Most modern process plants now implement pressure control equipment to monitor developments within their increasingly complex systems. Taking it further to ensure the plant remains safe, it is now essential to proactively manage variations in this pressure using relief devices to prevent explosions.

Traditionally, engineers used reclosing safety relief valves to address this danger. However, an increasingly common alternative to a valve is a non-reclosing rupture disc, designed to open and relieve overpressure at a pre-determined level.

Rupture discs like those from leading manufacturer, Elfab, are very simple and often preferable due their ability to withstand a range of pressure and processing conditions. Offering instantaneous and unrestricted relief for a complete discharge of pressure, rupture discs are less complex than valves in their construction and require a much lower up-front installation investment. Rupture discs also act as a much more effective seal due to their leak-tightness. Safety valves are one of the hidden culprits of fugitive emissions, which not only has environmental implications, but financial ones as well. For this reason, rupture discs are often fitted below valves to prevent these emissions from occurring.

The last 50 years have seen a complete overhaul of risk management, with most companies adopting a safety culture. The importance of pressure relief device accuracy, as well as the information available on board is now paramount. Many operating problems with relief devices stem from incorrect selection, so it is always recommended to consult specialists like Elfab before specifying any particular device. Indeed users need to be able to rely on their chosen device matching their exact specification requirements to ensure they perform as they should.

Given the clear advantages, many plant engineers now rely upon rupture discs and detection systems as a safety measure to manage their processes in a variety of pressure conditions. The introduction of computer-controlled production equipment has increased the accuracy of rupture discs like Elfab’s Opti-Gard™ disc, which offers a burst-pressure tolerance of ± 3%, a vast improvement on historical values of ± 10-15 %. Testing procedures have also contributed to this accuracy, with many rupture discs now being tested to over one million life cycles – over four times longer than previously achieved within the industry.  

Burst Detection Developments

Environmental concerns and the drive to reach zero emissions have changed the way many plants are run, particularly as unregulated leakages have implications beyond simply the environment: fines, sanctions and proposed government taxes on emissions could all have considerable financial repercussions.  As a result, the need for burst detection alongside rupture discs is vital, as plants need to quickly identify when a disc has burst.

Traditionally, detection systems featured a simple membrane design, complete with an insulated, electrically conductive path mounted between supportive rings. Following the functioning of the rupture disc, fluid flow would cause the membrane, and in turn the conductive path, to break, producing an open circuit signal and notification that the disc had functioned and needed to be replaced. The sensitive nature of this membrane design means it is vulnerable to sudden process changes and corrosive atmospheres, making it liable to give false signals. General maintenance inspections require the disassembly of the disc and holder installation, causing costly downtime.

Magnetic burst detection

Recent innovations have led to the development of detection systems which offer greater performance and reliability in a reusable design, offering both a higher level of protection and a cost-effective alternative to traditional methods of rupture detection. For example, Elfab’s Flo-Tel burst detection system operates on simple reed switch and magnet technology, the sensor fitting directly into the disc holder. The disc itself is provided complete with a small magnet. As the disc bursts, the magnet is pulled away from the sensor, giving an open circuit signal. Only the disc itself has to be replaced after it functions, eliminating the need to hold stock of detectors or order excessive spares. Unlike membrane systems, this method of reed switch and magnet detection is non-invasive to the process and so is not susceptible to process change and false signals, and therefore does not affect the performance of the disc. Since the sensor is non-invasive to the process, it is suitable for use in corrosive environments and can also be used in explosive atmospheres and high temperatures. Such detection is therefore Zone 0 compatible, meeting ATEX and IECEx approvals, with all components featuring a minimum IP66 rating. The sensor can be tested in situ without interrupting the process, making maintenance checks more efficient and simple.

If you would like to know more about how Elfab can support you in your safety-critical processes please contact the company on +44 (0)191 293 1234, email pr@elfab.com or go to www.elfab.com