Flowquip offers a wide range of steam flow meters. Our Vortex flow meters are the most popular choice for measuring dry saturated or superheated steam flow.
Steam is used in many different industries in various ways. It can be used directly in sterilization and humidification or indirectly as a medium for process and space heating. Due to its controllability, steam is ideally suited for these applications. Food processing, beverage production, and brewing all use steam, as do many pharmaceutical and petrochemical processes.
Several flow meter technologies are available to measure steam. The most suitable technology will depend on the requirements of each specific application.
Differential pressure flow meters measure steam using orifice plates, target meters, venturi, and pitot tubes. These devices are usually available at low cost but have significant disadvantages. Over time, the 'critical edge' of these devices will wear, causing a drift in accuracy. Additionally, range limitations of DP transmitters, which use square-root extraction to calculate flow, pose a problem. To overcome this issue, stacked DP transmitters are employed. However, care must be taken during installation to ensure DP transmitter impulse lines do 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, with users expecting flow errors in the region of 5% to 10% at best.
Turbine flow meters can be used for steam flow and offer a reasonable turndown ratio. However, if the steam becomes 'wet,' two-phase flow (a mixture of steam and condensate) will occur. Condensate can damage the turbine blades and affect 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 for measuring 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 can handle high pressures and temperatures. Additionally, they can handle the three main types of steam: wet, saturated, and superheated.
A vertical flow restriction, known as a 'bluff body,' is fitted inside the flowmeter bore. 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. Head-mounted electronics convert 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 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 for 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 saturated 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 dispatched with its own calibration certificate.
For more information on Flowquip’s steam flow meters, please call us on 01422 829920 or email [email protected]
