Vortex flow meters are a direct type of volume flow-measuring device. Few points considering to sizing a vortex flow meter Turndown ration. ( the ratio of maximum flow rate to minimum flow rate). Most vortex meters between 1:10 or 1:15. Vortex flow meter turndown ratio also depends on the viscosity of the fluid measured. Measuring the flow of a high viscosity will have a lower turndown ratio. Low flow measurement also a important factor when sizing the vortex meter. Compensation method. The purpose of a vortex type flow meters with temperature and pressure compensation is for when the volume deviates the actual flow, density compensation will correct the result well, especially for air, gas and steam application. Measuring velocity. The steam velocity recomended as acceptable for steam distribution systems: