PEFTEC 2019 - Abstract

Abstract Title: Most accurate calibration facilities for gas analysis
Abstract Type: Seminar
Session Choice: Standards & Quality Assurance
Presenter Name: Mr Karsten Kletschkus
Company/Organisation: Woesthoff Messtechnik GmbH
Country: Germany

Abstract Information :

Most accurate calibration facilities for gas analysis

In petrochemical plants and refineries, you find high precise analytical instruments used to optimize production processes and to ensure the quality of chemical products. Gas chromatographs are very often used for quality assurance of chemical intermediates or end products like LPG. Analyzers, used for occupational and plant safety, need exact calibration gases for their calibration too. A lot of analyzers based on chemical or physical methods, for monitoring, controlling and optimizing chemical processes within a refinery need to be calibrated periodically with precise calibration gases.

Calibration gases in gas cylinders are very common, but have major uncertainties and a short time of stability. They have long delivery times, a short durability and are cost-intensive.

It is more flexible and less expensive to mix calibration gases with a dynamic procedure by yourself. In use are dynamic mixing systems which control the gas flow by measuring mass- and thermal properties. These Mixing systems have a limited accuracy, need a high flow rate and have to be configurated for the used gas.

Wösthoff‘s programmable, automatic working gas mixing system DIGAMAT and the gas mixing piston pump DIGAMIX provide high accurate dynamically prepared calibration gases, independent which types of gases are mixed. The available systems are directly traceable to the SI-system due to their dimensional calibration. The calibration gas composition is directly calculated and expressed in substance amount fraction and volumetric fraction.

The automatic Gas mixing system DIGAMAT is programmable with a step functions of different concentrations steps with individual duration, depending on the demand of calibration gas. The curve of gas concentration can be stored in the on board memory and has a range of 0,1 Vol% through 100 % Vol., with an adjustable and programmable flow up to 250l/h. The DIGAMAT can be used to proceed automatic calibration processes.

The gas mixing pumps DIGAMIX can be used to mix calibration gas with 2 to 4 components, with adjustable fractions. Pure gases can be diluted in various steps from 100ppm to 10%Vol. Low fractions down to 1ppm are possible with a two-step dilution.

The DIGAMIX system meets the described method for dynamic production of calibration gas of ISO 6145-2 and DIN 51898 part 1 and part 2. The adjustments on the DIGAMIX gearbox can be transferred and recorded on a PC. The so saved data can be used with the protocol of DIN 51898-1 for documentation and quality assurance.

For both systems DIGAMAT and DIGAMIX materials, coatings and lubrication are chosen to allow the use of inert, corrosive and combustible gases and vapors, without damaging the systems and without any influence to the calibration gas.


The two Wösthoff gas mixing systems DIGAMAT and DIGAMIX allow to prepare most accurate calibration gases by the volumetric procedure according to ISO 6145-2  and DIN 51989, which are used in petrochemical plants. Pure gases can be diluted in  1 % and 10% steps or down to 1ppm. Both systems provide high flexibility, gases can be changed without any adjustments. Purchasing calibration gases can be reduced to inexpensive pure gases with long durability and short delivery time, where high accurate calibration gas mixtures can be made of.