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.

 

Model 921A Manual
Download PDF(1 MB) »

Model 921A Data Sheet
Download PDF(458 kB) »

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 PSIG 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 PSIG 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 PSIG 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 mm x 230 mm x 65 mm (5.125 in x 9.125 in x 2.625 in)

Transit Case

400 mm H x 380 mm W x 240 mm D (16 in x 15 in x 9.5 in)

Shipping

533 mm x 533 mm x 533 mm (21 in x 21 in x 21 in), container
9.5 kg (21 lbs)
Ships Federal Express with special shipping charges due to Dangerous Goods classification.

Weight

3 kg (7 lbs), net (instrument)
10 kg (22 lbs), with accessories

Environmental

Temperature

Operating: 0 °C to + 50 °C
Nonoperating: - 40 °C to + 75 °C

There are no additional Options available for this product.
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
AS0096300 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
AS0026900 Transformer Hose In-Line Filter Kit
AS0026901 Transformer Hose In-Line Filter Kit - Bag of Five
AS0035100 Annual Filter Maintenance Kit
AS0061790 Transit Case without Accessories (921A)
BT0000700 6.0V Lead Acid 4.0Ah Sealed (921A)
HP0018400 Plug Luer Male w/ Locking Nut

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.

No software downloads available for this product
 
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)

VersionRev LevelVersion Notes
24Oct2012
  1. Changed the TCG correction limits to match the range in the manual.

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 (30 kB) »

Instrument Air - Oxygen in Nitrogen Mixture (MSDS)
Download oxygen_in_nitrogen.pdf (107 kB) »

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