Differential Pressure Flow

Differential Pressure Flow

Differential pressure (DP) flow measurement infers flow rate by creating a restriction in the line and measuring the resulting pressure drop. Primary elements such as orifice plates, Venturi tubes, or Pitot tubes generate a differential pressure that is sensed by a DP transmitter; flow is then calculated from the DP signal using the appropriate coefficients and fluid properties.

DP flow is widely applied because it is well understood, broadly standardized, and deployable across gases, vapors, and liquids, including services with high process pressures and temperatures. It also enables standardization around transmitter platforms, impulse hardware, and calculation practices, which can simplify maintenance and documentation across multiple units.

Common applications include steam and utility balancing, boiler and burner feed control, gas consumption monitoring, and liquid transfer where DP elements are already installed. DP is also selected for custody-transfer or compliance-driven measurement when the primary element geometry, installation, and compensation are engineered and verified to the applicable standards.

Uncertainty management is central to DP design: DP scales with the square of flow, so rangeability and low-flow performance depend heavily on sizing and transmitter selection. Upstream disturbances, density variations, and impulse-line effects (plugging, freezing, or head errors) must be addressed through layout, conditioning, and compensation strategies, especially on steam. Remote diaphragm seals can protect transmitters from hot, corrosive, or plugging media, but their temperature behavior and fill-fluid characteristics must be considered during design. Permanent pressure loss should be evaluated explicitly as part of the lifecycle cost.

Endress+Hauser supports DP flow measurement with differential pressure transmitter families such as Deltabar, including smart transmitters for monitoring in liquids and gases. Paired with correctly specified primary elements, DP systems integrate cleanly into control and asset-management architectures while maintaining proven, continuous flow measurement in standard and severe-service applications.

At Eastern Controls, We are proud to be the exclusive authorized sales and service representative for Endress+Hauser.