Flanges for Heat Exchanger 1

[Oscarvs]

I have a problem to specify the appropiate material of flanges of a heat exchanger, this is a old equipment and only a section required replace, this section will be formed by a rolled plate (ASTM A-516 Gr 70) with a flange in each end. The original drawings of equipment are not available, only a detail drawing of flanged joints is available. First, we think use flanges according to ASTM A105 (26 in. diameter) but the dimensions on detail drawing are not similar to flange standard (dimension ANSI B16.47)
One supplier propose us fabricate flanges for steel casting with similar composition to ASTM A105.
Other supplier propose us fabricate flanges upon ASTM A216 WCB steel casting and then to forge according to ASTM A105.
I think that fabrication is the correct choice, because the dimensions required are not standard, but... How do I request these flanges?.

 

[Simdro]

Oscarvs,

I should supply us more information about your heat exchanger in order to clearly defined the situation.

Your flanges caould be made by ASTM A105 or ASTM A-350 LF2 thinking that the rolled material was made by ASTM A-516 Gr.70. You should take into account design data and fluid composition.

Anyway if the mating flanges are not standard you will purchase a custon flanges, which might be coupled with the existing one, specifying all necessary technical data to the selected mill supplier.

SD

 

[rneill]

It would not be uncommon for the original heat exchanger manufacturer to have designed their own flanges in accordance with the code rules for flange design. Obviously, since you are replacing a portion of the existing vessel, you will need to match the original dimensions and based on your information this will involve a custom flange.

I would expect that you would need to have the final flange design verified and that you might need a code stamp on the replacement part(s). This is something you might want to investigate.

Regarding the flange materials, I have only ever seen either ASME SA105, SA105N, or SA350 LF2 (Class 1 or Class 2) forged flange materials used with 516-70 shells. The choice would be dependent on service conditions (e.g., H2S, temperature, pressure rating).

 

[gr2vessels]

Oscarvs,
Are you an experienced pressure vessel design engineer to tackle this sensitive job? As you can see from replies, you are being reminded of the principles of designing flanges, taking in account many factors for material selection and even the applicable code selection.
If not, you should hire a professional designer to perform the design calculation for the replaced section.
Cheers,
gr2vessels

 

[SnTMan]

Oscarvs, you may be able to find your flange pattern in this OLD catalog:

http://www.hackneyladish.com/Catalog.aspx

See the section on "Large OD and TEMA Flanges"

Regards,

Mike

 

[ijzer]

SA-105 is used for piping planges. For girth flanges on e.g. heat exchangers SA-266 is the material you want

 

[rneill]

Yup, the SA105 & SA350 specs does indicate it is piping forgings and the SA266 spec does indicate it is vessel forgings but I've still only ever seen SA105 and SA350 forgings for vessel flanges (including body flanges)?

 

[Oscarvs]

Thanks Sirs,

I'm not pressure vessel engineer design, I work for a construction company, a client sent us a detail drawing for this job, my problem is... how request bids to flange suppliers?, obviously they need data about material, dimensions and ratings standards.
The reply of SnTMan and their reference to TEMA is new to me.
I think for the required flanges, dimensions should be according TEMA and material according to ASTM A105 forged and rolled steel.
Does it correct?

 

[rneill]

I really hate to say it Oscarvs but it does sound like this project is probably pushing you beyond your level of expertise. There is more to this than just fabricating the parts and I would strongly recommend you subcontract out to a vessel designer to prepare a full design for you which you can then have fabricated. A full design would involve preparing dimensional drawings, specifying all the the materials to be used, specifying the welds, completing the design calculations to ensure that the parts complied with the appropriate code rules, and specifying the QA/QC requirements.

Also, you should investigate the regulatory requirements in your location. In many locations, you would only be permitted to fabricate pressure vessel parts if you held a Certificate of Authorization from ASME and could Code Stamp the vessel and/or parts. In addition, fabrication may need to be inspected by an "Authorized Inspector".

I am aware of one situation where an end user provided drawings for two old heat exchangers and asked a fabricator to build "replacements in kind". The fabricator was not particularly knowledgeable on the ASME Code rules and by the time the vessels were finished, there were serious enough problems that the vessels did not meet the Code requirements and they were not accepted by the regulatory authority. I don't think the fabricator was ever paid for their work since the vessels could not be used.

ASME is the American Society of Mechanical Engineers and they publish a general pressure vessel code called Section VIII Division I which can be used for designing and building any pressure vessel including heat exchangers. Only very recently have they included specific rules for designing and building heat exchangers.

TEMA is the Tubular Exchanger Manufacturers Association and they have published rules relating to the specific design of heat exchangers for many years. Before ASME included specific rules for heat exchangers, the TEMA rules were used. Even now, the TEMA rules are often used instead of the ASME rules.

 

[SnTMan]

I would add to rneill's post tht TEMA covers a number of features that are not addessed by Code, such as baffle clearance, hole dimensions and tolerances and so forth that are applicable to S&T exchangers.

Regards,

Mike