Mass flow meters/controllers for low pressure drop or corrosive gas service

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Mass Flow Meters/Controllers for low pressure drop or corrosive gas service


> Introduction
Bronkhorst High-Tech B.V., the European market leader in thermal Mass Flow Meters/Controllers and Electronic Pressure Controllers, has more than 25 years experience in designing and manufacturing precise and reliable measurement and control devices. With a wide range of instruments,Bronkhorst High-Tech offers innovative solutions for many different applications in many different markets. The instruments are made to customers’ specification, in various styles, suitable for use in laboratory, industrial and hazardous areas, in such diverse applications as semiconductor and analytical installations, to name but two.

> OW-ΔP-FLOW series for low pressure L drop orcorrosive gases
In a number of applications for measuring and controlling gas flows there is only little differential pressure available and/or allowable. These are the applications for which Bronkhorst High-Tech developed the LOW-ΔP-FLOW series, in which the flow resistance is minimised by using a large bore capillary (thermal bypass sensor) in combination with a cylindrical flow splitter (laminarflow element). Based on this concept, mass flow capacities between 0…10 mln/min and 0…1000 m3n/h can be measured. At a flow up to 2 ln/min a pressure drop of less than 1 mbar is required. Furthermore the larger flow channels minimise the risk of clogging and facilitate the cleaning and purging of these LOW-ΔP-FLOW instruments, which will contribute to a significantly longer lifetime whenthe instruments are used on corrosive gas service. All fluid wetted parts are of electro-polished stainless steel. Optionally the flow meter body, sensor and flow element can be supplied in Hastelloy or Monel.

> Mass flow control with low differential pressure
The control of mass flow with small pressure difference comprises the LOW-ΔP-FLOW Mass Flow Controllers in compact construction(model series F-200/201/202). The integrated proportional, electromagnetic control valves of these MFC’s have extremely fast and smooth control characteristics. Depending on the operating properties, the maximum flow in these models is 1…50 ln/min air-equivalent. For the control of higher flow rates at very low differential pressures Bronkhorst High-Tech have devised special control valveswith pressure compensation bellows (series F-004). These control valves are close-coupled to the flow meter while the electric PI-control function is an integral part of the flow meter. This F-004 valve has proven to be an excellent alternative to large, slow and expensive servo driven valves.

> For laboratory or industrial conditions
The LOW-ΔP-FLOW series are derived from the laboratorystyle EL-FLOW series, however they can also be supplied with a rugged IP65 (dust and waterproof) IN-FLOW housing, suitable for industrial environments. The latter are also ATEX Category 3, approved for use in Zone 2 hazardous areas. In addition to the standard analog I/O-signals and the RS232 connection, there is the possibility of integrating an interface board with DeviceNetTM,Profibus-DP®, Modbus-RTU or FLOW-BUS protocol.

> LOW-ΔP-FLOW features
u very low pressure drop u suitable for corrosive gases u etted parts: electro-polished stainless steel; other on request w u also available with IP65 housing, ATEX approval Cat.3, Zone 2 u analog and digital (fieldbus) communication u alarm and counter functions

> Technical specifications
Measurement / control systemAccuracy (incl. linearity) Turndown Repeatability Settling time (controller) Control stability Operating temperature Max. operating pressure Temperature sensitivity Pressure sensitivity Leak integrity Mounting position Warm-up time : ± 1% FS (of Full Scale) : 1 : 50 (2 … 100%) : < 0,2% Rd (of Reading) : standard: 2…3 seconds : < ±0,1% FS (typical for 1 ln/min N2) :...