By Andy Fallon
Process manufacturing plants worldwide can benefit from wireless monitoring of rupture disks.
The last 50 years have seen a complete revolution in risk and hazard management systems and practices. Since the early 1970s when Imperial Chemical Industries pioneered hazard and operability studies, there has been a general consensus to adopt a “safety culture” in process plants. Safety issues have therefore warranted great attention due to their high significance in the running of these plants. With great investments made by process plants to ensure their applications operate with limited risk, and the addition of many OH&S acts specifying that employers will be found guilty of a breach if the company had a practicable way of identifying a hazard that it did not employ, it is disturbing that there has not been a greater take up of rupture detection systems alongside the regular purchase of pressure relief devices.
Pressure relief detection systems act as a simple, practical, and reliable means of highlighting when serious events take place within a process. In the modern world with environmental concerns, health and safety issues, and high downtime costs, the importance of having reliable sensors and detection in place to warn of risk is a necessity.
Relevance of Rupture Disks and Associated Detection Systems in the Modern Process Plant
Due to their excellent corrosion resistance, negligible leakage, and maintenance-free designs, rupture disks are becoming an obvious and cost-effective choice over other types of pressure relief devices. As modern process plants strive towards achieving a safety culture, other pressure relief devices such as pressure relief valves represent a significant threat to the goal of zero emissions and plant safety.
As process plants strive to be environmentally aware and increasingly safety conscious, it is surprising that the adoption rate of rupture detection systems is significantly low. With plant control systems and staff lacking remote indication of a disk rupture event, process plants could face serious environmental or safety issues leading to high and costly levels of downtime, especially with the size of today’s plants. The unreliability of the older detection systems, coupled with time-consuming and expensive wiring, has made the negatives of traditional detection systems outweigh the benefits. However, with the introduction of robust and reliable wireless systems coupled with newer fail-safe detection equipment, the barriers to poor adoption rates of these systems should have been removed long before now.
Poor Adoption of Rupture Detection Systems in the Industry
Significant advances in the development of wireless technology have been made over the past 5–10 years, and unlike traditional sensors, wireless options enable continuous monitoring of bursting discs using noninvasive sensors.
Figure 1: Detection uptake graph
(click image to enlarge)
Because of the number of problems with traditional rupture detection systems, the adoption of similar technology has been significantly lower than expected across the process industry. (Fig. 1 further highlights the poor uptake of burst detection systems in relation to the general sale of rupture disks.) Many traditional rupture detection systems such as membrane sensors, breakwire, or pneumatic switches are invasive to the process they monitor and can be either easily damaged or face damage following repeated use. More recent noninvasive rupture detection systems based on magnetic field sensing have eliminated a number of the issues caused with the traditional detection systems, but still have not been adopted as much as expected. Although modern magnet and read switch sensors require one-time installation, many believe that it is the initial wiring costs that have caused the poor uptake of this technology. With the wiring of such systems taking several days and costing between $40 and $60 per foot (almost four times this for explosion-proof or intrinsically safe wiring), it is not surprising that process plants believe the negatives of such detection systems outweigh the benefits.
However, modern wireless systems use radio waves instead of physical wires as the communication medium, which eliminates all the historic concerns the process industry has associated with both the traditional-type systems and more-advanced magnet and read switch detectors.
Challenges in Wireless Overcome
With wireless systems having a number of benefits outweighing traditional-type sensors, why aren’t modern process plants more forthcoming in adopting this technology?
With modern process plants and industry in general still believing that wireless systems are unreliable, have low battery lives, cause problems with integration, and incur a generally high investment cost, it is not surprising that suppliers are facing several issues on convincing customers to reap the ongoing benefits of wireless monitoring systems.
The fact that wireless technology is a fairly new phenomenon within the process environment poses a big challenge in the form of end-users not readily accepting the technology. Due to the critical nature of some of the industries, such as chemical, pharmaceutical, and oil and gas, reliability concerns assume high importance among end-users. Most analysts describe the process industry as staying cautious about the large-scale deployment of wireless sensor networks, not only because of concerns over reliability but also because of the perceived lack of standards. (Fig. 2 highlights the key challenges that are preventing the adoption of wireless technology.)
Improvements in wireless technology are starting to address these concerns with properly implemented wireless systems, now as secure as many traditional ones, complete with many wireless systems now boasting the additions of Web-based software monitoring. With the latest wireless burst detection systems being available for use in explosive atmospheres and conforming to the stringent quality standards, such concerns are becoming dated. Advancements in wireless technology are making such systems both fail-safe and reliable. And when used in the process monitoring of pressure relief devices, because wireless monitoring technology does not affect the operation of the bursting disc even if the radio-frequency signal was lost, the benefits of the technology strongly outweigh the concerns.
With modern wireless systems boasting battery lives from 2–5 years, maintenance schedules are dramatically reduced. Unlike wired systems or plants that have no detection systems in place, the wireless sensors require minimal regular inspection, reducing many costs associated with this process.
Figure 2: Challenges facing wireless technology
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There are a number of reasons to chose wireless systems over wired solutions, the most obvious being the installation costs. Estimates vary, but the upfront costs of wired systems (including installation, start-up, and the infrastructure to support a typical wired system) can far exceed the cost of detection itself. Wireless systems, however, have minimal installation costs, are easily expanded upon and can actually cut installation costs up to 90% by eliminating field wiring. Additionally, wireless instruments are quick to install, require minimal maintenance, and do not run the risk of having the communication path being affected by corrosion or being cut, burned, shorted, or dug up.
The advantages offered by wireless technology are likely to drive wireless device adoption, but not before the challenges prevalent in their adoption are overcome. With the perception of integration issues still being common, it is important that potential users of wireless technology are confident that signals cannot be affected by other wireless systems or completely lost altogether. With modern wireless systems operating on unique frequency wavelengths and having set data messages, concerns over interference should almost be eliminated. And with manufacturers designing their systems with the end-users in mind, radio-frequency signal boosters are available to ensure wireless technology can function in even the toughest of operating environments.
Customers in the process industry know they need greater visibility of their processes and immediate indication of disc rupture events. With wireless monitoring systems offering rupture disc indication within two seconds, a number of benefits can be achieved through implementation of such systems across these plants. With wireless systems being more readily available on today’s market and increased and stricter H&S regulations in place, wireless technology should be strongly advised.
A number of industry reports believe that the market for wireless devices and equipment will grow dramatically over the next four years. With the launch of products that comply with industrial standards, reduce integration issues, and lessen battery life concerns, such benefits can only support the main drivers to adopt and outweigh the benefits of wired systems. With many modern wireless systems boasting their own monitoring or Web-based software or SMS alerts, there is a range of solutions to meet the customers’ needs and it seems the benefits of wireless technology can only increase. Since the main driving force for wireless process monitoring is the dramatically lower installation costs, the first step towards wireless monitoring system adoption is encouraging the normally change-adverse process industries to use wireless technology wherever they can. And with the ability to easily integrate a reliable and robust detection system into existing plant infrastructure, such systems will allow companies to comply with environmental standards, thus taking a major step in moving closer to the frequently talked about “safety culture.”
Before any installation involving a wireless system, it is important to perform a site survey to determine if there are any potential radio-frequency problems and to gain a better understanding of the plant in which the wireless system will operate.
Andy Fallon is engineering manager, Elfab, with a history in electrical engineering. He has been heavily involved in the development of Elfab’s line of wireless rupture detection products. For more information call +44 191 2931234 or visit www.elfab.com.