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Boss flow gas metering emerson3/13/2024 ![]() ![]() The signal must, therefore, be amplified which is achieved with a preamplification board mounted on the turbine meter. The sinusoidal signal from each pickoff has low amplitude and may not normally be relied upon for transmission distances over 6 meters (20 feet). The total number of pulses collected over a period of time represents the total volume metered. Each voltage pulse represents a discrete volume. The rotor blades or rim buttons passing through the magnetic field of the pickoff generate a pulsing voltage in the coil of the pickoff assembly. As fluid passes smoothly through the flow meter, it causes the rotor to revolve with an angular velocity proportional to flow. One or two magnetic pickoffs are mounted in a boss on the meter body. Each Daniel turbine meter is comprised of a cylindrical housing that contains a precise turbine rotor assembly. Normal range or turndown is given as 10:1 which is often exceeded depending on meter size and required linearity.ĭaniel Series 12 Liquid Turbine Flow Meter Systems combine turbine meters and electronic instrumentation to measure volumetric total flow and/or flow rate. Range Range is the ratio of maximum flow to minimum flow over which the specified linearity will be maintained. Turbine meters have inherently high resolution. Resolution Resolution is a measure of the smallest increment of total flow that can be individually recognized, normally defined by a single pulse. Accuracy at a particular flow rate may be an order of magnitude better than “rated flow range accuracy.” Turbine meters exhibit excellent repeatability which is the most important parameter to be considered for many applications.Īccuracy Accuracy is a measure of how closely the instrument indicates actual flow and is generally expressed as a percent of true volume for a specific flow range. Repeatability Repeatability is the ability of a meter to indicate the same reading each time the same flow conditions exist. Advanced technology allows linearization of the meter registration within a flow computer, enabling further improvements in measurement accuracy. This value varies across the meter’s flow range with linearity being a measure of the variance of actual output from the average K-factor. Turbine meters have a nominal K-factor which is the number of pulses output for a given volume measured. ![]() Linearity is the measure of variation in signal output across the nominal flow range of the meter. The following terms are the most widely discussed parameters of turbine meter applications. Flow impinging upon the angular blade causes the rotor to spin at an angular velocity proportional to flow rate. The forward and rear suspension act as flow guides, ensuring fluid motion through the meter is parallel to the meter’s centerline. Flow through the turbine meter is from left to right. Lower angles cause too low of an angular velocity and loss of repeatability, while larger angles cause excessive end thrust.įlow Rate Is Proportional to Angular VelocityFigure 1 below is a cross section of the internals of a Daniel Series 1500 turbine meter. In general, the blade angle is held between 20° and 40° to the flow. A sharper blade angle provides a higher frequency output. The angle of the turbine blades to the stream governs the angular velocity and the output frequency of the meter. An expanding blade hangerįigure 1: Liquid Turbine Flow Meter Cross SectionĪssembly holds the turbine rotor in alignment with the fluid flow. The turbine meter and associated digital electronics form the basis of any liquid metering system. This incremental output is digital in form, and as such, can be totalized with a maximum error of one pulse regardless of the volume measured. In addition to its excellent rangeability, a major advantage of the turbine meter is that each electrical pulse is also proportional to a small incremental volume of flow. The pickoff’s output frequency is proportional to the flow rate. The output of the meter is taken by an electrical pickoff(s) mounted on the meter body. These features make the turbine meter an ideal device for measuring flow rate. The angular (rotational) velocity of the turbine rotor is directly proportional to the fluid velocity through the turbine. Fluid flow through the meter impinges upon the turbine blades which are free to rotate about an axis along the center line of the turbine housing. The basic theory behind Daniel liquid turbine meters is relatively simple. ![]()
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