SAFETY IN THE PLANT
Back to the drawing board F
How the miniaturisation of rupture discs is prompting the industry to re-think how it delivers protection against overpressurisation
or more than 85 years, the rupture disc has served as an effective passive safety mechanism to protect against overpressure or potentially
damaging vacuum conditions in tanks and other enclosed vessels. However, as these pressure relief devices become increasingly miniaturised to sizes as small as 1/8in to meet the demands of a new generation of smaller, lighter applications, the industry is running squarely into design and raw material challenges that often require reengineering the product itself. Fortunately, leading rupture disc
manufacturers have embraced this challenge with novel structures and design elements that have led to a new category of miniaturised options from 1/8in to 1in at all ranges of pressure including low (15-1,000 psi), medium (350-16,000 psi) and high (1,500-70,000 psi). The beneficiaries are expected to be equipment manufacturers and design engineers currently developing the next generation of aircraft safety systems, fire suppression systems, lithium batteries and battery packs, cryogenic systems, bioreactors, refrigeration systems, chemical systems and hydraulics.
THE EVOLUTION OF RUPTURE DISCS To understand the challenge requires an understanding of the origins of rupture disc technology. When it comes to pressure relief devices, the two most common are safety valves (reclosing) and rupture discs, also known as bursting discs (non-reclosing). Rupture discs are designed to fail within milliseconds when a predetermined differential pressure, either positive or vacuum, is
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achieved. The device has a one-time-use membrane usually made out of various metals, but also exotic alloys and graphite. In many applications the superior
leak tightness and flow characteristics of a rupture disc are preferred over safety valves, which are known to leak. In fact, it is a common industry practice to install a rupture disc on the inlet side of a safety valve to economically protect against corrosion and provide the required leak tightness. In another potential use unrelated
to pressure relief, rupture discs can be designed to activate as one-time fast acting valves or triggering devices to initiate a sequence of actions with high reliability and speed.
TRANSITION TO MINIATURE For decades, rupture discs have been used in petrochemical, aerospace, defence, medical, railroad, nuclear,
Rupture disc and safety head
chemical, pharmaceutical, food processing and oil field applications. In these applications, rupture disc sizes ranged from 1in to 6in, with larger
sizes up to 60in for the largest piping configurations. To install the product, the rupture disc is placed in a holding device, called a safety head, and installed between flanged pipe ends. However, as equipment
manufacturers strive to make their products smaller and lighter, the rupture disc industry has been challenged to deliver miniaturised options well under 1in in diameter. Due to a delicate balancing act
between the shrinking diameters, a complicated choice between two rupture disc design philosophies, the limitations of the specific raw materials utilised for the membrane, and the variations required to meet the requirements for low, mid and high burst pressures have forced rupture disc manufacturers to the drawing board.
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