Consequently the selection amongst rubber and metal joints is depending on the chemical surroundings and corrosion safety necessary. a. Expansion joint rubber flanges needs to be in connection with a flat surface area. Standard one/16″ lifted confront is OK. Unacceptable depressions or protrusions are standard of victaulic or related flanges. https://ejma-vs-asme-which-standa47802.sharebyblog.com/39303996/5-essential-elements-for-hvac-expansion-joint