DigitalFlow XGF8681-21-OIM-34-0 Flare Gas Mass Ultrasonic Flow Transmitter
Overview
DigitalFlow XGF8681-21-OIM-34-0 belongs to the Panametrics DigitalFlow XGF868i series compact explosion-proof ultrasonic flow transmitter. Adopting patented Correlation Transit-Time measurement technology and proprietary molecular weight calculation algorithms, it is engineered specifically for flare gas applications.The transmitter delivers real-time measurement of flow velocity, volumetric flow and mass flow, maintaining stable performance despite fluctuations in gas composition.
The XGF8681-21-OIM-34-0 has no moving mechanical parts and features an extremely wide turndown ratio up to 4000:1, providing consistent high-accuracy measurement at both low and high flow velocities.It supports single-path or dual-path transducer configurations and resists cross-flow disturbances in large pipelines. Designed for hazardous classified explosion-proof areas such as offshore platforms, refineries and chemical plants, it addresses common measurement challenges of flare gas, including mixed gas compositions, bidirectional pulsating flow, wide temperature and pressure variations, and humid media containing impurities.
The unit features a compact, lightweight enclosure with all electronics housed within an explosion-proof casing, enabling close mounting at pipeline measurement points to minimize cabling lengths. A complete measurement system consists of the transmitter, T5 / T17 wetted ultrasonic transducers, XAMP preamplifiers and RG62 coaxial cables.It works with PanaView host software for data logging, log export and parameter configuration. Additionally, it can interface with flare.IQ intelligent flare management systems to optimize emissions and precisely regulate steam injection.Transmitter EnclosureFlameproof aluminum housing with epoxy coating; stainless steel housing available as an option. Weather-resistant and corrosion-proof for all-weather service. Equipped with locking sealing structure, and marked with “Do not open when energized” in compliance with explosion protection standards.
This instrument serves as a core metering device for flare emission compliance measurement, leak tracing and energy consumption management within the oil, gas and chemical industries.
Technical Specifications
Medium & Pipeline Compatibility Parameters
Measured Media: Flare gas, vented hydrocarbon gas, biogas, digester gas, process off-gasApplicable Pipe Materials: All types of metal pipes, fiberglass pipes; consult Panametrics technical team for other materialsPipe Diameter: 100 mm (4 in) ~ 3000 mm (120 in)Flow Velocity Range: Bidirectional standard range 0.03 ~ 100 m/s; unidirectional extended range 0.03 ~ 120 m/sTurndown Ratio: 4000:1Transducer Types: T5/T5MAX wetted transducers, T17 wetted transducersTransducer Materials: Standard titanium alloy; optional Hastelloy, 316 stainless steel, Monel alloyProcess Temperature:- T5/T5MAX standard temperature version: -55°C ~ 150°C
- Low-temperature version: -220°C ~ 100°C
- High-temperature version: -50°C ~ 250°C
- Ultra-high-temperature version: -180°C ~ 300°CProcess Pressure: -2 psig ~ 1500 psig (87.6 ~ 10300 kPa)
Transmitter Electronics & Enclosure Specifications
Model: DigitalFlow XGF8681-21-OIM-34-0 (XGF868i Series Explosion-Proof Transmitter)Channel Configuration: Standard dual-channel, freely switchable between single-path / dual-path modeDisplay Panel: 2-line × 16-character backlit LCD, cyclically displays 4 measurement parametersOperating Keypad: Built-in 6-key magnetic operating panel; on-site configuration without opening explosion-proof housingDimensions: 208 mm Height × 168 mm DiameterUnit Weight: 4.5 kgIngress Protection: IP66, Type4XExplosion Protection Certifications: Class I Div1 BCD, Ex d IIC T6 Gb, ATEX II 2G, IECExAmbient Operating Temperature: -40°C ~ 60°C; Storage Temperature: -55°C ~ 75°CPower Supply: Standard 100~240VAC ±10%; optional 12~28VDC power supply, maximum power consumption 20 W
I/O & Communication
Analog Output: 2 isolated 4~20mA channels, maximum load 600 ΩAnalog Input: 2 isolated 4~20mA channels for temperature & pressure acquisition; optional configuration: 1×4~20mA + 1×RTD (-100°C ~ 350°C)Optional Frequency Output: 2 optically isolated frequency outputs, 0~10 kHzStandard Communication: RS232, HART 7 ProtocolOptional Digital Interfaces: Modbus RS485/TCPIP, Ethernet, OPC, FOUNDATION Fieldbus, Namur NE107
Supporting XAMP Preamplifier
Gain: 20/40 (optional 2/10)Operating Temperature: -40°C ~ 60°CConfiguration: One XAMP per transducer
Cable Specifications
RG62 A/U coaxial cable; cable length per transducer set: 3 m ~ 300 m; flame-retardant armored cable optional
Measurement Accuracy
Velocity Accuracy
- Pipe ID ＜ 150 mm: ±1.5% (calibrated single-path); ±0.75% (calibrated dual-path)
- Pipe ID ≥ 150 mm: ±0.75% (calibrated single-path / dual-path)
Low flow sensitivity (0.03 ~ 0.3 m/s):
- DN250 pipe: ±0.004 m/s
- DN350 and larger pipes: ±0.0015 m/s
Mass Flow Accuracy:
- Dual-path configuration: ±2.3% ~ 3.1%
- Single-path configuration: ±4.0%
Mixed Gas Molecular Weight Accuracy: ±1.8% ~ 2.0%Net Heating Value (NHV) Accuracy: Typical 2% ~ 5%Measurement Repeatability: ±0.5%
Straight Pipe Requirements:
- Without CFD correction: 20D upstream, 5D downstream
- With CFD correction enabled: 5D upstream, 2D downstream
Functional Advantages
Adaptive Measurement for Variable Gas Composition
