Photo Gallery C1: Undersized New Steel Pipe
Most professionals associated with the design and construction of any building or piping system has likely assumed that the pipe wall thickness specified for different products equals what is defined by ASTM. An ASTM, UL or FM stamp at a section of 12 in. schedule 40 pipe ready for installation means that the pipe wall is as defined by the stamp at 0.406 in. Right?
Well not really. Just like the incredible shrinking bag of potato chips, crackers, or cereal box, pipe manufacturers seem to have followed a similar path.
It begins with the fact that pipe can be produced +/- 12.5 % of its ASTM defined wall thickness and still be termed acceptable for sale and installation; a 25% tolerance which was appropriate in the early 1900’s when the code was first written and steel pipe manufacturing was in its infancy, but not today over 100 years later. Clearly American pipe manufacturing has improved in the past 100+ years!
Prior to three or more decades ago, almost all pipe was manufactured at or above true ASTM specifications, and in fact it is not unusual to still document pipe at older at well maintained buildings still exceeding new pipe specifications after 65 or more years of service. Today that trend has changed 180 degrees, with most new pipe now produced at or near its minimum allowable wall thickness, or 12.5% below ASTM specifications. And while such undersized pipe is still acceptable for sale and installation according to the ASTM code, we have well documented examples of new steel pipe exceeding 15%.
This trend seems to have begun 20 or more years ago with foreign pipe competitors seeking an edge; American manufactures quickly following their lead given the highly competitive and quite unfair world pipe market. Any steel pipe installed since 2000, therefore, should be suspect.
For this reason, we have documented in our UT investigations supposedly the same 8 in. ASTM schedule 40 steel pipe added to a hot water heating system 8 years ago having a far lower wall thickness than 8 in. schedule 40 pipe from the original system installed in the 1960s. One hundred or more such examples documented in our formal UT investigations have excluded any possibility of their being entirely random events. And although fairly limited, other engineering professionals have discovered the same issue.
The following examples document the wall thickness of new pipe not yet installed. For 12 in. schedule 40 pipe, its beginning wall thickness is not likely to be the 0.406 in. stamped on its side, but closer to 0.355 in. – ironically less than the specification for thinner 0.375 in. standard pipe. New pipe with a wall thickness even lower than 12.5% below ASTM has been documented; with similar results for Type K copper pipe actually below Type L and closer to thinwall Type M specifications.
Many of our below photographs, taken at pipe not yet installed, show both the wall thickness as measured by ultrasound, against the actual ASTM, UL, or FM stamp indicating its specified wall thickness. In contrast to common belief, stamped wall thickness dimensions only indicate what the pipe wall should be according to ASTM, as opposed to its true manufactured dimension. Although we have suggested the need to return to this early 1900s specifications in order to tighten up the 25% tolerance, there has been zero interest.
This issue is not only prevalent for steel pipe, but has been documented in our investigations of new galvanized steel, copper, cast iron, and ductile iron piping. As we have used as a headline in one of our Technical Bulletins available on this Internet site, “A Simple Dial Caliper May Reveal Surprising Results.”
