Here’s something interesting. I don’t think the photo is showing the product off very well but the idea is interesting.
http://epoxymoron.tumblr.com/post/3203319974/day-25-feb-5-2011-gemstones-in-plastic-tubing
I came across this online today. It’s pretty cool… looks like a fun little project.
I guess I’m a sucker for a good marble machine video. It’s a nice use of 200′ of plastic tubing.
I don’t have any experience with PEX tubing but this looks like a great project.
Radiant Heat Floor Video
Most of the time, when we’re talking about pressure, we’re talking about positive pressure inside the tube. Most commonly, it is measured in “Pounds per Square Inch” or PSI.
Generally speaking, the softer the tube, the lower that tube’s pressure rating. Another way to look at it is that the higher your pressure requirement, the less flexible your tubing can be. In my world, we deal a lot with a very soft and flexible 70A durometer polyurethane. It has really low pressure ratings. One of our standard 70A tubes has a working pressure at 75 degrees Fahrenheit of just 50 PSI. On the other end of the spectrum, we work with a high pressure formulation of Nylon 11. That tubing can go up to 800 PSI.
As mentioned in a previous post, pressure and temperature are related. All thermoplastic tubing will lose ability to handle pressure, as the temperature increases above 75 degrees.
Most of the points made in this post so far have referred to positive pressure. Tubing is also used in vacuum installations with negative pressure. Because vacuum situations vary so much, you will definitely want to get a sample and test it. Again in general terms, you can’t expect a tube’s positive pressure rating to equate to a negative pressure rating. In other words, a tube that is rated to handle 150 PSI of positive pressure would probably not be able to handle 150 PSI of negative pressure. Thicker walls are needed to improve a tube’s ability to work with negative pressure. Tubing with ribs or some other form of reinforcement may also be required.
This article is part of a series related to the S.T.A.M.P.E.D. article posted on 11/11/2010.
Arguably, the most important factor when selecting your tubing is what’s going to be in it. It will likely be in the closest, most continuous contact with the tubing material, for the longest period of time. How the tubing and the media react to each other is critical to the success of your plastic tubing.
Every thermoplastic has a range of chemicals and gasses that it excels in handling or does not handle well (or at all). The example that I like to use is, how can super glue – that will bond anything – not bond up the tube that is holding it? Or the old question, what makes Teflon(R) stick to the pan? The answer is that the plastic and the media are working in sync.
The starting point for determining what plastic to use is a chart showing chemical resistance of various plastics. There are entire research volumes devoted to the subject but using one of the readily available charts is the easy first step. There are many available online but the one I use is here: Chemical Resistance Chart.
I can’t over-emphasize the point that this is just where to start. Even those thick research volumes are only just so helpful. The best research is done by you. Even if you’re just going to run water through the tubing, get a sample and test it. Most manufacturers are happy to send you several feet of tubing to run a test. Make sure that your unique circumstance will work with the particular plastic that you’re considering for your project.
This article is part of a series related to the S.T.A.M.P.E.D. article posted on 11/11/2010.
One of the most interesting things about my job is seeing all of the uses people have found for plastic tubing. I’m sure all of the manufacturers have similar stories, but we’ve had our tubing used in movies, rockets, robots, and mops. It’s been used as handles for shopping bags, frames for crab pots and in art sculptures.
How you are going to use your tubing is a pretty important factor in deciding which tubing will work for you. One common issue we see is that people need it to flex and then spring back to its original shape. Another thing we see frequently are applications where the tubing is moving and rubbing against other tubing. If it’s too tacky, the tubes will get hung up on each other.
Color might be important to the application. You may want the tubing to color coordinate with your machine. On the other hand, you may have lots of tubing bundled for a long run. In that case you may want to color code your lines so it’s easier to connect your tubing.
Another consideration is if a single tube is what you want. Maybe you’d like several tubes bonded together. Maybe you are using short lengths of tubing and would like the manufacturer to cut it for you.
The point is that there are lots of ways that you might be using plastic tubing. It’s important to look at the whole project and think about what features you need the tubing to have. With all of the resins available, the right feature mix probably exists.
This article is part of a series related to the S.T.A.M.P.E.D. article posted on 11/11/2010.
