ASME Section IV Tubesheet Ligament

If memory serves, tube pitch = 1.25 x tube diameter. This may have been TEMA (Tubular Exchanger Manufacturers' Association) rather than ASME. That would make the ligament thickness nominally 0.25 x tube diameter, minus a little if the holes are drilled oversize.

Nominally approx. 0.25 X tube diameter, but what is the minimum allowed? I have a tube sheet that the operator drilled the hole in the wrong place!

Thanks

Oh, well that's a different question. Was that you in the other thread about the misplaced tube hole?

If the tubes are rolled into place, a misplaced tube hole (thin ligament) can be a real problem, because the thin ligament is likely to distort as the tube is rolled into it. If the tubes are welded, this is less likely to be detrimental. There may also be some sort of flange/caulk method that is even less problematical, but I am not familiar enough to know just what you can get by with.

Even with a thin ligament, there may be some rolling sequence tricks that can compensate, but this is skating on thin ice.

(In remote areas we used to get away with all sorts of shit, but this does not constitute a recommendation....)

Thanks,

Is there a way to determine what is an (code) acceptable ligament distance?

See ASME IV, Para. HG-346 Tubesheets with Firetubes Used as Stays.

• HG-346.1 Required Thickness, Maximum Pitch, and Design Pressure.

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Also, see the following paragraphs:

• HG-346.2 Maximum Pitch of Firetubes Used as Stays.

• HG-350 Ligaments

Abdel Halim Galala

GA,

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