Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 45)

Attaching Piping to Weigh Vessels 41
Figure 20-3.
From the above information:
Δh = .008" + .250" = .258"
E(steel) = 29,000,000
For schedule 40 pipe, D = 4.50, d = 4.03
l = 36"
hence:
.59(4.50
4
–4.03
4
) x .258 x 29,000,000
F1 = ________________________________
36
3
= 13,840 lb.
The first line of Table 20-2 (Example 1) summarizes the above
result. The other lines (Examples 2–5) represent the result
when one parameter is changed. The last column on the right
expresses the % change in F1 relative to Example 1 (13,840
lb).
Example 2 shows the effect of doubling the length of pipe
between the vessel and first support point. The 87% reduction
shows that F1 can be greatly decreased by increasing the
distance to the first support point.
Example 3 shows the effect of cutting the structural deflection
in half from .250" to .125" (the load cell deflection of .008"
remains the same). It is obvious from the 48% reduction in
Table 20-2 that F1 can be moderately decreased by reducing
the vessel’s deflection.
Example 4 shows the effect of using a lighter-wall schedule
10S pipe instead of schedule 40.
Example 5 shows the effect of reducing the size of the pipe
from 4" schedule 40, to 2" schedule 40. From the large 93%
reduction, it is clear why you should always use the smallest
diameter pipe suitable for the application.
These and other Do’s and Don’ts are summarized in
Section 20.2 on page 38. Note that while the emphasis here
is on attached piping, these recommendations apply equally
to attached electrical conduit and cables.
If several pipes are attached to a vessel, the vertical force
exerted on the vessel can be calculated for each individually,
as described above, then added together to get the total force
F acting vertically on the vessel. That is:
F = F1 + F2 + F3 …
where F1 is the force exerted by pipe 1, F2 the force exerted
by pipe 2, etc.
Accepted practice in the scale industry for ensuring that
piping does not adversely affect the required accuracy is to
ensure that the following relationship is satisfied:
F ≤ .1 x system accuracy (in%) x live load (lb)
For example, if a vessel’s live load is 50,000 lb and a system
accuracy of .25% is required, then
F ≤ .1 x .25 x 50,000
F ≤ 1,250lb.
i.e., the sum of all vertical pipe forces must be less than or
equal to 1,250lb.
* For 4” Schedule 10S, D=4.50, d=4.26; †For 2” Schedule 40, D=2.38; d=2.16
36'
Example Pipe Pipe Length (l) Deflection (Δh) Upward Force (F1) Percentage Reduction in (F1)
1 4” schedule 40 36” .258 13,840
2 4” schedule 40 72” .258 1,730 87%
3 4” schedule 40 36” .133 7,130 48%
4 4” schedule 10S* 36” .258 7,630 45%
5 2” schedule 40 † 36” .258 976 93%
Table 20-2.