Do you know the difference with minimum and average wall tubing?

Accuracy can be very important when you are dealing with metal tubing. It all depends on the final application. As with most things when it comes to engineering, there are some projects when a few millimetres can be the difference between success and ruin. So, you must make sure you choose accurately sized tubes. Any processing should also be accurate with a tight tolerance. We appreciate the latter and make it our goal when we offer tube expansion and more.

Wall thickness variations

Tube expansionOne of the most important things to look at is that the walls of tubing can vary slightly. It can differ depending on the type and how it was made.

If it is a welded tube like ERW the variation is typically due to the fact that tubes begin life as coils or sheets. The thickness here can vary because of the manufacturing. In addition, the rolling to create the tube can have an impact too.

Accuracy is usually easier with seamless tubes. These begin as billets and there is then extrusion or piercing to create the tubular form. An initial method here was to drill a hole and then extrude, but it would often result in inaccuracy with one side of the tube wall being thicker. Modern extrusion is more accurate though.

Minimum vs average thickness

A crucial thing to look at here is whether you have minimum or average wall tubing. They differ in terms of how the tolerance on the thickness is applied. That can have a big impact on whether the tube will suit your needs.

Average wall tube has a plus or minus 10% tolerance. That means it can vary by that amount above or below the stated thickness. For example, if you have .083″ tubes, it could be as thin as .075″ or as thick as .091″.

Minimum wall tubing is a little different. It still has the same total tolerance with a potential max 20% variation. However, it does not allow 10% either way. Instead there will be a minimal thickness and then the wall can be up to 20% thicker. Taking the same .083″ tube as an example, it would mean the min is .083″ but the max is .100″.

The impact on expanders

As you can see, there is a potential big different here. With things like tube expansion, it can result in serious problems if you don’t know whether you have minimum or average wall tubes.

The thing to keep in mind is you need to insert an expander into the tube. The variation in wall thickness could mean the tool you choose won’t fit. Generally you won’t have as much trouble here if you have average wall tubes. You should be able to choose an expander that will be able to deal with the upper and lower limits. It should be able to still offer the right range of expansion.

However, it is a different story with minimum wall tube. You will likely find that a standard expander will not have the clearance for the upper size limit. As a result, it may not be able to enter the tube. It may therefore be necessary to choose a smaller expander to make it fit and offer the full expansion range.

Speak to us about tube expansion

Multiform Tubes Engineering Ltd is an expert at adapting tubing. We know the importance of accuracy, particularly when it comes to things like heat exchanges and pipe lines. A tiny difference could have a big impact on the thermal transfer or allow leaks. We do our best to keep the tolerance as tight as possible to avoid issues like this.

So, if you need tube expansion, reduction, bending, or even drilling, you should choose us. Get in touch today and learn more about what we can do.