Air quality monitoring stations designed yo operate in extreme weather conditions
Bound for an exacting environment, a batch of AQM enclosures have been engineered to withstand extremes of weather and temperature in an overseas location where the power supply is subject to sporadic fluctuation.
The AQM enclosures are made from heavy-duty, corrugated steel with 150mm insulation to ensure that internal temperature is maintained at 21°C. This internal temperature level is maintained to ensure optimum optimum performance and operation of the instruments as, for absolute accuracy with gas monitoring, a steady temperature is essential. Also, calibration will be more accurate with less calibration drift.
Consideration was also given to the sample inlets - these are heated and lagged to ensure that any water vapour is fully condensed-out before reaching the analysers. In winter, one metre to two metres of snow is commonplace, therefore snow deflectors have been built on top.
The contract, awarded by a major, international engineering company, is for local authority monitoring and industrial fence-line monitoring of NOx, SO2, CO and H2S. The AQMs will be placed in outlying villages around an oil refinery and, operating as an early warning system, will detect any increase in pollution levels. There will be 11 alarm stations in the villages, four AQM stations and one central control station with computers.
An added difficulty to be overcome is a sporadic power supply. In order to deal with this problem, ET has included an integral, high capacity UPS/battery back-up system, providing eight hours of standby power.
The instrumentation within the enclosures is from API, Opsis and Met One Instruments for whom Enviro Technology is exclusive distributor. Sensitivity, range and reliability of the instrumentation are important factors. The API instruments fitted have a detection limit of 0.44ppb and can operate over a range from 0 - 20,000 ppb. All analysers perform unattended daily calibration checks, normally a two-week or monthly check by an operator is typical.
The environmental management software used is a specially customised version of the Opsis EnviMan program with all the displays and diagrams presented in two languages.
The EnviMan ComVisioner software is the core of the real-time data management functions in the EnviMan software suite. ComVisioner accesses monitoring stations, extracts data from them and puts this data on the EnviMan databases. Often, this data is used by the EnviMan Reporter, Sitebuilder and Forecaster.
ConVisioner also provides the possibility of automatic data validation, advanced data processing and calculations, report generation and other features. Any data, real-time as well as historical, can be made available for displaying in charts or as numeric values.
Because the infrastructure is not as good as in the West, the primary source of data collection is over the telephone network, using modems. Each station has its own PC and printer for data back-up and to enable local site operators to produce statistical analyses