A gas meter is a special flow meter, which is used to measure the volume of fuel gas such as natural gas and liquefied petroleum gas. Gas meters are used in residential, commercial, and industrial buildings that consume gas fuel supplied by gas utilities. Gas is harder to measure than liquid, because the volume measured is strongly influenced by temperature and pressure. The gas meter measures the specified volume, regardless of the quantity or quality of the gas flowed through the meter. Temperature, pressure, and heating value compensation should be made to measure the actual amount and value of the moving gas through the meter.
Several different gas meter designs are used, depending on the volumetric flow rate of the gas to be measured, the anticipated current range, the type of gas being measured, and other factors.
Gas meters in cold climates in buildings built before the 1970s are usually located inside the house, usually in a basement or garage. Since then, most are now placed outside although there are some exceptions especially in the old towns.
Video Gas meter
Jenis meteran gas
Diafragma/bellow meter
This is the most common type of gas meter, seen in almost all residential and small commercial installations. In that meter there are two or more chambers formed by the moving diaphragm. With the flow of gases directed by the internal valve, the chambers alternately fill and emit the gas, producing an almost continuous flow through the meter. As the diaphragm expands and contracts, the lever connected to the crank changes the linear movement of the diaphragm into a crankshaft rotating motion that serves as the main flow element. This shaft can induce an odometer-like counting mechanism or can generate electrical pulses for the computer stream.
The diaphragm gas meter is a positive displacement meter.
Rotary meter
Rotary meter is a highly precision machined instrument capable of handling higher volume and pressure than a meter diaphragm. In meters, the two "8" shapes are lobe-shaped, the rotor (also known as the impeller or piston), rotates in the proper alignment. With each turn, they move a certain amount of gas through the meter. The operating principle is similar to the Roots blower. The rotational movement of the crankshaft functions as a main flow element and can generate electrical pulses for a computer stream or can drive odometer counters such as.
Turbine gauge
The gas turbine meter sums up the gas volume by determining the speed of the gas moving through the meter. Since the gas volume is inferred by the flow, it is important that the flow conditions are good. Small internal turbines measure the velocity of the gas, which is transmitted mechanically to mechanical or electronic counters. This meter does not obstruct the gas flow, but is limited to the measurement of the lower flow rate.
Orifice Gauge
An orifice gas meter consists of a long straight pipe in which a properly known orifice plate creates a pressure drop, thus affecting the flow. Orifice meter is a type of differential meter, which all infer the gas flow rate by measuring the pressure differential across the designated and intentionally designed flow disturbances. The static pressure of the gas, density, viscosity, and temperature shall be measured or known in addition to the differential pressure for the meter to accurately measure the fluid. Orifice meters often do not handle various flow rates. But they are accepted and understood in industrial applications because they are easy to do in the field and have no moving parts.
Ultrasonic flow meter
Ultrasonic flow meters are more complex than pure mechanical meters, because they require significant signal processing and computational capabilities. The ultrasonic meter measures the velocity of the gas movement by measuring the speed of sound travel in the gas medium inside the pipe. Report of the American Gas Association. 9 includes the proper use and installation of this meter, and it specifies a standard sound-velocity calculation that predicts the speed of sound in a gas with known pressures, temperatures, and compositions.
The most complicated type of ultrasonic flow meter is the average speed of sound above a few lanes inside the pipe. The length of each lane is accurately measured at the factory. Each line consists of an ultrasonic transducer at one end and a sensor at the other. The meter creates a 'ping' with the transducer and measures the elapsed time before the sensor receives a sonic pulse. Some of these paths lead upstream so that the amount of flight time the sonic pulse can be divided by the number of flight lengths to provide an average speed of sound in the upstream direction. This speed differs from the speed of sound in the gas by the speed at which the gas travels inside the pipe. Other lines may be identical or similar, except that the voice pulse moves downstream. The meter then compares the difference between upstream and downstream speeds to calculate the velocity of the gas stream.
The ultrasonic meter is high-cost and works best without any liquid in the measured gas, so they are primarily used in high flow applications, high pressure such as channel pipe meter stations, where the gas is always dry and slender, and where small proportional inaccuracies can not be tolerated because a large sum of money is at stake. The ultrasonic meter decomposition ratio is probably the largest of any type of natural gas meter, and the precision and range capability of high quality ultrasonic meters is actually larger than proven turbine meters.
The cheap varieties of ultrasonic meters are available as a clamp-on flow meter, which can be used to measure flow in any pipe diameter without intrusive modification. The device is based on two types of technology: (1) flight time or transit time; and (2) cross-correlation. Both technologies involve transducers that are simply clamped into the pipe and programmed by the size and timetable of the pipe and can be used to calculate the flow. The meter can be used to measure virtually any dry gas including natural gas, nitrogen, compressed air, and steam. Clamp-on meters are available to measure fluid flow as well.
Coriolis Meter
A coriolis meter is usually one or more pipes with a longitudinal or axial axial part (s) that are eager to vibrate at the resonance frequency. Coriolis meters are used with liquids and gases. When the fluid inside the replaced part is resting, the upstream and downstream parts of the moved portion will vibrate gradually over each other. This vibration frequency is determined by the overall pipe density (including the contents). This allows the meter to measure the gas flow density in real time. After the fluid begins to flow, however, Coriolis forces come into play. This effect implies the relationship between the phase difference in the upstream and downstream vibrations and the mass flow rate of the fluid contained by the pipe.
