Cast iron fittings vs Malleable fittings

Bill Jirik,

Is it just me, but most of the pictures of installs posted here show the hydronic or steam piping being done with 150# malleable fittings rather then the traditional 125# cast iron fittings, is it cost, availability or ignorance that results in piping being done with maleables, personally with the cost of cast fittings, especially 5" and above, we have switched to more weld fitings for piping, however I still believe in screwed pipe for swing joints on large boiler headers. Any cooments?

Tony Conner_2

The Only...

...difference between cast iron & malleable iron is the MI has been heat treated to reduce the brittleness. That process also gives it a higher pressure rating. Comparing MI & CI, the corrosion resistance, metallurgy, and coefficient of expansion are identical.

The difference in the field is that you can hit a 125 CI fitting to break it for easy removal, and you can't do that with 150 MI. That's all.

EBEBRATT-Ed

Since most hydronic water systems are done in copper the oly place left for cast iron is steam as cast can't be used on gas. Since steam is slowly dieing off do to age less cast fittings are being sold the supply houses stock less of them so people buy malleable. The only downside is that they can't be broken apart.

ed

Long Beach Ed

My view...

Malleable has no place on a steam job. That's how I learned the trade and I curse the guy who put them on every job I can't get them off of...

Long Beach Ed

Brad White_9

Alternate view

I agree with the pros and cons presented. (No, not to sound like John Kerry: "I voted for Malleable Iron before I voted against it" )

The reasons for ease of breaking a fitting are clear. For specification purposes we use malleable. Too many times the CI has been over-torqued and nobody heard the "tink" of that last 1/8th turn. Pressure testing does not always reveal the crack, especially when it has never been heated... Malleable will take that extra snugging -within reason- without complaint. Especially where we prohibit "backing off fittings to fit".

This is not to say that the pipefitters are not careful, but we also often deal with the "lowest qualified bidder". The reality is, things sometimes get sloppy. Or the job site is noisy and the "crack heard round the world" is never detected.

As design-side engineers, we find the hassle of policing the work in the field to be not worth the effort to specify CI.

We are not unsympathetic to the needs of the pipefitter who has to make a modification. But a Sawzall and a wrench for an occasional modification is a small price to pay from our perspective.

Aside from the "smack it with a hammer" ease of disassembly and the possible minor cost premium, is there a reason NOT to use malleable?

My $0.02,

Brad

clammy

cast or mi

I would like to do all my steamers in cast but i always find it hard to get reducing tee and ells and the look of the mix cast and malable just kills me so i usually do them in malable and i have to agree on disammble doing ci is a breez but if ya use a porta band saw on the malable it ain't to hard either .Plus after it's cycled a few times and checked for leaks it sould be insulated so it's kinda hiding those malable fittings any way peace and good luck clammy

Tony Conner_2

The...

... residential market for steam is repair and replace, but there are loads of industrial steam installations. As soon as the safety valves lift at anything over 125 PSIG, the 125# CI stuff doesn't meet code. Even where it does meet the letter of the code, I rarely use 125# CI as I've seen water hammer break both flanges & fittings.

If you're a manufacturer or supply house, you'll make/stock what moves. And that won't likely be 125 or even 250 CI screwed fittings. You'll go with 150 & 300 MI, because industrial applications buy them.

Al Corelli

Boiler inspections in NYC will fail if malleble fittings are used. We left one on a return line and the inspector suggested that we change it or risk failure.

Some municipalities in Westchester County are also sticklers for this.
I like the CI fittings for steam jobs. Its the way my Dad and Grandfather did it. And NO, I don't put circulators on the return.

Brad White_17

Why is that?

Interesting, Al- about failing an instpecition, but I wonder what the rationale is? MI is tougher, I would think more shock resistant, should be as corrosion resistant. Am I missing something?

Unknown

Yeah , what are we missing ?

Did the inspector cite a specific code , or was this another " personal preference " code ? I can't understand why a steam boiler would fail inspection due to the use of malleable fittings . And is the availability of cast fittings over 2 inch as hit and miss for you as it is here on L.I. ? We stopped trying to locate any cast fittings , and we sleep just fine using malleable .

