General
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 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.
HF20, HF40 & HF60
The HF range started in 1998 with the HF20 using a graphite rotor rated to 20 l/min. The HF40 and 60 were added to double and triple the flow range up to 40 and 60 litres per minute. Materials now include stainless steel and titanium.
Features
Typical application
- Chemical Injection
- Hydraulics
- Wax Dispersant
- Corrosion Inhibitor
- Methanol
- PIB
- Scale Inhibitor
- Subsea flow
- Ashalphtene Dispersant
Key Features
- Compact
- Single Moving Part
- Pressure independent measurement
- No straight lengths
- Large Viscosity range, from methanol upwards
- Ultra High Pressure Capability (20,000psi, 1380bar if required)
- Very Low Flow Measurement
- Measures pulsing flow accurately
- Low Maintenance
- Tolerant of particulate up to 100+ microns
- Preserves Molecular Integrity of fluid
- Highly Durable
- Low pressure drop (<0.1 bar typical)
- Proven since 1986
Specifications
Technical Specifications HF range
| HF20 | 0-20 l/min | More detail in FLOW RATE tab |
| HF40 | 0-40 l/min | More detail in FLOW RATE tab |
| HF60 | 0-60 l/min | More detail in FLOW RATE tab |
| Accuracy | ±1% of reading, requires linearisation. | Provided by all Litre Meter instrumentation. |
| Pressure Rating | Dependent on Connection size and rating | More detail in CONNECTION tab |
| Temperature rating | -40°C – +100°C dependent on material and instrument; higher temperature possible. | |
| Viscosity Range | 0.5 – 100,000 cP or greater. | More detail in FLOW RATE tab |
| Recommended Filtration | A 100 micron filter is advisable for 100% long life serviceability. | |
| Dimensions | Refer to K0004 drawings Link in DOWNLOADS tab |
The HF20 and HF40 chambers are interchangeable, but the HF60 is considerably deeper
Reference: litremeter.com
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