GIRTH FLANGE DESIGN FOR TEMA HEAT EXCHANGERS 3

[VITALIS1977]

Dear all,
Could somebody assist me on my query concerning GIRTH FLANGE DESIGN for TEMA-R heat exchangers.?
I'm currently proceeding with ASME VIII div.1 calculations for a BEM type heat exchanger under TEMA-R, using a well known software.
In order calculate exchanger's girth flanges i'm prompted to provide flange geometrical data such as wall thickness, Flange I.D/O.D, Face I.D / O.D, hub length, thickness e.t.c.
How to I start placing values for these flange data?
For your information, I'am quite new in the area of heat exchanger design, so please treat my query accordingly.
Thank you in advance.

Elias

 

[MJCronin]

Have you contacted the vendor of your "well known software" and asked them about your data input ?

This inquiry is certainly covered by your purchase/continuing services agreements.

The software manuals, that came when you purchased the software, typically show a completed example.

Full body flanges for pressure vessels have been well handled by various software packages for decades now.

MJCronin
Sr. Process Engineer

 

[gr2vessels]

It's not all that dificcult, since you have some fixed data;-
- Shell ID = Flange ID
- Shell thickness = hub small end thickness, so you can now estimate a large end of hub.
- Now you can work out some dimensions to have an idea of bolting diameter and divide it by the minimum bolting distance, so you can estimate of number of bolts.
- from this basic data you can have a first cut of a flange geometry that can be filled in the program. You will be prompted during the evaluation of geometry the errors you can correct. The program will also calculate for you the minimum flange thickness for the geometry you corrected, so you can bring your pre-selected thickness to the program calculated minimum thickness (the most economical design).
This is one way to start learning the design of flanges, using the software to correct your errors. Then have it commented by an experienced designer who will point out the weakness of design, for your next practice design.
Cheers,
gr2vessels

 

[marty007]

One more note is to involve your sales team in the design process, particularly for the first few vessels you design.

Assuming you are designing to ASME VIII-1:
When designing a custom flange per Appendix 2, there will be many different solutions that will meet the code requirements. A common choice to be made is based on bolt/stud diameter:
[ol 1]
[li]You could use a large number of small diameter studs. This will allow you to reduce the bolt circle diameter, flange OD, and flange thickness. It will come at a cost however of more machining time and bolting time during assembly and hydrotesting. [/li]
[li]You could use a smaller number of large diameter studs. This will increase your bolt circle diameter, flange OD, and flange thickness. The blank material will cost more, but there may be savings in machining time and bolting time during assembly and hydrotesting.[/li]
[/ol]

This is the typical trade-off on flange design, and to determine which is the better design will likely require input from your sales team. They can put dollar amounts against the machining time and bolting time for assembly and hydrotesting. They can also obtain quotes for the raw materials. Only with all of the information in one place can you determine the most economical design.

Another point to consider are your customer's specifications. There may be limits on minimum/maximum bolt size for example.

Once you've gone through this design process a few times, you will start to gain a feel for which designs are most economical. It will depend on your location with respect to labor costs and material costs, so the best design is not the same for everyone.

Good luck.

 

[Duwe6]

"There may be limits on minimum/maximum bolt size for example." Yup.

Above 1-inch in diameter studs/bolts become increasingly hard to properly torque and have minimum torque values such that they cannot be hand-torqued without a multiplier. Try HARD to keep the stud sizes between 5/8" and 1-inch, with a preference for 3/4" and 7/8".

 

[AK23Static]

Girth flange design requires good judgement on bolt dia selection & spacing,

Bolt spacing should be enought for the maintenance point of view, but should not be more as would lead to leakages.

As pressure increases bolt spacing becomes less.

Use this for bolt spacing.

[highlight ]Bolt spacing = 2d + 6t / ( m+.5)[/highlight]

wherein

d- nominal bolt dia
m- gasket factor
t -girth flange thickness


cheers
AK
Beginning of every success is desire