Volume 8, Issue 7 - July/August 2007
It wasn’t all work and no play when members of the Insulating Glass Manufacturers Alliance (IGMA) met for their summer meeting June 10-13 at the Hyatt Regency in Huntington Beach, Calif., but the beach resort within eyesight of the famous pier did set the scene for getting down to business. Between discussing the possibility of new guidelines on capillary tubes and testing devices for insulating glass (IG) units, and revising drafted guidelines on visual quality and thermal stress, IGMA members were geared to take action during their summer meeting.
Discussion Reopens on Closing Capillary Tubes
Bill Lingnell of Lingnell Consulting Services, IGMA technical consultant, had been able to test capillary tubes donated by manufacturers since the group’s last meeting. “There [are] more kinds of capillary tubes than I ever knew existed in some ways,” Lingnell commented. However, he focused on a few suggested ways to close the tubes. He reported that he has used wire cutters and crimpers to close the hard stainless and soft stainless tubes, and has also tried putting a dollop of silicone on the end of the tubes, a method that seemed to work well. So far, Lingnell reported, results have been erratic, but using silicone after bending or crimping the tube seems to ensure that the tubes are closed.
“More than likely you’re going to have to have that dollop [of silicone],” Lingnell said.
One concern is that an unaccounted-for variable—the skill of the tradesman closing the tube—may create vaster differences in closed tubes than the variety of tested methods.
“Workmanship is going to vary in the field,” Lingnell said. “You’re not always going to have the same guy doing it.”
Lingnell said that he still has other methodologies to review, but is closer to reaching a conclusion that will allow him to prepare a technical bulletin on the subject.
Working group members also discussed the possibility of creating a document on the overall use of capillary tubes. At present, manufacturers have different suggestions for how to use capillary tubes, but there is no industry consensus on the topic. A motion to approach the Glass Association of North America about the joint development of guidelines for the use of capillary tubes, including information about how best to close them, met unanimous approval.
Gas Permeability Group Moves to Phase Two
The objective of the project is to develop a test cell configuration to determine the argon gas permeability of a section of an IG unit edge. The test cell will take into account the geometry and interactions of the components that make up the sealant/spacer system. It is intended ultimately to provide a tool to better estimate the argon loss rate from an actual production IG unit.
One member of the audience questioned the benefit of measuring the permeability of a section of the edge of the IG unit alone rather than the finished system.
“We know what the gas loss is of a finished unit, to a certain extent,” explained group chair Bruce Virnelson of PRC DeSoto.
According to Virnelson, data already exists on the permeability of finished units, and, since there is a great deal of variability in that data, testing edge sections may provide some answers about why the variability exists.
Following some final changes, the group aims to send out the request to laboratories to bid before the next meeting.
Working Group Reviews Thermal Stress Guidelines
Adding those considerations, the group added a statement to the document noting that heat-strengthened or tempered glass “will eliminate or substantially reduce instances of thermal stress.” Lingnell is updating the document in preparation for the next meeting.
The working group also noted that it sent out its Field Service Inspection Form requesting case studies on thermal breakage on March 8, but has only received a few replies. Some group members noted that as thermal breakage generally occurs in the winter, there might be no responses until December. The group agreed to send out a reminder that documented histories of thermal breakage and perhaps expand the request to a broader group.
Visual Quality Guideline Goes Back to Task Group
Lingnell commented that when making IG, the manufacturers don’t know where the glass is going, and therefore the visual quality shouldn’t differ depending on the project. But according to Rick Wright of Oldcastle, one can’t be expected to use the same criteria and catch the same blemishes on a giant commercial IG unit as it does with the smaller units more likely to be found in residential buildings.
Wright also was concerned that the IGMA document only addresses the inspection for point blemishes since, he said, the inspection process for linear blemishes is different. ASTM C1036 uses two inspection rules and, according to Wright, the IGMA document only follows ASTM halfway. Wright also noted that the sizes IGMA provides for point blemishes are different from the sizes listed by ASTM.
A motion to create two separate documents—residential and commercial—was found non-persuasive, so the discussion turned to the possibility of breaking one document into residential and commercial components in the areas where differences exist. A motion to do just that was approved unanimously, sending the document back to task group.
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Megan Headley is an assistant editor for DWM magazine.