Standard mixtures – Messer provides solutions - Messer Belgium
Standard Gas Mixtures
STANDARD GAS MIXTURES
High precision standard gas mixtures for routine applications
In addition to pure gases, defined gas mixtures are required for routine applications in a variety of areas - from banana ripening to laser applications and the operation of ionization chambers. Thanks to their consistent composition, Messer can produce these as standard gas mixtures. Messer’s many years of experience and its employees’ high level of expertise in development, production and analysis ensure that we are always able to offer our customers the high quality standard they expect.
Individual gas mixtures
In order to meet the special requirements of our customers, Messer also produces individual gas mixtures. These custom gas mixtures are manufactured on demand. Typical examples are test and calibration gases for analytical instruments. Messer offers a variety of mixture categories (Tecline, Traceline, Labline and Topline) which define the tolerance, uncertainty and stability period.
Characterization of gas mixtures
Characterization of gas mixtures
The composition of a gas mixture is defined by the amount of the various components in the mixture. Different units may be used for specifying concentrations. The amount of substance (% or ppm) is often used, as this unit is pressure and temperature independent. Also widespread are volume content and mass concentration. These pressure and temperature dependent units are defined at standard conditions (0°C and 1013 mbar). For the conversion from one unit into another Messer uses software based on the standard ISO 14912 (Gas analysis – Conversion of gas mixture composition data). The feasibility of a gas mixture is limited by chemical, physical and safety restrictions. For instance, gas mixtures containing both, oxidizing and flammable components can only be produced under limited conditions. A team of Messer´s experienced experts checks every single gas mixture which is produced for the first time and defines in detail all relevant process parameters. For the mixture´s calculation a specially developed thermodynamic software package is used. The (production) tolerance describes the permitted deviation of the actual concentration (actual value) of a component from the required concentration (rated value). Depending on the production process, the concentration range as well as type and number of components, the tolerance is normally about 5% to 10% relative. The actual value of a component can only be stated with a certain uncertainty. On the certificates Messer states always the expanded uncertainty with the coverage factor k=2 meaning that the true value lies with a probability of 95% in the specified interval. When gas mixtures are used for calibrating measurement instruments the content of a gas cylinder often lasts for many months. The stability period specifies the time from the date of manufacture, for which the actual value in the certificate applies. Usually this period is 12 months, although longer stability periods for many gas mixtures are possible (Longlife Option). In this context, the internal treatment of the gas cylinders plays a crucial role. The production of stable gas mixtures is only possible through thorough and consistent cylinder pre-treatment with extensive purging and evacuation cycles at high temperatures as well as appropriate conditioning procedures.