MANOMETER VS PRESSURE GAUGE

[moideen]

the pressure gauge and water flow manometer do the same job. My question related to measuring the flow rate of condenser or chilled water pump. The sqaure root of pressure drops across the balancing valve multiplied with cv rate of balancing valve. Why do not depend gauges to know the pressure difference across the balancing valve?? Third party companies use the monomer for commissioning purpose. I thing manometer gives the accuracy. what is your comment. Thanks

 

[btrueblood]

Yes, a manometer (or other direct differential pressure measurement) theoretically is more accurate, as you have one less source of error (one measurement instead of two).

 

[moideen]

btrueblood:thanks, now there differential pressure gauges which one time measure. but hese days using electronic manometers. do you think, is electronic manometers are more accurate than conventional u tube manometer??

 

[EdStainless]

With any electronic gauge there are issues of temperature coef, zero drift, span drift, and so on. For both the sensor and the electronics.
We had a Taylor analog dP, 9" dial with two revolutions, +/-2"H2O, that is across 48" of scale.

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P.E. Metallurgy

 

[moideen]

EdStainless: mixed views of discussions about analogue and digital manometers. some say the analogue is obsolete,and some say digital is accurate. it is confusing. in the past period, most of chilled water balancing companies those resorted the analogue meter to balance the chilled water flow for chiller and terminal units.you pointed the issue of digital like zero drift, can it be offset before proceeding the readings.

i googled Taylor made analogue meter but cannot find the link, i want to check whether available in Dubai. please type the web link

 

[gerhardl]

Dont forget that for any pressure measurement for flowing fluid an incorrect installment and placement in line is more likely to give a false reading than the inbuilt accuracy of the instrument itself.

Measurements taken to near a flow valve might give false values.

 

[EdStainless]

The problem with analog meters is that you don't have a continuous output to a monitor and control system. You get analog gauges with switches (Dwyer) but that is just pre-set limits.
People often use analog for set up and then run off of digital.
With either type there are cheap ones that are junk and expensive ones that have good stability and resolution.
The Taylor we had was old, I doubt that they have been made is over 20 years (maybe not in 40 years).

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P.E. Metallurgy