Sampling Location - US EPA Method 1 is performed to locate an appropriate sampling location to complete a velocity or particulate traverse. The sampling locations must meet certain criteria to be valid such as, the duct diameter size and the sampling location relative to flow disturbance locations to ensure laminar, non-cyclonic, flow in the stack.

Velocity Measurement - US EPA Method 2 is performed to determine the average stack gas velocity from measurement of the gas density and average velocity head using Type "S" (Stausscheibe or reverse type) pitot tube. Apex Instruments manufactures and guarantees Type "S" pitot tubes in accordance with the Method 2 design specifications. However, calibration is not standard with purchase of pitot tubes. Apex Instruments offers calibration equipment and services. A variety of materials, sizes and configurations are available. The most common are constructed from either 1/4 inch or 3/8 inch OD Stainless Steel or Alloy 600 tubing.

The Type "S" Pitot tube is constructed from two formed tubes with each leg or port on the same plane but facing opposing directions. The theory is based on when the pitot is faced into the gas stream flow the pressure difference between the two ports equates to the velocity pressure, DP. This differential velocity pressure is measured with devices, such as liquid manometers or electronic pressure transducers.

Type "S" Pitot Tube Design Advantages:

• Large sensing openings resist plugging in particulate-laden and
  saturated gas streams

• Compact design fits easily in sampling ports

• Maintains calibration in harsh environments

• High differential pressure readings are beneficial in low velocity gas streams

• Suitable for determining cyclonic flow and measuring yaw angle
  of the velocity vector

• Economically priced