Gas meter and associated methods
A device which: optically detects the presence of, measures the flow rate of, and identifies the characteristics of venting fugitive gas emissions. Specifically the device provides a spectral analysis of emission gas constituents; selective detection of the presence of venting hydrocarbons; measurement of venting emissions flow rates, the measurement of shut-in and flowing venting system pressures and the venting system temperatures. The flow rates are corrected, relative to the detection of the gas constituents and standard temperature and pressure (STP). These devices are configured to collect such data electronically and transmit via various telemetry systems, to a secure remote data network for reporting, access, evaluation, real-time monitoring and archiving as required.
1 . A gas meter comprising:
a channel comprising a modifiable channel portion with a modifiable cross-sectional area, wherein the cross-sectional area of the channel portion is modifiable by adjusting the position of a plunger to control the velocity through the modifiable channel portion for a given flow rate; and
a thermal mass flow meter which is positioned within the modifiable channel, and which is configured to measure the mass flow rate by heating a portion of the flowing fluid and then recording how that heat is dispersed by the flow;
wherein the gas meter is configured to operate in four states, the four states comprising:
a first state in which the plunger is fully down, and the thermal mass flow meter is in a calorimeter sensor mode;
a second state in which the plunger is fully down, and the thermal mass flow meter is in a Constant Temperature Anemometer sensor mode;
a third state in which the plunger is fully up, and the thermal mass flow meter is in the calorimeter sensor mode; and
a fourth state in which the plunger is fully up, and the thermal mass flow meter is in the Constant Temperature Anemometer sensor mode.
2 . The gas meter according to claim 1 wherein the gas meter is configured to control the cross-sectional area of the modifiable channel portion based on the gas flow rate such that at high flow rate the cross-sectional area of the modifiable channel portion is larger than at low flow rate.
3 . The gas meter according to claim 1 wherein the dynamic range of the gas meter is greater than 20,000,000, wherein the dynamic range is defined as the ratio of the highest measureable flow rate to the lowest measureable flow rate.
4 . The gas meter according to claim 1 wherein the modifiable channel portion is streamlined to promote laminar flow across the flow meter.
5 . The gas meter according to claim 1 wherein the gas meter is configured to control the cross-sectional area of the adjustable channel based on the measured mass flow rate.
6 . A gas meter according to claim 1 wherein the flow meter is configured to measure a flow of gas to provide a raw gas flow measurement and wherein the gas meter further comprises:
at least one gas property sensor configured to determine one or more properties of the gas and the environment;
wherein the gas meter is configured to provide a compensated gas flow measurement by adjusting the raw gas flow measurement based on the determined one or more properties of the gas and the environment.
7 . The gas meter according to claim 6 wherein the one or more determined properties of the gas comprise one or more of: the temperature of the gas; the pressure of the gas; the ambient temperature; the atmospheric pressure; and the composition of the gas.
8 . The gas meter according to claim 6 wherein at least one gas property sensor comprises one or more of: an IR spectrometer; a temperature sensor; and a pressure sensor.
9 . The gas meter according to claim 6 wherein the at least one gas property sensor comprises an IR spectrometer configured to determine one or more of:
the concentration of non-hydrocarbons within the gas;
the concentration of methane in the gas; and
the concentration of hydrocarbons within the gas.
10 . The gas meter according to claim 6 wherein the gas meter comprises a flow channel and a gas property channel, wherein the gas meter is configured to determine:
the flow rate from gas flow directed through the flow channel, and
at least one gas property from gas flow directed through the gas property channel.
11 . The gas meter according to claim 1 wherein the overlap between calorimeter and CTA modes sensing range is 25% of the full calorimeter scale.
12 . The gas meter according to claim 1 , wherein the sensing range signal overlap between the plunger fully down and fully up is 5% of the plunger up calorimeter full scale value.
13 . The gas meter according to claim 1 , wherein the positions of the plunger when fully up and fully down are defined by hard stops at the top and bottom of its travel.
14 . The gas meter according to claim 1 , wherein the gas meter is configured to determine whether to use a calorimeter sensor mode value or a Constant Temperature Anemometer sensor mode value based on a predetermined criterion.
15 . A method for determining the flow rate of gas, the method comprising:
flowing the gas through a channel, the gas channel having a modifiable channel portion with a modifiable cross-sectional area wherein the cross-sectional area of the channel portion is modifiable by adjusting the position of a plunger to control the velocity through the modifiable channel portion for a given flow rate;
measuring the mass flow rate through the modifiable portion using a thermal mass flow meter by heating a portion of the flowing fluid and then recording how that heat is dispersed by the flow; and
adjusting the cross-sectional area of the modifiable portion and the thermal mass flow meter between four states, the four states comprising:
a first state in which the plunger is fully down, and the thermal mass flow meter is in a calorimeter sensor mode;
a second state in which the plunger is fully down, and the thermal mass flow meter is in a Constant Temperature Anemometer sensor mode;
a third state in which the plunger is fully up, and the thermal mass flow meter is in the calorimeter sensor mode; and
a fourth state in which the plunger is fully up, and the thermal mass flow meter is in the Constant Temperature Anemometer sensor mode.