×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

On-Line Viscometer- Anything New?

On-Line Viscometer- Anything New?

On-Line Viscometer- Anything New?

(OP)
Has anyone worked with on-line viscometers recently?

We are looking for viscometers that can be installed in a batch reactor.  We are not interested in the pump-around style.  Also looking for something that can detect Acid Number.

We've tried IR about 10 years ago and they did not work. Have they improved since then?

Our product is Polyester resin at temperatures up to 220 deg C.

RE: On-Line Viscometer- Anything New?

My own experience with direct process control of a viscosity spec has been dismal for the primary reason that the product spec is always at some specified temperature, which in general will not be the same as the processing temp. Use of the Andrade equation to project process viscosity on to a product specification has proved in-adequate on most occassions. If this is your situation, a pump-around sample conditioning system (i.e. to deliver a sample stream at spec temp) still offers the best general hope for something useful. As this is a type installation which you wish to avoid, there may not be any good options at this time.

Note sure what your objective is, but the temperature conditions of your reactor seem fairly challenging especially if this resin is a solid at cool reactor conditions. Best wishes in your search, sshep

RE: On-Line Viscometer- Anything New?

controlnovice
There was a thread here a while back, I can't find it, but on of the suggestions was to use mixer horsepower as a measure of the viscosity of the material.  They rigged their agitator to show amps.  From the amp readings they deduced the correct final product viscosity.  
Maybe that will help.  Maybe someone else can find that thread for you.

Goodluck
StoneCold

RE: On-Line Viscometer- Anything New?

(OP)
Thanks StoneCold,

We've looked into that.

Unfortunately, our Chem E likes to oversize the agitators, so from beginning to end of the batch, we see very little amperage change.  (Plus, you should really look at kW, not amps)

RE: On-Line Viscometer- Anything New?

(OP)
Has anyone worked with the (fairly) new Encoded Photometric infrared analyzers (EP-IR)?

RE: On-Line Viscometer- Anything New?

I think that for polyesther resins the technologies are usually referred to as MFI or Melt Flow Indicators. These are often little more than a capillary style viscometer but they are intended for use at the reactor temperature.

Viscosity temperature relationships are often a problem when it is quality that you are interested in (as opposed to behaviour where the viscosity at the flowing temperature is all you are interested in).
Quality measurement usually needs the viscosity at a reference temperature.

However, the point is to discriminate between a quality measurement for quality assurance and a quality measurement for process control.
For process control all you really need is a repeatable value. If you have control of the reaction at the optimum conditions then the MFI will give a consistent and repeatable reading. This is often easier to achieve in a continuous reaction process as when it is under control the temperature should also be relatively stable.

Periodically take samples for laboratory analysis to keep track of what your on line measurement means.

In some reactions this is not practicable. For example, in methyl methacrylate batch reactions the process is initiated with heat and then, as polymerisation advances, the reaction turns exothermic and temperature rise becomes exponential. In this type of reaction you are looking for the quench point and this may be a window of only 20 seconds in a two hour batch. Tank measurement solutions have been very successful here. It is not always possible to use equation related temperature viscosity curves. The alternative is a matrix solution where you calibrate the matrix using a combination of process and lab data. The Matrix is simply a number of curves each of which represents the temperature viscosity relationship of a particular quality (e.g. molecular weight) product. The line temperature and viscosity are then ratioed to these curves to find the viscosity at a reference temperature.

If the application requires that a sample loop is necessary then the benefits can often outway the costs. Good viscoity measurement can pay dividends in reduced re-wrok and tighter quality control.

JMW
www.ViscoAnalyser.com

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources