Sample Pressure Considerations with Teledyne Oxygen Analyzers
A question frequently asked about Teledyne Oxygen Analyzers and analyzers in general is "what is the maximum allowable pressure of the sample?" The maximum pressure varies from model to model. However, our analyzers fall into two main categories -- those with flow control and those without some flow control.
Building flow control into a unit can take several approaches.
1. Needle valve
2. Orifice or restrictor
3. Pressure regulator
4. Flow controller
Adding these components will drastically affect the absolute amount of pressure the system can tolerate on its inlet. This is because the sensor chamber and associated tubing itself at moderate flows creates no appreciable pressure drop, and must be vented to atmospheric pressure to work properly.
Operating at elevated vent pressures can be done, but since most analyzers' electronics are designed and optimized to operate at atmospheric pressure, and since the sensors themselves are partial pressure devices, operating at high pressures can overload the electronics. Therefore such applications should be approached carefully. Consult Teledyne for recommended modifications (if required). If flow control elements are present, you may be able to connect higher pressures to the inlet of the analyzer.
If no flow limiting element is present, the maximum pressure that should be applied to the inlet is a just a fraction of a PSI (pound per square inch) -- just enough to establish a flow of about 1 SCFH (standard cubic foot hour). Lower flow rates can be used as well, just enough to prevent back diffusion of O2 from the vent of the analyzer / transmitter. An example of this type analyzer is Teledyne's InstaTrans-XD Oxygen Transmitter. In its standard configuration there is no flow control element.
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