Photo Gallery A5:  Grooved Pipe Failures

While we have found the various types of clamped pipe fittings used in HVAC and fire protection applications to provide many decades of outstanding and very reliable service, failures, when they do occur, have the potential to be utterly catastrophic.  Their basic design, while offering speed and cost savings, also introduce certain inherent vulnerabilities to corrosion.

As for all piping systems, the threat is relative to the level of corrosion activity.  High corrosion activity, and especially MIC, typically focuses at the gap between pipe ends; often reaching the groove itself.  A resulting small leak at the groove, if left to continue, then produces a two front corrosion attack at its most vulnerable connection point.  Least of concern is a gasket related leak, which may require re-torquing of the bolts or a gasket and clamp replacement.  Where the groove is cut rather than rolled, substantial wall loss occurs similar to threading pipe.  Any error in rolling or cutting the groove, whereby the depth at one side is deeper and the opposite side more shallow, can produce an additional threat due to reduced clamping strength.  The common installation of carbon steel clamps at galvanized steel or copper piping systems adds one further galvanic impact to such systems.

While full separation failures at clamped piping systems are rare, the result is typically catastrophic when they do occur.  Such failures at fully open 8 in. or 12 in. pipe sections rather than a pinhole leak will quickly dump the entire contents of that line, and likely the entire piping system, to all below floors.  For one past client where one of the four clamp retaining bolts to a 24 in. main condenser water system failed under 315 psi of pressure – the entire 39 floors of water, approximately 25,000 gallons, emptied into the basement refrigeration plant.  Unfortunately, the immense volume of damage caused well exceeded any initial cost savings.

For another, moderate corrosion activity finally reached the previously unknown cut-groove of a 12 in. condenser water supply line at the roof cooling tower after 3 decades, causing its total separation.  Occurring on a hot Sunday morning at 2 AM when most such catastrophes seem to schedule themselves, air conditioning quickly shut down.