Cast Iron Pipe - Dimensions and Wall thicknesses

[tjpengineer]

I have two samples of 14" nominal diameter cast iron pipe in plant water, underground service (per original plant drawings) that I have been asked to review for corrosion and remaining life. The UT wall thicknesses are in the 0.676" to 0.706" range. There does not appear to be any lining. Are there standard wall thicknesses vs. pressure class for CI? This is probably 40-50 years old. I cannot find anything or cast or gray iron pipe, only Ductile Iron. Any help would be appreciated!

 

[nickelkid]

You need to determine what code is applicable first.

General info:

- B31.3 allows a 2000 psi stress(S) in tension for grey iron A48-20

tm = minimum wall thickness
tm = (PD/(2*(SE+Py)))+ A

P = pressure
D = OD

For CI
E = 1
y = 0

A = .14 for CI pipe (0.18 for pit-cast)

 

[tjpengineer]

I just need a schedule of typical wall thickness to compare to my measured thicknesses for now. I suspect it was designed to AWWA. I may have to use B31.1 however to estimate min. thickness for remaining life.

 

[rconner]

There have been a great many manufacturers of many different types of gray cast iron pipe over the years, but perhaps the historical information from ACIPCO's website at

http://www.acipco.com/adip/products/Sect12.pdf,

along with some more measurements and investigation if possible (what is the measured outside diameter of the pipe, joint system etc.?) would help narrow this down. I think applicable USA standards for CIP 40-50 years ago included ANSI A21.1 (for thickness design) as well as A21.6 and A21.8 (for some different types of centrifugal casting manufacture, iron strengths etc.) From only your UT thickness measurements, however, it is possible this piping is even older (to older standards and/or lesser pit-cast iron strengths, as shown on the ACIPCO site).

 

[ApC2Kp]

tjpengineer,

You might be trying to get thickness data for "standard" cast iron pipe that probably was used 50 years ago. The best guess of the original pipe dimensions would be from manufacturers catalogs of that era, as suggested by post from rconner. There are a number of possible product dimensions. The other approach of calculating the required wall thickness also depends on the strength of the existing cast iron material - the ASME B31.1 or B31.3 codes might not be a fair tool for the calculation. The AWWA design tables might be better (if the old tables for cast irons could be obtained). The wall thickness of 0.67" on Nps-14 would seem to be substantial for most of the general and fire water water services to 200 psi.
A caution about using UT for measuring cast iron pipe wall thickness. The gauge block used for calibration of the UT transducer must be the same material as the pipe.
The UT beam has transmission characteristics for steel, vs ductile irons vs. cast irons. The elastic modulus is different for the cast iron vs ductile iron vs steel, so it could be appreciated that the UT beam time of flight is different for each. A physical measurement point such as the hub end of bell - spigot pipe joint might be used for calibration check of the UT measurement. Beware that the fittings material could be to a different grade cast iron vs pipe centrifugal cast vs pit cast iron pipe barrels.

 

[JohnBreen]

tjpengineer

If you work with this Material you should have a copy of the Ductile Iron Pipe Research Association (DIPRA) Handbook of Ductile Iron Pipe. Regarding standards:

http://www.dipra.com/standards/

Regards, John