Some metal manufacturers have already anticipated the renewal of C 585 without changes to tolerances. To reduce the number of complaints, they have to voluntarily increased their fitting outer diameters to accommodate some of the allowable larger sized pipe coverings being used to miter elbows. The C 450 committee, chaired by John Kalis of Kalis Engineering Company, recently completed a study on the miter points of elbows. The study was conducted by committee member, Gary Sproule of Sproule Manufacturing. There are multiple industry practices being used other than as provided in ASTM C 450.
Less miters equals less labor to fabricate a fitting.
Typically, this is not a problem if the contractor makes his own gored metal covers with the same amount of miters to match the insulation gores. However, if premade metal or plastic covers were purchased, these covers have been produced to fit the amount of gores or miters. The result is that the insulation may not fit the cover. MICA has its own miter schedule in the National Commercial and Industrial Insulation Standards manual. This manual is published by MICA and sold through the National Insulation Association.