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IGE/GM/8 Seminar 8th March 2007
Meter Selection
Andrew Wrath SICK UK Ltd
Product Specialist – Ultrasonic Gas Meters
IGE/GM/8 Part 1 clause 12.1.1 states,
“Any meter shall be appropriate to the load 
being supplied”
“Correct matching is required for both the size 
and characteristics of the load”
Selection of the appropriate meter relies 
on the exchange of information
Meter Selection ; exchange of information
IGE/GM/8 Appendix 3 Information on load
◊ Load details
- Minimum flow rate : Not zero !
- Maximum flow rate
- Estimated Qmax in 12 months
- Peak load
- Is continuity of supply required ?
- Details of downstream plant / equipment
◊ Special features of the load
- Plant that may cause pulsations / step changes
- MIP from consumer’s system
IGE/GM/8 Part 1 clause 4.2.2.1 states,
“The meter shall be selected to ensure that its error on the actual 
volume of gas used per annum does not fall outside 
+/- 3% for Qimax ≤ 160m³h-¹
+/- 2% for Qimax > 160m³h-¹”
This error is affected by both the meter accuracy and the range of 
flows over which the meter will be within the manufacturer’s 
specification – measuring range or turndown
(note to 4.2.2.1)
Uncertainty requirements that govern monitoring and trading in 
Carbon Dioxide measurements may impose stricter limits of meter 
performance to meet system uncertainties – refer to Appendix 12.
IGE/GM/8 Part 1 clause 12.1.2 states,
“Any meter of capacity ≤ 1600m³h-¹ std at 15°C and 1.01325 mbar 
must be approved by Ofgem or a metrological authority acceptable to 
Ofgem and must be stamped prior to delivery”
“For meters of capacity > 1600m³h-¹ std one of the following options 
shall apply
- the meter is OFGEM approved and stamped accordingly 
- a commercial agreement applies between the consumer, 
shipper/supplier, GT and the MAM which will specify the 
accuracy* requirements for installation, maintenance and 
validation requirements.”
*With “contract” loads, total system uncertainty is normally specified.
Metering Technology covered by IGE/GM/8
(refer to IGE/GM/8 Part 1 Sub-Section 2.1)
- diaphragm
◊Direct volume measurement
- rotary displacement (RD) 
◊Direct volume measurement
- turbine
◊Velocity measurement : volume inferred
- ultrasonic (USM)
◊Velocity measurement : volume inferred
Assistance offered in IGE/GM/8 Part 1
- Table 7
◊ Factors affecting meter selection, accuracy & 
performance
- Figure 35
◊ General guidance on selection of industrial and 
commercial meters
Table 7
FACTOR DIAPHRAGM RD TURBINE MULTIPATH ULTRASONIC 
Range of Qmax 6 to 160 m3 h-1 
212 to 5650 ft 3 h-1. 
25 to 2,885 m3 h-1 
800 to 102,000 ft3 h-1. 
65 to 25000 m3 h-1 
2275 to 882,875 ft3 h-1. 
800 to 85000 m3 h-1 
28,000 to 3001,900 ft3 h-1. 
Typical pressure 
range 
0 to 75 mbar. Others available as 
special case 
0 to 10 bar. Special meters 
available up to 38 bar. 
0 to 38 bar. 2 to 38 bar. 
Typical rangeability 
(and accuracy) 
Badged: 50:1 (± 2% to ± 3%) 
Usable: > 150:1 (± 2% to ± 3%) 
Dynamic: > 1000:1. 
Badged: 20:1 to 50:1 
 (± 1% to ± 2%) 
Usable: > 50:1 
 (± 1% to ± 2%) 
Dynamic: 500:1. 
Badged: 10:1 to 30:1 
 (± 1% to ± 2%) 
Usable: > 10:1 
 (± 1% to ± 2%) 
Dynamic: 75:1. 
Certified over 40:1 to 125:1 (± 1%) 
Usable: > 40:1 (± 1%) 
Dynamic: Not applicable. 
 
 
Effect of gas density Unaffected in design range within 
manufacturer's specification. 
Insignificant. Minimum flow is lowered with 
increased density, increasing the 
usable and dynamic rangeability. 
Meter accuracy does not deviate 
over the specified working range of 
transducers. Certain types of 
transducer will not operate at low 
densities dependent upon meter 
size, line density and gas 
composition. 
