Rotameter P

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The model “P” rotameters are manufactured in 1/8”, 1/4” and 1/2” diameters for very low volume measuring of gas and liquids. Three versions are available, a 60 mm scale (1P5), a 150 mm (3P5) for the same range of capacity and a 250 mm scale (4P5) for higher capacity. These units are ideal for purge systems, bearing lubrication systems, level control with tanks and flow measurement in gas chromatography. When these rotameters are coupled with differential pressure regulators, flow can be kept constant, even with varying upstream or downstream pressures.


  • A wide range of float materials and tapered metering tubes allow a wide range of capacities.
  • Floats and metering tubes are interchangeable between rotameters of the same size.
  • Top end seals only, this permits changing the metering tubes without removing the rotameters from installation.
  • PTFE stops mounted in metering tube ends prevent losing floats when metering tubes are removed (models 1P5 and 3P5).
  • Available various accessories such as needle and check valves, flow alarms, panel mounting, subject to further consultation.
  • Horizontal connections are NPT internal threads and permit 360° positioning in 90° intervals to obtain the desired viewing angle.



  • Metering tube: borosilicate glass;
  • Float: AISI 304 and 316 stainless steel, PTFE, ceramic, nylon, glass, tungsten carbide, and others subject to future consultation.
  • Packing glands: neoprene (standard), Viton1 and PTFE.
  • Parts in contact with process fluid: aluminum, AISI 304 or 316 stainless steel, brass, polypropylene and PTFE or others, subject to future consultation;
  • Parts with no contact with the fluid (frame): aluminum.


  • Scale: nominal scale lengths are 60 mm for 1P5 model, 150 mm for the 3P5 model and 250 mm for the 4P5 model.
  • Graduations: standard 1 to 10 for indirect reading for use with a factor tag provided.
  • Optional: separate scale attached laterally for direct reading in service conditions.

Precisão industrial standard: aprox. 10% do fundo de escala para modelo 1P5 e aprox. 5% do fundo de escala para modelos 3P5 e 4P5.


  • Industrial accuracy: aprox. 10% of fuIl scale (model 1P5) aprox. 5% of fuIl scale (models 3P5 and 4P5).
  • Special: for direct reading aprox. 5% of fuIl scale for model and aprox. 2% of fuIl scale for 3P4 and 4P5 models.
  • Reproducibility: within 0,5% of fuIl scale.
  • Rangeability: 10:1.
  • Maximum service pressure: 15 Kg/cm2 (210 PSI).
  • Maximum temperature: 120°C (248 F).


The regulator will maintain constant the differential pressure by manual adjustment of the needle valve flow control. The unit consists of a diaphragm in equilibrium with the inlet pressure of the process fluid one side and a spring loading and outlet pressure on the other side. Any variation in inlet or outlet pressure will cause a change in the diaphragm position and a consequent change with the control valve. This system maintains the differential pressures constants. When gases are handled, gas compressibility will make necessary to have one of the pressures (inlet or outlet) constant, so the pressure regulator V03 is for a constant downstream pressure and variable upstream pressures and model V04 is for variable downstream pressures with a constant upstream pressure. With liquids, the V03 unit with variable pressures on either the inlet or outlet side.


  • Minimium differential pressure to operate the regulator: 0,2 Kg/cm2 (3 PSI).
  • Materials: AISI 304 or 316 stainless steel or brass
  • Diaphragm: Standard, cotton cloth impregnated with nitryle rubber.
  • Alternative: PTFE
  • Springs: 316 stainless steel.

• EXAMPLE 2: 3P5 0402 V03 X 2

Rotameter with 60 mm nominal length, model “P” with horizontal inlet and outlet, size 04, 1/4” diameter connections, with needle valve on inlet side.

• EXEMPLO 2: 3P5 0402 V03 X 2 

Rotameter with 150 mm nominal length, model “P” with horizontal inlet and outlet, size 04, 1/4” diameter connections, with differential pressure regulator at inlet side and panel mounting.

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