TRAS 120 (technical rule for plant safety) – safety requirements for biogas plants
- We support you in implementing the requirements of the TRAS 120
- We take over the necessary documentation and the inspection deadline management for you, as well as the annual employee briefings
TRAS 120 (technical rule for plant safety – safety requirements for biogas plants) was published on 21 January 2019 by the Federal Gazette. It was developed by the Commission for Plant Safety (KAS) and serves as a source of information for the plant operators.
A trouble-free, safe system operation is thus to be ensured, with personal safety and environmental protection in the first place. It provides information on relevant sources of danger, basic requirements for biogas plants and special requirements for certain plant components. The topic of documentation also moves into focus with the TRAS 120.
In the following, we would like to give you a brief overview of the essential contents of the TRAS 120. The complete TRAS 120 can be viewed at the Plant Safety Commission.
Do you need support in implementing the requirements of the TRAS 120? SYSWE is your competent partner and supports you! Inform yourself now!
Essential contents of TRAS 120
Chapter 1: Introduction
Section 1.2: Requirement
Purpose of TRAS 120
- personal security
- environmental protection
- asset protection
A trouble-free safe system operation is to be ensured.
Including: startup, shutdown, maintenance
Section 1.3: Scope
- Permitted biogas plants (including biomethane plants)
- Operating areas according to 12th BImSchV
- Digesters on wastewater treatment plants (except pure sewage sludge digestion)
- Fermentation lines on MBT plants (mechanical-biological waste treatment)
- Recommendation for: Dry fermentation plants, biogas plants not requiring approval
The technical rule applies to the construction, condition and operation of biogas plants. It must also be taken into account in the design and planning.
Section 1.5: Hazards
The dangers on biogas plants are:
- Gas or substance release
- Fire (biogas, process media, plant components)
- Formation of hydrogen sulfide by process disturbances
A risk assessment (in accordance with TRGS 529) or a hazard analysis (in the event of accident management) must be carried out. All hazards are considered, including the start-up and shutdown process, the maintenance and the design, planning and installation of the plant.
In the further course of this section, the possible sources of danger at biogas plants are listed and explained.
Chapter 2: Basic Requirements
Section 2.1: General requirements
- The operator must design, build and operate the system in such a way that harmful environmental effects and other dangers are prevented.
- Countering still occurring hazards, measures are to be taken to limit.
- Stability proofs for all load-bearing parts of the plant.
- Stability, tightness (gases, liquids, solids), pressure resistance, discharge capacity and resistance to corrosion, etc. must be ensured by the operator.
- Operation of the system with the required safety equipment. Supply of these facilities via two independent systems necessary.
- Unblocked access to connections, fittings, safety and operating devices and all other parts of the system that are to be regularly monitored and maintained.
- Frost-proof operation of plant components where moisture from biogas can condense and contain aqueous mixtures or condensate.
- Against mechanical damage caused by vehicles and working machines, accessible parts of the system that are exposed to process media and operating materials (biogas, substrates and digestate) must be protected in the area of operating routes.
- Corresponding enclosures shall be erected against unauthorized access to the facility and control equipment which, when operated, causes danger to persons or damage to the environment, shall be secured against unintended operation.
- Considering the type of plant, the substrates, the site-specific loads (earthquakes, floods, wind and snow loads), the mode of operation and the proximity to protected objects based on the regulations relevant for biogas plants plant-related planned, designed, constructed and operated.
- For the production of biogas substances are not permitted as a substrate if they are not suitable or not conducive due to enzymatic or microbiological degradation and cause harmful environmental effects. Typical agricultural contaminants such as e.g. Earth attachments or sand are excluded.
- Substrates or fermentation residues that are solid and / or prone to auto-ignition must be identified. Inflammatory processes during the drying and storage of solid inflammable substrates and fermentation residues must be avoided.
- Biogas produced in fermentation tanks, including hydrolysis gas, shall be supplied to a gas utilization facility and (if it must be taken out of service due to breakdown or maintenance) if storage is not possible, to a permanently installed Additional Gas Consumption Facility, provided the composition permits incineration.
- The gas utilization facilities must be able to utilize all the minimal and maximum biogas produced.
- Overpressure safety devices in gas-exposed parts of the system are safety devices which serve exclusively to prevent impermissible pressures. The additional gas consumption device must take precedence over the response of an overpressure safety device.
