973-SF6 Gas Analyzer

SF6 gas analyser for GIS

Precise and Stable SF6 Gas Analyser

  • Simultaneous measurement of humidity, SF6 purity and SO2 concentration
  • Integrated gas recovery system with automatic pump back
  • Fully automated SF6 gas testing
  • Fundamental drift-free measuring principle
  • Measurement results at SF6 compartment or standard pressure
  • Intuitive user Interface
  • Colour touch screen
  • User verifiable calibration
  • Robust case for easy transportation

Optimal Solution for SF6 Gas Analysis

The 973-SF6 is an advanced SF6 gas analyser for measuring humidity, SF6 purity and SO2 concentration in SF6 gas-insulated switchgear (GIS) and other high voltage equipment.

With its internal gas containment and recovery system, the 973-SF6 provides high quality and environmentally safe measurement solutions within a single self-contained unit.

Pure SF6 is the standard filling within GIS, but gas compartments become contaminated with water vapour (H2O) through permeation and desorption from internal materials.

Whilst water vapour and SF6 do generally not react with each other, in the presence of a high-energy discharge, hydrogen and oxygen disassociated from water vapour will react with the sulfur and fluorine from SF6 to form decomposition by-products.

These include sulfur dioxide (SO2) and hydrofluoric acid (HF) that are corrosive to the internal components of gas compartments.

SF6 with low water vapour content (low humidity) significantly reduces the potential for the formation of these corrosive compounds, which is why accurate and repeatable measurement data is an invaluable part of any GIS preventative maintenance program.

Accuracy and Repeatability Using Advanced Chilled Mirror Technology

A polished mirror surface is cooled to the point at which condensation forms on the mirror surface, then the temperature is measured. Since this condensation temperature is specific to water vapour concentration, exact results are achieved without humidity sensors.

Chilled mirror technology is the most accurate and reliable humidity measurement technique available. Since the 973-SF6 employs the same condensation principle in determining SF6 purity, the same high levels of repeatability and long-term stability are attained for both key SF6 measurements.

Innovative and Cost-Effective SF6 Analysis

Unlike dew point humidity sensor-based systems that rapidly and continually drift out of specification, the 973-SF6 chilled mirror technology relies on the drift-free physical principles of condensation formation.

Whilst sensor-based systems may have a lower initial acquisition cost, ongoing charges for sensor replacement, re-calibration, and the lower reliability of their measurements, make the 973-SF6 a more cost-effective option, precise and long term solution.

Intuitive User Interface

Measurement results are presented on a clear full-colour touch screen in the units of choice. Results are held on the display for user notation and can easily be imported into Microsoft Excel using the software and cable supplied.

The 973-SF6 data format is compatible with test procedures issued by all major SF6 equipment manufacturers and standards organisations such as Cigré and IEC.

User Verifiable Calibration with Ice Test Function

The melting point of ice at atmospheric pressure is always 0 °C. The 973-SF6 takes advantage of this fundamental value to provide users with an immediate check of calibration stability with the Ice-Test function. During this automatic test, the mirror is cooled below 0 °C, causing water vapour from the air to condense and freeze on the mirror surface. The mirror is then warmed, and whilst observing the mirror, the user presses the on-screen button to confirm the point at which the ice melts.

The 973-SF6 measures the mirror temperature at this point and provides a pass/fail indication on the screen. The test can be repeated as often as required without affecting instrument performance.

Easy to Use and Minimal Maintenance

Taking a measurement using the 973-SF6 could not be easier.

Once connected to the gas compartment using the couplings provided, the user starts an automated test sequence, and the instrument does the rest. Measurement results are held on the instrument display until the user initialises the subsequent measurement. The SF6 gas pump back can be user programmed to take place as part of the automated sequence. Full analysis and gas pump back before is typically completed within 10 minutes and without user supervision.

973-SF6 maintenance is limited to occasional mirror cleaning and physical inspection of gas hoses. Automated tests and user warnings for key operational parameters such as pumping capability, cylinder capacity and correct pressurisation allow the system to be easily managed. There is no need for regular sensor replacement or return of the instrument for recalibration.

