5 Prerequisites Confirmed Before Installing Vortex Flowmeter on Gas Pipeline
Core Finding: A gas pipeline station's metering branch showed over 3% deviation from the downstream reference meter after commissioning, with erratic readings during low nighttime demand. Zero adjustment failed repeatedly. The root cause was not the meter itself, but unmeasured operating conditions: the gas carried trace condensate, and the design pressure value was used instead of actual measured pressure.
Why It Happens
Missing PT compensation & composition correction: Vortex meters measure operating volumetric flow. Natural gas is compressible; pressure changes significantly alter mass per unit volume. Without measured pressure, temperature, and gas composition (for density and compression factor), standard-condition conversion fails.
Liquid/dust contamination: Trace liquids or dust destabilize vortex shedding; droplets hitting the bluff body cause signal loss or inflated readings.
Vibration sensitivity: Pipeline vibration and pulsation from pressure regulators or compressors couple into the sensor signal.
Low-flow instability: At low velocities, vortex shedding energy weakens, SNR drops, and Reynolds number falls, making small-flow measurement unreliable.
5 Must-Confirm Prerequisites Before Commissioning
Single-phase, clean medium: Install upstream filtration separators; keep dust particle size and liquid content within meter limits. For wellhead gas with condensate or undehydrated branches, consider alternative measurement principles.
Measured pressure & temperature plus composition correction: Install PT probes per manufacturer's recommended location and insertion depth; feed signals to the totalizer, input gas composition and compression factor from analysis reports, and review periodically per gas quality change cycle.
Velocity & range matching: For natural gas, typical operating velocity is 5–30 m/s; position normal flow within 1/3–2/3 of the range. Calculate lower-limit flow by turndown ratio (typically 10:1–15:1) and verify Reynolds number.
Straight runs & vibration damping: Require 15D–20D upstream and 5D downstream (extend per manufacturer if elbows or reducers are present). Install upstream of control valves, keep distance from valves/compressors, and add damping supports if needed.
Explosion-proof & pressure rating: Select explosion-proof type and temperature class per hazardous area classification; flange pressure rating must be no lower than pipeline design pressure. Provide bypass and online comparison interfaces.
