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Up Topic Welding Industry / Technical Discussions / Boiler tube bending standards
- - By mnelson (*) Date 03-16-2007 12:42
Looking for a standard for boiler tube bending that addresses tube ovality and minimum wall thickness at the bend.  A typical tube size would be 2" OD X .260 MWT.  Typical material grades are carbon steel, stainless steel and chrome/moly.
Parent - By G.S.Crisi (****) Date 03-16-2007 13:57
Just a guess. Have you tried ASME Code Section I?
Giovanni S. Crisi
Sao Paulo - Brazil
Parent - - By 803056 (*****) Date 03-16-2007 14:23
I believe the ASME codes use the terms intrados and extrados (spelling may be incorrect) for the inside bend diameter and the outside bend diameters and place limits on the wall thinning that is permitted.

Best regards - Al
Parent - - By CWI555 (*****) Date 03-16-2007 20:00
Those terms (intrados and extrados) are used in Section III and XI as I recall. I am not aware of a specific standard in section I. I'll post again if I find one.
Parent - By js55 (*****) Date 03-16-2007 20:14
There is a PFI (Ppe Fabrication In stitute) standard, I don't remember which one (ES-24 I believe), that deals with tube bending. In it there will be standards dealing with intrados thickening, extrados thinning, buckling, and minimum radii per wall thickness and diameter. I don't rmember if it deals with that small of diameter. ASMe has tradiationally left ttube bending standards up to PFI.
Parent - By CWI555 (*****) Date 03-16-2007 21:50
There is some information in section I under PG 19 page 9 "cold forming of austenitic material" other than that, there is nothing I can find.
Parent - By G.S.Crisi (****) Date 03-20-2007 19:20
According to the booklet "Boiler tubes facts", published by the Boiler Tube Company of America, the main boiler tubes standards are the following:
ASTM A-178: ER Welded Carbon Steel Boiler Tubes.
ASTM A-192: Sms Carbon Steel Boiler Tubes for High Pressure Service
ASTM A-213: Sms SS and Alloy Steel Boiler and Superheater tubes
ASTM A-249: Austenitic SS Boiler and Superheater Tubes.

According to these standards, boiler tubes are specified by the outside diameter and the minimum wall thickness. Of course, when you bend them, the wall thickness of the thinnest section (i.e., the convex side of the bend), must not be thinner than the specified minimum thickness. Therefore, you should select a wall thickness a little larger than the one you need, so it's able to take up this reduction in thickness.

As for ovality, the mentioned standards refer to ASTM A-450, which I didn't have time to read. 

Giovanni S. Crisi
Up Topic Welding Industry / Technical Discussions / Boiler tube bending standards

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