In the field of bioengineering, bioreactors, as core production equipment, are widely used in various sectors of the biotechnology industry and serve as a key hub connecting raw material input, reaction processes, and product output. A bioreactor is not an isolated device but forms a complete fermentation system together with pipelines, valves, and auxiliary systems. As the "blood vessels" for material transportation, energy transfer, and waste discharge in fermentation systems, the operational safety of pipelines directly determines the stability, production safety, and economic benefits of bioreactors. Once pipelines suffer from leakage, blockage, corrosion, or pressure loss of control, it will not only cause fermentation interruption and product loss but also trigger safety accidents such as leakage of flammable, explosive, and toxic media, threatening personnel and environmental safety. Therefore, in the design stage of bioreactors, it is necessary to take pipeline safety as the core guidance, integrate advanced biotechnology concepts in combination with the characteristics of bioreactors, construct a systematic and standardized design scheme, avoid risks from the source, and ensure the long-term stable operation of fermentation systems.
The core difference between bioreactors and ordinary fermenters lies in that bioreactors are key carriers of biological reactions and need to adapt to dynamic changes in parameters such as temperature, pressure, pH, and dissolved oxygen. As the core carrier for parameter regulation and material transmission, the design level of the pipeline system directly affects the efficiency and safety of biological reactions. With the continuous upgrading of bioengineering technology, the scale of fermenters has expanded, system complexity has increased, and pipeline transmission media have become more diverse, including conventional materials such as culture media and nutrient substrates, as well as dangerous media such as high-temperature steam, acid-base solutions, and combustible gases, putting forward higher requirements for pipeline safety. Against this background, constructing a full-life cycle safety system for pipelines in fermenter design supported by biotechnology has become an important topic in the field of bioengineering.
To ensure the operational safety of pipelines, fermenter design should follow the principles of "source prevention and control, system management, and full-process adaptation", construct an implementation plan from five dimensions: material, structure, pressure and flow, leakage prevention and sterility, and later maintenance, run the safety concept through the whole process of design, manufacturing, and installation, take into account the characteristics of bioreactors and the integrity of fermentation systems, and achieve simultaneous improvement of safety and efficiency.
I. Rational Selection of Pipeline Materials to Consolidate the Safety Foundation
Rational selection of pipeline materials is the basic premise to ensure pipeline safety and the primary link in bioreactor design. Biological fermentation media are complex and diverse, with significant differences in requirements for corrosion resistance, temperature resistance, pressure resistance, and sterility. Improper selection is likely to cause corrosion, aging, damage, and leakage. Combined with the technological requirements of bioengineering and the achievements of biotechnology materials, pipeline material selection should adhere to the principle of "adapt to media, take sterility into account, and be durable and reliable".
For conveying media with high sterility requirements such as microbial culture media and nutrient substrates, 316L food-grade stainless steel is preferred, which has excellent corrosion resistance, high temperature resistance, and easy cleaning characteristics, can avoid microbial growth and material pollution, and meet the sterile operation standards of bioreactors. Pipelines conveying high-temperature steam and high-temperature fermentation broth should be made of high-temperature and high-pressure resistant alloy materials to ensure no deformation or rupture under high temperature and pressure. Pipelines conveying strongly corrosive media such as acids, alkalis, and disinfectants should adopt polymer materials such as polytetrafluoroethylene and polypropylene to prevent corrosive perforation from causing dangerous medium leakage. All pipeline materials must comply with national biological fermentation industry standards, pass strict testing, and be compatible with fermenters, valves, interfaces, and other components to avoid looseness and leakage caused by material mismatch.
II. Optimize Pipeline Structure Design to Improve Operational Stability
Pipeline structure optimization is the core link to improve stability and reduce safety risks. Bioreactor pipelines include feed pipes, discharge pipes, steam pipes, cooling pipes, exhaust pipes, sampling pipes, etc., with different functions, and targeted optimization of layout, connection, and caliber design is required to avoid stress concentration, material retention, and mutual interference.
In pipeline layout, follow the principle of "short path, few elbows, and avoid interference", shorten the pipe length, reduce pipe fittings, reduce flow resistance, and prevent pressure rise and material blockage. Vertical pipelines are equipped with fixed brackets to prevent deformation and fracture; horizontal pipelines are set with a reasonable slope to facilitate the discharge of condensed water and residual liquid and reduce the risk of corrosion and microbial growth. Pipelines should be far away from operating areas and electrical equipment to avoid short circuits and fires caused by leakage, and sufficient maintenance space should be reserved.
