Rice Lake Weigh Modules/Mount Assemblies - Manual (Page 15)

1-13
SYSTEM DESIGN Thermal Expansion
144.0"
84.0"
Figure 1-21
Vessels with attached piping can be subjected to severe side forces
as a result of temperature variations if the connections are not
executed properly. It is worth noting that vessels expand and
contract vertically as well as horizontally with changes in tempera-
ture. Rigidly-attached piping may magnify the effects of this
expansion, as seen in Figure 1-23. See Attaching Piping to Weigh
Vessels in Section 3 for detailed guidelines on this subject.
Figure 1-23
If the vessel is made from mild steel, the length will vary by ± .028"
(6.5 x 10 -6 x 144 x 30), and the width will vary by
±
.016"
(6.5 x 10 -6 x 84 x 30) as the temperature fluctuates by
±
30
°
F. It will
be apparent that if the load cell is held rigidly by the mount,
enormous side forces will be applied to the cell, hence the need to
use a mount which can accommodate vessel expansion/contrac-
tion due to changes in temperature.
In the case of a cylindrical vessel, the change in diameter (
∆
D)
resulting from a change in temperature (
∆
T) is given by:
∆
D = a x D x
∆
T
D
Example:
If a cylindrical vessel is 96" in diameter and made from 304
stainless steel and is subjected to a temperature rise of 80
°
F
as the result of being filled with a hot liquid, then the diameter
will increase by:
∆
D = 9.6 x 10 -6 x 96 x 80
= .074"
Figure 1-22