Possibly an application for ABB DP Transmitter Model 264DL which is specifically designed for Liquid Level Interface and Density measurement.

D-PS-264DL_5 Data Sheet (pdf, 313 KB)
http://www.tagteam.com/TagTeam/link.asp?id=511C2754

Ken Frisbie
ABB Inc.

 

How we take high and low pressure impulse line? How do we calibrate the DP with respect to Level?

 

Sanjib,
It's difficult to answer without knowing some more details, do you have a sketch you could send me or send your e-mail address and I will send you some typical details

roy_matson at yahoo dot ca

Roy

 

I have previously used a single straight tube density meter e.g.Solartron/Micromotion 7845.

This is a useful 1 meter long and arranged vertically in a manometer style arrangement it has been very effective at determining the interface (even if diffuse) in methanol and water separation system in a pharmaceutical plant.

There is a very good density difference between methanol and water which makes this particularly effective for controlling the underflow pump out.

It didn't matter if the interface was diffuse because in the operation the methanol water separator, as the two fluids separated the density in the bottom of the tank increased as the water content increased. Above a certain level it was virtually all water.
In the pilot installation a sight glass was installed in parallel to confirm the operation.

The interface height is simply a function of the density. 1000kgm/3 and the interface is above the top of the tube, 791kg/m3 and the interface is below the bottom of the tube. 895kg/m3 and it is halfway up the tube.... a useful sensor in that it would accurately report the mean density even if not homogenous...not sure how other sensors would respond under similar circumstances.

For pipeline applications e.g. common pipeline supply to tank farm the straight tube density meter (e.g. 7835 or equivalent accuracy coriolis meter etc) is used to detect the interface between different refined fuels including between diesel and green diesel etc.

There are two methods one of which uses a single density meter and a knowledge of the product density to control the divert and the second uses two density meters in series.

In this case it doesn't matter what the actual densities are so long as they are different and so long as the operator knows, from the denisty or from a knowledge of which products have been put into the pipeline which products he will see at the density meter.

In the two sensor installation the first sensor provides a first alert of the arrival of an interface so the operator can correctly set up the diverts.

All the while the pipe is full of a single product they density meters will read the same value, as the interface reaches the first density meter its reading will change and a density difference is detected by comparing the two density meters. When the interface reaches the second density meters they will again agree.
This method has been used by the UK Pipeline Operator. In some installations the upstream density meter may be a cheaper or less accurate sensor since it only provides a first alert.

Density software includes zoning which is simply a set of density alarms that can be programed to look for interfaces. (visit www.mobrey.com and download the manual for the liquid density single converter software version 7950/1).

 

Most "strip sources" are really a series of small Cs-137 point sources equally spaced along a strip. If you use a Co-60 rod source (radioactive metal wire wrapped around a steel spindle), you can generally make a good interface measurement on vessels that are much larger in diameter than 12" (6 ft or more). The gamma radiation from Co-60 is much more energetic than from Cs-137, so there is more penetrating power.

From a cost standpoint, it would certainly make sense to do the measurement with guided-wave radar if it is possible. In my personal experience, I have found that capacitance probes are another good low-cost, reliable method. But if there are other application considerations that make a non-contact solution attractive, then nuclear will work well.

Jon Buchanan
Berthold Technologies USA
865-483-1488
http://www.berthold-us.com

 

the Interface level are of two different Liquids with Specific Gravity 0.8 & 1.5 Respectively. & we have to Measure it with Water..
Can u tell me that how can we measure..????

Joshi
Mumbai, India

 

Hi there,

I will tell you what not to use first, in case someone comes up with some bright brain waves again as in this thread.

Do not use ANY type of DP instrument, the explanations why not is to long so just trust me on this.

Do not use a Capacitance probe regardless of how "well" everyone says they work. There are other specific reasons why I do not recommend them. They can also only measure one product, either the level or the I/F but not both.

You best instrument to use for I/F measurements is the Guide Wave Radar but they are difficult to setup and expensive. Very accurate, reliable and not that difficult to work with once you understand the basics of TDR technology and the concept of the dielectric constants of various products. Another advantage is that the GWR can measure the level and interface simultaneously and give out two different 4 to 20 mA outputs.

To see if they will be suited for your application go on the internet and do a search on "di-electric constants" and see what the DC values are for the products you want to use. The bigger this difference between these DC values are the more suitable the GWR will be for your application. Forget about the densities for each product, since the GWR is not density dependent. For example the DC value of water is 80 and the DC value of crude oil is between 1,8 and 4 so they work like a charm on a big product DC difference like this.

My second choice would be to use a displacer and my third choice would be to use a magnetic float type instrument. Both are cheap and easy to setup and reliable enough for most non critical applications. They can also only measure one product and if you have turbulence in the vessel you might have to buy and install stilling wells as well.

Nuclear will also work but the price and rules and regulations involved is a turn off. Also not easy to setup and to work with. This would be my last choice, if nothing else will work.

