Flowmeter Selection: velocity
Flowmeter selection guide covering 16 meter types across 6 categories (differential_pressure, velocity, mass_flow, electromagnetic, positive_displacement, variable_area, open_channel) — each record documents accuracy (% reading or full-scale), rangeability, pressure drop class, fluid compatibility, installation straight-run requirements, and relative cost class
| meter category | meter type | accuracy basis | accuracy pct reading (%) | cost class | cost relative | downstream diameters max | downstream diameters min (pipe_diameters) | fluid compatibility | fluid phase | fluid restrictions | installation notes | measurement principle | moving parts | notes | pressure drop class | pressure drop notes | rangeability | rangeability num | requires power | temp limit C max (degC) | temp limit C min (degC) | typical applications | typical pipe size in max (in) | typical pipe size in min (in) | upstream diameters max (pipe_diameters) | upstream diameters min (pipe_diameters) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| velocity | turbine_inline | percent_of_reading | 0.25 | medium | 2 | 5 | 5 | Clean viscous liquids and gases; petroleum products | liquid|gas | Requires clean fluid; no slurries; minimum viscosity less than 10 cP for gas version | Flanged body; upstream strainer recommended; calibrated in-situ | Rotor spins proportional to flow velocity | yes | High accuracy; AGA-7 approved for natural gas; OIML R 117; bearing wear limits life | medium | 1 to 3 pct of line pressure loss | 20:1 | 20 | yes | 200 | -200 | Custody transfer petroleum, clean water, cryogenic LNG/LOX, process gas | 24 | 0.5 | 20 | 10 |
| velocity | ultrasonic_doppler | percent_of_full_scale | 3 | low | 1 | 5 | 5 | Dirty liquids, slurries, wastewater - requires more than 100 ppm reflectors | liquid | Cannot measure clean liquids or gases; accuracy degrades with variable particle loading | Clamp-on external transducers; no wetted parts | Frequency shift of reflected ultrasonic signal from particles or bubbles | no | Lower accuracy than transit-time; best for relative measurement or flow verification; ISO 17089 | none | Zero permanent pressure loss (clamp-on) | 20:1 | 20 | yes | 60 | -20 | Municipal wastewater, slurries, sludge, dredging | 120 | 2 | 20 | 10 |
| velocity | ultrasonic_transit_time | percent_of_reading | 1 | medium | 3 | 10 | 5 | Clean liquids and gases; some clamp-on for any pipe | liquid|gas | Requires acoustically homogeneous fluid; entrained air or bubbles cause error | 2-path or 4-path spool; clamp-on external transducers available | Time-of-flight difference between upstream and downstream ultrasonic pulses | no | AGA-9 (gas) / AGA-7 approved; clamp-on versions plus or minus 1 to 2 pct; multi-path 0.1 pct achievable; zero pressure drop | none | Zero permanent pressure loss (clamp-on) or less than 0.1 pct (wetted spool) | 40:1 | 40 | yes | 200 | -200 | Custody transfer gas or liquid, clamp-on retrofit, water utilities, LNG | 120 | 1 | 30 | 10 |
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