INTRODUCTION TO GAS METERING

Principles of Gas Metering

• Natural Gas
– Compressible substance
• One quantity of gas can occupy different volumes at
different temperatures and pressures
– Quantity of gas is what is important
– Standard Volume vs Actual Volume
• Gas Meters
– Only capable of measuring Actual Volumes
– If pressure and temperature are known, actual
volume can be converted to standard volume
• Three different Actual Volumes
• Three identical Standard Volumes
– A SCF is defined as 1 actual cubic foot of gas at 60°F and
14.73 PSI
 Supercompressibility Factor

Meter Factor
Standard Volume

𝑉𝑠 = 𝑉𝐴 × 𝐹𝑃 × 𝐹𝑇 × 𝐹𝐹𝑃𝑉² × 𝐹𝑀

Actual Volume
Temperature Factor

Pressure Factor
 • Ideal Gas Law (PV = nRT)
– Pressure and Temperature Factors
– FP is much more significant than FT

𝑉𝑠 = 𝑉𝐴 × 𝐹𝑃 × 𝐹𝑇 × 𝐹𝐹𝑃𝑉² × 𝐹𝑀

• Supercompressibility • Meter Factor

– Corrects for
– Required when P > 100 PSI individual meter
– Corrects for differences performance
between real and ideal – Determined via
proving test
gasses – Typically ignored
– Gas composition needs to in custody transfer
be known applications
 𝑉𝑠 = 𝑉𝐴 × 𝐹𝑃 × 𝐹𝑇

• Temperature Factor
– Corrects the actual volume at a measured temperature to a
standard volume at the base temperature (typically 60°F)
– Absolute temperature units required (Rankin/Kelvin)
𝑇𝑏𝑎𝑠𝑒 459.67+60°𝐹
• 𝐹𝑇 = =
𝑇𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 459.67+𝑇𝑔𝑎𝑠
• Pressure Factor
– Corrects the actual volume at pressure to a standard volume at
the base pressure (typically 14.73 PSI)
𝑃𝑎𝑏𝑠𝑜𝑙𝑢𝑡𝑒 𝑃𝑎𝑡𝑚𝑜𝑠𝑝ℎ𝑒𝑟𝑒 +𝑃𝑔𝑎𝑢𝑔𝑒 𝑃𝑎𝑡𝑚 +𝑃𝑔
• 𝐹𝑃 = = =
𝑃𝑏𝑎𝑠𝑒 𝑃𝑏𝑎𝑠𝑒 14.73 𝑃𝑆𝐼
• Billing
– Gas is typically sold per energy content (e.g. GJ)
– Conversion to energy is based on gas composition
sampling (e.g. 0.001055 GJ/SCF)

𝐶𝑜𝑠𝑡 = 𝑉𝑆𝑡𝑎𝑛𝑑𝑎𝑟𝑑 × 𝐸𝐷𝑒𝑛𝑠𝑖𝑡𝑦 × 𝑃𝐸𝑛𝑒𝑟𝑔𝑦

𝐺𝐽 $
$ = 𝑆𝐶𝐹 × ×
𝑆𝐶𝐹 𝐺𝐽
Meter Types
• Diaphragm Meters
• Low Pressure (0-100 PSI)
• Low Flow rates
• Excellent Turndown (~100:1)

• Rotary Meters
• Medium Pressure (0-175 PSI, 0-1480 PSI in HP Models)
• Medium to High Flow rates
• Good Turndown (~50:1)

• Turbine Meters
• Highest Pressure (up to 1480 PSI)
• High flow rates
• Poor Turndown (~20:1)
 Rotary
Turbine

HP Rotary

Diaphragm
Diaphragm Meters
• Most appropriate for intermittent or low flow gas with
low pressure

• Typically Temperature Compensated

• Small Diaphragm
– 200 Series to 400 Series Meters (AC250 to AL425 e.g.)
• ~0 CFH to ~500 CFH (actual volume)
• Typical “House” meter
• Large Diaphragm
– 600 Series and larger (AC630 to AL5000 e.g.)
• ~0 CFH to ~5000 CFH (actual volume)
• Commercial/Large Residential application
Diaphragm 1” MNPT
Hand Hole Cover
Meter
Anatomy 20 LT
Top Cover Connection
Thread
Index
Seal
Meter Body Plug

Front Cover
(Transparent)

