150# Malleable Iron

Snowmelt

I am going ask a few questions one at a time first question is what steel do we use for steam boils
cast iron or malleable, also I seen 2 different ratings 150 & 300 #?

dko

You can use either, but preferences vary.

clammy

Cast is for steam 150 basically for low pressure steam unless specified and 300 for high pressure . Some use mailable for steam being it’s some times all that some supply house carry but the purest stick to cast except maybe unions which are mailable unless your going for steam union flanges which is great for larger pipe sizes and repairs in situation where things can’t be spread like steam main repairs .
Never stupid questions just stupid people guessing instead of asking . Nobody knows it all
Peace and good luck clammy

STEAM DOCTOR

On low pressure steam, only real benefit of cast iron, is ability to remove fittings, by whacking with a hammer. Fitting will crack. In 2023, with all of the various cutting tools and blades at our disposal, this rational is somewhat obsolete. Black malleable fittings are easily cut and removed, day in and day out. 

EBEBRATT-Ed

For low pressure steam you can use Cast Iron fitting which are rated at 125lb steam or Malleable iron which is rated at 150psi.

Either one is fine. Malleable is a little easier to work with and since steam is in decline some supply houses don't carry CI or there may be limited quantities.

You can also mix and match with no issues other than the way the fittings look if that bothers you.

Some fittings are only made in malleable iron like unions and caps and couplings. and some fittings like eccentric reducing couplings are only made in Cast iron. Most bushings are CI although steel is used in smaller sizes.

No need for 250#CI or 300# malleable on low pressure steam. just a waste of money.

Snowmelt

Thanks guys you all cleared that up for me….

STEAM DOCTOR

Street fittings are all malleable, as far as I know.