Kistler-Morse KM Weigh II - Manual (Page 112)

Appendix G. Calculation of Maunal Calibration Parameters
G-2
You will use the value you just obtained from
the Weigh II in the calculation of the pre-
calibration parameters. Calculation of the
parameters is dependent on the type of
sensor(s) on the vessel. Procedures for
calculation of the manual calibration values
are given below for the following sensor types:
• Bolt-on sensors (L-Cells and Microcells)
• Direct Support Sensors (Load Stands,
Load Discs, and Load Links)
Bolt-On Sensors
Note
In this procedure, you will need to use
the value for Cnts/mV that you
obtained from the Weigh II above.
The calculation of the parameters for perform-
ing a pre-calibration follows:
1. From your sensor manual/data sheet, write
down the sensor sensitivity (S) applicable
to your sensor. The sensor sensitivity has
units of mV/psi.
2. Summarized in Table G-1 are the stress
equations for skirt-supported, leg-sup-
ported, and beam-supported vessels. See
your sensor manual for a thorough expla-
nation of the terms in the equations.
3. Write down an estimate of the current live
load in the vessel, and call it ‘EstLL.’
4. Write down the maximum live load for the
vessel, and call it ‘MaxLL.’
5. Calculate the values for the
pre-calibration:
Scale Factor Weight = MaxLL
Scale Factor Counts
= S x Cnts/mV x MaxLL ÷ A(in
2 )
Setting Zero = EstLL
Note
The Scale Factor Weight and Scale
Factor Counts are input in the Manual
Menu, while the Setting Zero value is
input in the Auto Menu.
Example: You are using L-Cells to monitor a
15’ diameter skirt-supported vessel with
0.187” wall thickness. You estimate that the
vessel currently has 50,000 lbs of material in
it. The vessel can hold a maximum of
200,000 lbs. You go to the Disply submenu in
the Manual calibration menu and write down
the Cnts/mV — 699.05. Following the
procedure for pre-calibration:
1. S = 35 mV/1000 psi (from L-Cell manual)
Stress (psi) =
Live Load (lbs)
Leg-Supported Vessel:
Stress (psi) =
Live Load (lbs)
Beam-Supported Vessel:
= MaxLL (lbs)
Table G-1. Bolt-On Sensor Stress Calculations
Compression Area (in. 2 ) x # of legs
2 x shear area (in. 2 ) x # of supports
MaxLL (lbs)
Stress (psi) =
Live Load (lbs)
Skirt-Supported Vessel (without spars or columns):
=
3.14 x diameter (ft) x 12 in./ft x skirt thickness (in.) A (in. 2 )
=
MaxLL (lbs)
A (in. 2 )
A (in. 2 )