Meter
Connection Set
Diaphragm Meter Sizing
• All meters are sized based on actual gas volume flowrate
– Typical example: Requirements are “300,000 BTU at ¼ PSI”
– The BTU corresponds to the standard volume of gas, we generally
assume 1000 BTU per SCF of natural gas. This example equates to
~300 SCF/hr
– We cannot exceed a meter’s maximum capacity, so we would select
the smallest meter that is capable of measuring ~300 SCF/hr
– The best meter for this application would probably be an AL425
• The “425” corresponds to the maximum ACF/hr that the meter can measure at
¼ PSI (see table)
– Meters have limited connection size options – gas line may need to be
swaged up/down to accommodate the proper meter
 Diaphragm Meter Sizing
• Diaphragm meters are sized empirically using delivery pressure and
required flow to select the appropriate meter
(in scf/h of 0.6 SG Natural Gas)
Differential New Meters Discontinued: Rebuilds may be available
Gauge
Pressure Elster Sensus Elster Sensus Elster Sensus Elster Sensus Sensus Elster Elster
Pressure
("WC) R-275 415
(psi) AC250 AL 425 AC 630 AL 1000 RC 750 AL 800 RC 1600 RC1000 AL 1400 AL 2300
MR-8 MR12
0.25 0.5 250 275 425 415 630 1000 750 800 800 1000 1400 2300
0.25 1 355** 383** 583** 577** 860** 1400** 1033** 1100** 1067** 1400** 1933** 3200**
0.25 2 565 600 898 900 1320 2200 1600 1700 1600 2200 3000 5000
2 2 600 635 955 952 1390 2400 1688** 1850 1688** 2321** 3265 5440
5 2 656 690 1038 1035 1515 2700 1840 2100 1840 2530 3700 6200
10 2 - - 1154 1160 1710 3400 2080 2600 2080 2860 4600 7700
20 2 - - 1367* 1377* 2010 4100 2480 3200 2480 3410 5600 9400
25 2 - - 1462* 1473* 2160 4600 - 3500* 2640 3630 6200 10400
50 2 - - - - - 6600* - 5100* 3360 - 9000 15000
75 2 - - - - - 8540* - 6600* 3920** - 11650 19400
100 2 - - - - - 10100* - 7800* 4480 - 13800 23000
 Diaphragm Meter Options
• All Diaphragm meters available in m³ or ft³
• Most only have one possible connection size
– Some meters have two top cover options
• Small Diaphragm Options
– Pressure Taps
• Allows for live pressure measurement at the meter
– Pulsers
• Allows for wired transmission of meter index counts
– Electronic Radio Transmitters (ERTs)
• Allows for wireless reporting of meter index reads
• Large Diaphragm Options
– Pulsers
– ERTs
– Electronic Volume Correctors (Instruments)
• Live correction of variable pressure/temperature
• For LD meters, EVCs will typically only correct for
pressure
 Diaphragm Pulser Options
• Pulse weight (i.e. volume/pulse) will
depend on the specific meter and pulser
combination.
• Small Diaphragm Pulsers
– Elster Small Diaphragm Pulser (RVP-VI)
• (1 pulse/revolution)
• Measurement Canada (MC) Approved
– Riotronics Small Diaphragm Pulser
• (2 pulses/rev)
• For Non-Elster Meters
• Large Diaphragm Pulsers
– Elster Large Diaphragm Pulser (RVP-FI)
• (1 pulse/rev)
• MC Approved
– Riotronics Large Diaphragm Pulser
• (2 pulses/rev)
• For Non-Elster Meters
Rotary Meters
• Most appropriate for
consistent gas flow at 0-175
PSI
• Available with or without
temperature compensation
• High Pressure models
available (up to 1480 PSI)
• Mostly used for
industrial or large-scale
commercial applications
Rotary Meter Anatomy
Sight Glasses

