Gas meter prover
Encyclopedia
A gas meter prover is a device which verifies the accuracy of a gas meter
. Provers are typically used in gas meter repair facilities, municipal gas meter shops, and public works shops. Provers work by comparing a known volume of air across a meter with the gas meter's index or register. A series of mathematical computations are utilized to produce what is called a proof. A proof is a numeric value given to represent the accuracy of the meter as compared to the known volume of air used during the test.
used in gas meter proving, and has provided standards for the gas industry that is unfortunately susceptible to a myriad of immeasurable uncertainties.
A bell prover (commonly referred to in the industry as a "bell") consists of a vertical inner tank surrounded by an outer shell. A space between the inner tank and outer shell is filled with a sealing liquid, usually oil. An inverted tank, called the bell, is placed over the inner tank. The liquid provides an air-tight seal. Bell provers are typically counterweight
ed to provide positive pressure
through a hose and valve connected to a meter. Sometimes rollers or guides are installed on the moving part of the bell which allows for smooth linear movement without the potential for immeasurable pressure differentials caused by the bell rocking back or forth.
Bells provide a volume of air that may be predetermined by calculated temperature, pressure and the effective diameter of the bell. Bell scales are unique to each bell and are usually attached vertically with a needle-like pointer. When proving a meter using a manually controlled bell, an operator must first fill the bell with a controlled air supply or raise it manually by opening a valve and pulling a chained mechanism, seal the bell and meter and check the sealed system for leaks, determine the flow rate needed for the meter, install a special flow-rate cap on the meter outlet, note the starting points of both the bell scale and meter index, release the bell valve to pass air through the meter, observe the meter index and calculate the time it takes to pass the predetermined amount of air, then manually calculate the meter’s proof accounting for bell air and meter temperature
and in some cases other environmental factors.
Uncertainties commonly experienced, and possibly unaccounted for within a test when using bell provers can lead to incorrect proofs, by which an operator may adjust a gas meter incorrectly. Temperature inconsistencies between the bell air, meter and connecting hoses can account for most meter proof inaccuracies. Other factors may be mechanical such as stuck or sticky bell rollers or guides, loose piping connections or valves, a dent in the test area of the bell, incorrect counterweights, and human errors in the operation or calculations.
s (PLC) allowed gas meter repair facilities to automate most of the manual bell prover's process and calculations. Instead of manually raising and lowering the bell prover, solenoid valve
s connected to a PLC control air flows through the meter. Temperature, pressure
, and humidity
sensors can be used to feed data into an automated bell PLC, and calculations for meter proofs can be handled by a computer or electronic device programmed for such a purpose. In the early 1990’s, the PLC was replaced by PACs (Programmable Automated Controls) and modern computer systems. Sensors to read the index of a meter were added to further automate the process, removing much of the human error associated with manual bell provers.
driven provers with arrays of sonic nozzles (also known as a venturi
) to provide precise flow rates. Such a use eliminated the need for a bell, as the flow rate is provided through the nozzles. When sufficient vacuum is applied to a sonic nozzle it creates a constant flow rate. Bernoulli's principle
is applied to calculate the chosen flow rates chosen by the user or automated by a computer. Computers and PAC systems automate the process, and most sonic nozzle provers are capable of displaying not only meter proofs to a user, but are also capable of transmitting proofs as well as other important data to database systems across a computer network.
Gas meter
A gas meter is used to measure the volume of fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly...
. Provers are typically used in gas meter repair facilities, municipal gas meter shops, and public works shops. Provers work by comparing a known volume of air across a meter with the gas meter's index or register. A series of mathematical computations are utilized to produce what is called a proof. A proof is a numeric value given to represent the accuracy of the meter as compared to the known volume of air used during the test.
