Q: What should be considered when installing a liquid turbine flow meter?

Liquid turbine meters need: 1) Straight runs — ≥15D upstream, ≥5D downstream; 2) Upstream filter/strainer to protect bearings from particles; 3) Clean, low-viscosity liquids (water, diesel, light oils) — viscosity dampens the rotor; 4) Flow range within the meter calibration (avoid running below minimum); 5) Air removal — entrained gas causes over-registration.

Q: What matters when using a Roots flow meter for fuel gas metering?

Key points for Roots gas meters on fuel gas/biogas: 1) Certification : choose explosion-proof models (Ex d II BT4 or better); 2) Filtration : gas carries dust and rust — install an upstream filter with regular draining; 3) Temperature & pressure compensation : gas volume depends strongly on conditions — use a compensated model, otherwise custody transfer will drift; 4) Placement : keep away from pressure-regulating valves and strong turbulence; 5) Bypass : provide a bypass line for calibration and maintenance.

Q: Oval gear flow meter stalled or not counting — how to troubleshoot?

Three common causes of rotor stalling: 1) Debris in measuring chamber (most frequent): check for a torn filter element, disassemble and clean the gear chamber, replace the filter; 2) Fluid solidification : HFO and resins solidify at low temperature and seize the gears — steam-trace to restore fluidity, then rotate by hand; 3) Gear wear : long-term service on low-lubricity fluids (e.g. gasoline) widens gear clearances — return the measuring insert for replacement. Prevention: choose mesh size per viscosity, drain filters regularly, purge lines before long shutdowns.

Question 1

How does a metal tube rotameter (variable area meter) work?

Accepted Answer

A metal tube rotameter measures flow by the position of a float in a tapered metal tube: higher flow lifts the float higher. The float position is read magnetically — no external scale — making it suitable for opaque liquids, high pressure and hazardous media. Simple, robust, no external power needed; typical accuracy ±1%~±2.5% FS, best for small-to-medium flows and local indication plus 4-20mA output.

Question 2

What should be considered when installing a liquid turbine flow meter?

Accepted Answer

Liquid turbine meters need: 1) Straight runs — ≥15D upstream, ≥5D downstream; 2) Upstream filter/strainer to protect bearings from particles; 3) Clean, low-viscosity liquids (water, diesel, light oils) — viscosity dampens the rotor; 4) Flow range within the meter calibration (avoid running below minimum); 5) Air removal — entrained gas causes over-registration.

Question 3

How does a Doppler ultrasonic flow meter measure open-channel flow?

Accepted Answer

A Doppler ultrasonic flow meter measures flow velocity by detecting the frequency shift of ultrasound reflected off particles and bubbles drifting with the water (Doppler effect). Mounted above or inside the channel, combined with a water-level reading it computes flow via velocity-area method — ideal for sewers, channels and weirs without full pipes.

Question 4

Straight-run and vibration requirements for vortex precession meters?

Accepted Answer

As a fluid-oscillation meter it is sensitive to flow profile and vibration:

1) Straight runs: ≥10D upstream, ≥5D downstream (D = nominal size); add a flow conditioner after elbows or pressure regulators; 2) Vibration: pipe vibration corrupts the precession signal and causes false flow — keep away from compressors and pumps, add pipe supports or flexible couplings if needed; 3) Avoid two-phase flow: gas-liquid mixtures deviate strongly — keep gas dry or install a separator upstream; 4) Mounting: horizontal preferred, arrow aligned with flow.

Question 5

How does a vortex precession flow meter work and why is it good for natural gas?

Accepted Answer

A vortex precession meter uses forced oscillation: gas passes a swirl generator that imparts rotation, creating a helical vortex that precesses around the axis. The precession frequency is proportional to flow rate and detected by a piezoelectric sensor.

Why it suits natural gas: 1) No moving parts — no wear, long maintenance intervals; 2) Wide turndown (1:15+) covering peak-valley demand; 3) Moderate pressure loss, better than orifice plates; 4) Accuracy ±1%~±1.5%, adequate for general gas custody and process metering; 5) Integrated T&P compensation reads standard volume directly.

Question 6

What matters when using a Roots flow meter for fuel gas metering?

Accepted Answer

Key points for Roots gas meters on fuel gas/biogas:

1) Certification: choose explosion-proof models (Ex d II BT4 or better); 2) Filtration: gas carries dust and rust — install an upstream filter with regular draining; 3) Temperature & pressure compensation: gas volume depends strongly on conditions — use a compensated model, otherwise custody transfer will drift; 4) Placement: keep away from pressure-regulating valves and strong turbulence; 5) Bypass: provide a bypass line for calibration and maintenance.

Question 7

Roots (waist-wheel) vs oval gear flow meter — what is the difference and how to choose?

