Good Afternoon,

How can we measure Interface level measurement?

 

Usually with extreme difficulty.

If you can tell us what the interface is, and some information about each fluid, we might be able to help you.

Interface level measurement is the hardest level measurement application I know of. Help us out and tell us more.

Walt Boyes
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Radar, Bubble tubes, Displacer, Magnetorestrictive, DP cell, Conductivity, Capacitance, Nuclear, need I go on. But you need to tell us what the two fluids are.

Roy

 

two phase flow measurement.

 

It is methanol and water.

 

Thanks for your reply. It is liquid level, is water and methanol.

 

Sanjib,

You will not get an interface between methanol and water. The methanol will dissolve in water.

Roy

 

I thought methanol was 100%, fully miscible in water (completely soluble).

Is that not the case?

Please educate me. I don't understand why a two phase interface level measurement would apply to methanol/water.

David

 

Sorry, it is petrol and diesel. How do we calculate this level in DP type methol?

 

Are you talking about interface detection or interface level detection? The first refers to product detection within a hydrocarbon pipeline; the second refers to product detection inside a storage vessel.

Regards,

Tomy Zacharia

 

You can measure the interface between two fluids using a DP cell with High and Low connections or using two bubble tubes. First of all you need to establish the density of the fluids at the working temperature.

Diesel seems to have a wide range: 820-950 kg/m3
Petrol (Natural) 711.22 kg/m3 or vehicle 737.22 kg/m3
For example, if you have two bubble tubes 1,000 mm apart in petrol you will get a DP of 737 mm WC - this is your Zero. In Diesel you will get 820 mm WC - this is your 100%. For a DP mounted on tank taps 1,000 mm apart, assuming the top connection is filled with petrol,
when the interface is at bottom connection the DP would be zero because the HP and LP connection are both subject to the same column of petrol (assuming the temperature is equal), so your Zero is 0 mm WC. When the interface is at the top tap, the HP connection will see 108 mm more pressure than the LP.

I would have thought Petrol and Diesel would mix since they are both hydrocarbons, in which case the DP would indicate the mixture ratio.

Hope this helps,

Roy

 

>Are you talking about interface detection or interface level detection? The first refers to product detection within a hydrocarbon pipeline; the second refers to product detection inside a storage vessel.>

Please explain briefly with some examples. I need this for academic purpose.

 

Thank u roy. I need this for academic purpose. What is other method? Is there any DP type measurment?

 

Roy,
If the fluids are to be crude oil and water could you advise me about using DP to measure the interface level? Which method is more common in industry in accordance to new technology?

Thank you,
Vahid

 

Are you teaching or trying to get us to do your homework for you?

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:[email protected]
Read my blog SoundOFF!! At www.controlglobal.com/soundoff

 

Vahid,
I don't work with crude but do so with other hydrocarbons. We use bubble tubes in glass lined vessels and also DP cells on the side of tanks. I suspect displacer type transmitters are still very popular for the high pressure applications. Guided wave radar is another applicable method because the crude dielectric will be significantly different from water. The radar signal would penetrate the crude and reflect off the water.

Nuclear is another good method because water has a very high absorbtion rate for gamma rays.

I have been advocating electrodeless conductivity for short range interface, so far I have been unable to convince anyone to try it. One of the larger donuts should work over one or two inches.
I would need to know a lot more about your application before I would recommend the exact method.

 

Use GWR or Capacitance type level measurement. These are preferred one.

 

The problem with using nuclear for a oil-water interface level measurement is the distance between the source and the detector. If the vessel is larger than 12 inches or so in diameter, it may not be possible with a conventional nuclear level gauge. This measurement is often done with a standpipe so that the gamma source (a strip source) can be mounted closely enough to the detector so that radiation will penetrate the steel-water-steel to reach the detector (a strip detector). This is a very expensive measurement.

I really am starting to recommend using guided wave radar for this
application.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
[email protected]

 

I agree. but some notes about GWR:

I experienced some problems last days with a reflex radar interface level. We changed the process and now, aquous phase is lighter than organic phase,(and is on top of the organic phase) and then, radar waves can't penetrate the aquous phase and the interface detection isn't possible. Reflex radar requires the liquid with the highest permitivity between the emission point and the other liquid.
I solved the problem with a capacitive device.It works very well under all conditions

 

Yes, that's why there are many types of level and flow measurement
methods... one of the darn things will always more or less work.

Walt Boyes
Editor in Chief
Control and Controlglobal.com
www.controlglobal.com
Mailto:[email protected]
Read my blog SoundOFF!! At www.controlglobal.com/soundoff