Steel and Ductile iron Flanges !!

[sowhatso]

Can we weld a ductile iron flange or cast iron flange with steel pipe , and can we weld a steel flange with dutile iron pipe , to be more specifically :

Can we weld :

1. ANSI/AWWA C110/A21.10 Ductile iron flange with Steel pipe

2. ANSI B16.1 Cast iron raised face Class 250 , Class A Flange with welded steel pipe .

3. ANSI B16.5 RF Steel Class 300 flange with ductle iron pipe.

Thanks in advance for your help.

 

[MJCronin]

Who is going to take the first shot at this..???

-MJC

 

[metengr]

Can we weld :

1. ANSI/AWWA C110/A21.10 Ductile iron flange with Steel pipe

Yes

2. ANSI B16.1 Cast iron raised face Class 250 , Class A Flange with welded steel pipe .

I would not recommend it.

3. ANSI B16.5 RF Steel Class 300 flange with ductle iron pipe.

Yes

 

[ApC2Kp]

sowhatso,

There are fabricators that do welding of steel or ductile iron to the ductile iron pipe barrels for waterworks and gas piping applications,

http://www.napf.org

The ASME B31.1 Power piping and B31.3 Process piping codes do not allow welding of ductile iron. Their typical piping applications are higher temperature and pressures. The ductile iron welding might be more like brazing with a result of a less corrosion resistant joint. The mechanical strength of a welded ductile iron joint might also need to be evaluated.

The welding procedure for steel + ductile iron would be much different than common pre-qualified carbon steel weld procedure. There are a few cast iron weld procedures for repair of large cast iron machine components, but these usually require pre-heat of entire cast iron part to near red hot temperature to minimize cooling cracks of CI welds.

 

[JohnGP]

I think I might lose sleep over a steel Class 300 flange welded to ductile iron pipe. But maybe I'm just a nervous person. Perhaps if I knew more about the actual application I could be reassured (but I don't need to know).

John

 

[metengr]

The ASME B31.1 Power piping and B31.3 Process piping codes do not allow welding of ductile iron. Their typical piping applications are higher temperature and pressures.

Not entirely correct as written. ASME B31.1 only excludes this for boiler external piping. Otherwise, for use in water and non-toxic systems, material and welding is permitted. See 124.5 for Ductile iron and 124.4 for Cast Gray Iron limits.

 

[sowhatso]

Thanks for all your comments .

The actual application for the flanges is for a water transmission pipe line , the line is from ductile iron pipe. the line is reted for 350psi ,restrained push-on joints , for the connection between the ductile pipe and the piping inside the valves chambers we will use flange spigot spools, the standard flanges for the ductile pipe is ANSI/AWWA C110 / A21.10 whish is rated for 250 psi .The contrcator is proposing to use special type of ring gaskets to increase the presure rate for the flanged joints from 250 psi to 350 psi.we had a discussion to replace the type of flange to weld a flanges of higher pressure rate instead of using special type of gaskets .

This is why I asked this question !!!

I just need to know , if anyone of you has ever used special type of gaskets to increase the pressure rate of the flanged joints ???

 

[MJCronin]

so what...

Isn't it possible to configure the piping system so that the material changes (DI to CS)only at flanged joints ?

No dissimilar welding would be required ...

Wouldn't this be a better solution ??

 

[rconner]

AWWA standards require ductile iron flanged piping to either be threaded onto pipe ends (as prescribed by ANSI/AWWA C115/A21.15 standard), or of course also allowable to be integrally cast (in the case of fittings e.g. per AWWA C110 or C153 standards etc).
International standards, e.g. ISO 2531 and EN 545, allow also other fabrication options, e.g. by welding or backing/slip-on configurations along with thread-fabrication etc. While I suspect manufacturers can provide perhaps varied good-quality ductile iron fabrications capable of very high-pressure testing and service, the following is offered most in the context of AWWA thread-fabricated or integrally-cast ductile iron configurations with ductile iron flanges, of which I am most familiar.
I know at least some ductile iron manufacturers have considerable very high-pressure and other testing and experience, illustrating in general that good quality AWWA thread-fabricated pipes and joints have substantial capabilities beyond minimum standard ratings and requirements (and particularly when furnished with “specially designed gaskets” as now mentioned in the appendices of many ANSI/AWWA standards, including e.g. ANSI/AWWA C111/A21.11). Some of this sort of non-advertised strength perhaps comes from the circumstance that AWWA ductile iron flange thicknesses in many cases were initially established with much weaker and lower moduli gray cast iron piping material, and they are now routinely furnished by many manufacturers with only the much stronger, higher moduli, and tougher ductile iron flanges but to the same dimensions.
“Specially designed” gaskets are generally something quite beyond common highly-filled flat, sheet rubber gaskets. An example of such a gasket is molded American “Toruseal” e.g., as depicted on page 8-3 at

http://www.acipco.com/adip/products/Sect8.pdf

. Such gaskets, along with reasonable cost and maybe some increased security vs some imperfect support or cleaning/boilting etc. of piping, also are known to tolerate some more slight cupping or deformation of flanges and piping systems (that arguably might be more pronounced in some cases with e.g. “long-span” or very high-pressure application.)
While I am aware that some pipelines e.g. of 12” (~300mm) or smaller ductile iron piping involving some ductile iron flanged joints have been field tested at even more than 850 psi (58+bars), and even in sizes up to say 48” (~1200mm) at more than 435 psi (30+ bars), it may also be possible to join with or insert even higher-pressure rated welded or forged steel flanged piping items in otherwise ductile iron piping systems (though of course with other types of joints and components shown capable of handling such pressures).

In any case, with pressures higher than standard ratings I believe one should consult closely with the manufacturer(s) involved, as in some cases such applications might require special examination of all components involved in the pipeline, and also might be facilitated with special manufacturing, testing, or control etc. of some items. A chain is of course only as strong as its weakest link.

 

[sowhatso]

rconer ,

Thanks alot.