General Introduction
Positive displacement flowmeters, also known as PD meters, measure volumes of fluid flowing through by counting repeatedly the filling and discharging of known fixed volumes. A typical positive displacement flowmeter comprises a chamber that obstructs the flow. Inside the chamber, a rotating/reciprocating mechanical unit is placed to create fixed-volume discrete parcels from the passing fluid.
In the VFF the rotor Positive Displacement Flowmeters is basically a disc shape with an annular groove on its underside capable of holding and transporting flow from the chamber inlet to the outlet. Some fluid is also transported in a cavity formed between the rotor outside wall and the chamber wall. A centre ‘peg’ under the rotor is constrained to run in a circular groove in the body. A web (or plate) in the body is engaged with a slot in the rotor and this modifies the rotation to that of an oscillation as flow passes.
It is this oscillation that produces the compartmentation of the fluid into ‘positively displaced pockets’. The top of the rotor is equipped with a powerful magnet directly above the ‘peg’ that is on the underside and so this also has a circular path which allows it to engage and disengage a reed switch sensor located in the top cap above.
VFF4, VFF8 Positive Displacement Flowmeters
The VFF Litre Meter Positive Displacement Flowmeters range started in 1986 with the original VFF4 size rated to 4 litres per minute. The VFF8 has a rotor with twice the height and was therefore rated to 8 l/m. Subsequently materials have been improved and the new ratings increased to 400 and 800 litres per hour.
Typical Applications
- Chemical Injection
- Corrosion Inhbitor
- Scale Inhibitor
- Hydraulics
- Subsea Control fluid
- Subsea flow
- Wax Dispersant
- PIB
- Ashalphtene Dispersant
Key Features
- Compact
- No straight lengths
- Very Low Flow Measurement
- Tolerant of particulate up to 100+ microns
- Low pressure drop (<0.1 bar typical)
- Single Moving Part
- Large Viscosity range, from methanol upwards
- Measures pulsing flow accurately
- Preserves Molecular Integrity of fluid
- Pressure independent measurement
- Ultra High Pressure Capability (35,000psi, 2500bar if required)
- Low Maintenance
- Highly Durable
- Proven since 1986
Specifications
Technical Specifications VFF range
| Model | VFF4 | 0-400 l/hr |
| VFF8 | 0-800 l/hr | |
| Accuracy | ±1% of reading, requires linearisation. | |
| Pressure Rating | Dependent on Connection size and rating | |
| Temperature Rating | -40°C – +100°C dependent on material and instrument; higher temperature possible. | |
| Viscosity Range | 0.5 – 100,000 cP or greater. | |
| Recommended Filtration | A 100 micron filter is advisable for 100% long life serviceability. | |
| Dimensions | Refer to K0003 drawings | |
Download Datasheet: VFF size Flow Meters Litre Meter Positive Displacement Flowmeters
Reference : litremeter.com
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