METER TUBES FOR VORTEX FLOW METERS
MATTECH, s.r.o. supplies meter tubes as well as complete sets consisting of vortex flow meters and straight pipeline lengths at the inlet and outlet. The design of the meter tube is divided to three sections: inlet, in which the flowing fluid is straightened, measuring one (vortex flow meter) and outlet. Vortex flow meter is subcontracted by our suppliers. Straight lengths required by the customer are manufactured directly in our company. If the customer requires so, the meter tube manufactured according to the documentation of the vortex flow meter can be supplied separately.
Vortex flow meters fall into the category of electronic velocity flow meters. These meters determine volume flow indirectly based on the knowledge of flow cross-section and velocity of the fluid flow, and they evaluate it. The velocity is calculated by measurement of frequencies of so-called Karman vortexes, that are caused during bypassing the obstacle placed vertically to the direction of fluid flow. The vortex flow meter consists of two basic parts: a vortex body and a sensor detecting vortexes. The shape of the vortex body has a major impact on the stability of periodical vortex generation. The sensors detecting vortexes analyze changes of pressure and velocity of the flowing fluid in so-called vortex area. For this reason, there are used sensors working on capacity, piezoelectric, tensometric, temperature or ultrasonic principle. As for the throttling bodies these flow meters require straight pipe lengths for proper functioning of the meter tube.
The vortex flow meters are suitable for one-way measurement of clear, non-viscous and homogenous fluids, steams and gases without flow pulsations. Flow cross-section of the pipe must be running full with the measured medium with fully developed velocity profile. Vortex flow meters are determined for measurements of flow in the pipelines of nominal dimensions DN 15 to DN 400 for flows of units up to thousands of m3 per hour. Fluid changing their states are not desirable. These are simple and reliable measuring devices with long service life and small pressure losses. Output signal from vortex flow meters has a form of frequency which is advantageous for digital signal processing. Measured value of the flow is not influenced by changes in temperature, pressure or density of the medium. Their reliability is dependent on flow conditions. Their disadvantage is, that if the velocity of flow is low and Reynolds number Re < 4 000, the fluid flow is immeasurable and the flow meter has shorter service life due to limited service life of the inner electronic components. The meter tubes for vortex flow meters are made of carbon, stainless steel or refractory alloyed steel. Vortex flow meters require straight pipe lengths of min. 20D upstream and 5D downstream the meter. D symbolizes inner diameter of the pipeline. If the required straight lengths cannot be kept, it is recommended to install flow conditioners (straighteners) in the pipeline. Vortex flow meters can be installed in horizontal, vertical and tilted position. Concept of the meter tubes also minimizes eventual mismatches during assembly and operation of the vortex flow meters. Division of the meter tube to individual sections also enables easier maintenance control and subsequent verification of the meter.