Malleable Iron fittings ASTM A197 vs Forge Carbon Steel ASTM 105 1

[NCENG78]

Currently my plant uses interchangeably malleable iron and forged CS fittings. I was wondering if someone could help explain the advantages and disadvantages of both. Why would you use one over the other when the pipe is ASTM 106 or ASTM A53 Grade B.

 

[moltenmetal]

Didn't I reply to this? Perhaps I screwed up and mis-posted to someone else's thread?!

150# MI SCREWED fittings per B16.3 are often used with plain or galvanized steel pipe of the two grades mentioned. Pressure ratings are limited to 300 psig at ambient to 150# at steam saturation conditions (177 C) which is their maximum allowable temperature.

Typical services include water, low pressure natural gas distribution, air, low pressure nitrogen, (very) low pressure steam/condensate etc.

300# MI screwed fittings have ratings which depend on size and temperature and are much higher than the 150# fittings- but lower than those of A105 forged 3000# fittings. They're rare in the local area here and are easily mistaken for the stronger 3000# fittings. We don't use them as a consequence.

Neither can be welded- screwed connections only.

Beyond 2" therefore we tend to use Victaulic in these services (except steam/condensate), rather than the more expensive option of butt-welded steel fittings.

 

[vpl]

actually molten, I think the OP posted his question in two different forums. So you probably answered it over there.

Patricia Lougheed

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[NCENG78]

Sorry I couldn't find my post. I usually post in Chem Eng and somehow end up in Mech Eng. Thanks for all your help