advertisement
from the Oil&Gas department...
Crude Oil Volume Flow at 60°F Reference Temperature
Sensor technologies. topic
Posted by Frank19842003 on 23 July, 2010 - 5:28 pm
I need to measure crude oil volume flow compensated at 60°F from an crude oil plattform. Which flowmeter technology you recommend me to use. I donīt need just to measure volume flow but I also need to compensate it to 60°F (then I can compare all my different reading at the same temperature since pressure is almost constant).

I donīt want to use coriolis mass flowmeter since they are two expensive (3 inch pipeline). I was thinking in maybe using vortex. What do you think? Do you have experience measuring crude oil with vortex flowmeters? I heard that since the crude oil is very dirty it works at the beginning but then you have to do a lot of maintenance. maybe an ultrasonic clamp on flowmeter is better.

About compensating to 60°F, do you know how can I solve it without using a flow computer? Do you know some solution.

Thanks in advanced for your help.


Posted by Sam on 24 July, 2010 - 3:49 am
Hi there,

The turbine meter are used all over the world to measure crude in the most critical areas of the plant including the metering skid. It has been proven over the years as accurate and reliable and in a survey done by BP this was the meter they still recommend to use on the metering skids.

The vortex meter are also being used offshore but in my experience not a lot of technicians are familiar with it so that is not a meter I would go for. I have personally worked on the turbine meters and saw how accurate and reliable they are so that would be the way I would go.

When you do your design make sure you install two of them in parallel since they have to be taken out and send to the suppliers at least once a year for calibration verification checks. If you have two in parallel you just put a spool piece in place of the one and send it for calibration check and you still have the other one to do the measurements. When it returns you will receive a new K-factor from the suppliers and you can send the currently installed one away. In this way you can always have a reliable and verified flow meter to do your measurements, and accuracy can be proven on paper as well.
Speak to the supplier to help you with the volumetric flow compensation and ask then to implement that on a permanent basis during the calibration verification checks.


Posted by JMW on 26 July, 2010 - 5:45 pm
The turbine meter should be suitably calibrated for the application and used with suitably capable electronics. You do not give the operating conditions but typically you might need to compensate the flow meter for temperature and pressure effects on the meter factor and you may need viscosity compensation, depending on your oil characteristics.

You can find out about the sort of corrections available by looking at the manual for the 7950 flow computers on the Emerson website:

http://rosemount.d1asia.ph/mobreyglobal/downloads/view.asp?pageid=2 3&title=

and go to 7951 liquid flow computer. This also details the corrections to standard volume. These flow computers can be used with pulse input devices, e.g. Turbines, Vortex, dP and coriolis meters.


Posted by JMW on 4 August, 2010 - 9:48 am
I neglected to respond to your comment on the oil being dirty. We need to be careful here to understand what you mean. If this is crude from the well, presumably it also has gas and sand? or has it been separated and what you have is a heavy crude? If it is a heavy crude you need to be careful about turbines. The Faure Herman and SMith Meters turbines are designed for higher viscosity fluids but the concern with turbines and dirty fluids is that blade coating will affect performance and you may find you need to be careful about bearing wear.

Vortex meters are usually about as viscosity limited as turbines and they too do not generally like dirt. You really need to speak with the manufacturers.

If your crude density is reasonably constant then I guess you can use temperature to correct back to standard volume because the bulk modulus will be constant. That shouldn't demand any great calculating capability in the electronics.

This is one of those applications where expensive or not, coriolis may be the least problematic solution since you will be measuring mass flow directly and do not need to compensate for temperature and, since they measure density, you should also be able to get volume at line conditions and, by using the base density calculation, volume at reference conditions.


Posted by Sam on 5 August, 2010 - 3:02 am
Hi there,

I heard some talk about using the Coriolis meter on offshore installations and that some people believe the constant vibration of the platform or FPSO will cause inaccuracies in a Coriolis meter. I also think the constant vibration could have a effect on the meter's accuracy, especially if the vibrations vary from time to time.
What is your feeling on this?


Posted by JMW on 5 August, 2010 - 7:53 pm
The early coriolis meters tended to run at around 50-6oHz at which frequency they were very vulnerable to noise and vibration and indeed if two coriolis meters were mounted close to each other they could be affected by crosstalk.

AT higher frequencies noise is more rapidly attenuated. Modern coriolis meters tend to operate at higher frequencies, 400hz is suggested as typical, where the noise levels received by the sensor are thus much lower and, together with improved drive electronics, this makes them much less vulnerable to noise.

Some are successfully used on board ships for fuel metering to the engines where they have to survive the high vibration environment - the Marine approval tests are for quite high levels of noise - so I would suspect they are much less vulnerable to rig vibrations than previously.

