Pumping of Chocolate 2

[finite]

I am involved in a project that requires the pumping of chocolate. I am looking for information regarding the pressure drops in pipes as well as pressure drops in fittings, such as bends, valves. I would like to know if anybody has some tips regarding the reticulation of chocolate?

Thanks

Finite

 

[CarlB]

Is this a Valentine's day joke? Assuming not,....
If you know the viscosity (which must vary a lot with temperature, and with each 'recipe') you can go to a Moody diagram and determine friction factor verses Froude number. Then apply standard hydraulics formulae. You may have to do some temperature/viscosity measurements. I don't have any experience along those lines, think I'l go grab a handfull of M&M's and cogitate.. and look up reticulate...

Cheers,
Carl

 

[butelja]

I've never dealt with chocolate, but I've read that it is strongly non-newtonian and temperature dependant in its rheologic behaviour. A book you may want to reference is at the following web site:

http://www.chipsbooks.com/rheolflu.htm

 

[svanels]

I also never dealt with chocolate but it looks like you wil need a positive displacement pump.

You can use an internal gear pump (viking) check out:

http://www.vikingpump.com/engineer/10steps.htm

for some useful engineering data.

From

http://www.pumpschool.com/liquidlist/index.htm#C

I got the following:
CHOCOLATE

Other Names: Bitter chocolate, sweet chocolate, milk chocolate, chocolate liquor, chocolate coating.

Viscosity: Varies widely from 2,000 cPs. to several thousand cPs. depending on type and process; also varies over normal temperature range of 38ºC to 93ºC / 100°F to 200°F. Chocolate viscosity is often expressed in degrees MacMichael. This is a standard viscosity unit of measure in the chocolate industry.

Or you can look for a progressive cavity pumps, the so called moyno pumps, I have seen pumping of peanut butter with a pcp.

http://www.moyno.com/moyno/main.html

Regards Steven van Els
SAvanEls@cq-link.sr

 

Chocolate is a yield pseudo-plastic, like a Bingham plastic, and so calculating the pressure drop and flow regime is a simple mater once the rheological parameters are known. These will be a function of chocolate condition and temperature. Bend losses etc. are more difficult in non-Newtonians like these but there is some sparse data in the literature.

Let me know if you need more help

Lionel.Pullum@bigpond.com

 

[Kirst]

Dear Finite:

Well, as some people has told in this forum there's a very explicit way to size a pump for any kind of fluid you are involved with. The case of pumping chocolate or cooca mass is not as particular as we can think. Chocolate is Bingham's type Fluid and below a shear stress it remains static. You've to give it a more powerful impulse to make it moving and can pump it. Data above in the others replys will help a lot. In adittion, when you calculate the size of a pump you need to know the inlet presssure of the fluid, the outlet pressure, the viscosity of the fluid, the debit (or flow rate) you need and the equivalent lenght of the line. This equivalent lenght is the sum of the real lenght of the piping line and de fittings. Each fitting has an equivalent lenght E.g. 90° elbow = 9 ft. How ever, you must look such equivalent into a Chemical Engineering Book or Manual as "Chemical Engineering Hand book". For some information of pumping curve you can visit "

http://www.gowcb.com",

they have a catalog of very good pumps.

That's all.

Best Regards.

Chris

 

[jmw]

Just one caution, in many of the chocolate plant installations I've seen, a 3" line ends up with a 1" diameter flow path. Why? because of a lack of good insulation which results in chocolate solidifying on the inside of the pipes.

One other point, chocolate is "tempered" by work. I'm not sure i recall the types of pumps used (it wasn't my field) but with fluids that are sensitive to work a low shear pump might be required e.g. a piston type. My info on this is sketchy so I'd ask around on this or wait for some more informed replies.


JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[katmar]

There was an article in the Brazilian Journal of Chemical Engineering that addresses very much the problem you want, although it was not specifically aimed at chocolate. It is available for download at

http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-66322003000400012&lng=en&nrm=iso

My own experience of designing for fittings in laminar flow is that using K values from Crane 410 just does not work. It is worth putting in the extra effort and using the 3-K (Darby) or 2-K (Hooper) methods. Using published equivalent length numbers is surprisingly more accurate than fixed K values.

As to the pump - speak to the suppliers and find one who can show you a case history of using his pump for chocolate. Do not try to re-invent the wheel here, there could be big problems.

regards
Katmar

 

[25362]

I went looking for degrees MacMichael ([sup]o[/sup]McM) and found these are arbitrary units to measure the viscosity, or "thickness", of chocolate. Typical values range from 60[sup]o[/sup]McM (very thin chocolates to be poured into molds) to around 190[sup]o[/sup]McM (very thick chocolates suitable for hand dipping or forming around a center). I didn't find any correlation with poises or stokes.

