![]() As the bell is lowered, it discharges a known volume of gas through the meter being tested. Gas systems are recalibrated against a bell-jar prover – a calibrated cylindrical bell, liquid sealed in a tank. Recalibration can be done either in a laboratory or online using a prover. The maximum allowable pressure drop across the meter constrains the maximum operating flow in high viscosity services.Īll meters with moving parts require periodic testing, recalibration, and repair because wear increases the clearances. As viscosity decreases, the low flow performance of the meter deteriorates. The higher the viscosity, the less slippage and the lower the measurable flow rate becomes. Consequently, the maximum (and minimum) flow capacity of the flow meter is decreased as viscosity increases. In clean fluid services, however, their precision and wide rangeability make them ideal for custody transfer and batch charging.Īlthough slippage through the PD meter decreases (that is, accuracy increases) as fluid viscosity increases, pressure drop through the meter also rises. For this reason, PD meters are generally not recommended for measuring slurries or abrasive/corrosive fluids. PD meters operate with small clearances between their precision-machined parts wear rapidly destroys their accuracy. The process fluid must be clean and free from contaminants.Particles greater than 100 microns in size must be removed by filtering. Slippage between the flow meter components is reduced and metering accuracy is therefore increased as the viscosity of the process fluid increases. PD meters are available in sizes from 1/4" to 12" and can operate with turndowns as high as 100:1, although ranges of 15:1 or lower are much more common. While PD meters are operated by the kinetic energy of the flowing fluid, metering pumps determine the flow rate while also adding kinetic energy to the fluid. The frequency of the resulting pulse train is a measure of flow rate, while the total number of pulses gives the size of the batch. Each positive displacement design uses a different means of isolating and counting these volumes. By counting the number of passed isolated volumes, a flow measurement is obtained. How Does a Positive Displacement Flow Meter Work?Īll positive displacement flow meters operate by passing isolated, known volumes of a fluid through a series of gears or chambers within the meter. ![]() In industrial and petrochemical applications, positive displacement meters are commonly used for batch charging of both liquids and gases. PD flow meters are most widely used as household water meters and millions of such units are produced annually. They are ideal for flow measurement of viscous fluids, such as oils, fuels, and solvents that are difficult for other types of flow meters to measure. These meters do not require a power supply for their operation and do not require straight upstream and downstream pipe runs for their installation. My Sage flow meter was damaged in shipment.A positive displacement (PD) flow meter is a type of flow meter that provides high accuracy (☐.1% of actual flow rate in some cases) and good repeatability (as high as 0.05% of reading). How do I clean my thermal mass flow meter sensor? Image by Peggy und Marco Lachmann-Anke from Pixabay Other topics from the Sage Prime Manual you many be interested in are: Refer to the chart here for upstream straight run requirements. For this reason, the inline flow meter of these sizes will require an additional straight run. The ¼” and 3/8” models do not have flow conditioners. Obstructions such as valves, blowers, expanders, and PVC and HDPE pipes require additional straight run.Īll Sage inline flow meters, 1/2″ and up, have built-in flow conditioners. The meter also contains a sensor drive circuit, microprocessor meter board, and transmitter enclosure. The meter has a sensing element (a self-heated flow sensor and a temperature/reference sensor) mounted in the flow section where gas will flow. The user should not apply reducers with an inline flow meter. The meter is plumbed directly in the flow line by threading, flanging, or welding. The assembly section of the inline flow meter should match the size and pipe material of the conduit. For pipe sizes greater than 4” use the insertion-style flow meter. If other mounting styles are required, contact Sage. flanged ends are recommended for the 3” and 4” models). Sage Metering offers inline flow meter mounting styles for 1/4″ through 4″ pipe (threaded male NPT ends are standard up to 2-1/2” and ANSI 150 lb. In-line Flowmeters Download the Sage Prime User Manual In addition to the insertion-style flow meters, Sage offers inline or in-line thermal mass flow meters in ¼” through 4”, and here are some installation considerations.
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