Protective covers of expanded metal are used to prevent exterior damage to the expansion joint. Fire covers, designed oversize, are insulated on the I.D. to protect the expansion joint from rupture during a flash fire. They are normally installed on fire water lines. Sun covers protect the elastomer against UV radiation. When possible, it is not recommended to insulate over elastomeric expansion joints.
Macoga - Variations and optional devices for rubber expansion joints - Protective covers