Gas Mixer Model: 8205

Primary Applications: Welding Shield Gas, Food Packaging, Leak Detection

  • Flow rate capacity of 5,000 scfh for a variety of applications
  • Continuous gas analysis of the gas mixture with audio/visual alarms standard
  • Surge tank design will produce a highly accurate mixture from zero flow to full flow, no minimum flow rate requirement to maintain accuracy
  • Weatherproof design allows outdoor installation
  • Lockable enclosure protects against dirty environments and unauthorized tampering
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Model 8205
Common Mixture Ranges
0-30% carbon dioxide in argon.
0-10% oxygen in argon
0-50% helium in argon
0-50% helium in nitrogen
0-50% carbon dioxide in nitrogen
Mixed Gas Flow Capacity 0-5,000 scfh (0-134 Nm3/h) This is the mixed gas capacity at the mid-range setting. The capacity may be more or less depending on the mixture setting. Consult Thermco for more details.
Gas Mixing Accuracy
±2% of full range over 60°F to 80°F (15°C to 27°C)
±4% of full range over 32°F to 104°F (0°C to 40°C)
±8% of full range over -10°F to 104°F (-23°C to 40°C)
Stated accuracy assumes that the input temperature of the gases are equal.
Gas Analyzer Thermal conductivity type made by Thermco. The detector is expected to last the lifetime of the gas analyzer. The calibration is highly stable, recommended calibration interval is one year. Heated thermal conductivity cell allows this analyzer to be used at temperatures as low as -10°F (-23°C).
Ambient and Supply Gas Temperature Range -10°F to 104°F (-23°C to 40°C)
Standard Supply Gas Pressure 100-125 psig (6.9-8.6 barg) Supply pressures do not have to be equal.
Standard Mixture Outlet Pressure 10-50 psig (0.7-3.4 barg) Regulator provided by Thermco in gas mixer for mixture outlet pressure adjustment. Note: Gas mixers are frequently engineered for non-standard pressure conditions.
Gas Connections 1 inch female NPT pipe for major, minor, and mixed gas connections.
Surge Tank 60 gallon, ASME coded and CRN registered, pressure relief valve provided
Surge Tank Pressure Switch Solid-state sensing and output, rated 100,000,000 cycles
Power Requirements 115 VAC, 50/60 Hz, 0.5 amp. Available on request, 220 VAC, 50/60 Hz, 0.25 amps.
Weight 440 lbs. (200 kg)
Dimensions 60.0 in (152 cm) height, 55.0 in (140 cm) width, 25.0 in (64 cm) depth
Mounting Type Floor mounted

Additional Information


The model 8205 is designed to mix two non-flammable, non-corrosive gases. Common applications are welding shield gas, food packaging, leak detection and blanketing atmospheres.

Because the gas mixer uses a surge tank design, this type of system is ideal for applications that require maintaining a precise proportion from zero flow to full flow with high reliability. The 8205 is suitable for continuous flow or intermittent flow demand.

The model 8205 is designed for both indoor and outdoor installation.

Thermco Surge Tank System

All Thermco gas mixers use a surge tank. The Thermco surge tank system has the significant advantage of maintaining the accuracy of the gas mixture from zero to full rated flow rate. There is no “minimum” flow rate. Gas mixing systems without a surge tank will have a minimum flow rate below which the gas mixture becomes inaccurate. The Thermco surge tank system is able to accomplish this accuracy without complex control valves or flowmeters.

Standard Supply Gas Pressure

Gas mixers will be made for supply pressures of 100-125 psig (6.9-8.6 barg) and mixed gas output pressures of 10-50 psig (0.7-3.4 barg) unless ordered otherwise. Gas mixers are often made to special pressure conditions; consult Thermco for details.


Each gas mixer is supplied with one instruction manual which includes wiring and flow diagrams. A data sheet is prepared for each gas mixer specifying major parts of the gas mixer, operating pressure settings and recommended spare parts. Thermco has been providing service on gas mixers since 1964.


Improper use of this product can cause death, serious injury, or property damage. Personnel dealing with this equipment should read and understand warning labels and instruction manuals provided by Thermco. Only personnel familiar with industrial gases should attempt to install or service this equipment. Gases are under pressure and therefore the hazards associated with pressurized systems exist. Gases from high pressure cylinders must be reduced to the specified pressure before entering the gas mixing system to prevent the possibility of equipment damage and personal injury.

Only use oxygen in gas mixers specifically designed for oxygen service. Gas mixers not designed for oxygen service cannot be converted to oxygen service.

Flammable, toxic, liquid or corrosive gases should not enter these gas mixing systems.

Ordering Information

Thermco gas mixers are available through many local industrial gas suppliers. Thermco gas mixers may also be ordered directly from the factory. It is especially important to order the correct pressure conditions for the application. If there are questions, please contact the Thermco Sales Engineer.