Milestone Explosion Protection/Pressure Relief
Milestone Explosion Safety/Pressure Relief Competence in Safety Matters
The first Rembe rupture discs came onto the German market in the early 70s — at that time they were still completely machined by hand. Today, the company from the Sauerland region does not just develop and manufacture safety concepts for plants and equipment of the process industries. The focus is always on finding the optimum solution to protect the plant, people and the environment.
An explosion in a food production plant in Cairo on March 28, 2016 caused seven dead and around 60 injuries. For a company that stands for enjoyable products, such accidents are not only catastrophic in human terms. The associated damage to the image is sometimes immense, and its costs far exceed those of the reconstruction. Consumers and investors are increasingly making decisions based on their social and ecological conscience.
So it is not surprising that in the chemical, pharmaceutical and food industries, investments in plant safety are high on the list of priorities. Pressure relief and explosion safety, to which Rembe has been committed since 1973, are of key importance. In Brilon, Germany, as well as in eight subsidiaries around the globe, some 250 employees develop, produce and install safety concepts for plants and equipment. Consulting, engineering and service complement the products primarily developed and manufactured in-house. The overarching goal is always the optimum protection of production plants and the people who work in them. Because for the experts from the Sauerland, “Safety for life” is much more than just a slogan. It is a meaningful driver during the daily work and also a personal responsibility.
The process industries are under pressure — literally. If the pressure is too high or too low, the affected plant components can suffer severe damage. Therefore, in the event that the pressure rises above or falls below the specified limits, a reliable and fast reacting relief device is required. And this does not just apply to the enormous pressure wave of an explosion. Here, Rembe utilizes its decades of experience, which guarantee operators of process plants the ability to conduct honest analyses and attain a high product quality: “Because safety is more than just a product. It is a question of trust that we have earned with competence, transparency and responsibility. This enables us to optimise the processes, productions and products of our contracting entity in a targeted manner,” emphasises Rembe Managing Director Stefan Penno.
Preventive or Protective Measures
The basis of every explosion safety concept is a systematic risk analysis. The first step is to check the probability for the build up of explosive atmospheres and potentially effective ignition sources before classifying the effects of an explosion. Both evaluations are combined in a matrix. The key figures determined indicate whether and to what extent a plant or part of a plant must be protected.
Preventive measures are aimed at preventing an explosive atmosphere, for example by avoiding flammable substances or isolating the plant component. In addition, effective ignition sources should be avoided. The objective is always to exclude the prerequisite for an explosion from the very start by avoiding at least one of the three requirements of an explosion — oxygen, fuel, ignition source. This is particularly important in chemical and pharmaceutical processes, where critical substances are usually handled. However, preventive measures are not always feasible because:
- a safe and complete avoidance of effective ignition sources is almost never feasible due to the process;
- an isolation, especially with larger facilities, is usually too cost-intensive and/or not possible due to the process.
In these cases, plants and components must be protected in order to reduce the effects of an explosion to a tolerable level. In addition to a pressure-resistant design, explosion venting, isolation and explosion suppression are common ways of limiting the damage caused by an explosion. However, pressure-resistant plants are often not sensible due to cost and/or process limitations.
Explosion Safety in the Chemical and Pharmaceutical Industry
Silos must also be protected by explosion systems if it is not possible to exclude all potential ignition sources. Isolation is often not even considered due to the size of the facilities. Every production facility is unique and has different requirements. That is why Rembe's safety experts inspect the plants together with the operators and also think outside the box and beyond the order book. For example, it was possible to isolate a large silo complex of a construction material production contrary to the expectations. Rembe brought it to the attention of the company that the nitrogen produced as a by-product in a neighbouring plant could be used to avoid an explosive atmosphere in the own plant. For Dr.-Ing. Johannes Lottermann, Director Explosion Safety, intelligent solutions are more important than sales here: “Our aim is to sell the best solution, not just a product. This is the foundation on which successful partnerships develop.”
However, such preventive actions are often not possible, and protective explosion systems are demanded. These can vary considerably depending on the industry, product or requirement. Through this, it is possible to protect silos or spray drying plants through venting using explosion vents — such as the EGV explosion vent. It is suitable for processes with zero to low pressure or vacuum. When pressure rises, the EGV explosion vent opens at the defined breaking points and releases pressure and flames out of the vessel into the surrounding area. Thanks to the low surface weight, a high venting capacity and the full bore opening release will be possible.
Pharmaceutical processes in a batch operation with sometimes very short production times have to be cleaned frequently. In order to avoid cross-contamination through product residues, the explosion safety elements must also meet the hygienic requirements of the pharmaceutical industry. The patented, full-flat, chamfered gasket system of the EGV HYP hygienic vent panel is flush with the inside of the vent panel. An advance in terms of cleanability.
Explosion Safety in the Food Production Industry
Nowadays nobody would deny that the purity law is a guarantor for the quality of beer. It is also undisputed that the raw material malt poses a risk of explosion. Endangered plant elements include conveyors, silos, mills or elevators. If the plants are inside a building, it will become particularly tricky. Since neither the potentially explosive atmosphere nor ignition sources can be safely avoided here, explosion protection is the essential factor.
The flameless explosion venting technology invented by Rembe offers an elegant solution for the explosion safety in buildings, even in breweries. With the products Q-Rohr, Q-Box and Q-Ball a secure venting will be guaranteed. The flames are cooled extremely efficiently in the mesh filter of the flame absorber and are extinguished immediately. Neither flames nor pressure will escape. Complex safety concepts with complicated vent ducts can thus be avoided and the production plant can be set up in a process-optimised manner. The filter construction also guarantees that no burned or unburned substances can escape.
