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The Stolt Rotterdam tanker ship, filled with nitric acid, was unloading at the Krefeld-Uerdingen terminal on the Rhine River in November 2001. Nitric acid ran out of the stainless steel tanks into the ship's hull and damaged the structural steel. The ship then caught fire and sank at the terminal. Large quantities of nitrogen oxides were emitted, which drifted towards a residential area. Additionally, a mixture of acid and water was introduced into the Rhine River. The area became hazardous to people and the natural environment; however, the imminent danger for the residents and the environment was reduced because of the protective measures against pollution and the good teamwork between local authorities, fire brigades and the Bayer AG company. The acid was drained off of the ship using a controlled discharge of the acid into the river. Through the use of this measure, the ship was salvaged, limiting the pollution to the area and removing the health hazards to the people and the environment. After the ship was salvaged, the river police, along with assistance from the BAM Federal Institute for Materials Research and Testing, impounded the ship and selected corroded parts for further examination. Some of these components have been examined in detail by the BAM. These material investigations contributed to the elucidation of the origin of the leak in the floor panel. The cause of damage was deemed to be a result of a construction flaw at the enamelled valve on the load and discharge pipes.
The results from the comparative corrosion testing using the original structural steel and 60% acid revealed that the valves began to leak at least 8 h prior to the incident at the terminal.
The lecture about gas sensor characterization and calibration contains the content of 3S: Sensitivity, selectivity and stability, sensor drift, aging and poisoning as well as gas mixing systems for laboratory and field calibration, measurement uncertainty for sensor calibration and traceable calibration of gas sensor systems.
Pollution through emission of toxic gases is an increasing problem for the environment. It affects similarly agricultural, industrial and urban areas. In future, environmental emissions in ambient air must be monitored at even lower concentrations as nowadays. One environmental relevant compound is ammonia and its conversion product ammonium that have strong negative impact on human health and ecosystems. Most ammonia measurements in ambient air are performed in the range below 1000 nmol·mol 1 and thus there is a need for reliable traceable ammonia gas standards and in addition in situ analytical procedures for monitoring (in ambient air to avoid that thresholds are exceeded). Therefore, the use of reference materials is necessary for development accompanying test or for calibration, e. g. of structure-integrated sensors and mobile multi-gas sensors.
The developed gas standard generator produces gas mixtures that comply with the metrological traceability for ammonia gas standards in the desired environmentally relevant measurement range. The method is based on the permeation of ammonia through a membrane at constant temperature and pressure. The resulting ammonia penetrant gas flow is then mixed with a carrier gas flow to generate a gas standard flow of known concentration. The dynamic rage is enlarged by using a two dilution steps. Depending on the permeation rate, generable molar fractions are possible in the range nmol·mol-1 to a few µmol·mol-1. We present the design of an ammonia gas standard generator and first results of the characterisation of its individual components supporting the uncertainty assessment according to GUM for stable gas concentrations in this range. The relative uncertainty of the generated ammonia gas standard is smaller than 4 % (k = 2).
Traces of microbial volatile organic compounds (MVOCs) in air can indicate the presence of growth of moulds in the indoor environment. Ion-mobility spectrometry is a very promising method for detection of these MVOCs, because of its high sensitivity. For development of an in-situ method for detection of MVOCs, a portable ion-mobility spectrometer (IMS) was used and test gases of 14 MVOCs and their respective mixtures were investigated. IMS spectra were recorded as a function of concentration of MVOCs in air. Drift time and mobility of reactant ions formed in positive polarity mode were determined and correlated with the mass-to-charge ratio (m/z) of the MVOCs investigated. The estimated detection limit has a specific value for each MVOC and is in the range 3 to 96 µg m-3 (1 to 52 ppbV). Indoor trials show that IMS can indicate hidden mould growth.
The determination of the measurement uncertainty of quantitative and qualitative results is an important quality management tool, for example to describe measuring equipment, procedures, measurement results and the quality of products. The lecture presents the process description for the determination of the measurement uncertainty according to GUM, the determination of uncertainties in qualitative measurement results and the application of the measurement uncertainty for conformity assessment.
The evaluation of measurement uncertainty is essential for testing and calibration laboratories. This paper provides a general process description for the determination of the measurement uncertainty of quantitative data and its application to the conformity assessment with examples, and how to deal with the uncertainty of qualitative (Boolean) results, e. g. when "Alarm" or "No alarm" occours in an instrument display.
A new planar sensor element for continuous coulometric trace humidity measurements in industrial gases has been developed. In order to ensure precise measurements a calibration facility including a precision dew point hygrometer as a reference device was developed. The sensor can measure the humidity in the frost point temperature range of -20 °C to -80 °C and has an expanded uncertainty of 2 K, a fast reaction time and a settling time of the entire system from 15 to 30 min.
The metabolism of moulds results in the formation of various microbial volatile organic compounds (MVOCs). These substances can be used as an indicator for the presence of moulds in the indoor environment. Three different mould strains were cultivated on culture media and IMS spectra of gaseous mould metabolites were recorded using a portable mini system with a tritium source and a 5 cm drift cell. The headspace spectra are characteristic for mould species and their age. Typical gaseous components of the metabolites were identified and compared with results obtained from gas chromatography using a mass spectrometer detector. It was observed that the MVOCs formation depends on mould species and their growing stage with a maximum of MVOCs emission occurring during the first 10 days. These preliminary results show that IMS can be applied to detect MVOCs in indoor environment and indicate hidden mould growth.
Ammonia and its conversion product ammonium have a strong negative impact on human health and ecosystems. Most ammonia measurements in ambient air are performed in the molar fraction range (0.5 to 500) nmol/mol. There is a need for reliable traceable ammonia gas standards as well as in situ analytical procedures for the monitoring of ammonia in ambient air.
The permeation method is an effective tool for dynamically generating precise gas standards with a low uncertainty in the concentration range of a few nmol/mol to several µmol/mol in an inert carrier gas, e. g. pure nitrogen or purified ambient air. Here, we present our ammonia gas standard generator as well as results of the characterisation of its individual components supporting the uncertainty assessment according to GUM for stable gas concentrations in this range.
In order to detect ammonia in the nmol/mol-range, a suitable sensor has to be developed. In this contribution, we therefore additionally present first approaches on the development of such a sensor using optical fluorescence as transduction mechanism due to its intrinsically high sensitivity and high spatial resolution. Incorporation of a fluorescent dye, which shows fluorescence enhancement in the presence of ammonia, into a polymer matrix allows to reversibly recognize low amounts of ammonia. It can be concluded that fluorescence sensor is a robust tool for measurements of ammonia; however it needs calibration for the planed use.
Moisture content and water activity are important parameters for quality characterization of products like bulk materials, powders, granules. Thus, an exact determination is necessarily required in a wide range of industrial applications. Moisture of materials is the content of non-chemically bound water in a solid or liquid. Water activity (aW) is a characteristic/parameter of the non-chemically bound ("free") water in materials and is measured as humidity over a solid/liquid surface at constant temperature (equilibrium moisture content). It is an important parameter to characterize the quality of e. g. pharmaceutical and food products. In our contribution, we present the developed MOISHUM device for staged determination of water activity and moisture content of liquid and solid materials.