Rupture discs: bursting into life

Jon Lawson

Deborah Bevan reveals how two industry experts are working together to help cut the cost of wiring in rupture disc monitoring environments

Rupture discs have become an increasingly popular method of pressure relief in modern process plants, thanks to their ability to withstand a range of pressure and processing conditions. But with ever-increasing safety standards and environmental considerations to be satisfied in a particularly challenging economic climate, the need for reliable yet cost-effective detection systems – to indicate when a disc has functioned ¬- has become a pressing requirement. This has led disc manufacturers and customers alike to seek increasingly advanced systems that provide reliable detection without stretching budgets.

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.

This method of detection is useful in many ways, being suitable for a number of applications and as a low-cost option. However, the sensitive nature of the 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 unnecessary downtime. Another notable disadvantage is that the membrane is very easily damaged during installation and needs to be replaced, along with the disc. This can lead to expensive stock ordering and holding, while the potential for spurious failures or damage can result in unnecessary plant downtime while a replacement is ordered.

Latest advances

Recent innovations have led to the development of detection systems that 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. These products operate 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.

Unlike most burst detectors, which are activated by the flow created after the bursting disc has operated, Elfab’s Flo-Tel actuator is installed on the vent side of the disc and is activated by the operation of the disc itself, with the added benefit of not being subject to spurious alarms. Only the disc itself has to be replaced after it functions, eliminating the need to hold stock of detectors or order excessive spares.

Trust issue

The user’s trust in the reliability of such detectors has been recognised by Emerson Process Management, which understand the benefits and advantages of Flo-Tel and is working closely with Elfab, helping to bring to the market the first WirelessHART rupture disc burst detector, completely eliminating wiring costs.

The addition of Wireless Flo-Tel to Elfab’s range emphasises the commitment to providing customers with the latest rupture disc monitoring solutions to further reduce project cost and downtime, while further improving safety and reliability.

The enhanced wireless magnetic burst detection system offers a cost-effective solution when monitoring rupture discs and can easily be implemented on both new and existing sites. Customers can expect to eliminate the costs and complexity of additional wiring by saving an estimated 50% of the cost and 90% of the time required to install a conventional wired system.

Both new and existing customers can benefit from upgrading to WirelessHART technology by gaining immediate process alerts from an intelligent, real-time process monitoring equipment. Compatible with Elfab’s burst detection systems, Flo-Tel+ and Flo-Tel XD, Elfab’s wireless detection can be integrated and upgraded easily with Emerson’s WirelessHART Gateways. This allows for even further cost savings by eliminating the need for wiring on both new builds and on plant upgrades. Ultimately, the advancement of wireless burst detection technology is a superior and cost-effective alternative to wiring.

Deborah Bevan is with Elfab.

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