Mass flow meters offer exceptional stability

Edited by the Engineeringtalk editorial team Dec 25, 2000

Samac Controls has been appointed the UK Main Distributor for Kurz Instruments of California, particularly for the Kurz range of thermal convection mass flow meters

Samac Controls is pleased to have been appointed the UK Main Distributor for Kurz Instruments of California, particularly for the Kurz range of thermal convection mass flow meters, used to measure from small pipe flows of ultra-pure gases right up to large stack effluent flow monitoring.

The Kurz range of mass flow meters are Constant Temperature Anemometers (CTA), which offer significantly improved performance compared to the older "Hot wire" design of Constant Power Anemometers (CPA).

This means that Kurz instruments measure Mass flow of the monitored gas without any correction being separately needed for gas pressure or temperature.

The Kurz CTA technique gives exceptional stability at low flows, where the older CPA devices tend to have unstable readings because of the higher temperature reached by the active sensor.

A Constant Temperature Anemometer maintains a constant temperature difference between the heated detector element, or "sting", and the reference sting, which monitors the gas ambient temperature.

A solid state feedback control circuit is used to achieve this balance, and the power fed to the heated sting is monitored: it is this that gives the mass flow measurement.

Since the temperature of each sting remains constant, the Kurz CTA approach does not suffer from any thermal inertia problems, and this gives a fast response time to velocity change, of around 1 second.

The older CPA approach typically would give response times of 15-30 seconds.

Whilst Kurz sensors can be used on ultra-pure gases, and Kurz have developed a correlation gas calibration method to accurately predict the meter output for other gases or gas mixtures based on an air calibration, the sensor is unaffected by dirty or corrosive gases.

It can be used in stacks or flues operating at up to 500C, and overcome rapid temperature fluctuations.

The typical applications include combustion air measurement, flue gases, incinerators, aeration or digestion gases in wastewater treatment plants, air sampling systems in Nuclear fuel handling and power or waste treatment plants.

Many process gas measurements are made in chemical and petrochemical plants, where the relevant Baseefa/CENELEC approvals are available, and smaller pipe units have been used for process gas control in semi-conductor manufacturing plants.

Samac are appointing local sales and service offices for these Kurz products throughout the UK, and will be pleased to discuss potential applications via the Head office in St Neots initially.