Model 921A Combustible Gas Meter
Model 921A Combustible Gas Meter
Measure total combustible gases (TCG) in oil-filled transformer nitrogen gas blankets with this rugged, portable instrument.
The Arbiter Systems®, Inc. Model 921A Combustible Gas Meter is a rugged, portable instrument that measures total combustible gases (TCG) in oil-filled transformer nitrogen gas blankets. TCG measurements have been shown to be good indicators of transformer health.
The supplied cylinders of Instrument Air, Zero Grade Nitrogen and 1% Methane in Nitrogen calibration gases support field calibration, after which TCG measurements are virtually automatic.
The Model 921A also has a built-in gas pressure sensor. By connecting the gas sampling hose to the PSI port and pressing PSI, the blanket fill gas pressure can be accurately measured.
The Model 921A is provided with a hard-sided transit case, along with instrument air, nitrogen, and 1% calibration gas cylinders and all necessary regulators and accessories.
- Measures total combustible gases (TCG) in the field.
- Built-in gas pressure sensor.
- Includes regulators and accessories.
- Includes cylinders of Instrument Air, Zero Grade Nitrogen and 1% Methane in Nitrogen calibration gases.
- All shipments containing gas cylinders ship from the factory via FedEx Ground ONLY. Reshipping this non-flammable calibration gas through common carrier requires hazardous materials certification because the cylinder pressure is greater than 40 psi.
Input
TCG
| Inlet Pressure | 1 to 5 PSIG, nominal |
| Damage Inlet | Vacuum to 30 PSIG |
| Gas Inlet | Female Luer Fitting |
Pressure
| Damage Limit | Vacuum to 30 PSIG |
| Gas Inlet | Female Luer Fitting |
Air
| Purity | Zero-Grade Instrument Air, 21.00% Oxygen |
| Inlet Pressure | 20 to 25 PSIG or use supplied regulator |
| Air Inlet | Female Luer Fitting |
Measurements
TCG
| Range | 0 to 10.0% |
| Accuracy | ±(5% of reading + 1 count) |
| Resolution | 0.01% TCG |
| Calibration | 1% Methane = 1% TCG |
Sensitivity to Various Gases
(reading for 1% gas in nitrogen, typical)
| Methane | 1.00 |
| Carbon Monoxide | 0.48 |
| Hydrogen | 0.86 |
| Acetylene | 1.9 to 2.0 Note: Interactions between the catalyst and acetylene cause the sensitivity to gradually increase during a sequence of acetylene measurements. This does not affect the sensitivity to other gases, and the effect is reversed on standing. |
| Ethylene | 1.92 |
| Ethane | 1.64 |
| Air (100%) | -0.07 Note: The thermal conductivity of air, being slightly higher than that of nitrogen, will cause a negative reading by virtue of differences in thermal conductivity. While not optimized as a thermal-conductivity detector, this is an indication that transformer gas is not reaching the Model 921A. |
Pressure
| Range | 0 to 15 PSIG |
| Accuracy | 0.1 PSI |
Interface
Operator
| Display | 16 character alpha-numeric supertwist LCD |
Power Requirements
Internal Battery
| Type | Gelled-electrolyte lead-acid, 6 V / 4 AH |
| Operation | 400 measurements on full charge |
| Charging Time | 8 hours typical |
General
Physical
| Instrument/Size | 130 x 230 x 65 mm (5.125 x 9.125 x 2.625 in.) |
| Transit Case | 400 H x 380 W x 240 D mm (16 x 15 x 9.5 in.) |
| Shipping | 533 x 533 x 533 mm (21 x 21 x 21 in.), container |
| Weight | 3 kg (7 lbs), net (instrument) |
Environmental
| Temperature | Operating: 0 °C to +50 °C |
| Included | |
|---|---|
| AP0001800 | Wall-mount Power Supply: 12 Vac, 60 Hz; 12 Vdc, 0.8 A |
| AP0002500 | Automobile lighter adapter |
| AS0019100 | Calibration Gas Regulator |
| AS0019300 | Transformer gas hose assembly |
| AS0019402 | Calibration gas hose assembly (red) |
| AS0019406 | Calibration gas hose assembly (blue) |
| AS0019500 1 | Calibration Gas - Instrument Air |
| AS0019600 1 | Calibration Gas - Zero Nitrogen |
| AS0019700 1 | Calibration Gas - 1% Methane in Nitrogen |
| FT0001200 2 | Particulate Filter (ea) |
| PD0010700 | Operation Manual (921) |
| Available | |
| AS0019501 1 | Calibration Gas - Instrument Air - Case of 12 |
| AS0019601 1 | Calibration Gas - Zero Nitrogen - Case of 12 |
| AS0019701 1 | Calibration Gas - 1% Methane in Nitrogen - Case of 12 |
| AS0020500 | Syringe Adapter (Kit of 5 each) |
| AS0020800 | Bag of 10 Particulate Filters (FT0001200) |
| AS0026900 | Transformer Hose In-Line Filter Kit |
| AS0026901 | Transformer Hose In-Line Filter Kit - Bag of Five |
| AS0035100 | Annual Filter Maintenance Kit |
1 Ships from factory FedEx Ground ONLY. Reshipping this non-flammable calibration gas through common carrier requires hazardous materials certification because the container pressure is greater than 40 psi.
2 Two filters are included
No additional software information is available for this product
| Firmware Information (EPROM based firmware is not available for download) | |
|---|---|
| 921_Firmware_24Oct2012 | Requires an EPROM update at Arbiter. Not field installable. |
Firmware Version and Related Information
EEPROM Update (921_Firmware)
| Version | Version Notes |
|---|---|
| 24Oct2012 |
|
TCG Measurement Comparison
Download model_921a_vs_mcgraw.pdf (14 kB) »
Model 921A combustible Gas Meter Filter Replacement Instructions
Download model_921a_filter_replacement_instructions.pdf (132 kB) »
Model 921A Sensor Change Update
Download 921a_sensor_change_update.pdf (27 kB) »
1% Methane In Nitrogen (MSDS)
Download methane_in_nitrogen.pdf (233 kB) »
Zero Grade Nitrogen (MSDS)
Download nitrogen.pdf (131 kB) »
Instrument Air - Oxygen in Nitrogen Mixture (MSDS)
Download oxygen_in_nitrogen.pdf (107 kB) »
