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E.Glycol WATER CONTENT 3
- Thread starter Monagas
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1
- #2
What is the expected range of water content and is it likely to be aerated or not?
JMW
JMW
- Thread starter
- #3
With no air, the range of options is better.
The solutions I am familiar with are based on measuring the density of the solution using vibrating elemenyt density meters.
These can be tube or fork style and can include those coriolis mass flow meters with a decent density measurement and suitable software.
The density variation with concentration allows for very good resolution.
The instrument measures the density and the temperature.
Using a suitable referral algorythm the density at a reference temperature is determined.
The simplest approach is to then assume the relationship between the concentration and base density is linear. This is fine if you are interested in a specific concentration as the assumption will be most accurate at this value.
The alternative approach is to use a calculation where the %mass of water in glycol is then found using the density of pure water and pure glycol.
If the range of concentrations is quite wide and the errors in these simple approaches are significant, the relationship between concentration and base density can be modelled using suitable equations. With some manufacturers these equations are available as standard.
In water glycol diluation schemes that do not involve recirculation e.g. de-icing fluids for aircraft, there is no entrained air problem. In pharmaceutical refirgeration plant, and similar, there may be a problem with entrained air due to the nature of the installation. If there is air in the water/ethylene glycol then the choices are more limited and some loss of accuracy will be incurred using vibrating element technologies e.g. the Mobrey Entrained Gas Amplifier version of the 7845 tube density meter.
You might investigate the ultrasonic density meters as an option though care would be required if there is entrained air.
Tube density meters can measure to within 0.1-0.2kg/m3 and fork types to 1.0kg/m3.
You may find some typical examples of this type of measurement by following the web link below (in the signature).
Manufacturers to consider:
PEEK (Thermo Electron); Emerson Micromotion; Mobrey (now another Emerson company); Khrone for vibrating element systems.
For ultrasonics, Cannongate, SensoTech Gmbh.
For ethylene glycol/water data visit To decide the best solution, determine what accuracy you require and wif you are making a tank measurement or a pipeline measurement.
JMW
The solutions I am familiar with are based on measuring the density of the solution using vibrating elemenyt density meters.
These can be tube or fork style and can include those coriolis mass flow meters with a decent density measurement and suitable software.
The density variation with concentration allows for very good resolution.
The instrument measures the density and the temperature.
Using a suitable referral algorythm the density at a reference temperature is determined.
The simplest approach is to then assume the relationship between the concentration and base density is linear. This is fine if you are interested in a specific concentration as the assumption will be most accurate at this value.
The alternative approach is to use a calculation where the %mass of water in glycol is then found using the density of pure water and pure glycol.
If the range of concentrations is quite wide and the errors in these simple approaches are significant, the relationship between concentration and base density can be modelled using suitable equations. With some manufacturers these equations are available as standard.
In water glycol diluation schemes that do not involve recirculation e.g. de-icing fluids for aircraft, there is no entrained air problem. In pharmaceutical refirgeration plant, and similar, there may be a problem with entrained air due to the nature of the installation. If there is air in the water/ethylene glycol then the choices are more limited and some loss of accuracy will be incurred using vibrating element technologies e.g. the Mobrey Entrained Gas Amplifier version of the 7845 tube density meter.
You might investigate the ultrasonic density meters as an option though care would be required if there is entrained air.
Tube density meters can measure to within 0.1-0.2kg/m3 and fork types to 1.0kg/m3.
You may find some typical examples of this type of measurement by following the web link below (in the signature).
Manufacturers to consider:
PEEK (Thermo Electron); Emerson Micromotion; Mobrey (now another Emerson company); Khrone for vibrating element systems.
For ultrasonics, Cannongate, SensoTech Gmbh.
For ethylene glycol/water data visit To decide the best solution, determine what accuracy you require and wif you are making a tank measurement or a pipeline measurement.
JMW
- Thread starter
- #5
Well pointed out StoneCold: refractive index may also be a solution.
There are two options available, reflection and transmission devices.
Can't say offhand what the differences are but these can also be added to the list of possible devices.
Transmission instruments from Katronic, reflection devices are far more common and suppliers can easily be found e.g. K-Patents.
With all devices, be sure there really are no bubbles.
JMW
There are two options available, reflection and transmission devices.
Can't say offhand what the differences are but these can also be added to the list of possible devices.
Transmission instruments from Katronic, reflection devices are far more common and suppliers can easily be found e.g. K-Patents.
With all devices, be sure there really are no bubbles.
JMW
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1
- #8
It all sounds rather high tech to me...does this need to be an on-line measurement? If so density (the curves for glycol vs temperature are well known) via coriolis flowmeter, or refractive index should work well. Off-line, the same measurements can be made at insignificant cost.
