TRACKING NATURAL GAS WITH FLOWMETERS

www.che.com Feature Report ENERGY EFFICIENCY: Tracking Natural Gas With Flowmeters Thermal mass flowmeters provide advantages over other options for metering the consumption of natural gas by individual combustion units throughout the facility Wayne Shannon, Magnetrol International ith today’s increased emphasis on strategic energy management, many throughout the chemical process industries (CPI) and elsewhere are attempting to obtain better information on the natural gas consumption in their facilities. While custody-transfer flowmeters are typically in place at the property line (to track total...

Pressure drop FIGURE 2. In this thermal mass flowmeter, the sensors are an integral part of the body construction. This design can be used in pipe sizes from 0.5 to 4 in., and may be used with an optional, built-in flow-conditioning element FIGURE 3. Shown here is a typical curve showing the square root relationship between pressure drop and flow for differential-pressure-type flowmeters. At very low flowrates, there is little signal, which limits the ability to accurately measure low flowrates. Similarly, pressure drop increases with the square of the flowrate, and this may limit the turndown...

Feature Report counted using an external pickup that provides a series of electronic pulses with each pulse equivalent to one rotation. The pulses are then sent to the transmitter. The manufacturer provides a K factor to relate each rotation to a given gas volume. The number of pulses that are counted over a given time period provide both the flowrate and the totalized flow. Turbine meters have relatively high turndown capabilities with corresponding high measurement accuracy. Like the previously mentioned flowmeter types, the turbine flowmeter is a volumetric device that measures the actual...

FIGURE 7 (bottom right). This figure shows a fully developed flow profile in a pipe. It also shows the use of a compression fitting for positioning the probe in the pipe. This installation provides considerable flexibility and easy installation Flowrate, scfh FIGURE 6 (top left). This curve shows the relationship between the power and the mass flowrate for a thermal mass flowmeter in a 4-in. pipe. Such a curve is developed during the calibration of the instrument contact with the natural gas, the user should ensure that the temperature rise of the sensor is less than the autoignition temperature...

the relative change in heat transfer is comparatively less than the change in gas density, which is directly used by other flowmeters. Installation considerations Nearly all flowmeters require some straight run of pipe ahead of the flow sensor. Thermal mass flowmeters follow the same basic ' guidelines. The flow calculations used with an insertion-type flowmeter assume the presence of this fully developed flow profile and the placement of the sensor on the centerline of the pipe as shown in Figure 7. Theoretically the velocity at the wall is zero and the velocity on the centerline of the pipe...

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