In pipeline connection, sterile pipelines adopt welded connection to ensure no dead corners, no leakage, and no microbial retention; frequently disassembled pipelines adopt quick-install connectors equipped with high-performance seals such as silicone rubber, taking into account sealing and convenience. Flexible connectors are set at the connection between pipelines and tanks, pumps, and valves to absorb vibration and prevent fatigue looseness.
In caliber design, scientific calculation is carried out according to conveying volume, pressure, and flow rate to ensure matching with flow. An excessively small caliber will increase resistance and pressure and increase the risk of rupture; an excessively large caliber will cause material retention, difficult cleaning, and increased cost. Pipelines for easily crystallized and adhered materials should be appropriately enlarged in caliber and equipped with flushing pipelines for regular purging to prevent blockage.
III. Strengthen Pipeline Pressure and Flow Regulation Design to Prevent Overpressure Risks
Pressure and flow regulation is the key means to prevent pipeline overpressure, overload, and rupture. During fermentation, microbial metabolic gas production and pump valve start-stop will cause pressure and flow fluctuations. If exceeding the pipeline bearing limit, safety accidents are very likely to occur. Therefore, it is necessary to combine the operational characteristics of bioreactors to construct a complete pressure and flow monitoring and regulation system.
In terms of pressure regulation, a triple protection system of "monitoring-regulation-emergency pressure relief" composed of pressure sensors, safety valves, pressure reducing valves, and bursting discs is adopted, which is a typical application of biotechnology in fermentation system safety design. Pressure sensors are arranged at key positions such as tank outlets, steam pipes, exhaust pipes, and biogas pipes to collect pressure data in real time and upload them to the central control system. When the pressure exceeds the limit, the system immediately gives an audible and visual alarm and links with pressure relief equipment to quickly relieve pressure, maintaining the pressure within a safe range and avoiding pipe bursts and leakage.
Among various pressure regulation and pressure relief equipment, safety valves, pressure reducing valves, and bursting discs perform their respective duties and cooperate with each other, which are the core components to ensure pipeline pressure safety. Their selection, installation, and use are directly related to the operational safety of the entire fermentation system, and scientific and reasonable configuration is required in combination with the technological characteristics of biological fermentation, pipeline media characteristics, and pressure requirements.
1. Safety Valve: As the most commonly used reclosable pressure relief device in fermentation pipeline systems, its core function is to automatically open to relieve pressure when the pressure in the pipeline exceeds the rated pressure, and automatically close after the pressure drops to a safe range, realizing automatic pressure regulation and cycle protection, continuously playing a protective role without manual intervention, and is the first line of defense for bioreactor pipeline pressure safety.
Working Principle: Based on the lever principle or spring elasticity principle, by presetting the rated pressure value, when the pressure in the pipeline is greater than the rated pressure, the medium pressure overcomes the spring elasticity or lever gravity to push the valve disc open, the medium is quickly discharged through the valve port, and after the pressure drops, the spring elasticity or lever gravity resets, the valve disc closes, and the normal operation of the pipeline is restored.
Application Scenarios: Suitable for fermenter outlet pipelines, steam sterilization pipelines and other parts with gentle pressure fluctuations and continuous pressure protection requirements, especially pipelines conveying conventional media such as microbial culture media and high-temperature steam, which can effectively cope with the slow pressure rise caused by microbial metabolic gas during fermentation.
Key Selection Points:
(1) Rated pressure adaptation: The rated pressure of the safety valve should be determined according to the design pressure of the pipeline to ensure that the rated pressure is slightly higher than the normal working pressure of the pipeline, so as to avoid false triggering of pressure relief due to pressure fluctuations and timely start in case of overpressure;
(2) Medium compatibility: Select the corresponding safety valve material for different media in biological fermentation pipelines. For pipelines conveying corrosive media such as acid-base disinfectants, select safety valves made of stainless steel or polytetrafluoroethylene with strong corrosion resistance to avoid valve corrosion leading to seal failure;
(3) Discharge capacity matching: Select a safety valve with sufficient discharge capacity according to the maximum possible overpressure discharge capacity of the pipeline to ensure rapid pressure release in case of overpressure and prevent continuous pressure rise. At the same time, it must comply with relevant national standards and biological fermentation industry specifications to ensure the performance of the safety valve meets the standards.
