Most processes in pharmaceutical manufacturing are at low pressure. However, mechanical failures such as line blockages or a pump malfunction can cause a sharp rise in pressure. This risk increases if a heating system is involved, or in a few cases, where strong chemicals could be contaminated and react powerfully.
How do you protect these systems?
1 – Pressure Relief Valves (PRVs)
For non-aseptic applications, pressure relief valves are the first choice. These valves have a metal plate that is forced closed by a spring. When the pressure in the system rises above the strength of the spring, it forces the plate open and relieves the pressure. The pressure will then drop and the spring will close the valve.
2 – Bursting Discs
For aseptic and hygienic conditions, the use of bursting discs is preferred. These are metal discs made with a rupture line so that at a set pressure, they open without fragmenting, allowing the overpressure to be relieved. They are non-reclosable so need to be replaced after they have opened.
Which option best controls emissions and contamination?
Bursting discs have many advantages when it comes to stopping leakage and maintaining hygiene. Each PRV will leak small amounts over time. Cumulatively, this can really add up, accounting for a large percentage of routine organic emissions. PRVs can also be subject to corrosion and product fouling, increasing the chance of contamination. Contamination in the pharmaceutical industry can be disastrous and must be avoided at all costs.
With a bursting disc, leakage and blockage are eliminated. Since the discs are just a smooth face, there is a minimal area for material to build up and are easy to clean. This is not the case with PRVs, which have many crevices and angles.
What materials are used?
The materials bursting discs can be made of is another benefit using them provides. PRVs have many parts, and there is a limit to what they can be manufactured from. Some materials are available but are very expensive and have a long lead time. But bursting discs can be created from many different materials, allowing the specific chemistry of a system to be taken into account, if needed.
Can PRVs and bursting discs be used together?
Yes, this is actually a common solution. By combining PRVs and bursting discs, you can have the benefits of both. The bursting disc protects the PRV from contamination and wear and tear. In case of overpressure, the disc opens, allowing the PRV to function as normal. Once the pressure is relieved, the PRV will close the system so production can continue. The bursting disc can then be easily replaced once the production cycle is finished.
Bursting discs are an essential safety component in the pharmaceutical industry and provide a high-specification and versatile solution. Fail-safe, they eliminate the danger of potentially catastrophic pressure build-up, and can also play an important role in keeping fugitive emissions to a minimum.