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8500, 8505, 9775 Thermco Variable Ratio Mini-Gas Mixer


This item is custom built to fit your needs and has various part numbers. Please contact us for pricing and expected ship date. 



This item is custom built to fit your needs and has various part numbers. Please contact us for pricing and expected ship date. 


The models 8500, 8505 and 9775 are designed to create welding shield gas. These gas mixers are suitable for:
  • 0-50% CO2 in Ar (model 8500)
  • 0-10% O2 in Ar (model 8505)
  • 0-50% He in Ar (model 9775)

Each gas mixer is easily changeable by adjusting a single calibrated dial.

Since these gas mixers use Thermco's surge tank design, the gas mixture is highly accurate throughout the flow range.

The digital, solid-state pressure switch controlling the surge tank pressure provides extremely long life as well as diagnostics for the surge tank pressure condition.


  • All models are variable simply by turning a single dial.
  • Surge tank design allows infinite flow rate turn down from 750 to 0 SCFH while maintaining a precise mix.
  • All solid-state pressure switch which controls surge tank pressure is rated at 100 million cycles. This switch also provides a digital readout of the surge tank pressure, which can be observed through the front window.
  • Diagnostics – a light on the solid-state pressure switch illuminates when the surge tank is filling.
  • Optional pressure alarm system available


Model Range Flow Capacity Accuracy
8500 0-50% carbon dioxide in argon 0-750 SCFH (0-20.1 Nm3/h) ±1.5% carbon dioxide
8505 0-10% oxygen in argon 0-750 SCFH (0-20.1 Nm3/h) ±0.3% oxygen
9775 0-50% helium in argon 0-350 SCFH (0-9.4 Nm3/h ±1.5% helium

Note: 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 details.

Accuracy Under Typical Conditions:

(Example: For 25% carbon dioxide in argon mixture, the mix will be ±1.5% carbon dioxide; therefore, the mixture will be within the limits of 23.5% to 26.5% carbon dioxide.)

Ambient and Supply Gas Operating Temperatures:

32°F (0°C) to 104°F (40°C).

Supply Gas Pressure:

100-125 PSIG (6.9-8.6 barg)

Mixed Gas Outlet Pressure:

10-50 PSIG (0.7-3.4 barg). Regulator provided by Thermco in mixer for mixed gas pressure adjustment.

Gas Connections and Piping:

1/2 inch NPT female pipe for major, minor, and mixed gas connections.

Solid-State Surge Tank Pressure Switch:

The gas mixer utilizes a solid-state pressure switch to control the surge tank pressure. A digital readout of the pressure is built into the switch. Both the sensing element and electrical switch are solid-state. An LED indicator shows when the surge tank is filling. Use of this pressure switch virtually eliminates the most common cause of gas mixer failure.

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. Acceptable voltage range 104-126 VAC. Available on request, 220 VAC, 50/60 Hz, 0.25 amp. Acceptable voltage range 204-240 VAC.


Net 65 lbs. (29.5 kg); Packed 78 lbs. (35.4 kg).


27.50” (70 cm) height, 19.1” (49 cm) width, 10.25” (26 cm) depth.


Steel material, with door gasket for protection from dust. The door is provided with a lock. This enclosure is not designed for outdoor installation.


Wall or bench indoors.
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