The latest coup in flameless explosion venting for elevators from the “Sauerland Professionals” is the Q-Ball E: “Thanks to the innovative design, the weight of the Q-Ball is very low. While comparable products from other suppliers weigh between 100 and 200 kg, the Q-Ball is an absolute lightweight with just 25 to 50 kg,” explains Mr. Lottermann. This actually simplifies both the handling during installation and the requirements for an attachment to the elevators. “For more safety, we have also improved the venting effectiveness,” says the Rembe expert.
Process Safety — Mastering the Pressure
Even if explosions are not an issue: Overpressure and vacuum are present in almost all production processes in the chemical, pharmaceutical, food, oil and gas industries. If the pressure exceeds or falls below the defined limits, serious damage can be caused to the affected plant components, and personal injury can also occur. This can result in production stoppages and thus high economic losses. Therefore, in the event that the pressure is no longer within the permissible operating values, a reliable and fast reacting pressure relief system is required. The means of choice is often the rupture disc. In many cases it is even superior to safety valves:
- Instant response: Excessive overpressure and vacuum is relieved in milliseconds.
- Full bore opening available for pressure relief: While the mass flow of safety valves is limited, the rupture disc allows a maximum cross section opening.
- Leak-tightness: A rupture disc can be used to prevent leakages during normal operation.
What makes the “metal plate” with precisely defined breaking points so special? As is so often the case, the devil is in the detail. “There is no ready-made concept for the design of a rupture disc. We tailor each solution individually to the specific operating conditions,” emphasises Orhan Karagöz, Head of Process Safety Business Unit at Rembe. He and his colleagues must consider at least 53 different parameters, so that the rupture disc responds reliably to the defined burst pressure. These include the plant elements to be protected, process medium, operating pressure, vacuum/cycles, burst pressure and temperature, required nominal pipe size or mass flow to be discharged. “The rule of thumb hereby is: The earlier we get on board and the more comprehensive our information on the specific process conditions is, the more reliably the rupture disc will protect the process,” explains Karagöz.
Pressure Relief in the Chemical Industry
Many processes in the chemical industry require high pressures as well as clean surfaces, and entail risks of crystallization or the danger of bonding developments due to polymerization, e.g. in the plastics production. In these cases, the KUB reverse-acting rupture disc demonstrates its advantages. This highly dynamic product can, for example, be freed from deposits with a solvent without impairing its function. “That can not be said about other rupture discs. After all, they can not be touched,” Karagöz clarifies. In addition, the closed surface facilitates the cleaning. This is made possible by Rembe's specially developed, laser-based production process.
Another bonus: The reverse-acting rupture disc masters an operating pressure ratio of up to
98 % — depending on the application. This enables plant operators to increase their operating pressures, and thus also the yield. A fatigue of the rupture disc is not to be feared. Service personnel will also benefit from the robust rupture disc. Because it can be easily removed and reinstalled. “This is unique,” assures Karagöz. A special holder system prevents the rupture disc from being installed incorrectly. Special tools are not required for this. The KUB is also not damaged by the installation, since the burst pressure of the rupture disc is independent of the torque and therefore the required torques can be used for the flange gaskets.
Pressure Relief in the Food Production Industry
In order to protect aromatic oils from oxidation, for example, storage tanks are filled with nitrogen. The overpressure in the tanks also prevents contamination, as no foreign particles can penetrate from the outside. The nitrogen used is normally under pressure — for example in a 300 bar bottle. At least one reduction stage is required to feed it safely into the tank. After all, the fill pressure in these cases is only ten to 40 mbar. The nitrogen is fed in using a control valve. It ensures that the defined fill pressure is kept constant.
Nevertheless, there is a risk that either a reduction stage or the control valve will not function properly and that more pressure than required will be introduced into the storage tank. In this case a safe pressure relief device is required. Due to the low pressures, a rupture disc is out of the question. It would simply be too large to be installed on the small storage tanks. The choice thus falls on a pressure and vacuum relief valve that has to meet the highest demands: fast opening, high mass flow, easy cleaning. Here, standard valves quickly reach their limits, in contrast to the Elevent breather valve. Standard valves for pressures up to 100 mbar are usually made of cast housings whereas the Elevent housing, however, is made of deep-drawn stainless steel. A great advantage when cleaning. While the process medium in a cast housing can penetrate deep into the pores of the housing, causing unacceptable deposits, it can easily be removed from the smooth stainless steel surface of the breather valve.
Rupture discs are also suitable for processes with higher pressure. The crux of the matter: the type of installation. In less hygiene-sensitive organization units, a rupture disc can be installed between flanges or in a rupture disc holder. For sectors with high hygiene requirements, the KUB clean is used for an installation into a Tri-Clamp flange system. Due to the smooth surface of the sealing membrane, the integrated gasket and the direct installation in Tri-Clamp flange systems, there are no score lines, indentations or notches on the process side eliminating trapped product residues during production or cleaning cycles. In addition, the side of the KUB clean in contact with the process is designed in such a way that it is easy to clean.
Conclusion: An adequate protection of process plants safely against overpressure and explosions requires more than just any random component. Holistic concepts and individually tailored protective elements are required. It is good to have a partner by your side who does not compromise on safety.