Gas Mixer Model: 8515

Primary Application: Welding Shield Gas

  • Two gas mixture is set at the factory to the user specified setting
  • The mixture may be changed by the user to a new mixture with the assistance of a gas analyzer
  • The model 8515 is made especially for oxygen service
  • Surge tank design will produce a highly accurate mixture from zero flow to full flow, no minimum flow rate requirement to maintain accuracy
  • Option of the pressure alarm system
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Model 8515
Common Mixture Ranges
Two gases that are non-flammable and non-corrosive with one gas being oxygen.
Mixed Gas Flow Capacity 0-750 scfh (0-20 Nm3/h)
Gas Mixing Accuracy
For minor gas concentration >7%: ±5% of the nominal concentration.
For minor gas concentration 1% to 7%: ±0.35% absolute.
For minor gas concentration <1%: Consult Thermco.
Accuracies assume ambient and supply gas temperatures are in the range of 50° to 90°F (10° to 32°C) and supply gas temperatures are equal.
Ambient and Supply Gas Temperature Range 32°F to 100°F (0°C to 38°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 ½ inch NPT female pipe for major, minor and mixed gas.
Surge Tank 5 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 58 lbs. (26 kg)
Dimensions 27.5 in (70 cm) height, 19.1 in (49 cm) width, 10.3 in (26 cm) depth
Enclosure Steel material, with door gasket for protection from dust. The door is provided with a lock. This enclosure is not designed for outdoor installation.
Mounting Type Wall or bench indoors

Additional Information


The model 8515 gas mixer is designed to create a constant proportion of two non-flammable, non-corrosive gases. Common applications include shield gas for welding, leak detection mixtures and lamp filling.

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 8515 is suitable for continuous flow or intermittent flow demand.

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.

Optional Pressure Alarm System

A pressure alarm system is available to alert personnel in the event of low input gas pressure. When one of the input gas pressures falls too low to create an accurate mixture, a light specific to the low pressure gas is illuminated on the front door, and a horn on the enclosure sounds. The operator can silence the horn with a horn silence button on the inner door.

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.