- If it is necessary to open gas-exposed parts of the plant for maintenance work, the formation of a potentially explosive atmosphere and the emission of biogas must be avoided and, if this is not possible, minimized.
- Escaping dangerous gases are to be diverted safely. Ventilations should be carried out in such a way that a dangerous concentration of gases in the area of outlet openings is prevented.
Section 2.2: Fire protection
Fire loads in biogas plants can be:
- Existing materials, such as substrates, biogas, sulfur, lubricants and fuels, activated carbon, dried fermentation residues or
- plant components such as membrane systems, insulation of fermenters, pipelines, biofilters, combined heat and power plant, electrical installation.
Section 2.3: Explosion protection
- Required measures for explosion protection are mentioned in chapter 4.2 of TRGS 529, as far as nothing supplementary is regulated in this TRAS. It is primarily measures to avoid gas release (the system parts are permanently technically tight or technically tight) or ventilation and inerting apply.
- To prevent the formation of a potentially explosive atmosphere, the operator must equip the machine rooms with technical ventilation (see chapter 3.6).
- If the formation of a potentially explosive atmosphere can not be reliably prevented, TRGS 529 section 4.2 and TRBS 2152 part 1 or TRGS 721 and TRBS 2152 part 2 or the following apply to the definition of potentially explosive areas and the protective measures to prevent or limit the potentially explosive areas. TRGS 722. TRBS 2152 Parts 3 and 4 apply to the necessary protective measures to prevent the ignition of an explosive atmosphere or to limit the effects.
- Protective measures must be taken in potentially explosive areas. For dimensioning the protective measures, these areas can be divided into zones. This is recommended for biogas plants. Then, for certain applications, the sample collection for the rule of the German Social Accident Insurance (DGUV Rule 113-001, Explosion Protection Rules) can be used as a source of information for the classification of potentially explosive areas in zones and the protective measures used.
- In the absence of the assessment of how frequently and how long a hazardous explosive atmosphere can be present (zone classification), protective measures must be taken as if a dangerous explosive atmosphere were to be expected frequently and in terms of time.
- Insofar as it is determined in the course of self-monitoring or during a test that biogas is no longer “technically leak-proof”, further explosion protection measures are required until the leakage is restored without delay.
- Flame arresters for anaerobically formed hydrolysis gas must be suitable for hydrogen. Flame arresters for other biogas must be suitable for biogas. Both have to be considered as an autonomous protection system within the meaning of the Eleventh Regulation on Product Safety Act (Explosion Protection Product Regulation – 11th ProdSV) or Directive 2014/34 / EU of the European Parliament and of the Council of 26 February 2014 on the harmonization of the laws of the Member States relating to equipment and protective systems intended for use in potentially explosive atmospheres (Directive 2014/34 / EU). Their placement in a facility must enable safe and easy maintenance.
- Hazardous areas are to be marked at the access points.
- The occurrence of dust-explosive fines of the dried fermentation residues should be avoided. If this is not possible, take protective measures, such as avoiding effective ignition sources.
Section 2.4: Gas-contaminated parts of the system
- Measures must be taken to prevent the release of gases. In the event of the occurrence of disturbance-related releases, immediate measures must be taken to eliminate the underlying disturbance.
- Gas installations and their equipment, including all piping connections, shall be constructed, operated, inspected and maintained in such a way that they are technically leak-proof in the long term under the expected mechanical, chemical and thermal stresses resulting from the intended operation. If this can not be achieved according to the state of the art and safety technology due to design or construction, the corresponding gas-carrying parts of the biogas plant must be at least technically tight.
- Maintenance-related unavoidable releases of biogas in the course of maintenance are only permitted if the protective and safety measures required in the risk assessment and, if applicable, the concept for the prevention of incidents according to the Störfall-Verordnung have been determined and implemented accordingly and no danger can arise. After maintenance and repair work with air introduced into gas-bearing plant components, biogas with too high an oxygen concentration must not be supplied to the activated carbon adsorber.
- Leakage due to voltages, subsidence or vibrations of system components must be prevented by suitable installation of the system.