Again, because of the number of inferences, analog controls and intrinsic calculations to the coriolis meter, the meter is incomplete only with its physical components. There are actuation, sensing, electronic, and computational elements that must be there for the meter to work.
Coriolis meters can handle a wide range of flow rates and have a unique ability to drain mass flow - this provides the highest flow measurement accuracy that is currently available for mass flow measurements. Because they measure the flow density, the coriolis meter can also infer the gas flow rate under the flowing conditions.
American Gas Association Report No. 11 provides guidance for getting good results when measuring natural gas with a coriolis meter.
Maps Gas meter
Heat value
The volume of gas flow provided by the gas meter is just that, volume reading. The gas volume does not take into account the quality of the gas or the amount of heat available when burned. Utility customers are billed on the basis of available heat in the gas. Gas quality is measured and adjusted for each billing cycle. This is known by some names as the calorific value, heat value, or heat value.
The calorific value of natural gas can be obtained by using process gas chromatography, which measures the amount of each gas constituent, ie:
- methane
- ethana
- hydrogen
- carbon monoxide
- water vapor
In addition, to convert from volume to heat energy, pressure and temperature of the gas should be considered. Pressure is generally not a problem; meter is simply mounted right downstream of the pressure regulator and calibrated to read accurately at that pressure. Pressure compensation then occurs in the utility billing system. Variable temperatures can not be handled easily, but several meters are designed with built-in temperature compensation to keep them accurate within the designed temperature range. Others are corrected for temperature electronically.
Shows device
Each type of gas meter can be obtained with various indicators. The most common are indicators that use multiple watches (pointer style) or digital readings similar to odometers, but remote readings of various types also become popular - see Automatic meter readings and Smart meters.
Accuracy
Gas meters are required to register the volume of gas consumed in an acceptable level of accuracy. Any significant errors in registered volumes may indicate a loss to the gas supplier, or the consumer is overcharged. Accuracy is generally set in the law for the location where the meter is installed. The legal provisions should also specify procedures to be followed if accuracy is debated.
In the UK, the permitted error for the gas meter made before the European Measuring Instruments Directive is  ± 2%. However, the European Measuring Instrument Directive has aligned the error of the gas meter across Europe and consequently meters produced since the directive came into force must be read in Ã,  ± 3%. Meters whose accuracy is disputed by the customer should be removed for testing by an approved meter checker. If the meter is found reading beyond the prescribed limit, the supplier must return the consumer to measure the wrong gas when the consumer has that meter (but not vice versa). If the meter can not be tested or its readings are unreliable, the consumer and supplier must negotiate a settlement. If the meter is found reading within limits, the consumer must pay the testing fee (and pay the outstanding fee). This contrasts with the position on the electric meter, where the test is free and refunds are only given if the meter's start date of inaccurate reading can be determined.
Remote reading
Distance reading became popular for the gas meter. This is often done through the output of electronic pulses mounted on the meter. There are different styles available but the most common is the contact closure switch.
Calculation of flow measurements
Turbines, rotary, and meter diaphragms can be compensated using the calculations specified in the American Gas Association Report No. 7. The calculation of this standard compensates the volume measured by volume quantity in a set of basic conditions. The calculation of AGA 7 itself is a simple ratio and, in effect, a density correction approach for translating the volume or rate of gas under conditions that flow to a volume or rate at baseline.
The Orifice meter is a very commonly used type of meter, and because of its wide use, the characteristics of the gas flow through the orifice meter have been carefully studied. American Gas Association Report No. 3 deals with various problems relating to the natural gas meter, and it defines an algorithm for calculating the natural gas flow rate based on differential pressure, static pressure, and temperature of the gas with which it is known. composition.
This calculation partly depends on the law of the ideal gas and also requires the calculation of gas compressibility to take into account the fact that the real gas is not ideal. The most common compressibility calculations used are the American Gas Association Report No. 8, characterization detail.
Standard yarn size
Housing, commercial and industrial gas meters have their own standard thread size. The gas gauge connects to the customer's piping through swivels and nuts, which have a set of special yarn sizes. The size of the yarn was originally named for the amount of gas designed to flow through them in the case of gas lamps, for example 30-Lt. the meter can provide enough gas for 30 lamps and was referred at the end of the 19th century as a 30-light-gas-meter. This size is usually 10Lt, 20Lt, 30Lt, 45Lt, or 60Lt, although smaller and larger sizes are available. The size of the thread is a little, about 1/16 ", larger than the size of the nearest size NPT, to accommodate the corresponding internal diameter in the swivel.
See also
- Automatic Meter Reading
- Conditioning current # Effects on flow measurement devices
- Electrical meter
- Flow measurements
- Gas flow computer
- Gas meter gauge
- Meter-Bus
- Julius Pintsch
- Thermal mass flow meter
- Turnaround document (how to collect data from)
- Utility meter
- Water meter
References
Source of the article : Wikipedia
0 Comments