The Type D Composite Disk consists of a slotted metal top section and a plastic or metal seal membrane located at the concave or pressure side of the top section. The top section is the pressure zone and controls rupture rating of disk. Since the top section has open slots, the seal isolates it from process media and prevents leakage. Like the Type B Solid Metal Disk, the Type D composite disk is dome-shaped with an angular seating arrangement.
Pressure is applied to dished or concave side, subjecting disk metal to tension loading.
Seal material in the Type D rupture disk is thin and subject to damage by a foreign substance on seating surfaces or flanges. It may be desirable to use a heavier gauge metal ring permanently mounted to the seat area of the plastic or metal seal. This assembly is called Type DR rupture disk. When two rings are used, the assembly is called Type DRR rupture disks. When vacuum is involved-in any amount the seal MUST have a structural support.