29 March, 2024

Selecting a hydraulic flow meter

23 August, 2017

4. What effect might the flow meter have on the fluid and vice-versa?

This ‘effect’ can be measured by the energy loss due to the presence of the meter, better known as the pressure drop (∆P) across the device. This has two effects: Increasing the upstream pressure and generating heat.

5. How important is it to measure flow; what is your budget?

A better question might be, ‘What happens if you don’t measure flow?’ If the answer is ‘Nothing; it’s just one of many indicators we look at’, then you already know that you’re working with a very small budget. However, if the answer is, ‘the PLC will think that the machine lubrication has failed and stopped working’, then you know how much you might budget to stop that from happening.

The most common types of hydraulic flow meter are as follows:

Variable orifice flow meters

The idea of flow displacing an object, usually a piston or a ring, forms the basis of simple ‘variable orifice’ flow meters. The momentum of the fluid exerts a force on a piston that is held in place by a spring. Such meters typically have an accuracy of between 2 – 5% of full scale.

Gear type flow meters

These are positive displacement flow meters. On the inside, they look similar to a gear-type motor. Fluid passes around the outside of a pair of intermeshed gears, rotating the gears on their shafts. A transducer mounted above one of the gears generates a pulse each time a gear tooth passes under it. The rotation of the gears is proportional to the flow rate. Sometimes, two transducers are used to measure direction and improve resolution.

Turbine-type flow meters

In a turbine-type flow meter, a turbine rotor is mounted on a shaft between two sets of flow straighteners. The fluid passes through the flow meter and rotates the turbine blade. As for a gear-type flow meter, a transducer is mounted above the turbine and generates a pulse each time a blade passes under it. The frequency from the transducer is proportional to the flow over a limited range.

Other meter types

Oval gear meters are similar to conventional gear meters, but use two elliptical gears that rotate together at 90 degrees to one another inside a housing. The fluid is swept around the chamber by the gears, and the frequency of rotation is directly related to the volume of fluid through the meter.

The above article is an edited and abbreviated version of the 8-page ‘Guide to selecting a hydraulic flow meter’, published by Webtec.

www.webtec.com




Events
 
Buyers' Guide Search
 
Search for UK supplier by name
Browse by Product Group.
Magazine
MARCH 2024To view a digital copy of the MARCH 2024 edition of Hydraulics & Pneumatics Magazine, click here.

For a FREE subscription please click here

To visit the Library for past issues click here

JANUARY/FEBRUARY 2024 IssueTo view a digital copy of the JANUARY/FEBRUARY 2024 edition of Hydraulics & Pneumatics Magazine, click here.

For a FREE subscription please click here

To visit the Library for past issues click here

JULY/AUG 2023 Issue inc. BUYERS' GUIDETo view a digital copy of the JULY/AUGUST ISSUE of Hydraulics & Pneumatics magazine that includes the ANNUAL BUYERS' Guide for 2023, click here.

To visit the Library for past issues click here

BFPA YearbookTo read the latest BFPA Yearbook, click here ..
BFPA Training AcademyClick the image to go to the BFPA Training Academy website
Compressed Air & Vacuum Technology Guide 2018To read the official BCAS Compressed Air & Vacuum Technology Guide 2018 click here
Offshore Europe Journal
Newsletter
 
Newsletter