Introduction
Flow is an important physical quantity that needs to be controlled,monitored. There are so many flow measuring devices. lets discuss about Turbine flow meter.
Working principle
Turbine flow meter is used for translates the mechanical action of the turbine rotating in the liquid flow around an axis into a user readable rate of flow. Blades on the rotor are angled to transform energy from the flow stream into rotational energy. The rotor shaft spins on bearings. When the fluid moves faster, the rotor spins proportionally faster.
Turbine flow meters measure the velocity of liquids, gases and vapors in pipes, such as hydrocarbons, chemicals, water, cryogenic liquids, air, and industrial gases.
These meters are an ideal solution when high accuracy, compact size and fast response are critical requirements
Theory
Shaft rotation can be sensed mechanically or by detecting the movement of the blades. Blade movement is often detected magnetically, with each blade or embedded piece of metal generating a pulse. Turbine flow meter sensors are typically located external to the flowing stream to avoid material of construction constraints that would result if wetted sensors were used. he flowing fluid engages the vaned rotor causing it to rotate at an angular velocity proportional to the fluid flow rate.
The angular velocity of the rotor results in the generation of an electrical signal (AC sine wave type) in the pickup. The summation of the pulsing electrical signal is related directly to total flow. The frequency of the signal relates directly to flow rate.When the fluid moves faster, more pulses are generated. The transmitter processes the pulse signal to determine the flow of the fluid. Transmitters and sensing systems are available to sense flow in both the forward and reverse flow directions
The output signal voltage of the magnetic coil is approximately sinusoidal. The frequency range of the pulsing signal varies from meter size to meter size. However, standard ranges allow for maximum output frequencies at the nominal linear flow of 250, 500, 750, 1000, 1500, 2000, and 2500 Hz.
STRAINERS/FILTERS
Turbine flow meters are designed for use in a clean fluid service.However, the service fluid may carry some particulate material which would need to be removed before reaching the flow meter.Under these conditions a strainer/filter may be required to reduce the potential hazard of fouling or damage that may be caused by foreign matter.
Parts of turbine flow meter
1.Permanent conduit connection is standard.
2.ROTOR is pitched and pre-calibrated to determine accuracy.
3.END CONNECTIONS available, flanged or threaded, standard or special.
4.FLOW VANES increase performance at low rates
5.FLOW VANE HUB supports rotor assembly
.6.ROTOR SHAFT, BEARINGS, AND THRUST BALL are tungsten carbide for long service without lubrication other than by the liquid being measured.
7.RETAINING RINGS make disassembly easy.8.FLOW METER BODY is sturdy, one-piece construction, precisionfinished.
Installation
- The meter should be installed with the arrow on the meter body corresponding to flow direction of the line
- A 10-diameter length of straight unrestricted pipe must be upstream and a 5-diameter length of straight unrestricted pipe must be downstream of the flow meter. Both pipe sections should be the same nominal pipe size as the flow meter’s end connection.
- Throttling/Control valves should be located downstream of the flow meter
Applications
- Water-injection measurement
- Heater treaters
- Test and production separators
- Disposal wells
- CO2 injection
- Steam generator fuel and feed water
- Food and beverage industry
- Metering liquid fertilizer
- Water, fuel, and chemical measurement in plant settings
- Chemical tank loading and unloading
- Measuring liquid propane
Advantages
- high accuracy
- suitable for extreme temperature and pressure
- it can be used on gas and liquids
Disadvantages
- only for low viscosity fluids.
- moving parts
- sensitive to flow profile
- Require clean fluids.
