Double groove expanded tube to tubesheet joint

[piaengr]

The company I work for builds many shell and tube heat exchangers to ASME Section VIII Div 1. Typically they are low pressure low temperature exchangers (15psi/250 deg F). Almost always, we use double groove expanded tube-to-tubesheet joints. The grooves in the tube hole are typically located off center towards the tubeside face of the tubesheet. Does it matter where the grooves are located within the tube hole? From what I can find, TEMA does not specify. Is there anything wrong with placing the grooves on center or near the shellside face? My thought is that is really doesn't matter, but I am curious of what others typically see and if there is any logic to the groove location.

 

[vpl]

piaengr

May I suggest you try posting this in forum391 ? You might get a response there.

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[piaengr]

Thank you Patricia for the recommendation. I was considering posting in another forum. I will try the one you suggest.

 

[jehan17718]

The grooves are always on machined within the tubesheet face which is closer on the channel face and NOT the shell face of the tubesheet. Details of these grooves are typically given in company/ client standards.

U may need to post this question in the boiler and pressure vessel forum and not this forum.

-jehan

 

[gr2vessels]

It is incorrect statement that the grooves are always machined closer to the tubeside face of the tubesheet. TEMA and other codes do not specify a preferred location (side of the tubesheet) of the grooves because that is related rather to corrosion issues or tube expansion in the groove located in CRA cladding, etc.., not to the joint strenght.
Please also refer to the replies posted in the Exchangers forum to piaengr, to the same question.
gr2vessels

 

[jehan17718]

gr2vessels,

In my experience as a pressure vessel engineer I have never come cross any tube to tubesheet joint detail or a standard where the annular grooves are closer to the shell face of the tubesheet. you are however correct to state that many standards and codes do not comment on this detail.

-jehan

 

[gr2vessels]

Quite common to have a groove cut in the S/S cladding on the shell side face of the tubesheet, where the shell side corrosive environment has to be prevented of penetrating between the tube and tubehole cut in the tubesheet. You might even have one groove at each of opposite ends of the tubehole in corrosive service. To mention one typical case, Titanium tubes in a tubesheet cladded with Titanium on the shell side, have to be protected agains aggressive crevice corrosion by having an expansion groove in the Titanium cladding, since welding of the tubes could be impossible.
Howzat?
cheers,
gr2vessels

 

[piaengr]

Thank you to all of you for the input. I did re-post in another forum as suggested by vpl. Sorry for not coming back to this forum sooner. But again, thank you for the input.

 

[Christine74]

"Quite common to have a groove cut in the S/S cladding on the shell side face of the tubesheet, where the shell side corrosive environment has to be prevented of penetrating between the tube and tubehole cut in the tubesheet."

Note that TEMA requires both grooves to be in the base metal unless specified otherwise by the purchaser. See RCB-7.44.

-Christine

 

[gr2vessels]

Noted. The TEMA writers knew that the mentioned Clause won't last, so they opened two small doors named "should" and "unless"...so grooves may be cut in the Titanium cladding.
cheers,
gr2vessels

 

[jehan17718]

gr2vessels:

It was indeed an eye opener to me to know of cladding being on the SHELL side and grooves closer to shell side face of tubesheet as I have not come across such a detail. i would appreciate if you could post the sketch of such a type of tube to tubesheet joint

regards,

jehan

 

[gr2vessels]

Hi Jehan,
A whole documentation is near you, for a S&T exchanger (sea water cooler), Ti tubes and Ti cladded tubesheet, ask Deepak for this exchanger documentation in the 2006 Shell project. You could also refer to your own reply in the thread330-208578 dated 01.02.2008 in the Metal and Metallurgy engineering forum. Also, Google words like "tubesheet cladding groove" and you'll be surprised how many hits will pop-up (and prop-up the groove cut in the cladding). The principle is to cut the groove as close as possible to the source of corrosive environment, to prevent the penetration of the fluid between the hole and the tube, in case that the seal weld of tube to the CRA clad is not possible or is not practical.
cheers,
gr2vessels

 

[unclesyd]

We have many vertical orientated SS heat exchangers so the prevention of corrosion and or SCC at the top tubesheet is of paramount design.

I have an older Airtool brochure that shows two grooves and makes no reference to location or codes


Here are our design conditions.

Use 3 groves if physically possible with 2 grooves the minimum.
The grooves will be located as close to the shellside face as possible. As noted above this is to mitigate crevice corrosion problems associated with SS.
All tube holes shall be reamed to size.
All tube ends will be polished prior to assembly of the heat exchanger.
Roll beyond the shellside face using parallel rollers.
All tubes will be seal welded after rolling.
All tubesheets will have 4 vents.

This holds true for all other exchangers except the vents.

On the Ti clad sheets the grooves are in the SS again as close to the shellside face as possible.

 

[roca]

Jehan
You are getting confused
By Sheelside they are talking about the face of the tubesheet where the tubes start and is in contact with the tubeside fluid - not the back side of the tubesheet which is in contact with the shellside fluid

 

[jehan17718]

gr2vessels

From your reply dated 20 May 08 21:48 hrs, do i know you? pl reply.

Roca- if the other folks impy "shell side" as the face of the tubesheet where the tubes start/end (thereby meaning the face of the tubesheet wetted by the channel side fluid)then you are correct to say that I did get confused regarding the terms used in this discussion.

In my experience, I have always encountered grovves / cladding in the region closer to this face of the tubesheet but never in the region closer to the tubesheet face which is "wetted" by the shell side fluid. In case of cladded tubesheets the detail we typically follow is having 2 grooves in the base metal and one groove in the cladding (the cladding being applied on the face of the tubesheet which is wetted by the channel side fluid).

Hope our understanding matches now. pL correct me in case I am till wrong.

regards,

jehan

 

[piaengr]

To clarify my original post, when I used the term tubeside face I am referring to the face of the tubesheet that is wetted by the tube side fluid. The term shellside face refers to the face of the tubesheet that is wetted by the shell side fluid. This is typical terminology for me and those that I work with but from the sounds of it may not be the same for everyone.

 

[roca]

jehan

BINGO...!

 

[roca]

unclesyd
why do you have 4 vents in each tube sheet?
if it is a clad tubesheet please provide a detail
or is it a double tubesheet with a gap between the two to check for leaks?

 

[unclesyd]

In vertical exchangers it is vertically impossible to keep any surface above the top nozzle completely wet. As the majority of exchangers are counter-current coolers this area stays hot and tends to dry out and concentrate all the bad stuff on the tubesheet and the upper section of the tubes and the sheel if SS. Historically our biggest problem was SCC as we mainly use Austenitic SS tubes and sheets. Lately we have had to add MIC to the problem and the prevention of deposits has added an extra dimension.

The 4 vents are located on the compass points and are drilled to just outside the outer line of tubes. By keeping these open while running we are able to prevent the concentration of chlorides and formation of bug condominiums.

On the Ti clad SS tube sheets we have the vents to protect the SS clad base as the life of Ti tubes is more than 10 times that of the SS it replaced.

On the Ti clad tubesheets all groves are in the SS as close to shellside face as possible.