OFITE, 11302 Steeplecrest Dr., Houston, TX 77065 USA / Tel: 832-320-7300 / Fax: 713-880-9886 / www.ofite.com
5
Specifications
Instrument Geometry
True Couette Coaxial Cylinder
Motor Technology
Stepper
Motor Speeds
Variable: .01 – 1,000 RPM
Speed Accuracy
.001 RPM
Shear Rate Range
.01 – 1700 sec
-1
Automatic Tests
API Cementing and Mud Rheologies
Computer Requirements
DB-9 Serial Port, Windows 2000 or
XP. Recommended screen resolution
1024 × 768 pixels.
Rotor / Bob Specifications
Rotor Radius, RR, (cm)
1.8415
Bob Radius, RB, (cm)
1.7245
Bob Height, L, (cm)
3.8
Shear Gap, (cm)
0.117
R Ratio, RB/RR
0.9365
Maximum Shear Stress (Dyne/cm
2
)
1,680
Minimum Viscosity @600 RPM
<a>
(cP)
0.5
<b>
Maximum Viscosity @0.01 RPM
<c>
(cP)
10,000,000
Shear Rate Constant, KR, (sec
-1
per RPM)
1.7023
<a>
Lower viscosities can be measured by the HTHP Viscometer, however one must take into account the effect of bearing drag, Taylor vortices, zero
offset, etc. when looking at the expected accuracy of the reading
<b>
For practical purposes the minimum viscosity is limited to 0.5 cP due to Taylor Vortices
<c>
Maximum viscosity is based on Maximum Shear Stress and Minimum shear rate (RPM). However, due to practical and physical limitations, it may
be difficult to take these measurements.
There is considerable thermal lag within the test cell. The temperature
sensor sits inside the thermowell in the rotor. The test fluid surrounds
the sensor and the heaters surround the test fluid. It can take several
minutes for the heat from the heaters to reach the innermost portions of
the rotor. Therefore, the temperature reading in the ORCADA
®
software
always lags behind the actual temperature of the test fluid. Because
of this, OFITE recommends only changing temperatures in large
increments (greater than 50°F or 10°C). Making small adjustments to the
test temperature is unlikely to provide useful results.