explosion cladding

[Graja84]

Hello everyone, I'm would like to heare your opiniona about stainless steel tubesheet cladded with titanium by explosion according to ASME sec. VIII div. 1. Do you think it is posible to use requirements of paragraph UW-20.7(a)(1) and (2) and after perform this shear test and UT examination weld tube (titanium) to tubesheet (from cladded side) as a partial or full-strenght?
ASTM have specification B898 but as I'm assume its not allowed by ASME so far.

 

[EdStainless]

Explosively clad tubesheets are common. I don't recall the ASME rules, but I know that they are used.
So you need SS shell side and Ti tube side, correct? Does that mean that the shell and tube supports are also SS?
Are you sure that you have the Ti thick enough for the tube-to-tubesheet welds (usually just seal welds with clad tubesheets)?

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P.E. Metallurgy, consulting work welcomed

 

[SnTMan]

Graja84, I'm a little unsure of your exact question but offer the following. Keep in mind I am reading from the 2017 Ed, you should confirmn per the 2019 Ed.

UW-20.7 allows welded tube-tubesheet joints in integral clad construction to be considered as strength welded, full or partial, if testing of the cladding per UW-20.7 (a)(1) and (a)(2) is performed. The weld itself is classified (full strength, partial, or seal) per the rules in UW-20. The welds themselves do not seem to require any particular testing per UW-20.

The (a)(1), (a)(2) testing typically is done by the clad vendor, but could be done I suppose by the vessel manufacturer.

I am not familiar with B898, but unless there is an SB version it is likely not adopted by ASME. Clad tubesheets including Ti are common construction in Sec VIII, Div 1 heat exchangers however, this should not present an obstruction.

Ti clad on an SS tubesheet is unusual in my experience, although Ti clad on CS is pretty common. As far as I know, explosion bond is the only way to bond Ti to any dissimilar metal. You are going to want the clad to be at least 3/8 inch thick, 1/2 inch if you have pass groove in the cladding.

Depending on the difference in yield strengths between the tube and TS, rolled joints may be useless.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

 

[weldstan]

Normally NDE of titanium tube to tube sheet welds are PT examined. UT of these welds would be pointless. And normally these TI welds would be considered seal welds; however, they could be made and tested to meet strength weld requirements.

 

[Graja84]

Thank you all for your replies.

EdStainless - you are correc it is SS shell side and Ti tube side. Thickness of cladd is not a problem for me I just wonder to try use partial or full-strenght or just expand tubes and make a seal weld.

SnTMan -of course you right this test will be order from cladded plate (tubesheet) manufacturer. Yes as I reads some articles explosion bonding is best way to bond Ti with others materials. Thank you for your suggestion.

weldstan - Tube to tubesheet yes they are exam by PT but I'm talking about examination of cladd quality by making UT (straight beam) to check if there is any discontinuity between cladd and base metal

 

[r6155]

Graja84
Can you tell us diameter and thickness of tubesheet?

Regards

 

[EdStainless]

The clad producers have procedures for UT inspection. Talk to them. They will do various levels of inspection depending on what you want to pay for (number of test locations and sensitivity of test).
Since the Ti tubes are likely Gr2 they should be about the same strength as the tubesheet so rolled joints with seal welds should work fine.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[weldstan]

Cladding bond integrity can readily be confirmed by UT. As Ed stated above, the manufacturer of the explosive bond can easily do this for you. I have always included such testing in our purchasing specifications.

 

[Graja84]

r6155 - This is still in designe stage so hard to tell,

EdStainless - also think it should work fine

weldstan - yes probably I will also include this requirement in order.