part with cooling fins on it). You can mount the fan several inches away, and it will still work well to keep it cool.

[RonnieS]

Originally Posted by notmattlythgoe

I was amazed last year at how cool the fan kept it, especially with how hot it was getting prior to adding it. I don't think the compressor ever got hotter than warm to the touch.

Would you mind PM me a picture of how you attacked the fan to the compressor? We are just using zip ties at the moment. The fan keeps the compressor WAY cooler but worried about the zip ties possibly being melted.
-Ronnie

[cgmv123]

Originally Posted by Ronnie314

We are just using zip ties at the moment. The fan keeps the compressor WAY cooler but worried about the zip ties possibly being melted.

I would not be concerned about the zip ties melting. A quick Google search shows that most zip ties are made out of Nylon 6-6, which has a melting point of ~500° F. Even if the fan somehow fails, I don't think the compressor will get anywhere near that hot.

[RonnieS]

Originally Posted by cgmv123

I would not be concerned about the zip ties melting. A quick Google search shows that most zip ties are made out of Nylon 6-6, which has a melting point of ~500° F. Even if the fan somehow fails, I don't think the compressor will get anywhere near that hot.

Lets hope not right? lol. Thank you, will stick with simplicity and stay with the zip ties.
-Ronnie

[notmattlythgoe]

Originally Posted by Ronnie314

Would you mind PM me a picture of how you attacked the fan to the compressor? We are just using zip ties at the moment. The fan keeps the compressor WAY cooler but worried about the zip ties possibly being melted.
-Ronnie

Here is a picture of how we mounted the fan last year.

https://drive.google.com/file/d/0B6s...ew?usp=sharing

[MrForbes]

One of our students brought in a COTS computer fan, with a built in mounting bracket, it seems to work ok. We don't have a lot of pneumatics on our robot this year, so it won't be running the compressor often.