7 replies to this topic

[JKM]

Dear All,

 

I would like to ask whether for Vortex Flow Meter Sizing(Volumetric based), does density matter or not?

 

My Flowmeter is vortex type(volumetric) for Fuel Gas. During the design stage, certain density(0.8897 kg/Nm3 ) and molecular weight (19.92) was provided for the Fuel Gas. However during the actual operation time, Fuel Gas composition changed and actual molecular weight is 16.5.

 

I need to provide the calculation for the Boiler Efficiency. In this case do I need to consider density compensation or not. 

 

Best Regards

JKM

[breizh]

Hi,

Consider the document attached. Normally if the output is mass you need to measure Pressure and temperature together to calculate the density, expecting no variation in Molecular weight.  Vortex meter delivers a volumetric flowrate. 

Better to use a mass flowmeter for your application.

Breizh

[JKM]

Mr. Breizh,

 

Thanks a lot for your swift reply.

 

1. I cant not see any attachment in your reply. Kindly reattach.

2. The Flowmeter is already installed. So no case for changing the flowmeter type. I am from the EPC Contractor Side. I need to show the minimum boiler efficiency is meeting.

    Boiler Vendor sent the calculation and have considered density compensation. However Client is saying, that this is Volumetric Flowmeter. There is no point of density compensation. However Vendor is saying, that the MW(thereby density) is changed from the Design Value of 19.92 to 16.5 and therefore the Density Compensation is required.

 

Kindly let me know your view whether density compensation is required or not.

 

JKM

[breizh]

Hi,

Document attached, chapter 4

Breizh

Attached Files

•  industrial_flow_measurement.pdf   3.21MB   6 downloads

[shvet1]

@JKM

Do not be confused by what is written in the instrument documentation or a display. This device measures the mean velocity, not the flowrate.

User sees flowrate on a display because controller inside recalculates velocity to flowrate by coefficients. These coefficients are input by a user based on fluid properties predetermined by instrument Purchaser. 

 

Once fluid properties changes far enough from these predetermined design conditions readings on a display become false.

Edited by shvet1, 11 July 2024 - 06:14 AM.

[JKM]

@breizh Thanks a lot for sharing. It was useful to understand the basic principle of Vortex Flowmeter.

 

@shvet1 Thanks for sharing the insight but I am still not sure how density changes shall be compensated. Let me know if you have any idea.

[breizh]

Hi,

My reading from Google:

https://zeroinstrume...-disadvantages/

 

Not affected.

Breizh   

[shvet1]

a simple approach is:

flowmeter measures velocity, let it is 100 m/s

pipe is DN100, free flow area is 0.1*0.1*3.14/4= 0.00785 m2

measured volumetric flowrate is 100*0.00785*3600= 2826 m3/h

let actual gas density corrected to actual composition, temperature and pressure is 10 kg/m3

mass flowrate is 2826*10= 28.26 t/h

 

Do not substitute actual gas density by design or assumed one. This is a common mistake.

 

is it all clear?

Edited by shvet1, 11 July 2024 - 11:37 PM.