FCI releases Wet Gas MASSter Sensor for the ST80 Series Flow Meters

November 14, 2019 — Fluid Components International (FCI) announced the optional Wet Gas MASSter Sensor for the ST80 Series Flow Meters.

FCI's wet gas (WG) sensor delivers gas flow measurement in the presence of moisture and condensation droplets. Available with the Model ST80, this WG sensor can be applied for use in entrained moisture and rain-shielding applications.      

This WG sensor configuration features a mechanical design that shunts moisture, condensation and water droplets away from the thermal flow sensor, thus maintaining an gas flow measurement while minimizing errors that could occur from a cooling effect on the sensor that might cause a spike or false high reading. The Wet Gas MASSter Sensor option can be used in applications that have either moisture entrained in the gas (annular mist) or for protection against down the pipe rain in larger, vertical stacks.

A Best Practices Guide To Measurement in Moist or Wet Gas explains how this sensor configuration is designed for use in applications that have a high level of moisture or condensation present in the gas flow stream, which cannot otherwise be removed.  Moisture in the pipe takes a variety of forms that can range from a fog to mist to actual liquid droplets that often includes corrosive components such as hydrogen sulfide (H₂S).

The measuring principle of thermal mass flow meters involves heat transfer caused by gas flow. Any moisture or condensate in the gas stream that contacts the heated sensor can cause a sudden, momentary change in the heat transfer that can result in a spiked or fluctuating reading, which creates inaccurate or unstable flow measurement. Thermal flow meters using the constant temperature ∆T (CT) method are particularly reactive to moisture droplets, while constant power (CP) method meters, because their slightly heated sensor elevates the dew point, are less so.  

The FCI Wet Gas MASSter Sensor option for the ST80 Series relies on standard thermal constant power (CP) technology and optimizes the sensor head design and installation to minimize or prevent condensation from contacting the sensor. The wet gas sensor head mechanically shunts the condensate away and never allows it to reach the sensors, which eliminates moisture interference.