We should also note that one of the key applications that have been targeted by some coriolis meter manufacturers are for well head multiphase metering where the major obstacle has not been noise but dealing with entrained gas.

I would suggest that there is good historical cause to be wary of noise in high noise/vibration environments equivalent to marine vessel enclosed machinery space, but it is well worth checking with the manufacturers.


Posted by Sam on 6 August, 2010 - 5:19 am
Hi again,

Thanks a lot, that was very interesting and helpful. I am a big fan of the Coriolis meter and this vibration issue was the only thing that prevented me from using it offshore.

The Coriolis meter in my opinion is so versatile that it can be used on just about any flow application so I was a bit disappointed when this issue about vibration offshore was brought up. Thanks again.


Posted by JMW on 7 August, 2010 - 2:53 pm
There are three companies that I know have been working on multi-phase and marine applications, and you might wish to consult these initially:
Endress & Hauser
Invensys
Emerson/Micromotion

Others may be in a similar situation with their development. Certainly there are others which appear able to manage the high vibration environment even if they have not addressed entrained air.

Evolution is much in evidence with coriolis meters.

I recall that the first coriolis was a single tube which required a substantial anti-vibration base which was its reference for the vibration of the tube.

Then came the concept of vibrating one tube against another which removed one vulnerability. In most coriolis flowmeters one tube is vibrated against a second parallel flow path tube.

Sadly, the two single tube meters I most liked are neither now available and both were taken off the market for the wrong reasons, in my opinion.

The first was the Solartron single straight tube meter.
This operated at 800-1200Hz, which gave it very high noise immunity, and used nodal masses hung on the tubes as the reference for the phase angle measurements and the other was the Exac which was formed into a double loop so that the two loops being vibrated against each other were successive loops of the same flow path, which overcame all the problems of low splitting. I don't recall its operating frequency.

I don't know the exact history here but I'd guess the original mass meters tended to be vibrated at mains frequency of 50-60Hzwhich is very vulnerable to noise, but I imagine it was with the interest in density they shifted to running at the resonant frequency which required more sophisticated electronics. We tend to forget that microprocessor based electronics have done a tremendous amount for most flow technologies. With the ability to bring some pretty impressive processing power to running meters the ability to overcome problems through signal processing is impressive.
I admit to guessing here, the move to higher frequencies could have been a separate development but the higher the frequency the greater the noise attenuation and the better the signal to noise ratio in the electronics. That plus more power, phase lock loop drive etc brings about mass meters operating with better noise immunity.

One great advantage of coriolis meters is that almost from the beginning they represented a very effective accurate and versatile meter able to handle applications other meters could not and which means that despite their high cost they have sold in substantial numbers. This has generated a lot of inward investment and they have continued to push the envelope.
As problems arise there has been plenty of incentive and finance to solve them.

Well head metering is an important application as multi-phase meters mean there is no need for settling tanks.

Multiphase meters have been and mostly are a complex of sensors allied together to deliver separate gas and oil accounting.
Usually some form of volumetric flow meter and a phase cut sensor e.g. radiation detection to sort out the gas and liquid phases for separate accounting.

The advantages of coriolis are thus obvious, a single sensor measuring mass flow and density. The major problems would seem to be to get the sensor to work with entrained gas and high vibration.

As ever with mass meters the objective is to maximise production of a common hardware platform.

This means that they can deliver very competitive prices in most critical applications.

At the sizes mentioned here, Coriolis probably has the price advantage.

In larger pipe sizes and where there is no entrained air, Ultrasonic meters may be very competitive for fiscal metering and it maybe one reason why coriolis meter manufacturers are keen on applications where they have a key discriminating advantage.
Well head metering would seem to be such an application because US meters don't handle air too well - at the moment, I should add - and the cost benefits of metering compared to separators would appear significant such that cost is not a major issue.


Posted by KN on 9 January, 2013 - 1:39 am
In addition to Endress and Hauser, Micromotion, Invensys, Rheonic(GE), khrone, Yokogawa also have coriolis.

But if you are measuring The crude oil flow from separator, maintain enough Liquid head, more than the pressure drop created across the meter. Do not have any other equipment to create more pressure drop at the upstream of the meter. The meter works well if installation is done properly.

Calculate the pressure drop at the maximum operating viscosity,and maximum flow rates.

Your use of this site is subject to the terms and conditions set forth under Legal Notices and the Privacy Policy. Please read those terms and conditions carefully. Subject to the rights expressly reserved to others under Legal Notices, the content of this site and the compilation thereof is © 1999-2014 Nerds in Control, LLC. All rights reserved.

Users of this site are benefiting from open source technologies, including PHP, MySQL and Apache. Be happy.


Fortune
Fine's Corollary:
Functionality breeds Contempt.
Advertise here
Advertisement
our advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive