Tecfluid M21 Series - GRM Válvulas e instrumentación
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Tecfluid M21 Series

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Tecfluid M21 Series

Variable area metal tube flow meter

Tecfluid M21 Series


  • Metallic tube with a robust construction
  • Indication by means of magnetic coupling
  • Scales calibrated in l/h, m3/h, kg/h, t/h, %, etc.
  • High performance measurement in extreme workingconditions and high resistance to corrosion
  • Low pressure drop
  • Regulating valve optional
  • Vertical or horizontal connections
  • Damping mechanism to avoid float bounces in gas andsteam applications
  • Flow rate:- Water: 0.4 l/h … 1000 l/h – Air: 12 Nl/h … 30 Nm3/h
  • Accuracy: 4% (qG=50%)
  • Connections:- ¼” … ¾” BSP / NPT
    • Sanitary connections according to ISO 2852, SMS 1145, DIN 11851, TRI-CLAMP®
  • Materials: EN 1.4404 (AISI 316L)
  • Local indication
  • Options:
    • 1 or 2 limit switches
    • Electronic transmitter with 4-20 mA output for safe or hazardous area (Ex ia IIC T4…T6 Ga / Ex ia IIIC T85ºC Da protection, ATEX certified). HART protocol available on request
    • Constant flow regulator RCD / RCA



Working principle

The M21 flowmeter is a metal tube variable area flowmeter for low flows. It is based in the principle of variable area, which is obtained by a float that moves up and down inside a calibrated orifice. The force from the fluid, as it flows from the bottom to the top, displaces the float until it reaches an equilibrium point that is a function of: – E = force of the fluid flow – Pf = weight of the float – Al = free area of flow (Al = Ao, calibrated orifice area, – Af, float area) Each float position corresponds to a flow rate value. The float magnetic field moves the needle inside the housing by means of magnetic coupling to the flow rate point on a graduated scale.

Tecfluid M21 Series

Ao= calibrated orifice area

Af= float area

Pf= weight of the float

E= force of the fluid flow

Al= Ao-Af= free area of flow


  • Control panels and pilot plants
  • Control and measurement in machinery
  • Control and research laboratories
  • Water treatment
  • Heating-cooling industrial processes
  • Control of gas burners and treatment ovens
  • Chemical, pharmaceutical and cosmetic industries
  • Level control with RCD regulators


  • M21-R / N Vertical connections BSP / NPT
  • M21-HR / HNHoriz. conn. BSP / NPT, without valve
  • M21-HRA / HNA Horiz. conn. BSP / NPT + valve
  • M21-1 / 3 / 7 / 30 Sanitary vertical connections


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