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DFM All-Plastic Variable Area

Over the last twenty years many thousands of DFM units have been supplied to practically every industry in the UK.

All units are available on quick delivery from our extensive stock.

They are supplied with BSP female end fittings or PVC solvent weld sockets as standard. Stainless Steel inserts or Cast Steel unions are available at extra cost. See table in PDF document.


Tube Material: Polyamide, PVC, Polysulphon

End Fittings: Rigid PVC socket connections for adhesive pipe coupling. BSP threads available.

Special stainless steel inserts available.

Cast iron end caps for higher temperature

Float: 6 different overall lengths from 165-350mm

Float Stops: PVDF

0-Rings: Standard EPDM, Special Viton, etc. available

Technical Data

Accuracy: ±2.5% full scale

Max Pressure: 10 Bar operating (at 20°C - see chart for operating pressures versus temperature)

Temperature: PVC 60°C, PA 75°C, PSU 100°C (see chart) for operating pressures versus temperature

Scaling: L/Hour H20 standard plus 0-100% max flow. Special product scales available

Flow Ranges: See table in PDF file and quote model number

Installation and Use

Pipework: Usually supplied with with BSP or socket connections for imperial pipework. Metric socket fittings available at no extra cost.

Installation: Vertical - flow upwards. For best results ensure pipework vertical to within 2/3°.

Valves: For liquids may be installed upstream or downstream. For gases install valves downstream only.

Optional equipment: Up to 3 in number bi-stable or mono-stable switches, comprising volt free contacts to handle 240V 5 amp max current. A 4-20mA transmitter is also available ex stock. The unit is ATEX Exi Certified as standard.

DFM All-Plastic Variable Area




  • All plastic Construction
  • Choice of 3 different tube materials
  • End connections in a wide range of materials
  • Sizes from 3/8" upto 2 1/2"
  • 5 different tube lengths
  • Low Pressure drop
  • Custom scales for Liquids and Gasses Alarm and 4-20mA options Rapid delivery times