Turndown Ratio Turndown Ratio of a Flow meterof a Flow meter

Why is it an important consideration when selecting a flow meter?

Turndown ratio – Flow meters

• Turndown ratio is a flow measurement term that indicates the range of specific flow meter is able to measure with acceptable accuracy.

• Turndown ratio can be expressed as;• TR = Q (max) / Q (min)

• Where TR = Turndown Ratio• Q (max) = Maximum Flow• Q (min) = Minimum Flow

Turndown ratio – Flow meters

• Example #1;

• If a gas to be measured varies between 100000m3/day and 1000000m3/day

• This specific application has a TR = 10:1

• The flow meter required should have a TR of at least 10:1

Turndown ratio – Flow meters

• If the flow meter had a maximum flow of 2000000m3/day then the required turndown ratio (TR) would be 20:1

• Example #2;

• Consider a 12’’ ruler graduated to a quarter of an inch.Since the smallest distance that could be measured is ¼’’

Turndown ratio – Flow meters

• The turndown ratio is

• 12’’/ 0.25’’ = 48 i.e, (48:1)

• If the same ruler all the graduated lines below 2’’ are smudged, then in this case the turndown ratio would now be

• 12’’ / 2’’ = 6 (6:1)

Turndown ratio – Flow meters

• Note;

• Turndown Ratio is one of a number of considerations when choosing or sourcing for a flow meter for your application

• TR of a flow meter is mostly affected by the devices signal-to-noise ratio (S/N Ratio) which results from the fluid dynamics of the technology and the type of sensor employed.

THANK YOU !!!

Presentation prepared by ;

Benjamin Kyalo

Technical Sales Engineer

+254735211022

bwkkyalo06@gmail.com

www.google.com/+BenjaminKyalo

Nairobi, Kenya