Differential Pressure Flow

Differential Pressure Flow

Differential pressure (DP) flow measurement determines flow by creating a controlled restriction in the line and measuring the pressure drop across it. Primary elements such as orifice plates, Venturi tubes, and pitot tubes generate a differential pressure that is sensed by a DP transmitter; the transmitter then computes flow from the measured ΔP and the element geometry.

DP measurement remains a foundational approach because it scales from compact impulse-line installations to large, high-energy services and supports liquids, gases, and vapors over wide operating ranges. It is routinely applied where process pressures and temperatures are high, where standards-based calculation methods are preferred, or where a primary element can be selected to balance accuracy against permanent pressure loss and available straight-run. With modern transmitters or flow computers, steam and gas compensation can be applied for mass and energy reporting.

Benefits extend beyond flow. The same transmitter platforms are commonly used for differential pressure across filters, exchangers, and other equipment, and for level measurement in pressurized vessels when paired with appropriate impulse piping or remote seals. Assembly practices such as pre-assembled, pressure-tested valve blocks and standardized manifolds simplify commissioning and support consistent isolation and maintenance procedures.

Typical applications include steam and condensate service, boiler feedwater and utility water, combustion air and fuel gas metering to burners, flare and vent monitoring, and general-purpose liquid measurement in chemical, petrochemical, and power facilities. DP is also widely retained in modernization projects because primary elements can often be preserved while transmitters, communications, and computation are upgraded with minimal piping changes.

Selection and performance depend heavily on correct primary element sizing, tapping practice, impulse line routing, and fluid property inputs. Attention to condensation management, heat tracing where required, and plugging risk is often decisive for long-term stability. When combined with modern diagnostics, digital communications, and disciplined documentation of element data and calibration records, DP systems can provide dependable measurement with predictable lifecycle cost. Remote diaphragm seals can also isolate the transmitter in corrosive, plugging, or sanitary services.

Engineered Equipment Company, a leading supplier of specialized industrial equipment.