Index (Head)
Meter Body
Rotary Meter Sizing
• Rotaries are sized based on actual gas volume
flowrate
– For Dresser rotaries, roman numerals are used to describe
maximum flowrate (ex. 8C = 800 CFH, 11M = 11000 CFH)
• Turndown ratio is worse on rotaries than diaphragms
– There is a minimum flowrate required in order for gas to
be measured. This is why constant gas flow is important.
• Since meters are sized based on actual volume, a
smaller meter at a higher pressure can often be used
to save costs
• Ex. An 8C175 at 100 PSI can handle ~6000 SCFH
• Ex. A 5M175 at 2PSI can handle ~5200 SCFH
 Rotary Meter Options
• The rotary meter bodies are all entirely fixed.
Adjustments to the meter configuration are external to
the meter body.
• Index Options
– The index is what displays the meter read. Mechanical
indexes can be imperial (ft³) or metric (m³)
– Mechanical temperature compensation is available
• Pulsers
– Can be installed on index to provide wired reporting of
index read
• Instrument Drive
– 90° addition to the end of the index
– Allows for installation of EVC or RA-100 via mechanical
wiggler
• Microcorrector
– Functionally identical to an EVC, but in a smaller body
– Integrated pulse output capabilities
– Versatile programming options (units, multipliers, pulse
output options, fixed pressure factors, T-only option, PTZ
correction, etc)
 Rotary Pulser Options
• Rotary Pulsers
– Riotronics Rotary Pulser
• (2 pulses/rev)
• Mounts directly to mechanical rotary indexes
– RA-100
• (100 pulses/rev)
• Mounts to an instrument drive on a rotary
meter
• MC Approved
– Barchard Veeder Root Custom Explosion
Proof pulser
• (10 pulses/rev) or (100 pulses/rev)
• Mounts directly to mechanical rotary indexes
Electronic
Volume
Correctors (EVCs)
Instruments/Microcorrectors
• Functionally identical
• Highly configurable and customizable
• Precise measurement of gas pressure and
temperature
• Live calculation converts actual volume to
standard volume
• Pulsing options allow for easy integration of
ERTs or output pulse cable
Measurement
Canada and Other
Regulations
 Regulations
• Depending on application and location, many different
regulations can come into place. The Electricity and Gas
Inspection Act, Measurement Canada, Boilers Branches
(ABSA), Local Building Codes, ASTM, ASME, and others can
have a say in what is required

• Many, but not all, meters do have CRN numbers, MTRs and
other certificates. If there are any specific documentation or
certification requirements, it is important to collect that
information upfront because it will limit the applicable
options. If certifications are not available for a product,
generally speaking manufacturers will not pursue additional
certifications for sales less than a million dollars

• Measurement Canada has a large impact on metering Canada.

They are responsible for insuring all devices used to sell goods
based on a measurement are accurate
 Measurement Canada
• Measurement Canada enforces many laws, acts,
requirements, and bulletins. It is the responsibility of the
contractor to know and meet all requirements. General
Concepts to keep in mind are:

• Any time gas is sold off a meter, or a bill is divided using

meters, that meter must be sealed under Measurement
Canada

• To sell gas using a meter, the meter owner must be registered

with Measurement Canada and obtain a contractor
registration number. When meters are sealed they are issued
a certificate which detail meter information, test results, and
seal period. The meter owner (contractor) is responsible for
insuring all the criteria within the Electricity and Gas
Inspection Act are met, including that meters are re-verified
after their seal period has expired
 Pressure Correction
• Measurement Canada: Pressure correction is
required for pressures greater than ½ PSI
• Atmospheric pressure must always be
accounted for
• Only EVCs are capable of live pressure
correction
• Elevation or atmospheric pressure needs to
be programmed into the instrument
– Many pressure transducers measure gauge
pressure, so the atmospheric pressure needs to be
known in order to properly calculate the pressure
factor
• Pressure Factor Metering (PFM) is another
option for measuring standard gas volumes
– The use of a regulator keeps the pressure constant,
and the pressure factor is therefore known and
standard volumes can be calculated manually
 Temperature Correction
• Measurement Canada: temperature
correction is required
• EVCs, mechanical rotary TC indexes,
and diaphragm meters are all capable
of live temperature correction
– Diaphragm meters correct for
temperature internally
– Mechanical TC indexes correct for
temperature via internal temperature
probe
– EVCs precisely measure the temperature
via temperature probe, and then
calculates the temperature factor
electronically
 FAQs
• What is required to choose the correct
meter?
– Expected flow rate (BTU/hr, SCF/hr)
– Expected and Max Pressures (PSI, kPa)
– List of special requirements (pulsers, etc)
• How do I ensure my meter is properly
installed and functioning correctly?
– Refer to IOM for specific installation
requirements
– Review meter is sealed and correct
documentation is valid
– Clock the meter to ensure its maximum flow
rate is not exceeded
• See more FAQ at
barchardengineering.com/faq
For more information including IOM manuals, product
information and other literature please visit

BarchardEngineering.com/resources

780-436-6124