Subject: Analysis of Break Origin Samples from the Green Square and Nature Research Center Buildings, Raleigh, North Carolina.

Transcription

1 PPG Industries, Inc. Glass Business and Development Center, 400 Guys Run Road, Cheswick, Pennsylvania USA Telephone: (412) Fax: (412) Paul W. Bush Director, Technical Services March 6, 2015 Mr. Rick Wright Oldcastle BuildingEnvelope Technical Services 1507 Lancer Drive Moorestown, NJ Subject: Analysis of Break Origin Samples from the Green Square and Nature Research Center Buildings, Raleigh, North Carolina. Dear Rick, The purpose of this letter is to provide the results of PPG s analysis of the broken glass samples received from Lingnell Consulting Services on February 2, 2015 and reported to be from the Green Square and Nature Research Center Buildings in Raleigh, North Carolina. Correspondence beginning on November 25, 2014 and continuing through present indicates that at least a portion of the IGU construction contains a lite of Solarban 70 low-emissivity coated clear glass. Oldcastle BuildingEnvelope records confirm that several of the glazing constructions on the project utilize a lite of Solarban 70XL low-emissivity coated glass. There were no samples or description provided as to the source of the additional lite(s) of the IGU. It is our understanding that the project has approximately 5,000 IGU s installed and this is at least the ninth reported incidence of breakage on the project. The specific samples returned to PPG were two break origins and one small segment of separate broken glass without a break origin included. All were received after having been removed (prior to submission to PPG) from at least two different broken lites of glass. One sample was labeled as Sample 2 and the mating surfaces of Sample 1 were labeled Sample 1-1 and Sample 1-2. Each of the origin samples either contained a stone defect or had an impression of where a stone defect had once resided. The origin samples are listed below: Sample 1-1 Sample 1-2 Sample 2 Stone Present No Stone No Stone ANALYSIS: Each origin sample was analyzed initially via optical microscopy at 80x magnification using fiber optic illumination. Samples were then transferred to aluminum Scanning Electron Microscope (SEM) stubs and coated with a thin Iridium layer for Page 1

2 SEM/Energy Dispersive X-ray (EDX) analysis. Measurements were performed on a Leo 1530 field emission SEM with Noran System Six (NSS) software EDX system. Subsequent analysis of the small segment of separate broken glass by X-Ray Florescence (XRF) analysis was conducted in an attempt to determine the glass source and possible production time. RESULTS: For sample 1-1 the stone defect present was confirmed to be a nickel sulfide stone. For sample 1-2 and sample 2, evidence of a nickel sulfide stone was found in the respective impression areas analyzed. The analysis of the separate segment of broken glass determined that this substrate glass was PPG clear glass from our Wichita Falls, Texas production facility likely produced in the October, 2010 timeframe or prior. Top Left: Sample 1-1 Optical micrograph at 80x magnification using fiber optic illumination. Top Middle: Sample 1-2 Optical micrograph at 80x magnification using fiber optic illumination. Top Right: Sample 2 Optical micrograph at 80x magnification using fiber optic illumination. 1. A control area of sample 1-1 near the break origin was analyzed by Scanning Electron Microscopy - Energy Dispersive X-Ray techniques. The analysis area is represented by the small rectangle in the image below. The control area of the glass contained all normally present and expected elements. Sample 1-1 Control Area Page 2

3 2. For sample 1-1 the SEM / EDX inclusion analysis returned results of Nickel and Sulfur confirming that the inclusion present is a NiS stone. The analysis area is represented by the small rectangle in the image below. Sample 1-1 Defect Area 3. A control area of sample 1-2 near the break origin was analyzed by SEM / EDX techniques. The analysis area is represented by the rectangle in the upper right of the image below. The control area of the glass contained all normally present and expected elements. Sample 1-2 Control Area Page 3

4 4. For sample 1-2, the SEM / EDX analysis of the impression area returned results of Nickel and Sulfur indicating that the inclusion previously present was likely a NiS stone. The analysis area is represented by the small rectangle in the image below. Sample 1-2 Defect Area 5. A control area of sample 2 near the break origin was analyzed by SEM / EDX techniques. The analysis area is represented by the small rectangle in the image below. The control area of the glass contained all normally present and expected elements. Sample 2 Control Area Page 4

5 6. For sample 2, the SEM / EDX analysis of the impression area returned results of Sulfur indicating that the inclusion previously present was likely a NiS stone. The analysis area is represented by the cross hair inside the red circle in the image below. Sample 2 Defect Area (high mag) PPG has gone to great effort over the years to reduce the likelihood of nickel sulfide stones in our float glass. We do not include nickel in any of our batch components or handle the batch with any nickel bearing materials; however, there is no known technology that will totally eliminate the rare occurrence of nickel sulfide stones in float glass. Such inclusions are so small that they cannot be inspected out of the base annealed glass using any practical methods. For this reason, they are classified as allowable imperfections under the appropriate ASTM specification for flat glass. If the glass is fully tempered and the nickel sulfide inclusion is of a composition where its volume may expand, it has the potential to cause spontaneous breakage. For reference, I m attaching a copy of PPG s Technical Document #138, Heat Treated Glass for Architectural Glazing, which further discusses the causes of spontaneous breakage. In addition to our efforts to prevent nickel sulfide inclusions, this technical document also includes PPG s long standing recommendation that heat-strengthened glass be specified and used everywhere, except where tempered glass is mandated for safety or other purposes by code. In the history of PPG we are not aware of a single confirmed case of Heat-strengthened glass with spontaneous breakage due to nickel sulfide stone inclusions. In closing, we have no reason to expect an elevated breakage rate in the future due to NiS inclusions in the PPG glass on the Green Square Complex and Nature Research Center buildings; if additional breakage does occur we would like to be made aware of the situation and have the opportunity to analyze the samples. Page 5

6 Please let me know if there are any questions or if I can be of further assistance. Thank you for your business and continued support of PPG Glass Technology. Sincere regards, Paul W. Bush Director, Technical Services PPG Flat Glass The first Cradle to Cradle Certified CM Architectural Glass. Cc: Chris Ivers NCDENR E. Bloch; M. Seeton; D. Coleman - PPG Page 6