Measurements are made in Cuoette-type viscometers. These are viscometers in which the liquid whose viscosity is to be measured fills the space between to vertical coaxial cylinders, the inner one suspended by a torsion wire; the outer cylinder is rotated at a constant rate, and the resulting torque on the inner cylinder (or bob) is measured by the twist of the wire.

 

[jmw]

The Searle type is also used.
In the Searle type the inner bob rotates. In either type, the fixed element or the driven element can be on the torsion mounting according to manufacturer.

Some chocolate manufacturers produce their own viscometers, some with no outer sleeve.

Others are now using the new technologies such as the vibrating element sensors.

In many industries special units are used simply because of the technologies available. Today it is increasingly possible to correlate the measurement back to recognised units. As a consequence many older units of measurement are falling into disuse. Some persist even though now officially obsolete. e.g. Saybolt, Engler, Redwood.

The University of Ghent is conducting extensive research on chocolate technology. A search on their web site or an approach to the University may provide key data and recomendations.

JMW

http://www.viscoanalyser.com

Eng-Tips: Pro bono publico, by engineers, for engineers.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[stanier]

Go to this website and you can obtain the free book called Rheological Methods in Food Process Engineering.

The fluid is shear rate sensitive and the properties vary from increasing shear and decreasing shear. ie it is a dilitant fluid. Its propoerties vary in the time shear is applied and is thus described as thixotropic. These terms dilitant,thixotyropic, Bingham plastic and pseudo visco elastic are merely tags given by researches to describe the relationship between the material properties exhibited during a shear rate versus shear stress viscometry trial. Dont get too carried away with them. You have to do the lab work before you can give the properties a tag!


One sophisticated piece of equipment used for viscosity trials is the Weissenberg Rhegionometer. This can apply a shear stress at rates that are very low ie .00001s^-1. By measuring the shear stress at various shear rates one can cross plot each result to get the physical properties. At very low shear rates you can measure the yield stress effectively. Work by David Boger at Melbourne University is worth researching. ( He was awarded membership of the Academy of Sciences for his work in rheology)

As for pumping the stuff I used Mono progressive cavcity pumps. They do make a hygeinic unit. Pick a lrger slow running pump rather than the cheapest available. Keep the shear low. Make sure the piping is either heat traced or jacketted with hot water. By keeping the pipe wall surface at a temperature that will enable the fluid to flow you will avoid start up problems. The flow will effectively be plug flow. You may need an in line powered mixer to allow feed into other process equipment.

Avoid fast running gear or lobe pumps. Progressive lobe pumps run at low speed may be suitable but these have evolved since I left the food industry. Make sure the pump is jacketted or heat traced.

I have used these techniques to extrude chocolate onto biscuit bases, into ice cream etc.

http://www.egr.msu.edu/~steffe/freebook/STEFFE.pdf

 

[charmack]

I am the sales and operations manager for a Danish internal gear pump manufactory. We have for many years manufactured a special pump design for the pumping of chocolate. Chocolate as has been stated can be very troublesome to pump due to it being both heat and shear sensitive. Chocolate can “carmelize” within pump around the pump bearings and sealing device causing batch wastage. Key features of the pump to look for when selecting the right pump for your application are proper cut clearances and operating speeds in the range of 100 rpm. As for the system proper pipe sizing and the utilization of as few fittings as possible is the way to go.

 

[unclesyd]

You might want to try this website. I do know they have a pump that will pump a material that was very shear and heat sensitive.

http://www.discflo.com/index.html

 

[friartuck]

In the UK, we pump chocolate in pipe in pipe systems. The inner pipe contains the chocky and the outer (insulated) pipe contains warm water to keep the chocolate in a molten state. You might also try electrical heated tape wrappe around the pipe to keep it warm.

Once chocoltae solidifies however, I believe it becomes fit only for farm fodder.

drapes

 

[panelman]

friartuck, my wife say that chocolate is bad for farm animals but she would be pleased to dispose of any chocolate filled pipes you might need to get rid of

 

[finite]

thanks guys for all the help. the project is complete and a great success. the client now wants to extend the system by another 20%. The original system was, so I have been told, the longest chocolate piping system in the world. Once again thamks for the info

 

[cabalen]

Hi finite!

For the benefit of the doubt, maybe you could share to us the solution you have undertaken to this controversial, mouth watering subject matter "pumping of chocolate".

Cheers!