The right fuel flow meter for your application

K33 Flow Meter

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What is a fuel flow meter?

A flow meter is used to measure the quantity of fluid that has been moved during the transfer process. They have a visual display, which can be either mechanical or digital, for the user to read off the measurement. Flow meters are used within a variety of fluid transfer applications and therefore whilst they are always used to measure the fluid, the ways in which they work are slightly different.

With a nutating disk fuel flow meter, the fluid would enter the meter inlet where it comes into contact with the eccentrically mounted disk. This disk ‘nutates’ along the vertical axis that the disk is positioned along, and as it does so it provides indication of the amount of fluid that has gone through the meter.

Oval gear fuel flow meters use at least two gears that rotate at right angles to each other creating a T-Shape. The teeth of the two gears always mesh in the centre of the flow meter, ensuring that no fluid passes through this point. As the fluid pushes against the gears causing it to rotate, it moves the fluid held in the measurement chamber into the meter’s outlet. As this occurs, the fluid entering the inlet will be driven into the other measurement chamber which is now open, as the previous chamber closes. This cycle continues as the gears rotate and fluid is metered through alternating chambers. Magnets in the rotating gears then transmit a signal to an electric reed switch in order to measure the flow.

A turbine fuel flow meter converts the mechanical action of the turbine rotating in the fluid around an axis into a flow rate. As the fluid impacts upon the turbine blades it sets the rotor in motion, and when a steady rotation speed is reached it is proportional the fluid’s velocity.

Choosing a flow meter for your application

In terms of a diesel refuelling system, a fuel flow meter counts the amount of fuel transferred in that particular transaction so that the user knows how much they have dispensed into the vehicle. This is very much the same as with an AdBlue™ flow meter, whereas a heating oil meter is used to measure the total quantity of oil consumed by the heating system overtime.

As discussed, flow meters can differ on the fluid they designed for use with and whether they have a mechanical style tick over display or a digital, battery powered display. Fuel flow meters also differ in terms of how accurately they measure the dispensed fluid. In order for the flow meter to reach its stated accuracy level, the speed at which the fluid is being transferred must be within the flow meter’s flow rate range.

Flow rate is therefore another factor in which fuel counters differ. Flow rate is usually measured in litres per minute, unless it is a heating oil application where the fluid is consumed much slower and is measured in litres per hour. A standard diesel flow meter tends to have a maximum flow rate range of 120lpm, as this covers the general speed at which vehicle refuelling occurs. However, for higher flow systems such as bulk fuel transfer or the refuelling of large plant equipment, diesel flow meters with flow rates of up to 500lpm are often required. 

How does a pulse meter differ?

A pulse meter operates very similarly to a fuel flow meter in that it is the component in a system that measures the fluid that has been transferred. However, rather than having the read-out on a visual display, the pulse meter instead sends electronic signals (or pulses) to an external receiving unit. Usually, these meters will be set so that a pulse equates to a litre for a user-friendly read-out.

Pulse meters are ideal for when the quantity of fuel dispensed needs to be read by a third party unit, for example when linking the refuelling system to a fuel management unit or a larger building management system. Another way in which a pulse meter is used, is if the display needs to be readable from somewhere other than at the refuelling point, for example the fleet manager’s office. In these instances a remote pulse display will also be required.

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