Zero Emission Gas Analysis

The 973-SF6 includes built-in gas recovery, allowing analysis to be performed without the emission of SF6 gas to the atmosphere.

The 973-SF6 pumps a sample from the gas compartment through the measuring head and into the internal storage cylinder during measurement. Once testing is completed, the gas can be pumped straight back to the compartment.

Optionally, it may be held within the 973-SF6 for later pump back into a waste cylinder.

The 973-SF6 incorporates a completely sealed, high-pressure pump and gas path for precise, zero-emission gas analysis.

SO2 Measurement

The 973-SF6 is available with a built-in measurement of SO2 concentration (ppmv). The electrochemical SO2 measurement cell is conveniently located on the rear panel for simple user replacement with low cost, pre-calibrated, interchangeable SO2 modules. From 2012, all-new 973-SF6 instruments are ready for SO2 measurement, so if required, this option may be field upgraded using a plug-in sensor module and a software activation key. Earlier devices can also be factory upgraded; don't hesitate to contact us for guidance.

All SO2 sensors supplied by MBW are calibrated before delivery.

Transportable, Robust and Complete Analyzer Set

The 973-SF6 is supplied in a robust, shock-resistant, waterproof case suitable for use on-site and transportation.

Included in the instrument case:

  • 6 m self-sealing armoured sample tube
  • Self-sealing DN8 and DN20 couplings
  • USB stick with Excel Data Collection file
  • Calibration Certificate
  • 2.5 m power cable
  • Maintenance kit
  • Operating manual

Quality Assurance

High precision, together with excellent reliability and stability, make the 973-SF6 the gas analyser of choice for the major switchgear manufacturers.

All new and serviced instruments are delivered with a traceable calibration certificate that complies with the requirements of Quality Management Systems such as ISO9001 and provides the user with confidence in the measurements obtained.

Technical Sheet 973-SF6
Measuring Range
Forst/Dew Point-50 ... +20°C
Humidity Content by Volume40 ... 20.000 ppmv
Humidity Content by Weight5 ... 2.500 ppmv
Volume SF6 in %80 ... 100%
Inlet Pressure120 ... 1.000 kPa abs.
Forst/Dew Point≤ ± 0.5 °C
pppmv/ppmw≤ ± 1ppm + 6 % of reading
Volume SF6 in %≤ ± 0.5 %
Pressure≤ 3 kPa
Standard Features
Digital Input/OutputRs-232
Thermoelectric Mirror Cooling3-stage
Mirror Temperature SensorRTD (Pt100)
Screen5.7" LCD with touch screen
Internal Gas TubesStainless Steel 316L / FEP
SO2 PreparationMechanically and electrically prepared, measurement cell cover fitted
Gass ConnectorsSelf-sealing quick-connect fitting (Swagelok® QM Series)
CouplingsSelf-sealing SF6 coupling DN8 (VK/F-02/8) and DN20 (VK/F-02/20)
External Sample Gas TubeSelf-sealing 6 m stainless steel armored PTFE tubing
ORISOptimum Response Injection System
Transport CaseCustom fit foam lined Peli 1620
Power Cable2.5 m
Operating InstructionsEnglish, German, French or Italian
Calibration CertificatePressure calibration, 2-point dew/frost point, 3-point %Volume SF6
Internal SO2-Module
Measuring Range0 ... 100 ppmvo0 ... 500 ppmv
Accuracy≤ 2 % of range≤ 2 % of range
Sensitivity Drift≤ 5 % / year≤ 5 % / year
Lifetime2 years2 years
Additional Information
Supply Voltage
100-120 VAC / 200-240 VAC, 50/60 Hz (auto switching)
Power Conusmption
200 W
Max. Pump Back Pressure
900 kPa
Ad aria
Operational Conditions-10 … +40 °C, 98 %rh, non-condensing, altitude up to 2000 m
Storage Temperature-20 °C … +50 °C
Outdoor UsePermissible, instrument must be protected against exposure to water.
Weight and DimensionsInstrumentIn Transport Case
Width420 mm650 mm
Height155 mm370 mm
Depth390 mm510 mm
Weight16,5 Kg32 Kg

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