Effect of gas borne 
solids 
Normally unaffected but coarse 
filter recommended at higher 
pressures. 
Meter may stop rotating. Filter 
required. 
Blades may be damaged and 
freedom of rotation may be 
affected. Coarse filter required. 
Normally unaffected, but 
contamination of the transducers 
can affect meter performance. 
Effect of gas borne 
liquids for example 
water, oil, grease etc 
Corrosion possible. 
Freezing may result in damage. 
Materials of construction may be 
affected. 
Over-registration possible. 
Corrosion possible. 
Oil may be displaced from gears. 
Freezing may stop the meter.. 
Materials of construction may be 
affected. 
Under-registration possible. 
Corrosion possible. 
Freezing may result in damage. 
Lubricant dilution and rotor 
imbalance possible. 
Materials of construction may be 
affected. 
Inaccuracy possible. 
Liquids settling in the bottom of the 
meter, or grease on the internal 
walls reduce the cross sectional 
area and cause the meter to over-
read. Freezing may cause a 
temporary increase in uncertainty. 
Materials of construction may be 
affected. 
Pressure variations Excessive differential pressure 
variations will cause damage. 
Rapid change of differential 
pressure may cause damage. 
Rapid pressure changes may cause 
damage or registration errors. 
Particular problems when meters 
are installed interstage at higher 
pressures. 
Normally unaffected. 
Acoustic Noise Unaffected. Unaffected. Unaffected. Can be affected by acoustic noise. 
Precautions need to be taken with 
the location of the meter and its 
proximity to noise sources such as 
control valves, pressure regulators 
and partially open line valves. 
 
Diaphragm
Diaphragm
Range of Qmax 6 to 160m³h-¹
Typical Pressure Range 0 to 75 mbar
Typical Rangeability 50:1 badged
150:1 useable
1000:1 dynamic
Typical Accuracy ±2% to ±3%
Effect of Gas Density Unaffected
Effect of Gas Borne Solids Normally unaffected
Effects of Gas Borne Liquids Corrosion possible
Over read possible
Pressure Variations Damage if excessive
Acoustic Noise Unaffected
Rotary Displacement
Rotary Displacement
Range of Qmax 25 to 2,885m³h-¹
Typical Pressure Range 0 to 10 bar
Typical Rangeability 20:1 to 50:1 badged
>50:1 useable
500:1 dynamic
Typical Accuracy ±1% to ±2%
Effect of Gas Density Insignificant
Effect of Gas Borne Solids Meter may stop
(filter required)
Effects of Gas Borne Liquids Corrosion possible
Under-read possible
Pressure Variations Damage if rapid
Acoustic Noise Unaffected
Turbine
Turbine
Range of Qmax 65 to 25,000m³h-¹
Typical Pressure Range* 0 to 38 bar
Typical Rangeability 10:1 to 30:1 badged
>10:1 useable
75:1 dynamic
Typical Accuracy ±1% to ±2%
Effect of Gas Density Increase rangeability
Effect of Gas Borne Solids Blades may be damaged
(coarse filter required)
Effects of Gas Borne Liquids Corrosion possible
Inaccuracy possible
Pressure Variations Damage if rapid
Acoustic Noise Unaffected
Ultrasonic
Ultrasonic
Range of Qmax 800 to 85,000m³h-¹
Typical Pressure Range* 2 to 38 bar
Typical Rangeability 40:1 to 125:1 certified
>40:1 useable
Typical Accuracy ±1% 
Effect of Gas Density Generally unaffected
Effect of Gas Borne Solids Normally unaffected
Effects of Gas Borne Liquids Inaccuracy possible
Pressure Variations Normally unaffected
Acoustic Noise Can be affected
Assistance offered in IGE/GM/8 Part 1
- Table 7
◊ Factors affecting meter selection, accuracy & 
performance
- Figure 35
◊ General guidance on selection of industrial and 
commercial meters
Figure 35
Not 
preferred
Not 
preferred
Turbine & Ultrasonic
M
e
te
r 
P
re
ss
u
re
 (
B
a
r)
(N
o
t 
to
 s
ca
le
)
Meter Qmax m3 h-1
(not to scale)
0.075
3000160
10
38
50 250
Diaphragm
High turn down > 150:1 
On-Off Loads
Low operating Differential
Non Vital interruptible supplies
(Higher pressures available
some sizes)
Rotary
Turn down >50:1 
On-Off Loads
Modulating Loads
Low operating Differential
Limited space availability
Non Vital interruptible supplies
(Higher pressures available in a 
limited number of sizes)
Ultrasonic
Turn down >40:1 
High Instantaneous demand
and/or pulsating loads
Low operating Differential
N
o
t 
a
v
a
il
a
b
l e
85000
Turbine
Turn Down >10:1 
Steady state loads or where 
loadchanges are less than 
20% Qmax. Not suitable for 
repeated step load changes or 
pulsating flows. (see clause 
12.5.3)
Notes: 
1. Either meter is 
suitable for loads where 
a supply interruption 
cannot be tolerated due 
to meter failure (i.e. 
