Rupture disc overcoming common industry concerns

Myth busting the rupture disc

Optimising production is a priority for organisations within a wide range of industry sectors, such requirements are particularly prevalent in the oil, gas, chemical and petrochemical sectors. Operators in such organisations aim to achieve 100% reliability of their plants with maximum throughput and no unplanned downtime. Optimising production systems and ensuring the reliability of equipment procured for use within their processes is essential. Plant engineers within these sectors have long relied on rupture discs to quickly and reliably release unwanted, excess, pressure or vacuum from a process, and while technological capabilities of rupture discs have improved dramatically over recent years, there is still a lack of understanding of these developments throughout the industry.

The first rupture disc designs were very simple - flat pieces of metal installed between flanges, weakened to open at a predetermined point using mechanical scoring methods. Technological and design developments have enabled manufacturers to dramatically improve the quality and reliability of its rupture discs since this time, almost completely eradicating historic industry concerns such as pin-holing and leakages, premature failure and frequent replacements. This article separates the myths from the facts.

Myth no.1 – rupture discs frequently leak

Leakage of mechanically scored rupture discs can occur due to pin-holing or cracking of the score line. These mechanically scored discs are susceptible to damage due to mechanically induced stresses, corrosion, vibration and incorrect fitting techniques, all which can contribute to leakage along the score line. A foremost concern for plant owners operating within the oil and gas and chemical sectors is managing fugitive emissions and loss of media through leakages. Plant operators within these industries are subject to strict monitoring and control, with leakages being heavily monitored and fined. Unlike traditional designs, high quality rupture discs are not mechanically scored. One popular example: KUB reverse-acting rupture disc features a two-layer construction, whereby the burst pressure is controlled by a precision laser-cut profile on the downstream side of the process with the smooth, unblemished surface of the sealing membrane facing the process medium. The benefit of this is the disc is not affected by process media, there is no score line to be weakened during normal operation and the design is so robust it is not prone to fatigue from high pressure-cycles, all of which could have led to leakages. The KUB is also a unique torque-independent solution, meaning no special tools are required to install the disc into its flange position. Incorrect torqueing of a rupture disc can lead to damage which in turn could create an unnecessary, unknown leak path within the process - torque-independent constructions such as the KUB completely remove this concern. Solutions like this provide increased durability and service life compared to traditional designs, significantly reducing the problem of fugitive emissions through leakages of gases and eradicating the myth that discs create leak paths within a process.

Myth no. 2 – rupture discs frequently fail prematurely

For most operators, it is a real concern that rupture discs frequently fatigue, particularly for those who are operating systems under harsh, high cyclical conditions. If rupture discs fatigue, they can fail prematurely leading to unplanned shutdowns and loss of production. The KUB is the only disc to be manufactured using Euler’s critical load formula to determine the set burst pressure, creating a robust, high-performance rupture disc. Unlike other rupture disc solutions and earlier designs where a weak point is created in the metal allowing the disc to burst in an overpressure situation, modern discs like the KUB is a highly engineered product. As there is no one specific weak point on the rupture disc, it does not easily fatigue even when subject to high pressure-cycles, this maximises the lifespan of the disc in situ. Over torqueing a rupture disc during initial installation or following maintenance inspection can also damage the disc and affect the burst pressure, this overtime can also contribute to premature failure of the assembly. Effective planning and execution of shutdowns and turnarounds are critical for companies, if unprepared for an unforeseen rupture disc burst this can lead to costly downtime and plant shutdowns costing operators thousands in lost production, modern rupture discs challenge the myth that discs frequently fail while offering operators a solution to minimising plant downtime. These high-tech discs keep rupture disc costs to a minimum while keeping process uptime to its maximum.

Myth no. 3 – rupture discs need replacing frequently

Downtime associated with rupture disc change out can lead to costly process inefficiencies. Premature burst and high frequency of replacement are prevalent with older rupture disc designs. Mechanically scored solutions were easily affected by poor handling or damage to the dome causing the disc to open lower than its set burst pressure. Traditionally, frequent bursting was a common complaint, and while the disc was operating safely by opening early due to the damage it had been subject to it was causing significant disruption and process inefficiencies for operators. As the KUB is almost immune to damage, the risk of inadvertently dropping or touching the dome membrane during new installations or change outs is not a concern. This robust design increases the ability to get the process back up and running as quickly as possible after shutdowns without concerns that the burst pressure may have been affected and will, as a result, fail not shortly after the process has been restarted. The KUB is so robust it is also virtually impossible to damage during transport or in storage, meaning no nasty surprises when you come to use the disc. Torque independent designs are completely unaffected by incorrect handling, improper installation or even being dropped, the high-performance KUB is the most robust solution on the market even under harsh operating conditions. Not only does the KUB offer the maximum lifespan capability of any rupture disc on the market; it is also the most robust design – virtually immune to damage; it can easily and safely be reinstalled into its holder following maintenance schedules, meaning longer service life and lower replacement costs. Torque-independent designs; such as the KUB; do not use bite seals, instead a leak-tight, metal-on-metal seal. This allows the rupture disc to be reinstalled into its holder and reused safely following routine maintenance, reducing unnecessary replacement costs associated with assemblies using a bite-seal where a new rupture disc would need to be purchased following each inspection. Reducing and improving maintenance schedules plays a critical part in improving facility efficiencies, using modern rupture disc solutions that are not easily damaged and are not prone to fatigue; even at higher operating pressures; maximises the life span of the disc in situ while lowering ongoing replacement costs - busting the myth that discs require frequent replacement!