Principle of anubar instrument

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Thread Starter

N.Vedachalam

I am working as a instrument engineer in Ocean Development dept of Govt of India. Can you please explain to me the working principle of an anubar instrument.

-- vedachalam.
[email protected]
 
anubar is averaging pitot tube used for large flow rate. I think you are aware of pitot tube.
In case of anubar several holes are made on the insertion tube to get average pressure head. The generated differential pressure is generally low (in the range of 100 mm H2O )
 
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Alexander Benim

Annubar is nothing more than a set of Pitot tubes mounted on a on a bar /rim across the pipe. The principle of Pitot tube is that it measures differential pressure between and the static pressure tap and the tap of full pressure of a stream (static + dynamic (Rho*V**2) , where V - fluid local velocity ; Rho - fluid density. Thus, such differential is proportional to fluid velocity squared. Pitot tube is designed in such a way that the full pressure chamber opening is facing against the stream and the tip of the tube has conical aerodynamic profile. The static pressure tap opening is made on the cylindrical surface of the tube, i.e. in the plane perpendicular to the direction.of stream. Having a set of tubes (annubar) across the pipe allows good averaging of the velocity profile.

Alexander Benim
Compressor Controls Corporation
 
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Rohit Chandak

Dear Sir,

Thanks for this opportunity.

Averaging Pitot Tube is a technology while Annubar is a brand name for Dieterich Standard flow element (Averaging Pitot Tube) there are other brands available in the market with VERABAR, TORBAR, ANUBAR etc.

Anubar is a DP producing device which when integrated with a DP transmitter gives you a Flow Signal. It works on bernaullis principle. Anubar is a dual chamber tube with multiple sensing ports on both the chambers i.e. upstream & down stream. This flow element when inserted into the flow stream produces boundry layer there by having High Pressure & Low Pressure gradient around the sensor body. The presense of HP & LP ports in that gradient helps it to sense the pressure in respective chambers & when this two respective tubings are connected to DP Transmitter it gives you a flow signal.

We have been in this market for last three decades & one of the pioneers in introducing the concept in the Indian market. If you have any question or need additional information kindly let us know.

Regards,
Rohit
Fax: 091-712-539472
Email : [email protected]
 
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"Annubar" is a registered trademark of Emerson Process Management. Properly you should refer to flow meters of that type as Multi-port Pitot Tube Flow Meters.

Accuracy of an insertion flow meter is highly dependent on installation parameters. Multi-port Pitot Tube Flow Meters can be calibrated at the factory for decent accuracy even when mounted into a 90 degree elbow.

Because I am very conservative when figuring out accuracy, my rule of thumb is that the best an insertion flow meter of any type can do is about 1 percent of span. I will probably get argued with on this. However, if you estimate 1% of span, you may be pleasantly surprised, but not usually shafted.

Of course I can install any insertion flow meter where it will have an accuracy of +/- 25% of span...but so can anybody else.

Spitzer and Boyes LLC
837 Suncrest Drive
Aurora IL 60506
[email protected]
www.spitzerandboyes.com
 
> "Annubar" is a registered trademark of Emerson Process Management. Properly you

---- snip ----

> Because I am very conservative when figuring out accuracy, my rule of thumb
> is that the best an insertion flow meter of any type can do is about 1 percent of
> span. I will probably get argued with on this. However, if you estimate 1% of
> span, you may be pleasantly surprised, but not usually shafted.

> Of course I can install any insertion flow meter where it will have an
> accuracy of +/- 25% of span...but so can anybody else.

What would be a recommended flow meter with higher degree of accuracy over an anubar?
 
detail of air flow measurement in the 18inch duct line our maximum air flow of blower is 10,000m3/h.

plz give us detail of dp Transmitter and its flow element (annubar), and calibration of DP Transmitter.
 
In a vertical flow the two taps (where you connect the DP cell) should be horizontal. This is probably not critical for dry gas but steam for sure.

You can use an annubar designed for steam in a vertical line in a horizontal line but not the other way.
 
When you install it in a vertical line which way do the pressure taps
point, up and down or horizontal.

It probably doesn't matter for dry gas but does for steam and liquid they need to be horizontal for sure.

You can use one designed for vertical in horizontal but not the other way

Roy
 
M
An annubar is similar to a pitot tube.

The pitot tube measures the difference between the static pressure and the flowing pressure of the media in the pipe. The volumetric flow is calculated from that difference using Bernoulli's principle and taking into account the pipe inside diameter.
 
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