Differential Pressure Flow

Differential Pressure Flow

Differential pressure (DP) flow measurement determines flow by creating a controlled restriction in a line and measuring the resulting pressure drop. Primary elements such as orifice plates, Venturi tubes, and pitot tubes generate a differential pressure that is sensed by a DP transmitter; the transmitter calculates flow from the measured ΔP using the applicable fluid and installation parameters.

This approach is a proven, widely standardized method that supports continuous measurement across gases, vapors, and liquids, including demanding services with elevated pressures and temperatures. DP technology is especially attractive where established calculation standards, predictable failure modes, and broad mechanical design options (materials, pressure classes, and process connections) are required.

DP measurement spans a broad range of duties, from general process monitoring to utility and energy balances. A single transmitter platform can often support flow measurement as well as related tasks such as filter condition monitoring or level measurement when paired with the appropriate process connections, impulse piping, and sealing options for corrosive, abrasive, or hygienic services.

Common applications include steam and condensate systems, compressed air distribution, natural gas and fuel gas metering for burners and boilers, and liquid services where primary elements can be engineered for erosion resistance and stable discharge coefficients. With appropriate compensation, DP systems can deliver mass flow or standardized volume outputs suitable for performance monitoring, cost allocation, and regulatory reporting.

Engineering attention is typically directed to primary element selection and sizing, required straight runs, impulse line routing, and density/temperature inputs where needed. Tradeoffs include permanent pressure loss across the restriction and a square-root relationship between ΔP and flow that influences turndown. Maintenance planning often includes management of impulse line integrity and periodic inspection of the primary element for wear, fouling, or plugging. Pre-assembled, pressure-tested valve blocks can reduce installation variability and improve serviceability.

Instrumentation and Controls., an exclusive authorized representative of sales and service for Endress+Hauser.