Manual bell prover
Since the early 1900’s, bell provers have been the most common reference standardReference standard
A drug reference standard is a standardized substance which is used as a measurement base for similar substances. Where the exact active substances of a new drug are not known, a reference standard provides a calibrated level of biological effects against which new preparations of the drug can be...
used in gas meter proving, and has provided standards for the gas industry that is unfortunately susceptible to a myriad of immeasurable uncertainties.
A bell prover (commonly referred to in the industry as a "bell") consists of a vertical inner tank surrounded by an outer shell. A space between the inner tank and outer shell is filled with a sealing liquid, usually oil. An inverted tank, called the bell, is placed over the inner tank. The liquid provides an air-tight seal. Bell provers are typically counterweight
Counterweight
A counterweight is an equivalent counterbalancing weight that balances a load.-Uses:A counterweight is often used in traction lifts , cranes and funfair rides...
ed to provide positive pressure
Positive pressure
Positive pressure is a pressure within a system that is greater than the environment that surrounds that system. Consequently if there is any leak from the positively pressured system it will egress into the surrounding environment....
through a hose and valve connected to a meter. Sometimes rollers or guides are installed on the moving part of the bell which allows for smooth linear movement without the potential for immeasurable pressure differentials caused by the bell rocking back or forth.
Bells provide a volume of air that may be predetermined by calculated temperature, pressure and the effective diameter of the bell. Bell scales are unique to each bell and are usually attached vertically with a needle-like pointer. When proving a meter using a manually controlled bell, an operator must first fill the bell with a controlled air supply or raise it manually by opening a valve and pulling a chained mechanism, seal the bell and meter and check the sealed system for leaks, determine the flow rate needed for the meter, install a special flow-rate cap on the meter outlet, note the starting points of both the bell scale and meter index, release the bell valve to pass air through the meter, observe the meter index and calculate the time it takes to pass the predetermined amount of air, then manually calculate the meter’s proof accounting for bell air and meter temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and in some cases other environmental factors.
Uncertainties commonly experienced, and possibly unaccounted for within a test when using bell provers can lead to incorrect proofs, by which an operator may adjust a gas meter incorrectly. Temperature inconsistencies between the bell air, meter and connecting hoses can account for most meter proof inaccuracies. Other factors may be mechanical such as stuck or sticky bell rollers or guides, loose piping connections or valves, a dent in the test area of the bell, incorrect counterweights, and human errors in the operation or calculations.
Automated bell prover
The invention of programmable logic controllerProgrammable logic controller
A programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...
s (PLC) allowed gas meter repair facilities to automate most of the manual bell prover's process and calculations. Instead of manually raising and lowering the bell prover, solenoid valve
Solenoid valve
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports...
s connected to a PLC control air flows through the meter. Temperature, pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
, and humidity
Humidity
Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
sensors can be used to feed data into an automated bell PLC, and calculations for meter proofs can be handled by a computer or electronic device programmed for such a purpose. In the early 1990’s, the PLC was replaced by PACs (Programmable Automated Controls) and modern computer systems. Sensors to read the index of a meter were added to further automate the process, removing much of the human error associated with manual bell provers.
Sonic nozzle prover
The natural evolution of the automated bell and PAC controls led itself to the use of vacuumVacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
driven provers with arrays of sonic nozzles (also known as a venturi
Venturi effect
The Venturi effect is the reduction in fluid pressure that results when a fluid flows through a constricted section of pipe. The Venturi effect is named after Giovanni Battista Venturi , an Italian physicist.-Background:...
) to provide precise flow rates. Such a use eliminated the need for a bell, as the flow rate is provided through the nozzles. When sufficient vacuum is applied to a sonic nozzle it creates a constant flow rate. Bernoulli's principle
Bernoulli's principle
In fluid dynamics, Bernoulli's principle states that for an inviscid flow, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy...
is applied to calculate the chosen flow rates chosen by the user or automated by a computer. Computers and PAC systems automate the process, and most sonic nozzle provers are capable of displaying not only meter proofs to a user, but are also capable of transmitting proofs as well as other important data to database systems across a computer network.