[Process Selection] Welding of titanium heat exchangers

It can be welded manually or automatically using machinery! The prerequisite is: pure argon gas protection must be used during welding, and the surface to be welded must be extremely clean! No pollutants of any kind!

How should the sealing weld between the final cylinder and tube sheet be protected? I would appreciate some guidance.

You’re referring to the last sealing joint, right? I remember that the tube sheet should normally be slightly smaller than the cylinder; there is a step on the side of the tube sheet, and the shell is welded directly to that step – ordinary TIG welding on the outside is sufficient. The crude method is to replace the argon in the shell side; this works well when the shell side is small. Pure titanium equipment is rare; it’s probably composite plates, right?

Any two more questions? Even if we follow the method you mentioned, what about oxidation if the back side isn’t protected during welding? 2 Both the tube sheet material and the shell side cylinder material are TA2; they are not composite plates. I have communicated with the client multiple times, but they insist on using pure titanium for everything.

1. If pure titanium is required, I’m not sure from what perspective this decision is made. From a corrosion resistance perspective, using pure titanium for the shell means that titanium will also be subject to significant corrosion – at least at a level of 1 or more. But then again, can typical titanium heat exchange tubes withstand such conditions? Should the heat exchange tubes be thickened? If thermal expansion is taken into account, I personally think using expansion joints is better than using pure titanium. Titanium is too expensive; maybe its price has dropped recently. 2. Make the tube sheet thicker, so that the welds at the junction between the shell and the tube sheet are as far away as possible from the inside of the shell; this way, the heat-affected area is in contact with minimal air. Additionally, options such as argon purging of the shell, creating a negative pressure, or some other method to remove oxygen from the shell can be considered. 3. I watched them weld the chimney on site; there was no clean workshop either – it was done outdoors, and it also had a blue-purple color. I have only worked on the tube side of TA1. I think it’s best to avoid using titanium for the shell side from a chemical engineering perspective; welding isn’t an issue, but detection is difficult, and it becomes even more complicated in similar cases

Thank you. Originally, the shell side of this equipment was supposed to be made of 304L material, while the tube sheet was to use composite material – which would have been sufficient. But now the customer insists that everything be replaced with pure titanium. Also, I’m not quite sure about what you said regarding making the tube sheet thicker so that the welds at the junction between the shell and the tube sheet are as far away as possible from the shell’s flash area. Could you explain that again? If possible, it would be best to send a simple diagram. I’m still very grateful to you.

I’m currently in quarantine at home; all my documents are at the office. I’ve handled similar tasks before, so it should be fine to work with them for now

Perhaps it is to prevent the tube-side medium from leaking into the shell side through the tube joints; I think using a double tube sheet would be better than pure titanium

Thank you! The tube sheet of our equipment also serves as a flange, and for the connection between the tube sheet and the cylinder, only butt or fillet joints can be used.