Short answer: a non-fragmenting disc is used whenever the disc is installed upstream of a pressure relief valve, and also when pieces of the disc could damage or block downstream equipment, instruments or discharge headers.
A non-fragmenting disc opens into petals that remain attached to the disc ring, thanks to score lines that define the opening line and a "hinge" that retains the petal. Scored reverse-acting and scored forward-acting discs are usually non-fragmenting. Solid forward-acting discs and graphite discs, on the other hand, can release fragments when they burst.
- Ahead of a pressure relief valve: the codes require that the disc cannot affect the operation of the valve; in practice, a non-fragmenting design is required.
- Discharge to shared headers or recovery systems: prevents metal pieces from traveling through the relief network.
- Sanitary processes: prevents particles in the product.
More detail in the rupture disc types guide.