Difference Between Cast and Ductile Iron?

6/25/2018

What is the difference between cast iron and ductile iron fittings? Is there a preference between the two for use in sprinkler or clean agent system fittings?

Note: This is a Daily Discussion question submitted anonymously to us by a toolkit member.

4 Comments

JOE link

6/26/2018 09:25:38 am

My understanding is that domestic-only sourced fittings will use cast or malleable iron as ductile iron fittings are only produced internationally. I believe malleable iron can be galvanized, but both cast and malleable iron fittings are typically more expensive than ductile iron. We most often see ductile iron fittings for smaller diameter, threaded pipe.

Bill Shipman

6/26/2018 10:06:51 am

My understanding is that Cast Iron is brittle and can be easily broken. Ductile however is virtually unbreakable. In fire sprinklers interior piping we can use either. However, over tightening a C.I. fitting will cause it to crack, Over tightening a ductile fitting will cause it to stretch.

Pari

6/27/2018 11:53:15 am

NFPA 13 Table 6.4.1 does not mention ductil iron pipe but cast iron pipe class 125 and 250

Dave L.

6/29/2018 10:15:58 am

Note that section 4.2 of NFPA #2001 Clean Agent Fire Extinguishing Systems states (along with other important restriction & requirements for pipe and fittings) that cast-iron and class 150 fittings shall not be used.

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Difference Between Cast and Ductile Iron?

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