- Fermentation tanks, gas storage tanks, membrane systems and pipelines shall be constructed and operated in such a way that they can withstand the stresses to be taken into account. In particular, static loads, including stresses, operational stresses due to pressure and temperature as well as external influences due to wind, snow, ice, hail and UV radiation must be considered.
- Fermentation tanks, gas storage facilities, gas consumption facilities as well as the plant parts for the treatment of biogas must be able to be shut off from other parts of the gas-treated plant. The fittings used for this purpose must be arranged directly on the respective system components, clearly labeled (see chapter 3.1, paragraph 2), easily accessible in case of danger and safely operated from a safe position or operated remotely.
- Every fermentation tank and every gas storage tank must be equipped and operated with suitable overpressure and underpressure safety devices (eg hydraulic / mechanical equipment).
- Gas systems are to be dimensioned taking into account the expected volumetric flows and flow resistances so that an inadmissible negative pressure is not to be expected during normal operation. Before triggering low-pressure fuses, the gas extraction must be reduced and, if necessary, terminated. As far as this is not guaranteed in existing systems, the oxygen concentration must be monitored to detect the ingress of air. The monitoring devices must be arranged on the pressure side of the biogas compressor.
- Prior to overpressure protection, a gas appliance must be put into operation (see chapter 3.8).
- Compressors for biogas must meet the requirements for equipment of equipment group II at least equipment category 3 as defined in Directive 2014/34 / EU.
Section 2.5: Safety distances
- For biogas plants, safety distances must be observed to ensure safety.
- Safety distances between gas-contaminated plant components of biogas plants and neighboring plants, facilities, structures or traffic routes serve the purpose of protecting the biogas plant against the effects of a damage event outside the biogas plant, such as heating due to fire or mechanical damage (external protection distances).
- Safety distances are also distances that protect the individual parts of a biogas plant against mutual interference in normal operation or damage, z. As the gas storage before firing adjacent equipment or structures on the biogas plant (internal protection distances).
- Protective distances and preventive fire protection measures shall be designed in accordance with the requirements of Annex VII. Other safety distances are to be determined taking into account local conditions.
- In the case of existing plants, the protective distances can also be completely or partially replaced by measures of protective fire protection (such as stationary, automatic cooling and extinguishing systems).
Section 2.6: Operation, Organization and Documentation
- Business organization and documentation
- Technical knowledge
- Testing and maintenance
- Measures for malfunctions: alarm and emergency plan, safety exercises and emergency power concept
Section 2.7: Special requirements for installations for the acceptance of special input materials
- The following requirements apply to plants that accept special feedstocks or chemically stabilized substrates as part of their approval.
- If special starting materials or chemically stabilized substrates are to be assumed, by the dangerous concentrations of toxic gases such as hydrogen sulfide and ammonia and carbon dioxide in an assumption or in a mixture of feedstocks with each other or with substrate can not be excluded, has previously been a case by case safety Person responsible for the operation.
- The operator may only accept special input materials, except biowaste from households, and chemically stabilized substrates if he has the following information:
- Waste code number, as far as waste is concerned,
- race procedures
- essential ingredients and additives (stabilizers for transport) or their chemical composition,
- pH value (if necessary of the eluate),
- and actual transport and acceptance conditions to be observed and
- a statement by the producer on possible risks of acceptance and pre-treatment, especially when mixed with other substances.
- The operator has to carry out a quick test before accepting substrates according to paragraph 3. This must include the following measurements:
- Temperature measurement,
- pH measurement (if necessary of the eluate) and
- determination of the reaction and gas formation on contact with acids and alkalis (see TRGS 529, section 4.4.3, paragraph 1) as well as intended mixing.
- If substrates are accepted in accordance with paragraph 3, the following information must be documented in an operating log:
- Producer of substrates,
- Information and explanation of the producer,
- assumed substrate mass,
- results of the rapid tests referred to in paragraph 4,
- type of pretreatment and
- function of gas extraction in accordance with paragraph 9.
- The filling of receiving containers with flowable or pumpable starting materials is only permitted in closed containers via fixed connections. If possible, a vapor recovery with the delivery vehicle is to be established.
- Receiving containers for non-flowable or pumpable special feedstocks must be suitable for the intended use and must be kept closed. The opening of a not completely emptied and cleaned receiving container is only permitted directly for the filling process with non-pumpable starting materials.
