BAKER HUGHES - Drilling Fluids Reference Manual

Hydraulics
Determination of PV and YP
The commonly used V-G (viscosity-gel) meter, or direct indicator viscometer, was specifically
designed to facilitate the use of the Bingham Plastic Model in conjunction with drilling fluids in the
field. The instrument has a torsion spring-loaded bob which gives a dial reading proportional to
torque and analogous to the shear stress. The speed of rotation (rpm) is analogous to the shear rate.
When the V-G meter (with the proper rotor, bob, and spring) is used, the dial reading is determined
as:
where,
θ = YP + PV⎛
-------- ω ⎞
⎝ 300 ⎠
θ = dial reading
YP = yield point
PV = plastic viscosity
ώ = rotation speed (rpm)
Figure 1-9
Fann Model 35A 6 Speed V-G Meter
Reference Manual
Baker Hughes Drilling Fluids
1-14 Revised 2006