Mechanical Installation 7828 Density Transmitter Technical Manual
2-6 78285000_AB
2.2.2 VISCOSITY EFFECTS
The 7828 can be affected by the viscosity of the fluid surrounding it. This is manifested in
two ways:
1. An error in the density measurement, due to the effect of viscosity on the vibration of
the fork tines;
2. In T-piece installations, where the 7828 is retracted into a pocket away from the main
fluid flow, high viscosity impedes the flushing of fluid near the tines. This may mean
that, if a step change in density occurs, the fluid being measured will not representative
of the fluid in the main flow, and the density response time may be extended
significantly.
A summary of these effects and the action to be taken to minimise them is given below:
Viscosity range Remedy
T-piece installations only:
Less than 100cP:
Greater than 100cP:
1
None required
Density measurements may be unpredictable; use
flow-through chamber or free stream installation
All other installations:
Up to 500cP
None required
500 to 20,000cP steady: Perform simple on-site calibration to derive density
offset adjustment (see Calibration section)
500 to 20,000cP variable:
- where changes in density
and viscosity are correlated:
- where there is little or no
correlation between viscosity
and density:
Perform three-point on-site calibration to derive
revised K0, K1 and K2 factors - consult Solartron
Consult Solartron for advice.
Above 20,000cP Density measurements may be unpredictable
1
Where the main flow is greater than 1.5m/s and there is no waxing present, the T-piece
installation can be used for viscosities not exceeding 250cP.
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