Malleable Iron Rupture Pressure?

[yamoffathoo]

I'm looking for empirical data on rupture pressure for malleable iron fittings manufactured to ASME B16.3 to provide a basis for a Safety Margin argument.

The only other data I have is five 1"nps threaded elbows that were all exposed to 2500 psig air and did not leak!

 

[unclesyd]

This would not be unusual for a smaller fitting to see these pressures if Class 300 or AARl fittings. We I work for the 8 bump (Stockham} )valve and fittings company we proof tested Class 150 to from 300 PSi to 600 psg The Class 300 to from 900 psig to 2500 psig. The AARL fittings would easily go to 3500

Look at the technical and cad data tab.

http://www.anvilintl.com/ProductSearch/ProductInfo.aspx?ProductId=9992

 

[yamoffathoo]

Unclesyd,

Did you do any destructive tests? I am looking for empirical data on rupture pressure, thanks.

 

[moltenmetal]

My experience with testing these to failure is limited and only at room temperature, but in those cases it was impossible to keep ahead of the leakage with our little hydrotest pump to get the pressure high enough to make them fail.

 

[unclesyd]

A long, long time ago I witnessed and performed these tests at Stockham valve and Fittings. I looked a my journal from thet time and I don't have any numbers for the tests. I don't recall any actual burst pressure but all were very high compared to the Class rating max allowable pressure. There was no concern unless a there was a failure below 3 times and below 2 times on the larger fittings. There were some scatter due the fittings being a casting and coming from 3 production lines. The malleabilising process can play a big roll in the achievable bursting pressure, but in our case it virtually eliminated by using a continous furnace versus a batch type.

One way you can verify that the fittings are OK is test one to 1.5 times your working pressure or to the max allowable by standards. This not 100% but will point out any damage caused by the pressure excursion. You also might check the dimensions normal to the pipe axis as these fittings will yield.
Depending on your size and Class you can use the tables in the catalogue as you can rest assure that fittings are being tested to at least 1.5 times the max allowable.

In the last several years I've sen some pretty bad fitting from offshore. They were shot on Galvanizing and would bend on itself without breaking. along with extremely poor threads.

 

[metengr]

You might want to check with various companies that make their own fittings to ASME B16.3. The reason I mention this is that they must either show by calculation or by burst testing their design is suitable for the pressure/temperature Class.

 

[blacksmith37]

And, one reason actual tests give high results is that ;for small low pressure fittings (and valve bodies) ,the mfgr uses the same mold pattern as a higher pressure part to reduce inventory/ mold patterns.