The chemical sector is undoubtedly one of the sectors that contributes the most to the GDP (Gross Domestic Product) of a country. With the above, quality becomes a determining factor for the product to be accepted by the general public. This quality comes accompanied by attention to every detail of the process. Variables such as temperature, humidity, PH are key for each product to go on the market as it should be, but there is one variable that deserves to be addressed in detail: the pressure at each degree of temperature.
Pressure is defined as the force per unit area and is crucial when determining the optimal mixing and preparation conditions of a product that goes on the market. The pressure behavior is different for each degree Celsius of temperature, meaning, for example, that a hermetically closed container does not behave the same at 10°C as at 200°C. If the pressure conditions in a heat exchanger tank or reactor become uncontrolled, by not relieving or removing excess pressure out of the container, either towards the atmosphere or another depressurized container, when the process warrants it, the product itself can be lost, or if the pressure exceeds the design conditions of the equipment that prepares them, it can cause considerable damage, even causing the death of an employee.
What to do for pressure relief?
Pressure relief is defined as the controlled removal of excess pressure that exists in hermetically closed equipment. If the relief is uncontrolled, equipment breakdown is imminent and can be so violent that it can cause damage to peripherals, even injuring or killing someone. In the chemical industry there are specific solutions for pressure relief: The use of rupture discs or also called Pressure Relief Devices (PRD).
Rupture discs (PRD) are defined as a device capable of opening a metal membrane, which may be made of stainless steel, Inconel, Hastelloy or others materials on request, preformed at a pre-established pressure and temperature; It uses no moving parts and is 100% reliable. The chemical industry requires very high standards of care and rupture discs must be able to adapt to this industry. For example, they must meet the following requirements:
1. Accuracy: Rupture discs must be capable of acting at a very high accuracy, preferably 95%. The accuracy of a rupture disc is determined by the technology used in its manufacturing, guaranteeing the value of the rupture indicated on the disc, or at least as close to that rupture.
2. High cycling: Rupture discs must withstand high cycling since at the time of preparing mixtures in chemical reactors there may be a variation from positive to negative pressure and vice versa, compromising the reliability of the rupture disc (PRD) causing the discs open easily, releasing the pressure ahead of time.
3. High resistance to oxidation and corrosion: Oxidation is the presence of oxygen in the environment and corrosion is defined as the deterioration of a material as a result of an electrochemical attack by its environment. Rupture discs (PRD) must meet the demand for high resistance to oxidation and corrosivity, and that is where the versatility of the type of material with which rupture discs are made comes in; The versatility of having rupture discs (PRD) in 316/316L stainless steel and other unconventional special materials (Inconel® 625 and Hastelloy® C276).
The use of plastic coatings such as FEP (fluoroplastic fluoroethylene propylene), PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene) in the seat of the rupture disc has become a frequent practice to avoid corrosion in them, since the presence of corrosion is very high in chemical plants.
4. Protection of safety valves: Rupture discs (PRD) that are fitted in series with a safety valve are the most ideal for protecting their seats. Polymerization processes in chemical reactors make the products very viscous, causing the moving parts of the valves to stick and prevent them from working. By placing the rupture disc (PRD) in series, the life of the seats is extended and the valve will work perfectly.
Rupture disc (PRD) applications in the chemical sector
Pressurized foam injection
Foam injection in chemical processes has become a widely used practice when fires occur inside a plant. The foam covers large areas, effectively preventing the spread of fire. The use of rupture discs (PRD) in the depressurization of the tank that stores the foam is ideal for this application, thanks to the speed of response of these devices.
Shell and Tube Heat Exchangers
Shell and tube heat exchangers are still widely used in the chemical industry, these are made up of thin tubes embedded inside another larger tube called casing. The small tubes carry a single fluid that needs to be heated or cooled by another fluid on the outside that is contained by the casing. In the event that one of the small tubes breaks due to the effects of abrasion or corrosiveness, mixing between the two fluids is imminent causing exothermic reactions and therefore pressure elevation. This is where the use of rupture discs (PRD) connected to the casing comes in to relieve uncontrolled pressure from the heat exchanger.
Chemical reactors
Chemical compounds, such as acrylic acid, phenolic resins, and vinyl monomers, are important components in the production of many industrial and consumption. These chemicals are produced through an oxidation reaction in large reactors. A common safety risk within these reactors is a violent, runaway polymerization reaction. The runaway exothermic reaction can result in excessive pressure, potentially greater than that for which the vessel is designed. Therefore, pressure relief systems are vital, both to prevent injury to workers and to limit damage to equipment.
Especially in batch processes, frequent filling and emptying, as well as the polymerization process itself, creates fluctuating pressures within the reactor, therefore Therefore, the overpressure relief device must be able to resist this cyclic process, which often occurs at high temperatures. An unwanted opening or leak of the security system will result in product loss, which can be extremely dangerous and costly. To prevent a large capacity disc from opening due to human error or small irregularities in the process, combination with an additional smaller rupture disc in parallel with a slightly lower burst pressure is recommended.
Fike is an American company with more than 75 years in the market; It develops and manufactures custom rupture discs (PRD), especially for the chemical sector. 
Taking into account the applications of the chemical industry, ATLAS and AXIUS reference discs are handled, with a large capacity of:
- Accuracy due to its G2 technology, that is, a disc whose structure is made with a laser to guarantee opening with 95% accuracy.
- High cycling resistance; between 10,000 and 100,000 cycles.
- Resistance to corrosive media; These discs have the capacity to be made of materials such as 316/316L stainless steel, Inconel® 625 and Hastelloy® C276, additionally with FEP, PFA or PTFE membranes to extend the useful life of the device.
All Fike rupture discs feature:
- ASME Certification: Each rupture disc can come with its characteristic seal providing reliability when operating.
- Material certification: Fike offers a guarantee that the material offered meets all the specifications agreed upon in the commercial offer.
- Explosion certificate: Fike says that a specialized field to carry out test explosions; For each batch that is manufactured for a client, three extra units of rupture discs must be manufactured, exploded, and with the measurement of the rupture pressure at the appropriate temperature, the batch of rupture discs is stamped and sent to the client.