Flowquip offer a wide range of Steam flow meters. Our Vortex flow meters are the most popular choice for dry saturated or superheated steam flow measurement.
Steam is used in many different industries in a number of ways. It can be used directly in sterilisation and humidification, or indirectly as a medium for process and space heating, to which it is ideally suited due to its controllability. Food processing, beverage production and brewing all use steam, as do many pharmaceutical and petrochemical processes.
Various flow meter technologies are available to meter steam. The most suitable will depend on the requirements of each specific application.
Differential pressure flow meters used to measure steam include orifice plates, target meters, venturi and pitot tubes. All have the advantage that they are usually available at low cost but also have significant disadvantages. All these devices have a ‘critical edge’ which over time will wear and cause a drift in accuracy. Range is also an issue due to limitations of DP Transmitters which use square-root extraction to calculate flow. In an effort to overcome this problem stacked DP Transmitters are employed. Care must be taken on installation to ensure DP Transmitter impulse lines will not become blocked over time.
Variable Area flow meters are usually mechanical devices or available with a limited choice of output signals (usually 4-20mA). Accuracy is the main problem where the user can expect flow errors in the region of 5% to 10% at best.
Turbine flow meters can be used for steam flow and can offer a reasonable turndown ratio. However the principle drawback is that if the steam becomes ‘wet’ then two-phase flow (a mixture of steam and condensate) will occur. Condensate can damage the turbine blades and effect metering accuracy.
Coriolis flow meters are an emerging technology for steam measurement but suffer from the same main problem as turbine flow meters. Two-phase steam flow may not cause damage to the meter but will certainly have a detrimental effect on accuracy.
Vortex flow meters are very reliable when used to measure steam flow and do not suffer from the disadvantages listed above. On the contrary Vortex meters offer unique advantages. They cause minimal pressure drop, and they can handle high pressures and temperatures. They also have the ability to handle the three main type of steam; wet, saturated and superheated.
A vertical flow restriction, known as a ‘bluff body’ is fitted inside the flowmeter bore and as flow passes by this bluff body vortices are generated alternately on each side, similar to the rippling effect of a flag blowing in the breeze. Sensors within the flowmeter body count the vortices as they are generated. There is a direct relationship between volumetric flow and the number of vortices generated and head-mounted electronics converts the signals received from the sensors to display instantaneous flow rate and totals.
Flowquip’s Vortex Shedding Flow meters are available for 15mm to 300mm pipelines in flanged or wafer configuration. They offer the advantage of a wide flow range with the added benefit of no moving parts. An integral, or remote mounted, LCD indicates flow rate and total and provides options of a pulse and/or 4-20mA output. Typical flow turndown is 30:1 with measuring errors of 1 to 2%. An integral temperature sensor enables the flowmeter to measure mass flow of wet and dry sat steam and, with the addition of an external pressure transmitter, superheated steam. Hazardous Area applications can also be handled as ATEX Approval is a standard option. Each flowmeter is individually calibrated and despatched with its own calibration certificate
For more information on Flowquip’s steam flow meters, please call us on 01422 829920 or email email@example.com