LF Flow Meters

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Information about the VFF meter

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.

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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.

LF03, LF05 and LF15

The LF (or Low Flow) meters are the smallest in the VFF range. LF15 was introduced as our smallest meter in 2003 and was originally rated to 1.5 l/min (hence LF15). The LF05 joined the family in 2012 and is a third of the size. The LF03 is the smallest of the LF range and is a fifth of the size. Although internally they vary, the external chamber size is identical enabling interchangeability. Flows start at 0.005 l/hr (0.00008 l/min, 0.001 GPH).

Typical Applications

Chemical InjectionHydraulicsWax Dispersant
Corrosion InhbitorSubsea Control fluidPIB
Scale InhibitorSubsea flowAshalphtene Dispersant

Key Features

CompactSingle Moving PartPressure independent measurement
No straight lengthsLarge Viscosity range, from methanol upwardsUltra High Pressure Capability (60,000psi, 4000bar if required)
Very Low Flow MeasurementMeasures pulsing flow accuratelyLow Maintenance
Tolerant of particulate up to 100+ micronsPreserves Molecular Integrity of fluidHighly Durable
Low pressure drop (<0.1 bar typical)Proven since 1986 

Technical Specifications LF range

Flow ranges 
LF030-18 l/hr.  More detail in FLOW RATE tab
LF050-30 l/hr.  More detail in FLOW RATE tab
LF150-90 l/hr.  More detail in FLOW RATE tab
Accuracy±1% of reading, requires linearisation. Provided by all Litre Meter instrumentation.
Pressure RatingDependent 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 Range0.5 - 100,000 cP or greater.  More detail in FLOW RATE tab
Recommended FiltrationA 100 micron filter is advisable for 100% long life serviceability. For LF03 & LF05 size 40 micron filter is recommended.
DimensionsRefer to K0001 drawings. Link in DOWNLOADS tab

Interchangeable PBC between LF03, LF05 and LF15. Different rated chambers can be retrofitted as field demands change.

Pressure Balanced Chamber (PBC)

This describes the rotor and the chamber in which it rotates. It's a separate item that can be removed for inspection and calibration. A side benefit is that it enables pressure independent measurement.

Key Benefits:

No distortion of the chamber at higher pressures
No measurement inaccuracy due to pressure
Enables selection of optimal materials for the chamber to match the rotor i.e. PVD coated stainless steel.
Enables selection of optimal materials for the pressure vessel. i.e. super duplex stainless steel
Enables construction of a duplex bodied flowmeter – duplex material does not lend itself to the tolerances required in machining
Interchangeable with other ranges

All VFF flowmeters are custom calibrated across the customer specified min – max flow conditions and working viscosity. The minimum flow rates achievable are dependent on fluid viscosity.

Flow Ranges and viscosity

  Minimum Flow Rate Measurable at Viscosity, L/hr
  1 cP1.5 cP2.5 cP7.5 cP10 cP25 cP50 cP250 cP
LF03 - 18 L/hr maxStandard0.60.330.120.0750.0600.0380.0260.012
 Low Flow0.
 Ultra Low Fow0.
LF05 - 30 L/hr maxStandard1.50.830.300.1250.1000.0630.0420.03
 Low Flow1.00.550.200.0830.0500.0420.0280.02
 Ultra Low Flow0.40.220.1250.0520.0250.0200.0150.008
LF15 - 90 L/hr maxStandard3.752.
 Low Flow2.51.3810.750.50.350.20.02
 Ultra Low Flow10.550.

Standard Connections


Pressure Rating, barDescription
5501/4 inch female NPT
5303/8 inch female NPT
5301/2 inch female NPT
5003/4 inch female NPT
13803/8″ Autoclave Engineers Medium Pressure female fitting (SF375CX20)
13809/16″ Autoclave Engineers Medium Pressure female fitting (SF562CX20)
13803/4″ Autoclave Engineers Medium Pressure female fitting (SF750CX20)


RF, Raised Face

Flange RatingNominal Pipe Size
ANSI 1501/2″, 3/4″ or 1″
ANSI 3001/2″, 3/4″ or 1″
ANSI 6001/2″, 3/4″ or 1″
ANSI 15001/2″, 3/4″ or 1″
ANSI 25001/2″, 3/4″ or 1″

RTJ, Ring Type Joint

Flange RatingNominal Pipe Size
ANSI 1501″
ANSI 3001/2″, 3/4″ or 1″
ANSI 6001/2″, 3/4″ or 1″
ANSI 15001/2″, 3/4″ or 1″
ANSI 25001/2″, 3/4″ or 1″



Techlok, Galperti, Destec upon request

Higher pressure ratings achievable with F51

Custom: Call for further options.

