Screw Positive Displacement Flowmeter
Product Overview
A screw (twin-screw) positive displacement (PD) flowmeter accurately measures the volumetric flow of liquids by capturing fixed volumes in rotating screw elements and delivering them from the meter inlet to the outlet. Designed for viscous, lubricating, and shear-sensitive fluids, these meters offer high accuracy and repeatability over wide viscosity ranges and are common in oil, fuel, polymer, food and chemical industries.
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How it works (simple explanation)
Two intermeshing screws rotate inside a precision housing. Fluid is trapped in the cavities formed between the screw threads and the housing and is conveyed axially from inlet to outlet. Each full rotation displaces a fixed volume — counting rotations (or partial rotations) converts directly to delivered volume. Electronic pickup converts shaft movement into pulse or digital output for rate and totalization.
What it measures
- Volumetric flow rate (instantaneous flow, e.g., m³/h or L/min)
- Totalized volume (cumulative flow)
- Can be combined with temperature/density compensation to provide mass flow or corrected volume where required.
Key advantages
- High accuracy and excellent repeatability (especially at steady flow).
- Performs reliably with high-viscosity fluids (oils, heavy fuels, resins).
- Low sensitivity to fluid compressibility and moderate particulate content (depending on design).
- Wide turndown ratio — good linearity from low to high flow.
- Robust mechanical construction — long service life and easy maintenance (replaceable rotors/seals).
- Can provide direct volumetric output without need for complex flow conditioning.
Applications
- Oil & gas (lubrication oils, fuel oils)
- Chemical processing
- Hydraulic systems
- Polymer and resin measurement
- Food & beverage (syrups, oils)
- Paints, inks, and adhesives
Installation
- Needs straight pipe runs (at least 5×D upstream and 2×D downstream straight pipe)
- Can be installed in horizontal or vertical pipelines
- Suitable for indoor and outdoor installations
- Optional remote or integral transmitter
- Recommended to use a strainer upstream
- Suitable for bi-directional flow (model dependent)
- Ensure fluid cleanliness for long service life
Technical Specifications
Parameter | Specification |
Meter type | Twin-screw positive displacement |
Standard sizes (DN) | DN15 (½”) – DN200 (8″) |
Typical flow range | 0.1 L/min – 400 m³/h (model dependent) |
Accuracy (volume) | ±0.15% to ±1.0% of reading (model / flow band dependent) |
Repeatability | ≤ ±0.05% |
Maximum operating pressure | Up to 250 bar (model dependent) |
Operating temperature | –40 °C to +200 °C (higher with special materials) |
Viscosity range | 0.5 cSt up to 1,000,000 cSt (extremely viscous fluids supported) |
Wetted materials | Stainless steel 316L, carbon steel, duplex, special alloys |
Seals / gaskets | PTFE, Viton, NBR, EPDM, FFKM (options) |
Connections | Flanged (ANSI/EN), threaded, sanitary tri-clamp (options) |
Outputs / signals | Pulse (open collector), Reed, 4–20 mA (via transmitter), HART/Modbus (optional) |
Power (electronic) | 24 V DC typical; optional loop-powered electronics |
Enclosure rating | IP65 / IP67 (electronics housing) |
Certifications | ATEX/IECEx (optional), SIL ratings (optional), FDA/EC for sanitary versions |
Mounting orientation | Horizontal or vertical (consult datasheet) |
Typical weight | 5 kg (small) — 200+ kg (large) depending on size/material |
Typical maintenance interval | Depends on fluid/contaminants — annual inspection recommended |