Accepted Answer

Both are positive displacement meters; the key differences are rotor design and operating characteristics:

1) Rotor structure: Roots rotors are two-lobe, non-meshing, driven by external timing gears — no tooth contact, minimal wear, ideal for long-term high accuracy; oval gears mesh directly and are simpler; 2) Rangeability: Roots meters offer wider turndown (typically 1:20+) and better low-flow performance; 3) Fluid fit: Roots versions exist for gas (fuel gas/biogas), while oval gears are mostly for liquids.

Selection: gas metering → Roots gas type; high-viscosity oils → both work, prefer Roots for long service life.

Question 8

Oval gear flow meter stalled or not counting — how to troubleshoot?

Accepted Answer

Three common causes of rotor stalling:

1) Debris in measuring chamber (most frequent): check for a torn filter element, disassemble and clean the gear chamber, replace the filter; 2) Fluid solidification: HFO and resins solidify at low temperature and seize the gears — steam-trace to restore fluidity, then rotate by hand; 3) Gear wear: long-term service on low-lubricity fluids (e.g. gasoline) widens gear clearances — return the measuring insert for replacement.

Prevention: choose mesh size per viscosity, drain filters regularly, purge lines before long shutdowns.

Question 9

Why are oval gear flow meters ideal for high-viscosity fluids?

Accepted Answer

Oval gear meters are classic positive displacement devices: two oval gears driven by differential pressure rotate and displace a fixed volume per revolution. Accuracy correlates with lubricity and is only weakly affected by viscosity — higher viscosity means less slip and better accuracy, which makes them ideal for diesel, heavy fuel oil, crude oil and resins.

Typical accuracy ±0.2%R~±0.5%R; widely used for marine bunkering, depot loading and chemical batching.

Question 10

Does a dual-rotor flow meter need straight pipe runs?

Accepted Answer

No. As a positive displacement meter, measurement is independent of flow profile, so no upstream/downstream straight runs are required — a clear advantage over velocity-type meters (turbine, vortex).

Installation tips: 1) Install a filter (100-200 mesh) upstream to protect rotors; 2) Horizontal or vertical mounting allowed, follow flow arrow; 3) For high-viscosity fluids in winter, heat tracing prevents rotor stalling; 4) Flush new pipelines before installing the meter.

Question 11

How does a dual-rotor flow meter work? What fluids is it suitable for?

Accepted Answer

A dual-rotor flow meter is a positive displacement (PD) meter. Two meshing helical rotors form sealed measuring chambers with the housing; fluid flow drives the rotors, and each revolution displaces a fixed volume, enabling precise totalization.

Key traits: high accuracy (±0.2%R~±0.5%R), insensitive to viscosity changes — ideal for diesel, heavy fuel oil, lubricants and chemical liquids, including custody transfer.

Question 12

Can the LGF-PA66 Be Installed on Vertical Pipes?

Accepted Answer

Yes. The LGF-PA66 supports horizontal, vertical and inclined mounting, but three rules must hold:

Flooded first: the measuring tube must always run full. On vertical runs the flow should go bottom-to-top, so the pipe stays flooded at low flow or when a pump reverses; top-to-bottom vertical mounting is not recommended - the tube may not stay full and accuracy suffers.
Keep the electrode axis horizontal: on horizontal pipes, orient the two measuring electrodes on the horizontal centerline (never straight up/down), so gas bubbles cannot collect on the upper electrode and sediment cannot blanket the lower one.
Meet straight-run requirements: >= 5D upstream and >= 3D downstream (D = pipe diameter); add more upstream length or a flow conditioner when elbows, valves or pumps sit close by.

High points in a pipeline trap air - do not install the LGF-PA66 at the system's highest point; if unavoidable, fit an automatic air vent there. Low-lying valve pits are fine: the LGF-PA66 rating is IP68, supporting long-term immersed conditions.

The transmitter head rotates to multiple angles for easy reading on site; a split-type setup can move the transmitter outside the pit for convenient maintenance, linked to the sensor by dedicated shielded cable.

For more details, please visit our product pages or contact our technical team.

Question 13

Oilfield Water Injection Metering: LGF-PA66 Selection Guide

Accepted Answer

An oilfield injection system splits into a low-pressure distribution side and a high-pressure wellhead side - the metering logic differs completely.

For low-pressure lines inside injection stations and wellhead manifolds (typically <= PN16/25), the LGF-PA66 aviation-grade electromagnetic flow meter works well: PN16 rating covers distribution networks, and +/-0.2% accuracy satisfies per-well injection allocation KPIs. The PTFE liner resists chlorides, sulfates and other aggressive ions in injection water; choose 316L, Hastelloy or titanium electrodes based on water chemistry. For polymer-flooded injection water, verify conductivity first - polymer solutions tend to be less conductive, but anything >= 5 uS/cm meters stably; below that, contact our technical team for an assessment.