‘Flanged’: Call for further options.

ANSI 10,000: Call for further options.

Pressure Rating, barDescription
7061GR4 Grayloc Hub Connection
6561GR5 Grayloc Hub Connection
4961GR7 Grayloc Hub Connection
2901GR11 Grayloc Hub Connection

Materials Coding: Body and Cap

SS316 Stainless Steel (UNS S31603)
44F44 6Mo SS Body & Cap (UNS S31254)
51F51 Duplex Body (UNS S31803) & F44 Cap (UNS S31254)
53F53 Super Duplex Body (UNS S32750) & F44 Cap (UNS S31254)
55F55 Super Duplex Body (UNS S32760) & F44 Cap (UNS S31254)
HAHastelloy Body & Cap (UNS N10276)
TITitanium (UNS R50400)
CodeManufacturing Method
BBBody ‐ Not Forged / Cap ‐ Not Forged
APBody ‐ Forged / Cap ‐ Not Forged
FFBody ‐ Forged / Cap ‐ Forged
CSCustom Specification

Materials Coding: Chamber & Rotor

CodeChamberLidC/L CoatingRotorR CoatingMagnetDescription
APN60N60PVDN60PVDEncapsulated 316PVD Coated N60 Chamber and Rotor
TATi5Ti5PVDTi5PVDEncapsulated TiPVD Coated Titanium Chamber and Rotor
TCTi2Ti2noneCarbonnoneEncapsulated TiTitanium Chamber and Carbon Graphite Rotor

Call for further options

Materials Coding: Seals

PPTFE Encapsulated Viton
NAEDNitrile non explosive NBR
MPInconel/PTFE Encapsulated Viton

Call for further options

Display for VFF meters


  • Exd‐ CSA(US): Class1 Div1 (B,C,D); Class 1, Zone 1, AEx d IIC T5 Gb
  • CSA(CAN): Class1 Div1 (B,C,D), Exd IIC T5 Gb, Tamb -20°C to +75°C
  • ATEX: Ex db IIC T5, Ex tb IIIC 80°C
  • IECEX: Ex db IIC T5, Ex tb IIIC 80°C
  • IP 66/IP68 dual certified
  • Ambient temperature: ‐20 to +75°C
  • 2 or 4 wire 4‐20mA HART 7 programming and monitoring
  • Compact lightweight 316 stainless steel housing
  • Rotatable through 360° for optimised viewing angle
  • 2 VFF sensing options ‐ standard and hi‐res ‐ both with bidirectional sensing
  • Removable LM‐MC storage card for data logging & offsite programming
  • Resettable and non‐resettable Totaliser
  • Batch control
  • Power: 12 – 30 Vdc


  • Safe area or ATEX / IECEX / FM / CSA Exia
  • 2 wire 4‐20mA HART output (HART is optional)
  • Material: GRP or Aluminium
  • IP 67
  • Ambient temperature: ‐40 to +70°C
  • Rotatable through 360° for optimised viewing angle
  • Resettable and non‐resettable Totaliser
  • Batch control
  • Power: 12 – 30 Vdc, Battery or Loop powered


  • Safe area or ATEX II 2G Ex ia IIC T4 Gb
  • 2 wire 4‐20mA HART output (HART is optional)
  • Material: 316 SS
  • IP 66/IP67
  • Ambient temperature: ‐40 to +120°C
  • Rotatable through 360° for optimised viewing angle
  • Resettable and non‐resettable Totaliser
  • Power: 15 – 30 Vdc,can be Loop powered