Glass Cookware Failure Analysis: Pyrex Pie Plate Failure

Fracture Surface at One Failure Origin

Assembled Pie Plate Showing Several Failure Origins

Read Consulting Failure analysis lab performed a glass failure analysis. An annealed borosilicate glass Pyrex baking dish failed as a result “thermal shock”. There were multiple origins for the failure, and these all initiated at damage sites on the bottom of the Pyrex baking dish. Because the bottom of the pie plate was convex, setting the dish down and moving it on hard (abrasive) surfaces such as tile counter tops created a “rim” of damage. When the hot dish was placed on a cold surface,thermal shock created tensile stress  on the bottom of the dish, and this caused the failure to initiate at the several preexisting damage sites. This baking dish is appears old and shows signs of heavy use. 

"Scuff" Damage on the Pie Plate Bottom

Window Defect Analysis Capabilities

Reflected Zebra Board Image that Shows
Window Roller Distortion Created
During The Thermal Temper Process

Window Scratches Caused by Poor
Cleaning Procedures

The window experts at Read Consulting are often asked to evaluate windows for defects. Many of these are Low-E windows that are also tempered. Two typical defects found are scratches and roller distortion.
Often the scratches are created during post construction cleaning. Roller distortion is formed when the float glass windows are thermally tempered.
Window Scratching: This is evaluated per ASTM C 1036 and is graded by the visibility of the scratches under controlled light conditions. Typical cleaning scratches are demonstrated in the above photo.

Window Roller Distortion (Tempered Glass Roller Distortion): This is evaluated per ASTM C 1048. Distortion in reflection using s standard "zebra board" (i.e. a standard striped pattern).  The photo above shows a sample of roller distortion found on a coated window. This test was done by reflecting the zebra board off the window outer surface. This test was performed on both window exterior surfaces. Often the amount of distortion allowed is defined by the construction contract. 

Plastic Failure Analysis: Fusion Welded HDPE

Poor Welding of a Carrier
Pipe Joint There was no
 Melting on a part of the joint

Read Consulting, a California failure analysis lab, has performed numerous plastic failure analysis on various types of plastic pipe. This includes PVC, CPVC, Delrin and Polypropylene. In this case a plastic failure analysis was performed on a failed containment waste transition line made with fusion welded high density polyethylene pipe. The line was several miles long. The interior transmission pipe had an OD of 8 3/8" and a 1/2" wall thickness.  The containment pipe had  12 3/8" OD with a wall thickness of 1". There were numerous leaks in the line,  and all were found to result from poor fusion welding procedures. The upper right photograph shows a weld on the interior carrier pipe that leaked. In this case the ends of the pipe had not been properly welded before the pipes were fused. This resulted because the pipe end never contacted the heater plate. Obviously, the fusion weld procedures were not properly followed.  It is important to follow exactly the manufacturer's recommended procedures when fusion welding high density polyethylene pipe. In addition, all joints should be leak checked before being buried in the ground. Poor fusion welding creates leaks that are hard to find and are very expensive to remedy.