- These receptacles and enclosing structures, if any, shall be connected to an exhaust gas and exhaust ventilation system capable of operating at all times, which will produce a permanent negative pressure in the receptacle unless the receptacle is completely emptied and adequately cleaned. The extracted gases are usually supplied to an exhaust gas purification device.
- In the event of failure of the suction device, an alarm must be given to the person responsible for the operation and in the system, the filling must be stopped immediately and the danger zone evacuated by persons.
- In-premises reception equipment requires stationary gas detection equipment with metering points in each receptacle and building that are at least responsive to hydrogen sulphide. Taking into account the properties of the input materials intended for processing, the monitoring should be extended to other gases if necessary. Before dangerous concentrations are reached in a reception container or building, a visual and audible alarm must be given to the person responsible for the operation and to the system. As a result, the filling must be stopped immediately and the danger zone evacuated by persons (see TRGS 529 section 4.4.3 paragraph 2).
Section 2.8: Lightning Protection
- Lightning protection devices are differentiated in external and internal lightning protection. According to DIN EN 62305, the external lightning protection system consists of a capture device, a discharge device and a grounding system. The internal lightning protection system consists of lightning protection equipotential bonding and / or electrical insulation in relation to the external lightning protection. Reference is made to the regulations of TRBS 2152 Part 3 for lightning protection in areas with a hazardous explosive atmosphere.
- Internal lightning protection is required for all systems.
- An external lightning protection is required for installations, as far as lightning as ignition source must be avoided and is in these cases in protection class II to implement (see DIN EN 62305). If there is no division of the potentially explosive areas into zones, external lightning protection is required for the areas.
- In addition, safety-relevant plant components of biogas plants within the scope of the accident regulations, unless it can be demonstrated that a serious danger is excluded, with an external lightning protection system (especially for the gas storage) equip.
- Safeguard measures shall be taken to ensure that the presence of persons at or near gas-exposed parts of the installation is prevented for the period of thunderstorms.
- The lightning protection must meet the following requirements:
- Discharge devices of the external lightning protection must not be connected to devices of the internal lightning protection (equipotential bonding).
- Discharge devices of the external lightning protection must not be connected to metal working platforms and railings or stairs.
- Catching a direct impact on the structure (with a catching device).
- Safe dissipation of the lightning current to earth (with a discharge device).
- Distributing the electricity in the earth (with a grounding system).
- Preventing dangerous sparking within the building to be protected, which may be caused by the lightning current flowing through the external lightning conductors or in other conductive parts of the structure.
- The lightning protection system must be installed in such a way that no arcing, melting, spraying and sparking effects occur as far as possible.
- The capture equipment shall be installed at a sufficient distance from membrane systems and gas storage facilities (melting by thermal radiation, flying sparks).
- Trap devices must not be located within potentially explosive atmospheres, at least not in zones 0 or 1.
Chapter 3: Special requirements for plant components
Section 3.1: Identification of plant components
- Parts of the system containing dangerous substances, substrates and fermentation residues are to be marked in such a way that the substances contained in them and the dangers they cause are identifiable at all times (see § 8 (2) GefStoffV). Pipelines must be marked according to DIN 2403.
- The safety-relevant parts of the system must be marked in such a way that their identity and function are recognizable. In particular, these are overpressure and underpressure safety devices as well as the components of the membrane systems. The marking must be easily recognizable and safely accessible.
Section 3.2: Substrate pretreatment and task
- Additives and auxiliaries
Section 3.3: Fermentation tank
- All fermentation tanks of a biogas plant are to be equipped with facilities for displaying the current substrate or digestate level. Fermentation tanks must be operated with automatic devices (fill level monitoring) to detect and report impermissible substrate or digestate levels. Upon reaching the switching value substrate or gärrestfördernde facilities have to be switched off automatically to the affected container at the upper limit or at the lower limit further removal of substrate or digestate can be prevented. The monitoring of the upper and lower level must be carried out as a protective device in accordance with VDI / VDE 2180.
- All fermentation tanks of a biogas plant are to be equipped with viewing windows to detect foaming. Fermentation tanks must be operated with automatic devices (foam monitor) to detect and report improper foaming. Upon reaching the switching value foam-reducing measures must be initiated in the affected container and automatically lowering the level of substrate or digestate (pumping) are triggered. Foam monitors are to be designed as protective equipment according to VDI / VDE 2180. With a suitable design, the function of the foam monitor can also be taken over by the overfill protection.
