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Correction Factors for a Steam Flow Orifice

Several devices are available to measure the flow rate of gases, liquids and steam. However, orifice plates are the most widely used, as they are durable and remain efficient over a long lifespan. Orifices manufactured according to national standards have the added advantage of not requiring calibration, making them more economical compared to other flowmeter devices.

  1. Steam Flow Orifice

    • A steam flow orifice measures the rate of steam flowing through an operating system, thus enabling overall management. For example, steam injection systems are used in the animal feed industry, and the rate of flow is measured to regulate the amount of steam used in the production process. It also allows for the identification of the primary energy users in the system, which saves on overall energy costs.

    Operation

    • Steam flow orifices function by creating a differential pressure as steam flows through the plate. This is converted to either an analog or digital signal that is measured via impulse lines using a differential pressure transmitter. This measurement represents the instantaneous flow rate of steam.

    Correction Factors

    • Unlike liquids, the density of steam rarely remains absolutely constant, and the pressure within the system also fluctuates. As a result, adjustments need to be made to flow measurements to avoid interpretation errors. These adjustments are referred to as correction factors. Some steam flow orifices are fitted with computerized systems that automatically include correction factors in the final measurements. Correction factors are also applied manually using various equations.

    When Correction Factors Are Used

    • Correction factors are required when the properties of steam within the system changes --- such as its density, pressure or temperature. For example, a correction factor is applied when steam moves from what is described as saturated to superheated steam. The presence of unevaporated water molecules, referred to as wet steam, also warrants the use of correction factors, as steam quality is considerably reduced.

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