- Thread starter
- #9
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1
- #10
Hello,
For EG/water content measurement, most common and accurate is refractive index measurement. This is possible with refractometer installed in the small side stream, very accurate, with temperature compensation. Here can be mentioned that refractive index is very temperature dependent and instrument must be temperature compensated.
Refractive index and density are bot nonliner functions of temperature.
Preconditions are: glycol must be clean without turbidity-presents of particles and/or air bubbles.
If you using glycol from the sump of the distillation column this turbidity is always present and this kind of measurement is not possible. Please describe your process with more details.
For EG/water content measurement, most common and accurate is refractive index measurement. This is possible with refractometer installed in the small side stream, very accurate, with temperature compensation. Here can be mentioned that refractive index is very temperature dependent and instrument must be temperature compensated.
Refractive index and density are bot nonliner functions of temperature.
Preconditions are: glycol must be clean without turbidity-presents of particles and/or air bubbles.
If you using glycol from the sump of the distillation column this turbidity is always present and this kind of measurement is not possible. Please describe your process with more details.
- Thread starter
- #11
Thank you Mr Smiro. I like that.
We´re pumping from the EG surge tank that is located downstream of the column reboiler.
So you think that we must to install a kind of filter to avoid the turbidity, before the installation of the refractometer ?
Any recommendation will be appreciated
My best regards
We´re pumping from the EG surge tank that is located downstream of the column reboiler.
So you think that we must to install a kind of filter to avoid the turbidity, before the installation of the refractometer ?
Any recommendation will be appreciated
My best regards
A firm in Finland, K-patents, manufactures on-line refractive index meters (temperature compensated) that measures % concentration in water.
A recent installation revealed that the refractive index process head needed an option to keep it from filming over due to a very small percentagle (0.3%) of additives in the solution.
Works well.
A recent installation revealed that the refractive index process head needed an option to keep it from filming over due to a very small percentagle (0.3%) of additives in the solution.
Works well.
If you are thinking of the refractometer route, as Smiro suggest, then also consider a transmission refractometer as this is unaffected by bubbles or turbidity:
(Coating is a common problem for refractometers and to be investigated in this case.
Vibrating element density meters have a successful history with ethylene glycol solutions: PEEK and Mobrey both having success with single pass systems where there are no entrained gases
e.g. blending/ concentration control for aircraft de-icing,
But in pharmaceutical plant, where it is recirculated through the refrigeration plant and the concentration managed (to compensate for dilution due to steam/condensate leakage across valves at the reactor jackets when they swithc from heating to quenching the reaction) there is often significant aeration in the hot well and here the Mobrey vibrating tube EGA (Entrained Gas Amplifier)instrument is used.
This can handle up to 100% air and is used for such fluids as coffee excracts where 50% CO2 may be included prior to spray drying (to proivde the granulated texture).
As Smiro also suggests, temperature is a factor for refractometers and vibrating element transmitters; two influences to be considered:
1. the effect of temperature on the measurement which in the vibrating element densitometer is the effect of Youngs Modulus and which is factory calibrated
2. the effect on the density of the fluid. Usually the instrument will include alogoythms to convert between the density at the measurement temperature to the density at a reference temperature. Once this last is known then the concentration can be determined. The algorythm requires a knowledge of the temperature density relationship Vs concentration for the fluid. (see the Houghton Chemicals link above).
JMW
(Coating is a common problem for refractometers and to be investigated in this case.
Vibrating element density meters have a successful history with ethylene glycol solutions: PEEK and Mobrey both having success with single pass systems where there are no entrained gases
e.g. blending/ concentration control for aircraft de-icing,
But in pharmaceutical plant, where it is recirculated through the refrigeration plant and the concentration managed (to compensate for dilution due to steam/condensate leakage across valves at the reactor jackets when they swithc from heating to quenching the reaction) there is often significant aeration in the hot well and here the Mobrey vibrating tube EGA (Entrained Gas Amplifier)instrument is used.
This can handle up to 100% air and is used for such fluids as coffee excracts where 50% CO2 may be included prior to spray drying (to proivde the granulated texture).
As Smiro also suggests, temperature is a factor for refractometers and vibrating element transmitters; two influences to be considered:
1. the effect of temperature on the measurement which in the vibrating element densitometer is the effect of Youngs Modulus and which is factory calibrated
2. the effect on the density of the fluid. Usually the instrument will include alogoythms to convert between the density at the measurement temperature to the density at a reference temperature. Once this last is known then the concentration can be determined. The algorythm requires a knowledge of the temperature density relationship Vs concentration for the fluid. (see the Houghton Chemicals link above).
JMW
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