- All fermentation tanks of a biogas plant must be equipped with facilities to prevent inadmissible pressures (overpressure and underpressure protection). The overpressure and vacuum fuses must respond without auxiliary power and close again automatically after reaching the permissible pressure range again. The overpressure and vacuum fuses must be functional even in frosty conditions.
- Overpressure and vacuum fuses must be installed according to the manufacturer’s specifications. It must be ensured that pipelines and flanges are mechanically loaded only within the permissible range. If necessary, the weight of a pressure relief device is to be intercepted separately. They must be dimensioned so that with maximum filling of the gas storage, the maximum amount of biogas formed and supplied can be safely removed.
- The gas inlet opening of pressure and vacuum fuses should be arranged so that blockages are prevented by foaming substrate in the overpressure and vacuum fuses safely.
Section 3.4: Piping, fittings, pumps
- Substrate and fermentation residue pipelines of a biogas plant must be equipped with a shut-off valve directly on each fermentation tank (see also AwSV). The shut-off valves must be easily accessible even in case of danger and can be operated by a secure footing or be carried out remotely operable.
- Displacement pumps in pipelines with substrate or digestate residues must, to the extent that it is possible to exceed the design pressure of the downstream piping system, be equipped with means for detecting, alerting and limiting impermissible pressures to protect the downstream piping system.
- Seals on wall penetrations for substrate or digestate lines and connections must be secured against slipping out (eg due to hydrostatic pressure, movement of the duct due to temperature differences or aging of the seals). Seals on substrate or fermentation residue-carrying pipelines, fittings and pumps must be checked as part of the self-monitoring (Chapter 2.6.3) and tested before commissioning and as part of periodic expert tests (Chapter 2.6.4 Paragraph 5).
- Requirements for gas-exposed system components, such as pipelines, are contained in Chapter 2.4.
Section 3.5: Diaphragm Systems, Gas Storage
- General requirements
- Attachments of membranes
- Inflation unit
- Level measurement
Section 3.6: Machine Rooms
- In order to prevent a dangerous explosive atmosphere, engine rooms must be equipped with sufficient technical ventilation.
- These rooms must be equipped with automatic devices for reporting gas hazards (gas warning system) and fire hazards (eg smoke detectors). The alarm must be transmitted to the person responsible for the operation and additionally visually and acoustically displayed outside of these rooms.
- In the fuel lines (biogas and ignition oil) to gas appliances each has a remotely operable Sicherheitsabsperrarmatur be installed.
- The remote-operated shut-off valve can be omitted in individual cases, if the gas lines in the engine room to the first automatic Sicherheitsabsperrarmatur in the gas control system due to the design are permanently designed technically tight and the technical ventilation device is designed so that in the case of maximum gas release 20% of the lower explosion limit (LEL) is below.
- In the event of a fire alarm, the ventilation must be switched off automatically and the safety shut-off valves closed.
- The gas warning system must be constructed in two stages (20% and 40% LEL). When the first alarm threshold is reached, a technical ventilation device must be switched to maximum power. When the second alarm threshold is reached, the safety shut-off valves must be closed automatically. Gas appliances in engine rooms and compressors must be automatically shut off.
- The safety shut-off valves must be integrated in the emergency stop of the CHP and can be operated from a protected point. They must be fire-resistant (F90) separated from the installation room or fireproof in accordance with ISO 10497. The shut-off must be such that the additional gas appliance is not shut off as well (see chapter 3.8 number 5).
Section 3.7: Activated carbon adsorber
- Too high oxygen content in the biogas, too high loading of the activated carbon in the adsorber with sulfur or locally insufficient flow (lack of removal of heat of reaction), it can lead to self-ignition of the activated carbon and thus also to the release of sulfur dioxide (acutely toxic).
- At an appropriate point (between activated carbon adsorber and CHP), an automatic device must be provided for the continuous measurement and detection of undesired reactions in the activated carbon adsorber. For example, carbon monoxide or sulfur dioxide can be detected in the biogas after the adsorber. The device must be able to trigger an alarm on the person responsible for the operation and in the system.
