Photo Gallery C3:  ERW Seamed Pipe

Up until about 25 years ago, ASTM A53 seamless pipe was the only material recommended or specified for any HVAC system.  This was due to the greater vulnerability of the weld seam through either incomplete welding, issues with the filler material, or its lifetime greater susceptibility to various forms of corrosion.  Since then, lower cost ERW pipe has taken over the market, having first been accepted throughout the fire protection industry.

The higher incidence of failures at ERW weld seams clearly documents the problem to still exist, although from our experience, it seems more prevalent at foreign produced pipe.  One clear benefit of US produced steel pipe is its superior ERW weld quality, with other issues of undersized pipe and higher corrosion susceptibility remaining equal to foreign products.

The identification of  defective ERW weld seam is often made visually by measuring a straight line of pinhole failures, but can also be determined using ultrasonic testing.  An external cut or groove down the entire length of pipe is another reliable clue.  A defective groove, more common to find internally, is not visible once the pipe is assembled.  Although ASTM has strict specifications relating to ERW seamed pipe, and specifically to the fact that any visual cut or groove defect defines rejection, it seems often ignored.  In the examples below showing an obviously defective or incomplete ERW groove, that defect was ignored by the manufacturer, the plant inspector, the supplier, the contractor, the fitters, the field inspectors, and everyone coming in contact with it.  Only years later was the defect revealed as a result of its premature failure.

This form of pipe failure  may be isolated to one or a few examples, or system wide – thereby making a reliable fitness for service or threat assessment difficult.  Often, the problem will be associated with pipe of only one size, or from only one manufacturer.