Gauging the benefits of rupture discs over valves. By Michael Lloyd.
As pressures on process plants increase, operating expenses must be cut at every opportunity. Reducing downtime, limiting stock variation and ensuring the process is operating efficiently are challenges faced by many industries. Most modern plants now proactively manage variations in pressure using relief devices to prevent hazards caused by over-pressurisation. However, using the most suitable equipment is key to achieving these critical cost savings.
Traditionally, engineers used reclosing safety relief valves to address this danger. However, alternative devices, such as rupture discs, are now a popular substitute. They are simple to install, maintenance-free and often preferable due their ability to withstand a wide range of process conditions.
Offering instantaneous and unrestricted pressure relief, rupture discs require a much lower up-front installation investment. Furthermore, they act as a more effective seal due to their leak-tightness; valves are one of the hidden culprits of fugitive emissions. Although they can be adjusted and reused, valves are restricted in the size and materials available, as well as the media for which they can be used. Overall, the most costly drawback of a valve is the ongoing service requirement for recalibration and maintenance.
The introduction of computer-controlled production equipment has greatly increased the accuracy of rupture discs, which now offer a burst-pressure tolerance of ± 3% – a vast improvement on historical values of ± 10-15%. The benefits of this development include the reduction in variation, lower stock holdings and the ability to pump a process harder to produce more product. Testing procedures also contribute to improved precision, with many discs now being tested to over one million cycles, and reducing the level of fatigue experienced by earlier designs has given users more confidence in the rupture disc solution.
Knowing that a disc has burst ensures limited downtime, leading to increased efficiency and greater profitability – key performance indicators for any business. The incorporation of a sophisticated, magnetic, non-invasive burst detection system that is integral to the rupture disc now means that only the disc has to be replaced after it functions. This gets the systems back up and running faster, reduces purchasing time by eliminating stock and further cuts costs of ongoing wiring – re-instating alternative burst detection systems requires a qualified electrician. Recent failsafe detection is also not susceptible to process change and false signals, so does not affect the performance of the disc. The sensor can be tested in situ without interrupting the process, making maintenance checks more efficient and simple.
To control pressure build up within modern process plants, traditional valves are being replaced by rupture discs due to the latter’s improved specification and reliability. The development of sophisticated integral burst detection has enabled plants to further cut costs, increase efficiency and become more profitable. Recent technological advances in rupture discs and associated detection systems have gained the trust of users in safety-critical plant processes worldwide, making them the preferred pressure relief option to protect against disastrous explosions.
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Michael Lloyd is with Elfab in Tyne & Wear, UK.