Ductile iron pipe stress analysis

Dear Sir,

I have some doubt while doing pipe stress analysis with ductile iron. In ductile iron all joint are flanged joints (flange and pipe are castings). There is no seperate dimension for flange length.

IF there is seperate flange lengtn, then i can consider tha flange as regid, remaining r pipe. As well all dimensions r as per DIN std.

Kindle advice how to handle this analysis.

By
Venkat

The B31 rules were created for carbon steel welded pipe and standard welded fittings... you are analyzing something which the current SIF / flexibilty factors do not directly cover .

However ny experience has it that Flanged DI pipe has threaded flanges screwed onto the DI barrels so the SIF associated with a screw joint might give you an approximation for that joint.

Check the suppliers catalog for data.

To N. Venkat,
Ductile iron piping systems can be analyzed, however the analysis is not as straight forward as a carbon steel welded system, as John Luf does point out.
Your ductile iron pipe spools could have threaded flanges on the pipe barrels, or the flanges could be cast integral with the pipe, depending on the diameter or length limitations. Fittings will have integrally cast flanges. Dimensions are all different from carbon steel pipe and fittings. Pipe O.D./I.D. and fitting dimensions (radius and lengths) will be different with effects on flexibility. The pipe, if centrifugal cast, will have different properties than sand cast pipe or fittings. The DIN standard ductile iron piping would have some additional differences from ANSI ductile iron piping in dimensions and materials.
Most ductile iron piping systems are not operated near the material limits. The weight of flanged joints is probably the next most significant load after pipe and contents for designing adequate supports. I would recommend modeling a rigid element for the length of pair of flange thicknesses with weight of flanged joint including the bolts. If the pipe spool has threaded flanges, then add SIF for the spool flange connection.

Dear Mr. Richard Yee,

My case is centrifucally casted ductile iron pipe. Flange and pipe and casted. I don't have particularly flange thickness. I am having supplier catelog, they mentioned remainig all the details apart from thickness.

Shall i take ANSI slip on flange lenght as a element length? I have weight of flange and pipe per meter.

I consider if 1200mm pipe spools (300mm dia, as per DIN Std), first feed the data of flange (lentgh as per ANSI slip on flange and weight as per supplier catelog) and feed the spool length ( flange length subtracted fom total length) and again flange.

Kindly advice me whether my method is correct or not.

To N. Venkat,
Your approach for length dimensions and weight of flange is a reasonable approximation for ANSI ductile iron flanged piping. If the flanges are to be DIN pattern, then you might want to compare thickness and weight of DIN flange to ANSI flange and adjust according to ratios. Remember to include weight for bolts.
There is a ductile iron piping catalog from CLOW company available on-line:
www.clowwatersystems.com/clow_catalog.pdf
Much of content is for bell-spigot systems, but there is also data on flanged D.I. piping.
Page 15 Long Span flanged pipe
Page 52 Flanged fittings
Page 73 Flanged pipe
Page 83-85 Flanged piping

Looking at said PDF ductile iron pipe has a thread cut in its barrel and has a flanged screwed onto it... so add a node at the hub of a threaded flange give it a Sif for threads per whatever code is applicable and make the rest of the flange a weighted ridgid....