Hospitals)
2. Damping of 
oscillations may be 
required.
(see clause 12.5.3.2)
Note: Where there is an overlap, the darker green denotes the preferred type of meter within the flow.
IGE/GM/8 Seminar 8th March 2007
Installation effects and accuracy
Andrew Wrath SICK UK Ltd
Product Specialist – Ultrasonic Gas Meters
IGE/GM/8 Part 1 clause 4.2.2.3 states,
“Pipework and components within the 
installation should be selected and designed to 
ensure the meter reading will not be 
influenced by greater than 0.3% of the actual 
reading”
The system should be designed to ensure that 
the pipework or any of the components of the 
system do not affect the meters accuracy by 
greater than 0.3% of actual reading.
Generation of non ideal flow profile, perturbation
Typical causes
◊”Jetting”
- Single bend
- Multiple bends in the same plane
- Regulator
- Valve
- Filter
◊”Swirl”
- Multiple bends out of plane
Disturbed flow profile exist for “x” d from generation and may be a 
combination of the above. The countermeasure is to design the 
system to include the correct number of straight lengths on the meter 
inlet.
Effects of non ideal flow profile, inaccuracy of meter reading and 
possible damage to meter.
Single Bend
Double Bend OOP
IGE/GM/8 Part 1 : Table 2
MOPmi ≤ 7 bar MOPmi > 7 bar METER 
TYPE Pipe 
upstream 
Pipe 
downstream 
Pipe 
upstream 
Pipe 
downstream 
Diaphragm Not critical Not critical Not critical Not critical 
RD Not critical Not critical 4D 2D 
Turbine 10D 5D 10D 5D 
USM 
(multipath) 
 10D 5D 10D 5D 
Where “D” = meter diameter ( nominal bore )
Other considerations
◊Location of thermowells (IGE/GM/5)
◊Reducers should be concentric; eccentric 
reducers not to be used
◊Strain is not placed on the meter body
Additional requirements for Multipath Ultrasonic Meters
◊Diameter change inlet spool to meter body
1% maximum allowed (AGA 9)
1% preferable, 3% maximum (ISO 17089)
(typical 0.05% systematic error per 1% step 
change)
◊Concentricity
◊Installation in proximity to noise generating devices 
(pressure control valves)
Refer to AGA 9 or ISO 17089 (draft)
Flow conditioners will sometimes allow installation 
lengths to be reduced but increase pressure loss.
Flow conditioning plate Meter with integrated plate
Tube bundles not recommended
Not effective with asymmetric profile (jetting)
Typical tube 
bundle installed 
in inlet spool
– Effect of inclusion of flow straightener
– Without straightener
≥ 10D
Flow direction
TP
– Effect of inclusion of flow straightener
– With straightener
≥ 2D
T
≥ 2D
Flow direction
Flow conditioner
P
IGE/GM/8 Part 1
Clause 7.6.3.4
“Where the meter is 
installed in accordance 
with the manufacturers 
instructions and these 
are less onerous than 
the values given in 
table 2, such 
instructions shall be 
obtained from the 
manufacturer in 
writing and retained 
with the site records”
Manufacturer’s tests are normally documented by independent bodies
Example of test results
-1,0
-0,5
0,0
0,5
1,0
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
flow rate [m³/h]
de
vi
at
io
n 
[%
]
90°-bend 5D 90°-bend 10D 90°-bend 20D
U-bend 5D U-bend 10D
natural gas
10bar(g)
Good Installation
Turbine Meter
Good Installation UFM
Summary
◊Exchange of information is critical in the selection of 
the appropriate meter
◊One solution does not fit all applications
◊Use the expertise of meter manufacturers
◊Use IGE/GM/8