As with our previous post, we will be focusing on helping to ensure your exchanger has a long-lasting tube-to-tubesheet joint. Today we’re going to discuss properly setting your tubes, a key component to proper tube-end prep prior to welding.
What is Pre-Setting?
Pre-setting is a simple step that most shops use before welding their tube joints. The idea is to lock the tubes into place so they can be welded. Often, we see manufacturers using a mechanical roller to lightly “tack roll” the tubes in place and keep them from moving. Unfortunately, using mechanical rollers for setting tubes can actually cause some issues with both welding and the expansion process.
Common Issues
Over the years, we’ve found that when using a mechanical roller for pre-setting tubes, operators will typically use some sort of lubricant to keep the roller from overheating and wearing down too quickly, and to prevent it from galling the tube ID. Unfortunately, using a lubricant creates a need to thoroughly clean the surface of the tube face, tube ID, and tubesheet prior to welding, to prevent any weld contamination. This cleaning and related inspection can add significant time to the welding operation. Depending on the size of the exchanger, this can mean days of cleaning and inspection prior to welding.
For those shops using a soap or alcohol as a lube, the issue may not be weld contamination, but rather the fact that the roller creates a light seal at the tubesheet face. This seal will often cause blow-back during the joint welding process. Of course, you can ask any skilled welder and they will tell you that blow-back isn’t that big of an issue, as they can usually see this and rectify it during the weld process. However, this relies heavily on the experience and skill of the individual welder, and isn’t the case at all with automated welding systems that may lose arc or embed an air pocket behind the weld due to this. In either case, whether human or orbital welding is used, there is a need for additional inspection, verification, skill, and/or weld repairs caused by setting tubes with a roller.
The Solution
The solution to these issues is to use a proper tube setting system such as HydroPro’s WeldLock system. The WeldLock was developed specifically for locking tubes prior to welding, thus the name. By utilizing a segmented expansion ring, the tool creates contact between the tube and tubesheet at either 3 or 6 specific points. It does this while expanding the tube uniformly, centering it in the hole and creating gaps for weld gasses to escape between the tube and tubesheet. Plus, the tool doesn’t require any lubrication, so weld contamination isn’t an issue.
In centering the tube in the hole, the WeldLock creates an equal gap around the entire circumference of the tube. This helps to ensure a consistent and quality weld, regardless of the welding method used. On top of this, the WeldLock system consistently sets your tube protrusion by actuating off the tubesheet face.
Like all of HydroPro’s products, The WeldLock is also a customizable tool that can be adapted to your specific requirements. The tool can be used on enhanced tubes, in automation applications, and is currently utilized on production lines around the world. Click here to watch how RMA Poland is utilizing our WeldLock tooling in their fully automated heat exchanger production line.
Conclusion
By using the WeldLock tube setting system, you can ensure your tube-to-tubesheet joints are properly prepared for welding or final expansion, all while saving hours (or even days) on your heat exchanger project. To learn more about the WeldLock system or any of HydroPro’s other products, visit www.hpro.com/tubepro-weldlock. Of course, if you have any questions about your specific application you are always welcome to discuss your requirements with an expert at HydroPro by calling (573) 732-3318 or emailing engineering@hpro.com. HydroPro is dedicated to the success of your tube expansion operation and to offering solutions to extend the life of your exchangers.