Analyzer instruments like gas chromatographs must be calibrated regularly. This way they can accurately determine the chemical composition of compounds. While calibrating gas chromatographs, the measurement values of the chromatographs are compared with a calibration standard that has a known accuracy. The values of the device are adjusted accordingly. For gas chromatographs, such a standard is a gas mixture with an accurately known composition.
For operators of gas chromatographs, there are two ways to generate these gas mixtures:
Bronkhorst low-cost mass flow controllers offer various flow ranges to create gas mixtures with the option to communicate with Modbus protocol. The preparation method of calibration gas mixtures must comply with ISO 6145-7 standards.
The FLEXI-FLOW features a new concept of measuring mass flow and pressure is based on a technology called TCS, Through Chip Sensor. This new sensor exists of a capillary tube made with MEMS technology and combines the best of two worlds; a fast and stable flow sensor applied in our proven bypass construction for a reliable and highly accurate flow measurement.
The FLEXI-FLOW truly is flexible to use and can both measure and control mass flow and pressure in one instrument. This gas flow controller is one of the most compact ones in our product portfolio. It allows users to save space in their system and a reduction of weight and was designed specially with analytical and research labs in mind.
The EL-FLOW Base Series is another one of Bronkhorst’s gas mass flow controllers that can provide the accuracy and repeatability required for users to mix their own calibration gas. Up to 12 gas cylinders are connected to an equal amount of mass flow controllers. The accurately controlled gas flows enter a mixing chamber, after which, the mixture is fed to a gas chromatograph for calibration purposes.
Bronkhorst can supply instruments to support setups for a single cell stack up to stacks of 100’s of kilowatts. Flow meters and controllers like the IN-FLOW ‘High-FLOW’ F-117DI Series are used for testing and for high power use or commercial use, which require wider load dynamics or highest durability.
Bronkhorst has developed the IQ+FLOW mass flow sensor, which uses micro solid state technology (MEMS) that reduces the footprint dimension to 0.75″, or half of conventional mass flow meters. The IQ+FLOW offers ultra compact flow and pressure meters and controllers.
The ISO 6145-7:2009 standard describes a procedure to prepare calibration gas mixtures using commercially available thermal mass flow controllers. The accuracy of the final gas composition that leaves the gas mixers is calculated by dedicated software that considers the uncertainties in the gas flows and in the gas composition of the initial gas cylinders.
Compared to the purchase of gas cylinders with pre-mixed gas mixtures, the preparation of gas mixtures on-site has some advantages. For example, the lifetime of pre-mixed gas mixtures can be limited. The costs for these pre-mixed gas mixtures are quite high, and there’s no guarantee that the concentration of the gas is still good or that the mixture is still homogeneous over time.
Therefore, it can be beneficial for users to prepare gas mixtures on their own with very low concentrations of specific compounds. This yields the main argument for on-site gas preparation: as an operator you don’t have to invest in cylinders of gas mixtures. It gives a lot of flexibility and freedom to calibrate an analyzer in your own time.
The entire ‘package’ of good purchase price, improved accuracy and flexibility as well as the integrated Modbus protocol has been reason for the customer to choose for Bronkhorst devices.
Copyright 2024 © All Rights Reserved Worldwide
