CS overlayed with Titanium?

[Peter113]

Hi,
we have several heat exchangers with CS + Ti cladding on tubeside selected because the service is sea water (máximum operating temperature: 47ºC). The tube and the tubesheet shall be Ti and CS + Ti cladding (tubeside) respectively with a strength weld joint.

My question is:
1) Any references/experiences in the restauration of Ti cladding, i.e, weld overlay for the tubeside courses. Do you have any weld overlay welding procedure (Ti overlay with CS base material).
2) Any references/experiences with Ti lining for this particular application.

A prompt answer will be very appreciated

Thanks in advance
Peter

 

[unclesyd]

You can not weld Ti to Cs.
Can you give a little more information about your Hx construction.

The shellside of the tubesheet is Ti?

What is the tube layout and pitch?

You have a strength weld on the shellside?

Why do you need to repair the Ti side?

 

[Peter113]

thanks for your support,

herebelow you have the requested information:

MOC
Shell side: CS
Tube side: CS + Ti clad.
Tubesheet: CS + Ti clad (on tubeside)
Tubes: Ti

TEMA type: There are different designs (AEL, AJL, NEN, BJS, BEM, BJM, BES and HES.

Strength weld joint on tube side.

Tube pitch: 25.4 - Layout: 30

I mean with Ti restauration, the reposition of cladding (with weld overlay) on circunferentials and longitudinal weld courses.

regards

 

[moltenmetal]

I've seen explosion-bonded Ti clad tubesheets used. Welding between the tube and tubesheet is feasible but welding is done delicately to avoid iron contamination of the Ti tubesheet cladding.

Weld overlay cladding of Ti on CS is NOT possible.

Tubes are roller expanded into the CS tubesheet and then seal welded to the face of the cladding. Whether this is considered a "seal" weld or a "strength" weld depends on the thickness of your tubes I guess.

It's also possible to loose-clad a tubesheet with Ti, similar to what is done with tantalum etc.

 

[stanweld]

While you cannot overlay Ti on carbon steel, you may be able to patch the corroded area with thin Ti sheets. A repair method may be provided if you provide more detail of the repair locations; e.g., tubesheet, channel, adjacent to tube-to-tubesheet welds, etc.

 

[SnTMan]

Peter113, we have sucessfully used Ti tubes - Ti clad tubesheets for seawater and river water service. As others have said the TS is explosion bond clad. Welding the tube-TS joint should not be a problem.

Channel construction cannot be Ti clad / overlay for the reason mentioned above, i.e. you cannot weld Ti to CS or other common backer materials.

We have used CS channels with an interior coating of Plasticor or similar material, and with anodic protection. This is important as the CS material will preferentially corrode quickly if any flaws develop in the coating. We have used both passive and active anodic systems.

Another option is an alloy channel of a weldable material. AL-6XN is sometmes specified for these services, and my understanding is that it can be welded to CS. BTW, your N-type channels will be a potential problem in Ti-clad TS and CS channels, as you cannot really seal the crevice where the channel cylinder overlaps the TS. A gasketed A-type channel is a better design.

Your floating heads could be troublesome, although I suppose an interior coated CS design with passive anodes is possible, and again solid alloy is an option.

Hope you find this useful, sorry for the late reply, too much work lately.

Regards,

Mike