The Complete Guide to Welding Tube to Tubesheet

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The application of heat transfer is one of the fundamental concepts in power and energy engineering. Thus, the construction of heat exchangers, condensers, or boilers has always focused on improving the heat transfer mechanism in a typical power generation plant.

The industrial heat exchanger will require excellent assembly of tubes and sheet metals within the shell,  so they do not deform and fail under extreme heat and pressure conditions. During fabrication, an effective way to enhance efficiency is through a detailed understanding of the prevalent welding form involved — tube to tubesheet welding.

Welding Tube to Tubesheets

The process of tube to tubesheet welding involves creating a joint between well-prepared tubes and tubesheet to fix them in place. The tubes function to transfer the heat between fluids involved in the process of heating or cooling. But the temperature within the heat exchanger can go as high as 1000° C, and at such a high temperature, the weld can often lose its strength and toughness, leading to premature failure of the system. The complexity of fabricating this weld further exacerbates the challenge. The most common issues in tube to tubesheet welding include –

  • Multiple tubes placed within close proximity
  • Difficulty in gaining complete access to the joints
  • Heat input control for thin tubes
  • Ensuring welders’ safety while welding stainless steel tubes and tubesheets

The following standards have been established to help manufacturers gain an edge against these issues of welding.

 

Standard Coverage
ASME BPVC Section VIII Mandatory design, fabrication, installation, and inspection specifications for the vessel.
API Standard 660 Recommendation for material selection, preparation, fabrication, and testing of the shell-and tube-type heat exchanger.
Tubular Exchanger Manufacturers Association (TEMA) Specification for selection of tube to tubesheet joint type and tubesheet thickness.
AWS D18 Standard for sanitary welding of tubes and vessels

 

Only through the combination of the right welding process, ideal weld preparation, and quality welding equipment, the resulting weld will have the uniformity and precision desired for high-quality tube to tubesheet welding.

 

The Different Mechanisms of Welding Tube to Tubesheet

A successful tube to tubesheet welding will involve accurate adherence to the weld preparation technique, recognition of ideal joint preparation, and welding techniques. Depending on the application, there can be the following joint types –

  1. Protruding tubes – the tube protrudes slightly through the sheets
  2. Recessed tubes – the tube is slightly recessed below the tubesheet thickness
  3. Flush tubes – flush welding tubes to tubesheet

It is important to note that welding these joint types will require a mandatory cleaning and edge preparation (V-groove, J-groove, or no groove). The thickness of the tubesheet should be based on the type of heat exchanger being fabricated — i.e., floating head or u-tube heat exchanger. The thickness should always include a minimum allowance for corrosive conditions.

Once the tubes and tubesheet are set in place, usually, welders opt for TIG (tungsten Inert Gas) welding for the fusion process. TIG further offers the following options —

  1. Heterogeneous – use of filler material that is different from the base metals
  2. Homogeneous – filler material and base metals are the same
  3. Autogenous – no filler material

The TIG welding can be done manually or using orbital solutions. Orbital welding is the preferred choice as it minimizes concerns regarding quality and joint accessibility, which is still a concern with the manual process.

Orbital welding with specialized weld heads can optimize the heat input, voltage, gas flow, and weld head movement, which are crucial parameters for the precision welding of tubes and tubesheets. The automated process and compact weld heads can easily access each tube to tubesheet connection to ensure uniformity and reliability of weld.

Resources

Here are some of the AMI resources you can refer to for related information on tube to tubesheet welding and heat exchanger fabrication.

Quality Solutions For Welding Tube to Tubesheets

Since its inception, AMI has focused on providing solutions for a wide range of welding needs. For your tube to tubesheet welding needs, AMI offers the following solutions –

These weld heads and the integrated system can weld in any position and access any connections to ensure quality welding of every single joint. Furthermore, using a compatible power supply and remote monitoring system with this automated process is sure to improve the precision and quality of welding tube to tubesheets.

Model 96 tube to tubesheet weld head from AMI

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Arc Machines, Inc. has been a leading provider of orbital welding solutions– including specialized weld heads, power supplies, and monitoring systems that are ideal for welding tube to tubesheet. For inquiries regarding these and other products, contact sales@arcmachines.com. For service inquiries, contact service@arcmachines.com. Arc Machines welcomes the opportunity to discuss your specific needs. Contact us to arrange a meeting.