The following are some of the failure analyses conducted by Stephen C. Grigory, P.E.

Plastic Gas Main Blowout

This failure is still in litagation.  A blowout occurred when a fitting was being fused to a live gas main resulting in injury and damage.  SGA recently completed a failure analysis for the defendant.

Ten-inch Diameter Rubber Elbow Failure

A large rubber elbow in a plant air conditioning system failed  flooding the basement of the plant.  The humidity rose to unacceptable levels causing production to shut down for several days.  While there were manufacturing flaws in the part that failed, that were produced during lay up, it was shown that a properly installed new elbow would not carry the maximum rated pressure listed in manufacturers literature.

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Bucket Truck Boom Failure - Investigated the failure of the boom on a bucket truck with a 90-foot lift that resulted in the death of two employees. A fiberglass-to-steel joint in the boom failed allowing the bucket to swing down against the side of the truck with two  men secured with saftey belts.  Our investigation reveled that while simple stress analysis would show the joint to be structurally sound, failure to consider assembly tolerances produced a weak bond between the fiberglass and steel.  The poor joint was a generic problem that had to be corrected on all booms for that model lift truck.

Stopple Failure in a Large Diameter Steam Line The second deposition was video taped because of the graphical nature of some of the technical presentation. A long time client, Team Inc of Alvin Texas, was held liable for a product failure that was supposedly due to design deficiency. The product was a stopple installed on a large steam line in a power plant in Corpus Christi, Texas. The stopple failed and caused a shut down of the plant and loss of revenue. SwRI was asked by Team Inc. to analyze the handling of the stopple prior to installation and to review some minor manufacturing defects to see if the cause of failure could be determined. I calculated the external horizontal load that would be required to fail the stopple in the manner in which it failed but had no knowledge of any possible source of a horizontal load. It was

later revealed that the line from the crane used to set the stopple in place had remained attached to the stopple and was attached to the stopple at the time of the blow out. Further, the crane was acknowledged to be defective and "walked", meaning load was applied to the line even with the brake on. Still, no indication that any but a vertical load had been applied since the line had to be vertical to set the stopple in place. However, in the course of the deposition the attorney for the plaintiff scattered photographs of the site on the table that were taken prior to the blow out. A single photograph showed that the boom on the crane had been moved to one side. In the boom position shown, the angle of the line between the crane and the stopple was sufficient to produce a significant horizontal load. I picked this photo up, measured the angle and calculated the horizontal load applied to the stopple based on the load applied to the line when the crane is "walking" (information supplied by the crane owner). This load was significantly larger than the horizontal load I had calculated nearly two years earlier as necessary to fail the stopple. The lawsuit against Team Inc was dropped.

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Fatigue Failure of a Rubber/Steel Laminated Pipe Joint

A laminated spherical joint invented by Lockheed for use as a gimbal on solid rockets has found extensive use in structural systems such as pipe joints and anchors for tension leg platforms.  A company tested a joint in flexture until failure.  The number of cycles was considered small and we were asked to determine if there was some flaw in manufacturing that would cause premature failure.  A cross section of the joint is shown here.  The joint works on the principle that rubber maintains flexibility in shear when highly compressed.  The thin layers of rubber do not extrude from between the steel layers.

Failure of a Large Diameter Butt Fusion Joint in HDPE Pipe

A 24-inch diameter HDPE pipe leaked under a freeway crossing and had to be extracted and replaced.  The failure was in a butt joint.  Examination revealed that the leak started in a cold fusion zone of the butt weld and propagated through the wall.   The product was industrial waste water.

Failure Analysis of Large Diameter PVC Pipe Fittings

Recent failure analysis of PVC pipe fittings used in water and chemical lines have been conducted.  It is evident that the engineers specifying PVC for cold temperatures and in large diameters need to be aware that these factors along with high wall thickness accelerate fatigue and make plastics prone to fast fracture.