The DigitalFlow XGF8681-21-OIM-34-0 incorporates a patented molecular weight calculation algorithm. It maintains accurate readings despite variations in hydrocarbon, nitrogen and water vapor contents. The transmitter outputs real-time average molecular weight of mixed gas and enables precise mass flow conversion without the support of online gas chromatographs.Stable Metering with Ultra-Wide Turndown
The exceptional 4000:1 turndown ratio covers minimal venting under standby conditions and high flare gas flow during emergency relief. Measurement errors remain controllable across 0.03 m/s low velocity up to 120 m/s high velocity, accommodating the full operating range of flare systems.Zero Pressure Loss & Maintenance-Free Design
Neither the transmitter nor transducers contain intrusive restriction components or moving mechanical parts. There is no risk of medium blockage or abrasion. For dirty, humid and impurity-laden flare gas, periodic disassembly and cleaning are unnecessary during long-term operation, cutting on-site labor costs and production downtime losses.Compact Explosion-Proof Enclosure for Confined Hazardous Areas
The compact flameproof housing of the DigitalFlow XGF8681-21-OIM-34-0 allows direct mounting close to pipeline measurement points. It simplifies wiring on offshore platforms and congested pipe racks, complying with strict Zone 1 explosion protection standards.Built-in Net Heating Value (NHV) Calculation
No additional calorimeter is required. The unit directly delivers net heating value of flare gas to accurately regulate steam injection. It mitigates methane emissions caused by incomplete combustion and fulfills compliance metering requirements for global environmental regulations.Dual-Path Solution Against Cross-Flow Interference
Dual-path transducer configuration offsets measurement deviations induced by vortices and asymmetric flow profiles in large pipelines. The single-path setup with a 6° downstream compensation angle preserves measurement performance at low and high flow rates without complicated flow conditioners.Local Digital Calculation & Multi-Protocol Communication
All computations for flow rate, molecular weight and heating value are processed locally. Multiple communication options including HART, Modbus and Ethernet support seamless connection to DCS systems. The on-board LCD displays real-time instantaneous flow, totalized flow, molecular weight, temperature and pressure parameters.Leak Tracing & Plant-Wide Material Balance Support
Minor flow fluctuations enable rapid detection of valve internal leakage and pipeline seepage. Combined with molecular weight composition data, the system facilitates leak source identification, supports plant-wide mass balance calculation and reduces feedstock loss and steam consumption.Hardware Features
Ultrasonic Transducer AssemblyTitanium wetted transducers suitable for highly corrosive flare media. Two process connection types: flange and compression fitting. Compatible with cold tapping and hot tapping installation under operating pressure.
Magnetic Keypad OperationParameters configuration, zero calibration and data retrieval can be performed via external magnetic keys without opening the flameproof enclosure. This eliminates ignition risks associated with opening housings in hazardous areas.
Dual-Channel Hardware ArchitectureStandard dual signal acquisition boards support simultaneous flow measurement on two separate flare pipelines. Fault on one channel will not interrupt metering on the other channel.
Remote XAMP PreamplifierIndependent preamplifiers matched with transducers can be integrated into transducer assemblies or installed remotely, extending signal transmission distance up to 300 meters.
Versatile Transducer Selection for Multiple MediaA full range of T5/T17 transducers for low, high and ultra-high process temperatures. Hastelloy and Monel transducer options are available for severely corrosive service conditions.
Onboard Diagnostic & Self-Check FunctionBuilt-in diagnostics for sound velocity and signal strength. Instrument performance verification can be conducted without shutdown, meeting periodic verification requirements for environmental metering.
Standardized Accessories
Coaxial signal cables, packing insertion assemblies and explosion-proof locking fittings are supplied as standardized components with high spare part interchangeability.
Application Fields
- Flow metering for flare headers and branch vent lines in refineries; emission compliance monitoring and precise steam injection control
- Mass balance calculation for process tail gas and relief valve flare gas in petrochemical plants; rapid troubleshooting of leakage faults
- Flare system measurement on offshore oil & gas platforms; flow acquisition in confined Zone 1 hazardous areas for unattended offshore metering
- Heating value and mass flow monitoring for biogas and digester gas combustion flares
- Flow control of vented off-gas and incinerator feed gas at power plants and coal chemical facilities to reduce energy waste from inefficient combustion
- Plant-wide material balance calculation; tracking feedstock loss and quantifying leakage points
- Online emission data collection for environmental supervision, supporting regulatory reporting metering requirements
- Steam energy saving optimization; automatic adjustment of injected steam volume based on real-time flare gas mass flow to lower steam operating costs
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