High-pressure wellheads (above 16 MPa) require dedicated high-pressure electromagnetic meters or other technologies - the LGF-PA66 must not be installed directly at the wellhead. This is a hard boundary.

Most injection well sites are remote without grid power, so pair the LGF-PA66 with an EC32 or EC60 low-power RTU: Modbus RS485 data acquisition, 4G/NB-IoT backhaul to the oilfield IIoT platform, solar panel plus battery supply, and IP68 protection for outdoor well sites. Once per-well injection data uploads automatically, allocation adjustments and loss analysis no longer need manual meter reading.

For more details, please visit our product pages or contact our technical team.

Question 14

DN300+ Pipelines: LGF-PA66 Full-Bore vs Insertion Flow Meter

Accepted Answer

Compare on three dimensions: accuracy, cost and maintenance.

Accuracy: the full-bore LGF-PA66 is rated +/-0.2% (+/-0.5% optional). An insertion meter infers the mean velocity from a single-point measurement and is sensitive to asymmetric velocity profiles - typical accuracy is +/-1.0% to +/-2.5%. Custody transfer and DMA district metering with leakage KPIs require full-bore meters; insertion types only fit internal rough metering and trend monitoring.

Cost: the price advantage of insertion meters mainly shows above DN600. Between DN300 and DN600 the gap narrows sharply, and the LGF-PA66 uses an aviation-grade PA66 composite body - cheaper in material than a traditional stainless full-bore meter and about 40% lighter at the same size, so hoisting and flange assembly in large valve pits is easier. Total installed cost is not necessarily higher than insertion.

Maintenance: an insertion probe sits inside the pipe, fouls and tangles with debris, and needs periodic shutdown and withdrawal for cleaning - hard to do on pressurized supply mains. The full-bore LGF-PA66 has an unobstructed measuring tube, is essentially maintenance-free, and has lower life-cycle O&M cost.

Bottom line: choose the full-bore LGF-PA66 for DN300-DN600; consider insertion only above DN800 with tight budgets and trend-monitoring use. Custody-transfer points should always be full-bore.

For more details, please visit our product pages or contact our technical team.

Question 15

Can the LGF-PA66 Measure Slurry and Sediment-Laden Water?

Accepted Answer

Yes. By its measuring principle the electromagnetic flow meter has no moving parts and no obstruction in the flow path, so it is inherently suited to media with solid particles - exactly where the LGF-PA66 beats mechanical water meters and turbine meters. Sediment-laden water, slurry, mining slurries and wastewater with suspended solids can all be metered reliably as long as conductivity is >= 5 uS/cm.

On abrasion: the LGF-PA66 measuring tube is lined with PTFE, one of the most wear- and corrosion-resistant liner materials in the industry. Electrodes come in 316L, Hastelloy or titanium - 316L is fine for ordinary sediment-laden water; for mine dewatering or high-chloride water we suggest Hastelloy. The PA66 composite body itself is strong and tough, and it does not suffer the liner delamination that rubber-lined carbon steel bodies show under long-term vibration.

Two sizing tips:

For large particles or high velocity (>3 m/s), step the bore up one size to lower flow velocity - liner life extends noticeably;
For slurry service, set a proper low-flow cutoff and use the empty-pipe detection function to avoid signal jumps when sediment settles on electrodes during shutdown.

LGF-PA66 and the split-type LGF series are widely used for slurry metering in mining, dredging and municipal wastewater.

For more details, please visit our product pages or contact our technical team.

Frequently Asked Questions

How does a metal tube rotameter (variable area meter) work?

What should be considered when installing a liquid turbine flow meter?

How does a Doppler ultrasonic flow meter measure open-channel flow?

Straight-run and vibration requirements for vortex precession meters?

How does a vortex precession flow meter work and why is it good for natural gas?

What matters when using a Roots flow meter for fuel gas metering?

Roots (waist-wheel) vs oval gear flow meter — what is the difference and how to choose?

Oval gear flow meter stalled or not counting — how to troubleshoot?

Why are oval gear flow meters ideal for high-viscosity fluids?

Does a dual-rotor flow meter need straight pipe runs?

How does a dual-rotor flow meter work? What fluids is it suitable for?

Can the LGF-PA66 Be Installed on Vertical Pipes?

Oilfield Water Injection Metering: LGF-PA66 Selection Guide

DN300+ Pipelines: LGF-PA66 Full-Bore vs Insertion Flow Meter

Can the LGF-PA66 Measure Slurry and Sediment-Laden Water?

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