Christian Egli_2

Breaking things, no issue

I find the argument about breaking cast iron fittings nearly irrelevant because I can just as well hit on malleable iron. Hit twice, just the right smack, the fitting expands and comes loose with not much effort. Everything can be reused - if it's worth it.

My father always got a big kick out of disassembling things no one else could.

For the rest, I am way more annoyed by the tink problem Brad White described and by the esthetics problems that irritate Clammy so much.

Is there a corrosion difference issue with CI or MI? I know there are other more exotic cast irons that do not corrode at all.

It's interesting to note that Europeans use mostly bended and welded steel pipes in home heating, down to the 1/2 like size.

Unknown

You hit it Christian

The only issue I would say is relevant is the corrosion factor . Cast is much more meaty than its malleable counterpart . I wonder which pipe type is more corrosion resistent .

I've spun apart years old cast and malleable fittings - the ones that had Teflon on the threads spin much easier than without .

soot_seeker_2

Code

The old NYC code specified Cast Iron on steam work. As the City reserves the right to be more restrictive than the International code, they still require cast iron. Anything else will fail an inspection.

Yes, you have to find a real supply house or order the stuff in bulk. No Home Depot stuff if you want to file a NYC job.

soot_seeker_2

Code

The old NYC code specified Cast Iron on steam work. As the City reserves the right to be more restrictive than the International code, they continue to require cast iron.

Anything else will fail an inspection. They are concerned with corrosion resistance and wall thickness of cast iron.

Yes, you have to find a real supply house or order the stuff in bulk from Ward through a supplier. No Home Depot stuff if you want to file a NYC job. None of those Italian gas valves either. Instant failure.

Al Corelli

We get all our CI from Westchester Square Supply. My family has dealt with them for generations. They still have 3.5 inch stuff, including reducing tees and other oddball fittings. I was at Blackman in Flushing today. had to swap a V85 that had a forklift blde-sized hole in the front section under the burner door. Noticed it before it went downstairs. Had to drive from White Plains to Flushing to swap it out. Great way to spend the morning with two helpers sorting the truck and cleaning the basement. Gotta go back tomorrow to wire it.

I think Blackman has steam fittings. They should. They're a big outfit.

As for the inspectors and the code issue? I never ask them which part of the code. They seem to work off a cheat sheet, and are not willing to listen to an explanation. Plus, the latest ones do not seem to have a great knowledge of boilers in general at all.

Here in Westchester, Even the strictest inspectors will at least listen. Much less "seat of the pants" than NYC.

EBEBRATT-Ed

Used to be able to by "wrought Iron" steel pipe. It was supposed to be more corrosion resistant than regular steel pipe. Engineers used to spec. it for underground work. It was a little bit harder on the dies. You could tell the difference because it had a red stripe on the outside of the pipe.

Don't know for sure if it is still available.

ED

Brad White_17

Now known as

Ductile Iron. Still quite available especially for underground work. Lots of graphite, long grain structure, essentially the same as wrought iron. Oddly, ductile iron is fairly recent as a pipe material. Probably 50-60 years? Dan would know.

Tony Conner_2

Wrought Iron...

... and ductile iron pipe are different animals. Wrought iron pipe hasn't been made for 50 years or more. There were mills getting out of wrought iron production during WWI (not WWII) because they had a hard time selling it, as it cost about 30% more than steel pipe. I don't know of any ductile iron pipe that is rated for any kind of service like steam or compressed air.

Tony Conner_2

No Difference...

... in corrosion resistance between cast iron & malleable iron. Steel pipe will corrode and fail at the threads before the fittings will be affected.

Albert Huntermark

Code

I'm not from New York, nor have I seen any of their codes, however, when they where written the writers were probably worried that galvanized or even brass fittings may be "slipped" in. Myself, I like the looks of CI fittings and try to use them. But as the other Wallies have mentioned, sometimes you can only get the MI.

PukaHead

Cast Iron Fittings vs Malleable Fittings

In the State of Hawaii, unless a fitting or valves has a steam rated stamp on it you cannot use it for boiler works. Malleable and non malleable fittings are in itself a separate issue. Though it has been stated in this forum ( and not saying that it is wrong or right) that the corrosion qualities are similar. I have seen in buildings the non -malleable  fittings corrodes 3 times faster than non, for the same applications.