BPRVs and rupture discs are both favoured over relief valves, as they offer full-bore openings. However, which one is most suitable for your application? Pressure management company and bursting disc manufacturer, Elfab, presents a balanced and informative overview of the two.
A central worry about BPRVs and rupture discs is that they will fatigue over their lifespan, resulting in additional costs and maintenance time for businesses.
Buckling pins cannot fatigue because they buckle at a set point and are not exposed to process conditions. Traditionally, rupture discs were susceptible to fatigue, although efficiencies with more modern designs have rectified this. In fact, some rupture discs are now offered with a 3-year warranty compared to the traditional 12 months.
A concern for many is the associated manufacturing, operating, temperature, and set point tolerances of both rupture discs and BPRVs. This is especially true for those who need precision to operate as close to the set point as possible.
Most buckling pins will have maximum operating pressures of 95% to 98% of the set point. Reverse-acting discs are available with 3% tolerances and 97% operating ratios.
Leading to failure and increased costs, corrosion is another high-priority concern. For buckling pin relief valves, the pressure relieving part — the pin — is external to the process conditions, meaning relatively cost-effective materials can be used for this component as it will never be in contact with the process media. This ensures low repurchase costs and confidence that the product should not be affected by this problem.
Because of this, the buckling pin valve can be created from compatible and normally affordable materials, such as carbon and stainless steel. The valve body must be made from a corrosive-resistant material, which will usually incur a higher charge.
Rupture discs are in contact with the process medium, so are crafted from highly non-corrosive materials including graphite, Hastelloy and tantalum. For modern rupture disc designs, in the instance a rupture disc is affected by corrosion, the discs will fail-safe, meaning customers will be made aware there is a potential problem.
One benefit of rupture discs is that they can be combined with burst detection systems to deliver alerts should a disc fail due to corrosion. In addition, double disc assemblies can be used to allow manufacturing to continue until a suitable maintenance schedule is due to take place.
To experience the benefits offered by both BPRVs and rupture discs, the correct installation is critical, especially given the dangerous environments they’re used in.
The design of buckling pins — and now modern rupture discs — means that it’s virtually impossible to install them incorrectly. This has been supported by the creation of specialist installation tools such as disc alignment tags, flange mounted installation locks and RFID detection.
It is widely recommended that burst detection systems are used alongside the pressure relief device. This is the only safe and reliable way to get a notification that the product has functioned.
Buckling pins allow you to easily see when a pin has activated, as it has two conditions: straight and buckled. However, it still relies on an employee noticing this state and doing something about it.
To avoid relying on hearing a rupture disc burst, many are encouraged to install a burst detection system. Such detectors give an instantaneous notification of a burst, and can even be wired to a control room to shut down a process as a further safety measure. This protects against a loss in productivity and environmental hazards, while also improving overall safety.
High maintenance costs
Of course, to ensure high levels of safety, regular maintenance is required. Buckling pins are relatively maintenance-free and offer the major advantage that they can be inspected without breaking the line. Replacement pins can also be installed in a matter of minutes without disrupting the line.
With rupture discs, there is no visible sign of its state without removing it from the holder. However, now tools are available to help companies do so, allowing them to check its state without stopping the line, making the maintenance of both solutions equally as rapid and as environmentally friendly.
Rupture discs or BPRVs?
So which one should you choose: rupture discs or BPRVs? To decide, consider the size of the line and the initial investment versus long-term investment. As modern designs offer comparable performance characteristics, considerations based on an application would make for a better decision-making process, rather than worrying about these common misconceptions that on the whole have been eradicated through continued advancements.