For critical applications go for the GWR if possible.

 

You could use the VDM250.2 portable density/viscosity meter.
Since you have a good density difference the density only version is quite suitable. This is manufactured by LEMIS
See http://www.viscoanalyser.com or http://www.lemis-process.com

 

Check this transmitter that can measure density and interface level:

http://www.smar.com/products/dt300series.asp

 

Dear Sanjib,

Should you need the interface level to control this level in a vessel. let me know the densities and I will redraw a system I designed and installed in a petrochemical plant almost 40 years ago.

No moving parts, no electric or electronic parts (and no need for a level indicator, though I can easily add one)

My email for offlist contacts:
as [at] neda.net

 

Dear Joshi
Salaam

Please can you explain what you mean by:

"..... & we have to Measure it with Water.."

AND, what do you need the interface level measurement for??

I will appreciate more details, maybe offlist if you prefer.
as [at] neda.net

 

Dear Joshi
Salaam
Would you kindly explain what you mean by .. measure it with water.

And if you need interface level to control it look at my reply to Sanjib in this thread or drop me a line offlist at [email protected]


Abdollah Sadjadian

 

Dear Sam
We have different application, organic layer is heavier than water & difference in density is about 0.15 only, we understand displacer requires minimum 0.2 specific gravity difference.

We would appreciate your feedback

Jari
[email protected]

 

Hi there,

In a situation like this you have various options that will work but since I cannot know what the vessel looks like I can only give you some basic info.

In my previous post I said that capacitance probes should not be used and the reason for that is that it is very difficult to setup and in some cases virtually imposable.

It is a long story to explain but in your case the capacitance probe could be the best option since they do work well once you get them setup properly.

The way to do it is simple and not a problem.
The problem is if you will be able to do it in your application.

Set all the generic parameters on the meter then fill the vessel, or standpipe next to the vessel, with the lightest product (water in your case) to the 100% mark on your vessel or standpipe. At this point you set the LRV based on what pf the probe reads. You then need to drain all the water and fill the vessel up with bottom heavy product also to the 100% mark and set the URV based on the pf that the meter display. The principle of calibration is based on the concept of 100% of top product is 0% of bottom product and 100% of bottom product is 0% of the top product. The principle stays the same, even if you work with flooded vessels and two outputs.
If you have a sight glass on the vessel that will be a big help or if the vessel is accessible and you can actually see inside the vessel that will also be helpful.

Like I said the capacitance probe work well if you have all these extra features on the vessel to help during initial setup. In a closed online pressurized vessel it becomes virtually imposable to do without any other reference instrument to work from.

The other option is to use a magnetic float type instrument.You will use the one float to measure the interface and a different float instrument to measure the top product level. You obviously need to make sure the density of the bottom float instrument is 1,5 more than the density of the water float (sg=1) so that the I/F float will sink through the water and only float on the heavier bottom product. The calibration is as simple as moving the floats by hand to the position on the guide rod where zero and span should be and set the values. In your case with both floats at the bottom of the rods will be zero and with both floats at the 100% mark on the rods will be the span settings.

To stabilize the readings in a turbulent application, you can install the floats in stilling wells and play with the damping.

 

Dear Jari
Salaam

If the ultimate aim is to control interface level and separate the two liquids give me the exact sg of your heavier than water liquid and I will redraw a system I designed and implemented 40 years ago to separate water (sg=1) and DDB (sg=.865) without any instrumentation whatsoever.

Abdollah Sadjadian
[email protected]

 

Good Afternoon,

Displacer type of level transmitter if used for the measurement of Interface level at Water/Crude Oil Separation tanks, how long normally would it take to give stable / representative reading after flushing/calibration (where the lower tapping is from about 5 ft of Tank height(having almost 100% water) and higher tapping of chamber is from about 9 ft of 40ft high Tank (having about 10% oil-90% water)?
What is the best procedure of commissioning the LT chamber?

 

Try this company. In the past they made a great RF level meter.

Atis Inc, Automatic Terminal Information Systems Inc, Atis
7110 Satsuma Drive
Houston, TX 77041-1812

(713) 937-4993

 

You can measure interface level with a guided wave radar level transmitter
http://www.processonline.com.au/articles/34104-New-EDDL-is-guiding-radar-interface-level-made-easy-

long URL, copy from http:// all the way to easy- in a single line into your browser address bar if clicking doesn't work

Commissioning is demonstrated in this video:

Cheers,
Jonas

 

Hello,

To use a differential pressure transmitter to measure interface, search the internet using ISA Multivariable approach to Level Measurement.
This site will explain the theory and provid a picture and a formula. Follow the formula and picture and this should help you with your problem.

 

Try this site. We use it successfully to measure interface in black liquor and soap. Very a lot more difficult application than what you are doing. This would suite your application well. It can handle applications with high solids, fouling and interfaces of two very tight liquid densities.

see: www.sms2000.ca