Brookfield DV2+Pro Viscometer Manuel d'utilisateur télécharger pdf (Page 61)

Brookeld Engineering Labs., Inc. Page 61 Manual No. M03-165-F0612

An Example of the Bingham Model at Work

A manufacturer of drilling uid applies the

Bingham Model to ensure the quality of their

product. Results from a recent batch, shown

in Figure VI-3, showed that the yield stress

and plastic viscosity were both below the

pass/failcriteria,whichwouldcausetheuid

to insufciently hold-up the cuttings.  The

shipment was cancelled and the root-cause of

theproblemwasidentied.

Drilling Fluid

Plastic Viscosity (

h) = 6621 cP

Yield Stress (

) = 166.4 dynes/cm

V1.3.4 The Casson Model

τ=

+ hD

√ √

√

( τ=shearstress,

=yieldstress,h =plasticviscosity,and D =shearrate)

What does it tell you?

The Casson model provides parameters similar to that of the Bingham model. However, unlike

theBinghammodel,itwasdevelopedformaterialsthatexhibitnon-Newtonianowafteryielding.

TheCassonmodelindicatestheproduct’syieldstress(

) which is the amount of shear stress

requiredtoinitiateow,andtheproduct’splasticviscosity,n,whichistheviscosityoftheproduct

after it yields.

Figure V1-17

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Brookfield DV2+Pro Viscometer Manuel d'utilisateur Page 61