FMR Rotary Gas Meter for high pressure Flow Meter Group

About Flow Meter Group B.V. (FMG)

FMG is an engineering/manufacturing company specializing in the development and production of energy and gas measurement systems. Located in the Netherlands, FMG produces a wide range of rotary and turbine gas meters, volume conversion devices, master meters and calibration benches. Unique product features include self diagnosis and tamper prevention. All products and services are certified by the Dutch NMi and comply with the latest EU and/or OIML directives.

Flow Meters

FMG offers a large variety of flow meters ranging from very small (100 dm3 /h) up to very large (40.000 m3
/h) flow rates and in pressures from atmospheric to 100 bar (1440 psi). All FMG meters comply with international safety and metrological standards. Meters designated for fiscal use are tested, certified and approved by the Netherlands Metrological Institute NMi.

FMG has added extra features to the meters in terms of increased accuracy, protection from manipulation, increased rangeability and superior performance in order to go beyond the minimum requirements of the existing standards.


The FMG series of rotary gas meters are designed to meet the highest demands of reliable and accurate measurement of gas flow. The meters are MID approved (MID 2014/32/EU) and fully comply with EN12480:2002, EN12480:2015 and OIML R137 1&2 (2014). The compact exchangeable aluminum cartridge allows local repair and on-site cleaning.

The robust design of the casing and the cartridge make the meter less sensitive to installation stresses caused by the connecting piping.A significant amount of misalignment of the connecting piping/flanges can be tolerated by the meter without affecting the meter performance by jamming the impellers.

The aluminum casing of the FMR (body and front plate) is designed for working pressures up to 20 barg with a safety factor of 4. The square impellers and the improved position of the main bearings and shafts, make the meter less sensitive to overload and pressure shocks.

The aluminum index and the protection of the LF pulsers with the associated magnets, make the meter less sensitive for manipulation by externally applied magnets or other external forces. Tampering of meters with strong neodymium magnets is one of the major concerns of utility companies, as this kind of manipulation is very difficult to detect or prove. In order to be prepared for the “smart grid”, the index can also be equipped with an intelligent encoder.

The unique proprietary oiling system, where the oil is distributed directly to the timing gears by means of a disc, eliminates oil loss at high rotor speeds and will lubricate the timing gears at very low loads. All plugs and oil sight glasses are in the front of the meter, allowing the meter to be installed in very compact installations.

FMR Rotary Gas Meter Principle

The FMG rotary gas meter is a displacement type gas meter. The actual measurement is performed by two figure 8-shaped impellers (rotors) rotating within a measurement chamber. During a full revolution of the rotors, a fixed volume is displaced from the inlet to the outlet of the meter. The number of revolutions represents the amount of volume passed.

The volume is displayed on a direct read counter type index. Several low and high-frequency pulses can be used for flow computing or control purposes.


The FMR series of rotary meters is suitable for custody transfer gas measurement of all non-corrosive gases such as natural gas, propane, butane, air, hydrogen, etc. Typical applications are:

  • Gas distribution in low, medium or high-pressure networks
  • Industrial applications
  • Master meters for test benches

Main Features

  • Flow range 0.2 – 1000 m3/h
  • Diameters DN25 – DN200 (1” – 8”)
  • Pressure rates PN 10 – 100, ANSI 150 – 600
  • Compliant with EN12480:2002
  • Compliant with EN12480:2015
  • Compliant with OIML R137 1&2 (2014)
  • Compliant with MID 2014/32/EU
  • MID temperature range -40 to +70ºC
  • Large rangeability > 1:160
  • Cartridge design
  • Robust construction
  • Multi position
  • Square impeller technique
  •  Compact installation
  • Easy local repair
  • On-site cleaning
  • Tamper proof exchangeable index
  • Seals according EN 549 (seals for gas appliances and gas equipment)

General Information


Each FMR rotary meter is tested with atmospheric air to traceable (Dutch NMi) calibrated references.   It has been proven – as part of the type approval testing – that the difference between the accuracy at atmospheric air and at high pressure natural gas is negligible.

Meter Body Design

To maintain the high accuracy and large rangeability, it is essential that the displaced volume does not change within the range of operating conditions. By separating the meter body from the actual pipeline and using the same material as the impellers, changes in displaced volume due to installation stresses, operating pressure and thermal expansion are eliminated.

