What is a turbine flow meter?
Generally, a turbine flow meter is a device that measures how much volumetric flow is moving through a pipeline per unit of time based on the volume of gas or liquid passing through it.
Flow meters of this type are composed of three main components:
Pickup sensor (with transmitter)
Turbine (rotor, impeller, blades)
A turbine consists of a shaft that is fixed in a pipeline and an impeller. This impeller is a multibladed wheel attached to a shaft rotating on bearings. The blades have magnetic poles on their edges.
Flow technology can be divided into two types: axial and tangential. Axial installation directs the flow parallel to shaft axis, whereas tangential installation directs it around the circumference.
The materials that are used for the rotor and bearings are selected according to the type of medium and the level of accuracy that is required.
There are two components to a pickup sensor system, an induction coil (or Hall sensor) and a signal transmitter (transducer). As the rotor speed increases, the induction coil generates electrical impulses and transfers them to a recording device, which is connected to the induction coil. It is not uncommon for devices to be equipped with two such coils in order to take measurements about forward and reverse flow direction. Hall sensors simply detect changes in magnetic fields.
Typical mounting methods include using flanges that are attached to pipelines and mounting the housing with non-magnetic cast steel (or aluminum, or even plastic).
The straightening of vanes is also important. For this purpose, plates are installed parallel to the flow direction of the medium to ensure that stream jets are evenly distributed across all blades. Additionally, mechanical stabilizers are mounted inside the structure in order to prevent turbulence. By the way, Vortex flowmeters work by creating a vortex that is unique to them.
How does it work?
Turbine flow meters are used to measure volumetric flow rates through flow velocity analysis. They operate by tracking the rotation speed of multi-bladed rotors.
In this way, turbine flow meters work in much the same way as a bicycle. As you pedal faster, you move faster. Flows of liquid or gas act as the driving force while turbine rotors act as the wheels. Let us take a closer look at how a turbine flow meter works.
The main flow of water or gas is diverted directly onto the blades by straightening vanes once it enters the turbine section.
It is the mechanical energy that pushes on the blade surfaces that make them rotate. The larger volume of substance that passes through a pipeline, the more mechanical energy that is created, and consequently, the higher the angular (rotational) speed of the blade.
An electrical pickoff sensor detects changes in magnetic fields when blades with magnets pass near it at a certain speed. A device with an induction coil induces an electrical pulse in it. A Hall sensor simply captures those changes. It's similar to using a magnetic flow meter.
The frequency with which these changes occur is monitored and sent to the transmitter, and the frequency of such signals is directly proportional to the velocity at which the changes occur.
The following equation describes the relationship between volume flow and pulse frequency for a turbine flow meter:
F= k * Q
F- Displays how many pulses the pickup sensor detects per minute or second
Q- Volumetric flow (m, gallons, liters / s)
k- coefficient, also known as k-factor (for example, the number of pulses per meter. We discuss it in more detail below).
In addition, the transmitter analyzes the received data and converts it into an analog or digital signal.