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John2014

Hi, We have a 1 tonne Paint mixing machine, what sort of test could I put onto the motor to measure the resistance of the stirrer as the product thickens up. At the moment we have to stop and open the machine to test the thickness. Would be great to just mix and have a gauge highlight when product is thick enough.
 
A clamp meter would indicate the viscosity at least to some degree although indirectly.
 
marvo is correct
monitoring current would tell you indirectly that the paint is thickening but may not be that accurate
failure of motor lubricant and bearing failure would also caused increased loading and current draw
viscosity and flow metering would be accurate in this case as trev has stated

this site has excellent equipment that may serve your purpose better
http://www.paclp.com/news_events/google/viscometers/?gclid=CIO13vzqhMECFSdk7Aod90MAxw
 
I concur,clamping it,would not be a reliable indicator of viscosity,as temperature of motor,gearing and paint,would all vary,making this a bit hit and miss. Just checked the link above,and apart from dipping a fid and counting drops...(what the old explosive manufacturers did...) it looks the way forward. Also,any method chosen would have to take into account any air entrainment or chemical reaction,to obtain the results required. :bow:
 
Aren't viscosity tests supposed to show this mate?
Yep, viscosity tests would be the most accurate but I don't know of any method that doesn't involve stopping the mixing process and taking a sample. Monitoring current wouldn't be as accurate because it's an indirect indication and there's other factors that have an effect on the run current as quite rightly pointed out above but it is a very cost effective solution that might be able to determine when the mixture is close to the required viscosity at which point less of the conventional tests might then be required.
 
If you have regular maintenance and a common load to the motor then a current monitoring relay should be suitable for your needs .. periodic checks will confirm reliablility and any adjustment needed for wear over the years for bearings etc ... I could easily provide a user adjustable preset that stops the motor as the product get to a certain thickness using a current relay or a VSD with current monitoring relay outputs, its all about the specifics of your requirements and no direct answer can be given but there is always a solution in my experience.

PS not negating any of the previous posts but we lack info and all posts relevent until more info.
 
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I've seen current (or phase angle) monitoring used in similar applications and it's been surprisingly accurate but I guess it would depend on the mechanical advantage arrangement etc. It would be easy to investigate though, it might even inadvertently be available if the machine has a VFD on the motor.
 
There’s only one reliable method when viscosity control is concerned. Constant flow monitoring.

If the OP sends me a PM I’ll put him in touch with a company that makes the gear.
 
Had a look into this earlier.
One method is monitoring the torque on the agitator motor, as the previous suggestions, but it's not very accurate.
There's a whole array of viscometers to choose from, but you'll need to get the professionals in to offer a solution (see Tony's post above).
And probably not cheap!!! If you're just small scale doing the occasional batch, stick with the manual sampling. :)
 

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