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Safety-critical solutions R

upture or bursting discs are non- reclosing, fail-safe devices. The rupture disc is among the most

misunderstood and least appreciated safety device used in systems where pressure or vacuum are present and where excess pressures or vacuum may need to be controlled and relieved when conditions exceed the safe design parameters. Over the years, operators and end users have been lulled into a false sense of security that the design engineers and system process/instrumentation designers have covered all the possibilities with sophisticated control and monitoring systems – nothing can go wrong so why do we need a rupture disc? In fact there are many reasons why we need rupture discs. These include: fast opening times, typically <2ms, reacts to sudden pressure rises far faster than any valve; full-bore opening, unlike safety valves where the orifice restricts the flow; and 100% isolation of process fluids; no leaks until the disc opens. Unfortunately some designs of rupture discs have not changed much over the past 80 years and we still find the old and unreliable scored or indented discs being

specified today. The lack of understanding in the advancement of laser technology in the manufacture of rupture discs leads to the mistaken belief that the older and less reliable designs are the only ones available.

Rembe is setting out lead the way in advanced laser technology. It produces rupture discs with advanced design features that increase their reliability and operational life far beyond those of scored discs. So why do so many design engineers get it wrong when they set out to do the FEED work? It is mainly because they were never taught what a rupture disc does and does not do.

Rupture disc selection is based on the information given in the datasheet of the RFQ or tender. Sometimes this is minimal, whereas in reality the volume of information needed is much higher. As many as 53 different points are needed to ensure that the disc is engineered to the full specification so it will operate correctly. With regard to “disc failure”, the term normally applied in the industry to the disc opening, operators try to avoid them, when in fact the disc opening means it is doing

its job, protecting the plant. If you run the plant above its rated

capacity, something that is done regularly, but you still use the same disc design characteristics for normal operations, why blame the disc for opening? If you have new pressures and temperatures then the disc needs to be designed for those parameters,. To recap, a rupture disc is your most important safety device, as long as it has been specified correctly at the design stage. It is fail-safe: whatever else goes wrong, a properly designed and engineered disc opens at its set pressure. Electronics, pneumatic and mechanical devices can fail, human error can cause operational errors in the pressure system, yet the rupture disc still opens, making it your best device to protect your plant. n

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Sanitary rupture disc to avert PED compliance

he AGT SC is a reverse-acting rupture disc designed specifically for the European pharmaceutical, food and beverage, and biotech industries, allowing considerable cost reduction by avoiding the need for compliance with PED regulations (Pressure Equipment Directive 97/23/EC). It is also ideal to protect sanitary processing equipment from overpressure because it often needs to be cleaned and sterilised with an inherent pressure safety risk. The device features an instantaneous fully opening pressure relief area for protecting equipment, vessels, systems and people from an overpressure condition

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exceeding 0.5 barg. There are several sanitary rupture disc

benefits. The standard low pressure allows for a considerable cost and time savings benefit in that there is no requirement of third-party inspection as compliance validation to PED can be avoided. It meets ASME BPE and USP Class VI criteria with others on request. The construction provides cleanability for CIP/SIP applications.Finally, it enables increased productivity due to extensive cycle life performance. n

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