Rupture disc

Forward-Acting Rupture Disk

The forward-acting rupture disk is dome shaped and is oriented into a system with the process medium (phase application) pressure along the concave side of the disc. When there is an increase in the process pressure beyond the designed or allowable operating pressure, the tensile strength or low cycle fatigue strength of the material is reached and rupture occurs. This type of rupture disk is employed in systems that typically have operating ratios at about 80% or less. They are usually designed to act in tension, somewhat like a balloon. There are different types of forward-acting rupture disks: forward-acting composite disk, forwardacting solid metal disk, forward-acting scored metal disk, and graphite disk. They have the advantage of being cheaper than reverse-acting rupture disks. 

Reverse-Acting Rupture Disk

 The reverse-acting rupture disk is also dome shaped, but is installed with process pressure against the convex side of the disk, thereby placing the rupture disk in compression. It is designed such that as the designed burst pressure of the rupture disk is attained, the compression loading on the disk causes it to reverse back into a forward-acting disk and then burst. This causes the disk to open by a predetermined knife blade or scoring pattern penetration. Reverse-acting rupture disks are employed in systems where operating ratios are as high as 95% or less. They can be used in combination with relief valves, which means that they can be non-fragmenting. Reverse acting rupture disk can also be used in vacuum or larger back pressure applications without special supports. They have the advantage of controlling burst pressure at close tolerances.