- The activated carbon adsorber must be designed at the gas inlet and outlet with shut-off valves and bypassed by a bypass. Furthermore, it must be equipped with a connection for inerting (eg by means of nitrogen).
- For inerting an activated carbon adsorber, the required amount of inert gas must be kept available.
- The change of the adsorber or the activated carbon must be made on the basis of the specifications of the manufacturer of the adsorber. Before changing the adsorber or the activated carbon, the adsorber must be flushed with the activated carbon with inert gas. Charged activated carbon from the adsorber must not be stored without additional (fire) protective measures and must be disposed of properly without delay.
- Used (loaded with pollutants) activated carbon (or not emptied adsorber) must be disposed of as hazardous waste (with the waste code number 15 02 02 *) according to the waste legislation.
Section 3.8: Additional gas appliance
- An additional gas consumption device must fulfill the general requirements for gas-exposed system components (see chapter 2.4, especially in the long term, technically tight, corrosion-resistant, frost-proof – including condensate drainage – and comply with explosion protection requirements).
- The aforementioned requirements can also be met by other solutions, provided that the safety equivalency is demonstrated.
- Torches should be designed so that the combustion tube obscures the flame.
- Torches must be erected and operated at the distance from the manufacturer to the adjacent parts of the facility and to the areas occupied by persons. For this a calculation of the distances is necessary. In this case, a limit value for the thermal radiation of 1.6 kW / m² (at a height of 2 m) shall be used for the occupied area of persons and 5 kW / m² for adjacent parts of the facility (height of the center of the flame). The determination of the safety of the location-related protective and safety distances and their calculation must be documented.
Section 3.9: Drying equipment for digestate
- Installations rooms with technically heated drying systems for fermentation residues or liquid manure, where the temperature of the heating medium can exceed 60 ° C, must be separated from rooms with other parts of the installation by firewalls or sufficient spaces (see Annex VII) and with automatic detection and reporting devices Fires are equipped. The fire detectors must be suitable for installation in a dusty environment.
- Electrical equipment must be regularly cleaned of dust deposits and checked for impermissible temperatures.
- Heating devices must be equipped with a temperature limiter, which limits the temperature of the hot air to drying, with fermentation residues to a maximum of 70 ° C, and triggers when exceeding the 70 ° C alarm.
- Before organic drying products are poured into a pile, they must be cooled to ambient temperature.
- Systems for drying organic substances may only be operated if the temperature and water content of the dried products are checked regularly. Attention is drawn to the risk of spontaneous combustion of incompletely dried organic matter in heaps.
- The formation of hazardous explosive atmospheres in drying systems must be checked. If this can not be ruled out, appropriate safety measures must be taken.
Section 3.10: Process Control Technology
- According to VDI / VDE 2180, the process control technology (PCS) facilities required for biogas plants must be subdivided into PCT facilities, PCT monitoring facilities and PCT protection facilities.
- For the PCD protective devices, a safety integrity level (SIL) must be specified in each case and the devices must be designed accordingly. The PCT installations shall be included in the testing and maintenance in accordance with Chapter 2.6.4.
- PCT facilities shall be designed and installed in a tolerant manner with regard to functional impairment due to contamination. Alternatively, PLT devices must be arranged so that they can be controlled and cleaned.
Section 3.11: Electrical Engineering
- Electrotechnical equipment must be designed by a responsible electrician (master, technician, engineer) (see DIN VDE 1000-10) and set up by electricians (journeyman, skilled worker) (see DIN VDE 105-100).
- For activities in potentially explosive areas, system components with high currents (I> 32 A) and system components of the internal or external lightning protection, the electricians must provide appropriate additional qualifications.
- The power supply of the biogas plant and the power feeding facilities must be designed so that in case of fire, the separation of the system from the power grid can be done from a safe place.
- Electrical rooms must be equipped with automatic fire detectors (smoke detectors) which will trigger an alarm to the person responsible for the operation and the system.
- Electrical rooms must be designed with sufficient ventilation or cooling devices for the necessary heat dissipation. The ambient temperature in control cabinets must not exceed 40 ° C and on average over 24 h 35 ° C (see also DIN EN 60947). The ventilation system must be designed as technical ventilation. Cooling and ventilation equipment must be controlled according to temperature.