If you are planning to use steel tubing for a project, whether it is ERW tubes, LSAW, HSAW, or other options, you need to think carefully about longevity. There are a number of factors that have an impact on service life. One of the most important is cyclic loading. We want to have a closer look at it here.
What is it?
Many applications subject tubes to cyclic loading. Rather than continuous loading, this means they undergo cycles with varying levels of pressure, stress, and strain. The cycles can lead to fatigue and deformation (ratcheting), ultimately causing cracks, leaks, or even failure.
Because there is so much risk with certain applications, including oil and gas, water, nuclear, and chemical processing, it is vital to think about the impact of cyclic loading. Ideally you want materials that will provide a long service life and improve safety.
There are a couple of crucial things you need to think about when selecting tubing for applications. First is the number of cycles to failure. It should be as high as possible. Avoiding low-cycle fatigue is most important. It happens when there are high levels of stress and strain in relatively few cycles, creating a huge amount of plastic deformation and a higher chance of damage or complete failure.
Different types of tubing
A key thing is to look at different types of tube and their suitability for cyclic loading situations. There are cases when ERW tubes are ideal. However, in other situations it will be better to opt for LSAW or HSAW.
Starting with ERW, they are suitable for moderate cyclic loading. Critically, they will retain the fatigue performance here, reducing the risk of deformation, cracking, and other issues. One thing to note though is you need high quality welds. A smooth weld zone is essential. However, the fact that welds have relatively low penetration means they aren’t suitable for a number of high load applications.
In comparison, LSAW tubes are generally the best choice for high cycle situations. The crucial detail is the welds are incredibly tough and stable. Add in the longitudinal weld seam, and you have tubing that can resist higher pressure cyclic loading. The longer fatigue life is excellent for critical applications like oil and gas.
Finally, we have HSAW tubes. They are really interesting due to the helical (spiral) weld. It provides some notable benefits, including distributing stress more effectively. However, it also has drawbacks. Critically, it results in a longer weld seam. That means there is a higher chance of potential defects. It is essential to test the tube before using it for high cyclic loading applications.
Ask us about ERW tubes
Union Steel Tubes has been providing high quality ERW tube for a very long time. We have a wide selection, including various shapes and sizes, different wall thicknesses, and more. To add to that, we can cut it to any length and provide a choice of finishes too.
So, if you want ERW tubes, speak to us. We can advise you about choosing them for a variety of applications too, including those with cyclic loading.