2. Pressure Reducing Valve: Its core function is different from that of safety valves, focusing on "active regulation and stable pressure" rather than emergency pressure relief. It is mainly used to reduce high-pressure media in pipelines to a stable pressure required for biological fermentation processes, avoiding impact of high-pressure media on pipelines, valves, and bioreactors, and ensuring the stability of fermentation processes and equipment service life. Working Principle: By adjusting the gap between the valve core and valve seat, the flow resistance of the medium is changed to achieve precise pressure regulation. When the inlet pressure of the pipeline fluctuates, the pressure reducing valve can automatically adjust the gap size to maintain stable outlet pressure, ensuring that the medium pressure entering the bioreactor or subsequent pipelines meets the process requirements.
Application Scenarios: Mainly concentrated in high-pressure medium input pipelines, such as steam input pipelines and compressed air pipelines. The inlet pressure of these pipelines is usually high, and pressure reduction by pressure reducing valves is required to meet the normal working pressure requirements of fermenters and bioreactors. It can also be used in the pipeline system of biogas fermenters to adjust biogas pressure to a safe transportation range.
Selection Principles:
(1) Pressure regulation range: Select a pressure reducing valve with a regulation range covering the inlet pressure of the pipeline and the outlet pressure required by the process to ensure that the regulation accuracy meets the fermentation process requirements;
(2) Medium adaptability: Select high-temperature and corrosion-resistant pressure reducing valves for high-temperature and corrosive media. For example, pipelines conveying high-temperature steam use cast steel pressure reducing valves, and pipelines conveying acid-base media use polymer material pressure reducing valves;
(3) Flow adaptation: Select a pressure reducing valve with matching flow according to the medium conveying volume of the pipeline to avoid failure of pressure reducing valve regulation caused by excessive flow. At the same time, the sealing performance of the pressure reducing valve should be considered to prevent medium leakage from affecting the sterility of the fermentation environment.
3. Bursting Disc: Also known as explosion-proof disc, it is a non-reclosable safety pressure relief device used in conjunction with safety valves as the last line of defense for pipeline pressure safety. It is mainly used to deal with extreme situations where the pressure in the pipeline rises sharply. When the pressure reaches the preset bursting pressure, the bursting disc ruptures instantly to quickly discharge a large amount of medium to prevent pipeline explosion accidents, complying with the relevant requirements of the national standard GB 567-2012 "Bursting Disc Safety Devices".
Working Principle: Composed of a bursting disc and a holder, by presetting the bursting pressure value, when the pressure difference in the pipeline reaches the preset value, the bursting disc ruptures or falls off immediately, and the medium is quickly discharged through the ruptured channel. After pressure relief, the pipeline needs to stop running and replace with a new bursting disc to resume use. It has the advantages of simple structure, sensitive and accurate, no leakage, and strong discharge capacity, and can work reliably in viscous, high-temperature, low-temperature, and corrosive environments. It should be noted that since the bursting disc is a disposable device, it cannot be restored after use, and a large amount of medium discharged during the bursting process will cause certain material waste, which is also the main limitation in its use.
Application Scenarios: For parts where pressure may rise sharply instantly, such as fermenter waste gas discharge pipelines and biogas transmission pipelines. These pipelines may experience a sharp pressure rise due to abnormal microbial metabolism, pipeline blockage, etc. When the safety valve cannot relieve pressure in time, the bursting disc can play a role to avoid explosion accidents. In addition, for pipelines conveying highly toxic and expensive media, the tight and leak-free characteristics of bursting discs can effectively prevent medium leakage and reduce losses and environmental pollution.
Selection Points:
(1) Bursting pressure setting: The calibrated bursting pressure of the bursting disc should be determined according to the design pressure of the pipeline and the maximum allowable overpressure value to ensure that the bursting pressure is slightly higher than the maximum allowable working pressure of the pipeline, and the bursting tolerance should be controlled within the specified range;
(2) Material selection: Select the corresponding bursting disc material according to the characteristics of the pipeline medium. Metal materials (such as stainless steel, Hastelloy) are suitable for high-temperature and high-pressure media, non-metallic materials (such as graphite, fluoroplastic) are suitable for highly corrosive media, and graphite bursting discs can also withstand a certain temperature, adapting to pipelines conveying highly corrosive fermentation auxiliary media;
(3) Type selection: Select forward-acting, reverse-acting, or flat bursting discs according to the pipeline installation scenario and medium characteristics. Reverse-acting bursting discs are suitable for scenarios with large pressure fluctuations, and forward-acting bursting discs are suitable for conventional pressure protection scenarios; Fourth, discharge capacity: Ensure that the discharge capacity of the bursting disc is greater than the maximum safe discharge capacity of the pipeline to ensure rapid pressure relief when the pressure rises sharply. At the same time, the operating ratio of the bursting disc should be considered to avoid fatigue damage of the bursting disc under normal working pressure.
