Bio Quell Clarus

The development of the BioQuell Clarus was the result of an investigation into why the industry was experiencing problems on revalidating previously qualified hydrogen gassing cycles. In the first instance, the focus on the investigation was on quality issues in resistance variation of BIs. However, the investigation extended to the process itself with studies to establish the optimum conditions for biological decontamination efficacy. BioQuell noted that kill time at 6 log reduction of Geobacillus stearothermophilus and repeatability of kill time was faster and more consistent when conditions reached saturated equilibrium vapour pressure; hence, micro-condensation was formed. It became evident that a different set of process conditions was required, which needed a different system design to meet the requirement.

Although there was evident success of the Steris VHP 1000, this system was a single closed-loop system that was not designed for, nor could control, conditions of micro-condensation. This has led BioQuell to develop a closed-loop, HPV generator that incorporates a number of advances that primarily maintain and control micro-condensation conditions in the bio-decontamination cycle phase.

• The Clarus is based on a dual-loop, closed-circuit design with two changeover air/gas circulation routes for different phases of the process, so that each circuit can be optimised for the process requirement at that stage.

• During the initial cycle phase of relative humidity and temperature conditioning, the air circulation path is through a refrigeration process dehumidifier, which is in continuous operation. In contrast, the VHP 1000 has a chemical dryer, which requires a regeneration period after ten hours or so of operation and requires 18-hour regeneration time. This is a major disadvantage where continuous production is taking place.

• Once the preconditions have been achieved, the gas circulation path changes over with a vapouriser in circuit. At this time, there is no catalyst in the same circuit, so vapourised hydrogen peroxide is permitted to build in concentration to saturated conditions, resulting in micro-condensation (typically nonvisible) developing on the surface of the separative enclosure requiring bio-decontamination.

Effectively, the Clarus uses the condensation process to deliver the hydrogen peroxide disinfection agent directly onto target surfaces.

• Following the bio-decontamination phase gas residuals are removed by changing the gas circulation route back to the conditioning circuit, which includes a catalyst. This cycle phase, (d), is called aeration.

• Aeration is a process of reevaporation of micro-condensation from surfaces and breakdown of hydrogen peroxide to water and oxygen by a catalyst. The generated water from the aeration process is removed by the conditioning circuit refrigeration dryer and collected in a waste bottle.

• Clarus does not continuously break down and replenish the HPV in the system. Instead, the vapour only passes the catalyser at the end of the cycle, the gas being topped up by the evaporator as need be, during the gassing phase. This results in a major reduction in the consumption of hydrogen peroxide solution.

• The BioQuell Clarus range of gas generators includes two units that are for supply to clients, Clarus L and Clarus C, and two units that support a gassing service, Clarus R and Clarus S, provided by BioQuell and authorised parties.

• Clarus L is typically used for bio-decontamination of laboratory equipment, safety cabinets, incubators, ventilated cage racks, small isolators, etc. Clarus C is used for isolators requiring a high level of parametric control and, because of the evaporation and control, capacity can be used for cleanrooms up to 200 cubic metres. Clarus R is theoretically infinitely scalable in capacity and has been validated up to 750 cubic metres cleanroom volumes. Clarus S is primarily for biological safety cabinets.

• The Clarus C uses easily obtainable industry-standard bottles of 30 percent hydrogen peroxide solution rather than specially developed, dedicated cartridges. Clarus L uses a dedicated fill volume charge for sealed handling and is without residuals, as the 10- to 175-ml range of bottles provide the optimum amount to be used for each developed gassing cycle; a bar code reader assists traceabilty.

• All Clarus hydrogen peroxide gas generators include an integrated electrochemical cell H2O2 gas monitor that gives a direct readout of the gas concentration of the HPV, typically measured directly in the separative enclosure. H2O2 gas concentrations are printed together with all other critical cycle references and real-time data.

• The Clarus C offers an optional condensation meter which, when fitted inside the isolator, can control and optimise the delivery of hydrogen peroxide to the system, holding the concentration at the point of micro-condensation.

• The Clarus range is supported by gas distribution devices utilising rotating jet nozzles to provide very efficient gas distribution without the cleaning challenges provided by the traditional gas mixing stirrer fans mounted in the separative enclosure.

• Clarus gas generators are configured to operate with aeration assistance devices to reduce the overall cycle time. Assisted aeration may be via the enclosure HVAC or via catalyst systems that work in association with the gas generator catalyst.

Figure 7.9 shows the overall appearance of the Clarus C gas generator.

The Clarus gas generator range utilises Siemens PLC control, with digital readout and alarm of the operating parameters and automatic printout. Comms ports, RS232 and RS 485, are provided for connection to remote equipment, data logging and interface to other PCs.

