Flow Indicators

A flow indicator provides a visual into pipelines or sealed vessels, allowing the user to see immediately if flow is occurring and to observe the flow's colour, volume, and condition.

Flow indicators can be mechanical or electronic. Likewise, they can be online or external. In-line, they are when inside the pipe or interacting directly with the fluid.

Mechanical Flow Indicator

The rotameter, which can be read using an analogue scale or a tube, is the most common type of mechanical flow indicator. Some rotameters provide an electrical output signal as well.

Electronic Flow Indicator

Electronic flow indicators produce an analogue (usually 4-20 mA) or digital output signal. That is why electric flowmeters are used in industrial process control, automation, and monitoring systems, though they can also be used to display flow on a screen in the field.

How Does a Flow Indicator Work?

The operation of a flow indicator is determined by the type of indication it provides. Flow indicators work on the same basic principle. Flow through the devices generally moves something or nothing in the case of a simple sight glass.

The flow usually moves a ball or spins a paddle wheel. Flaps, chains, and other unusual moving mechanisms are also employed. If no mechanism is present, the flow can still be verified by closely inspecting the glass tube to see if there is flow. A flow indicator with a moving mechanism can be visible from a greater distance.

PVL Flow Indicators

Pressure Vacuum Level Ltd has been selling high-quality flow indicators for over 28 years. PVL provides these devices for various industries.

Don't hesitate to contact us if you have any questions about our flow indicators or other products.

Other Products

PVL customers can rely on us for high-quality products. Flow Indicators are only a handful of the products we provide customers across the United Kingdom. We are also a significant supplier of Vacuum Switches and Transducers.

  • Process connection: female thread 1/8 "NPT
  • Metering range: 0.005..25 l/min
  • Pressure resistance: PN 6 bar
  • Media: water, gases
  • Weight: 0.13 kg
  • High temperature resistance
  • Double-sided large-surface window
  • Natural glass    
  • Display of flow rate
  • Nominal width: DN 8.0.25
  • Process connection: female thread G 1/4..G 1
  • Display range: 0.7..60 l/min
  • Pressure loss: up to 0.7 bar
  • Pressure resistance: up to 0.7 bar
  • Pressure resistance: PN 16 bar
  • Suitable for both liquids & gases
  • 3/8″ to 2″ BSP sizes
  • Optional high & low switch points Optional 4 – 20mA transmitter
  • Pressures up to 16 bar
  • PVC or cast iron connections
  • Ranges covering 0.7..100 l/min H2O
  • Ranges covering18 to 700 l/min air (1 bar)
  • 16 bar max
  • Brass connections
  • No moving parts internally
  • Internal wiper provides ability to clean the glass without removing the device.
  • Installation location as desired    
  • For heavily soiled or coloured fluids    
  • 360 ° visibility
  • For 8 mm pipe
  • 0.005 - 5l/min display ranges
  • 1/4” BSP threaded connections
  • Maximum temperature 100 °C
  • Switching contact option(VFR)
  • Brass or Stainless Steel
  • All plastic (POM or PVDF) flow indicator
  • Can be installed in any position
  • Low ‘start-up’ benefit due to low friction design
  • 3/8″ and 1″ BSP sizes
  • Maximum pressure 16 bar
  • Maximum temperature 60ºC
  • Easy to fit to existing pipework
  • Sizes from 1/4″ to 2″ BSP
  • Large glass area allow viewing from any direction
  • Maximum pressure 6 bar
  • Maximum temperature 70°C
  • Brass body
  • Integral flow indicator & scale
  • Brass housing
  • Plastic sight glass
  • Ranges from 0.6 to 8 l/min
  • Temperatures up to 100°C max
  • Max pressure 10 bar
  • 3/4″ BSP male/female thread EPDM Seals
  • Rotor on both sides directly behind natural glass
  • Installation location as desired
  • Mechanical flow indicator
  • With twin rotor for quantitative flow display
  • Medium temperature 100°C
  • High temperature resistance
  • Double-sided large-surface window
  • Natural glass
  • Display of flow rate
  • High temperature resistance
  • Double-sided large-surface window
  • Natural glass
  • Visualisation of the flow rate
  • Ball rises in glass dome to indicate flow
  • Stainless steel body
  • Sizes from 1/4" to 1½" BSP
  • Maximum temperature 200°C
  • Maximum pressure 16 bar
  • Suitable for liquids and gases
  • Nominal pipe sizes 8mm to 25 mm
  • 2 - 80 l/min switching ranges
  • 1/4” -1” BSP threaded connections
  • Maximum temperature 100 °C
  • Viscosity stabilised option (NJV)
  • Brass or Stainless Steel