In practical engineering, the three types of equipment cooperate to form a complete pressure protection: pressure reducing valves are responsible for daily voltage stabilization, safety valves are responsible for conventional overpressure relief, and bursting discs are responsible for ultimate protection under extreme working conditions. For pipelines of combustible and toxic gases, bursting discs and safety valves should be connected in series to improve reliability. Combined with patented technology, pressure protection and dehydration devices can be integrated in the biogas pipeline system to automatically adjust positive and negative pressure, reduce water vapor corrosion, extend equipment life, and further improve the safety of fermentation systems.
In terms of flow regulation, flow sensors and flow control valves are configured to monitor and accurately regulate flow in real time to avoid impact and wear. Buffer tanks are set on material pipelines to stabilize flow and pressure, reduce pipeline fatigue, and extend service life.
IV. Improve Pipeline Leakage Prevention and Sterile Protection Design to Keep the Safety Bottom Line
Leakage prevention and sterile protection are core measures to ensure the safety of fermentation systems and product quality. Pipeline leakage will not only cause material loss and fermentation interruption but also trigger accidents such as fire, explosion, and poisoning; microbial pollution directly leads to fermentation failure. Therefore, dual protection capabilities must be strengthened in the design stage.
Leakage prevention design takes "monitoring + isolation + control" as the core. Ultrasonic leak detectors and gas alarms are installed at leak-prone points such as valves, flanges, and pump ports to realize real-time monitoring and rapid alarm. Liquid dikes and diversion ditches are set in the tank area to prevent leakage diffusion and facilitate collection and treatment. Pipelines conveying flammable and dangerous chemicals shall comply with specifications, not pass through irrelevant areas, no valves and leak-prone parts shall be set across passages, and cut-off valves and 8-blind plates shall be set at the inlet and outlet of workshops to strengthen the cutting capacity.
Sterile protection takes "sealing + cleaning + sterilization" as the core. The feeding and discharging pipelines of bioreactors adopt seamless welding to eliminate dead corners and gaps. Supporting CIP online cleaning and SIP online sterilization systems are equipped, using food-grade cleaning agents and steam sterilization to completely remove biofilms and miscellaneous bacteria and meet sterility requirements. The inner wall of the pipeline is smooth and free of dead corners, facilitating cleaning and drying, and inhibiting microbial growth structurally.
V. Strengthen Pipeline Later Maintenance Design to Ensure Long-term Safe Operation
Later maintenance is an important guarantee for the long-term safe operation of pipelines. Pipelines will be affected by corrosion, erosion, and vibration during long-term operation, resulting in aging, damage, leakage, and other problems. Therefore, the design must take maintainability into account to reduce operation and maintenance difficulty and cost.
Pipeline layout should reserve sufficient maintenance space, avoid dense and concealed arrangement, and maintenance platforms and passages are configured for key valves and pumps. Standardized and universal accessories are preferred to facilitate quick replacement and reduce maintenance costs. A standardized maintenance system is established to clarify the cycle of inspection, cleaning, sterilization, and anti-corrosion, focusing on troubleshooting hidden dangers such as corrosion, looseness, and seal aging to ensure that the pipeline is always in good condition.
Conclusion
Pipeline safety is the foundation for the stable operation of bioreactors and efficient production of fermentation systems, as well as the core requirement for safe production in the field of bioengineering. Against the background of the rapid development of biotechnology, fermenter design must take pipeline safety as the guide, construct a systematic scheme from five dimensions: material selection, structure optimization, pressure and flow regulation, leakage prevention and sterility, and later maintenance, and run the safety concept through the whole process. Through scientific design and system management, risks such as leakage, corrosion, overpressure, and pipe burst can be effectively reduced, ensuring the long-term stable operation of bioreactors and fermentation systems, and providing solid equipment support for the high-quality development of bioengineering and biotechnology industries.