The bio-decontamination cycle can be configured to run at positive or negative pressure. Clarus C has circulation flow rates of 30 m3/h and variable H2O2 injection rates up to 8 g/min. Clarus L has circulation flow rates of 20 m3/h and a fixed H2O2 injection rate at 2.8 g/min.

Clarus C holds up to 99 cycles in a software HMI library and Clarus L holds 10 cycles. Each cycle has a defined recipe with input parameters developed through a process of cycle development before PQ qualification.

Calculations for injection rates to achieve micro-condensation conditions for given enclosure volume are completed using a unique computer program. The science and basis of the program follows the monograph by Watkins et al. (2002).

HPV seems likely to become fairly standard as the preferred method for bio-decontaminating industrial-scale isolator systems, and so it is worth examining the process cycle of Clarus C in a little more detail at this stage. Figure 7.10 is the schematic flow diagram.

• The system is driven by a multistage centrifugal fan capable of developing up to 3 kPa to overcome the pressure drop through the Clarus itself, the isolator and its HEPA filters, and all of the associated ductwork.

• Through the conditioning circuit, the fan delivers air to the catalyser and then to a dehumidification column with a refrigerant dryer, which cools the air to 10°C. Any condensate is pumped to the waste collection receiver bottle. In addition, any residual hydrogen peroxide remaining in the Clarus C dosing column at the end of the cycle is pumped to the waste collection bottle so that all new cycles start with fresh valid agent.

• Air then passes over a reheater to bring back the delivered air temperature to normal conditions before delivery to the enclosure.

• Airflow rate is measured by passing return airflow through a standard orifice plate and monitoring the pressure drop across the plate with a high-resolution pressure transducer.

• An integrated pressure control system takes air in via a HEPA filter and expels an air/gas mixture out via a catalyst/HEPA filter to maintain set pressures (positive or negative) whilst in closed-loop

Clarus Port Schematic

Figure 7.9 The BioQuell PLC Clarus Hydrogen Peroxide Gas Generator. The compartment in the lower right front panel carries the supply of 30 percent peroxide solution. The smaller compartment on the left carries the condensate collector. The gas supply and return hose connections are out of sight on the back of the enclosure in this view. (Courtesy of BioQuell PLC.)

Figure 7.9 The BioQuell PLC Clarus Hydrogen Peroxide Gas Generator. The compartment in the lower right front panel carries the supply of 30 percent peroxide solution. The smaller compartment on the left carries the condensate collector. The gas supply and return hose connections are out of sight on the back of the enclosure in this view. (Courtesy of BioQuell PLC.)

Schematic Flow Diagram

Diagram Hydrogen Peroxide Manufacture

Valve

Figure 7.10 A Schematic Drawing Showing the Operation of the BioQuell PLC Clarus Hydrogen Peroxide Gas Generator. (Diagram provided by BioQuell.)

Valve

Figure 7.10 A Schematic Drawing Showing the Operation of the BioQuell PLC Clarus Hydrogen Peroxide Gas Generator. (Diagram provided by BioQuell.)

operation. A reference tube is connected between the gas generator and enclosure to facilitate pressure monitoring and control via the Clarus system.

• The gas generator will drive air around this circuit until it has been dried down to the required humidity, typically 40 percent RH. The catalyser and dryer are then closed off and the flow path changes to the vapouriser circuit.

• The dry, warm air now enters the evaporation module (vapouriser), where hydrogen peroxide solution is delivered to a hot plate and flash evaporates at 125°C. The final gas generator delivery temperature is 60°C.

• The hydrogen peroxide is transferred from a standard bottle reservoir via a peristaltic pump to a dosing column that uses pressure transducer measurement, operating under the command of the PLC controller, which calculates and accurately delivers at defined injection rates. The system constantly accumulates the delivery rate and modulates to ensure accurate total delivery weight (grams) for the complete cycle.

• The HPV then passes through the isolator via heat-traced hoses, to limit any losses via condensation on route, and is returned to the Clarus once more.

• A HEPA filter on the gas return prevents the ingress of particulate matter that might poison the catalyser and contaminate the vapour-iser.

• At the end of the gassing phases, the gas path switches back to the conditioning circuit, initiating the aeration phase with the air/gas mixture passing over the rare-metal catalyst bed, which breaks it down to water vapour and oxygen.

• All cycle phases can be either controlled to PLC set time points or parametrically to conditions measured by critical/calibrated instruments.

• As with Steris for the VHP 1000, the Clarus manufacturer, BioQuell, is able to advise clients on the application and the validation of the process. Full support documentation (IQ, OQ, O and M Manual) is normally provided, as well as QA and operator training.

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Responses

  • salvatore
    Why electrical ventillation fan on bioquell claraus c?
    8 years ago
  • Abraham
    Why H2O2 bottle can not be used after single use during VHP decontamination of Isolator ?
    11 months ago

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