Cartridge Design

All FMR meters consist of an aluminum cartridge inserted in a meter body. The cartridge can be removed and inserted with the body remaining installed This allows local repairs such as replacement of the main bearings and on-site cleaning to be carried out without removing the meter body.

Particular owners of older networks, suffering from dirt and/or condensate, will benefit from the ability to remove the cartridge. FMG has a cartridge exchange program to replace older cartridges with new calibrated ones.

Robust Construction

In the new cartridge FMR design, the impellers, timing gears and bearings are fixed and positioned by a synchroplate. Since this synchroplate is machined in one operation, the tolerances can be controlled and maintained at a very high level. As a consequence, the clearance between the impellers and the meter body is equally divided and as such maximized, making the meters less sensitive to dirt and debris.

The short impeller and high strength shaft connecting the timing gear to the impeller overcomes flexing or bending of the impellers, hence the meters are less sensitive to flow and pressure shocks. Severe intermittent on/off applications are typically handled without damage. Temporarily overloading the meter up to 50% of the maximum capacity will not cause any degradation of the metrological quality.

Superior Metrological Performance

Starting with the G40, all meters are approved according to EN12480:2002, EN12480:2015 and OIML R137 1&2 (2014) for rangeabilities up to 1:160 and as such can, on request, be designated as Class 1.5 meters. In situations where the installation or gas conditions are severe, the risk of rejection is greater when recalibration is done against in-service tolerances.

The designation of class 1.5 (instead of 1.0), while still maintaining the class 1.0 accuracy limits, could be of interest since the in-service tolerances of a class 1.5 meter are significantly larger than the class 1.0 tolerances

Square Impeller Technique

The use of square impellers not only makes the meter very robust and short, but also improves the accuracy and range ability. The unregistered leakage causing an error at minimum capacity, thus limiting the range ability, is significantly smaller for square impellers (shorter profile) compared to the traditional long impellers.

Basic Index (Standard)

The basic index consists of a UV-resistant polycarbonate cover glued to an aluminum frame. The aluminum frame will give strength to the index and as such sufficient protection against mechanical interference (Tampering). The index is 100% sealed (IP67) by multiple layers of glue. The index can be rotated over 350° for flow directions right-left, left–right and top-down. The index is equipped with multiple LF switches and normally closed tamper contacts.

Universal Index

The extremely strong double walled, aluminum, index is designed to withstand any external interference. To protect against large forces applied to the index window, an additional glass window is mounted beneath the polycarbonate window. This glass window will break in case excessive force is applied to the index.

On request the index can be sealed up to IP67. Four slots in the outer extrusion can be used for various add-ons such as multiple connectors, additional outgoing shafts, marking plates with bar codes, etc. The use of slots makes the index multifunctional and as such “prepared for the future”.

Instrument Drive / Side reading

The instrument drive plate can be used to mount auxiliary equipment like chart recorders or mechanically driven volume correctors. The rotation of the outgoing shaft is equal to one m3 or CF or (sub) multiple thereof. A single or double counter can be added to the instrument drive. The instrument drive can be rotated over 350°, hence allowing both horizontal and vertical installation.

The instrument drive can be equipped with low frequency pulsers, an encoder as well as a reverse flow lock, preventing meters from registering backwards as a result of tampering. On request the index can be supplied as side reading (without instrument drive) allowing the meter to be installed in an extremely high or low position. The rotating direction of the output shaft can be changed on site.

FMR Rotary Gas Meter Specifications

  • Metrological approvals:
    • Compliant with EN12480:2002
    • Compliant with EN12480:2015
    • Compliant with OIML R137 1&2 (2014)
    • Compliant with MID 2014/32/EU
  • ATEX approvals:
    • Sensors compliant with Ex ia IIC T4… T6 Gb (-40ºC ≤ Ta +70ºC)
    • Encoder compliant with Ex ib IIB T3… T6 Gb (-25ºC ≤ Ta +55ºC)
  • Flow rates:  0.2 m3 /h up to 1000 m3 /h
  • Nominal diameters:  From DN25 to DN200 mm (1” to 8”).
  • Mounting position:  Horizontally or vertically Body Compliant to Pressure Equipment Directive 2014/68/EU
  • Temperature Range:


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