Rice Lake Z6 Single-Ended Beam, SS Welded-seal, IP67, OIML C3 - Manual (Page 46)

42 Load Cell and Weigh Module Handbook
Example 2
T h e v e s s e l s h o w n i n F i g u re 2 0 - 4 h a s t h e f o l l o w i n g
characteristics:
• 40,000lb live load
• Mounted on 4 each 20,000lb single-ended beams
with full scale deflections of .010"
• Structure deflection of .375"
• Accuracy requirement of 0.5%
• Material is stainless steel throughout
Figure 20-4.
1. Determine allowable F value from equation 2,
F ≤ .1 x system accuracy (%) x live load (lb)
F ≤ .1 x 0.5 x 40,000
≤ 2,000 lb
The sum of all vertical pipe forces must be less than
or equal to 2,000lb.
2. Determine total deflection. Since the live load
represents only ½ of the load cell capacity, the load
cell deflection will be
.010
____ = .005"
2
Total deflection Δh = load cell deflection + structure
deflection
= .005 + .375
= .380"
3. Determine F
X
for each pipe using the formula:
4. Determine F using the formula: F = F1 + F2 + F3 +
F4
F = 1,029 + 391 + 648 + 239 = 2,307 lb
Since F calculated for the vessel is greater than the value
determined in Step 1, this is not acceptable. There are several
solutions.
• 1) Accept a lower accuracy (perhaps 1%, instead of
.5%).
• Reduce the deflection of the support structure.
• Improve the piping by:
•
using smaller, lighter pipes
• use flexible hose or bellows
• increase the distance to the first pipe support
points
If we apply 3 above to this vessel then we would focus our
attention on the main offender, pipe 1. The problem can be
solved simply by increasing the distance to the first support
from 72" to 82", yielding an F1 = 697lb. Hence, F = 697 + 391
+ 648 + 239 = 1,975lb.
This is less than 2,000lb, so the design is now acceptable.
20.3 Vessel Restraint Systems
While many of the mounting arrangements offered by Rice Lake
Weighing Systems are self checking, there are situations
where additional vessel restraints may be required to steady a
vessel subjected to constant vibration, or to restrain a vessel
from toppling or falling in the event of some unforeseen
circumstance. Two main types of restraint systems are stay
rods and check rods.
F
X
=
.59(D 4 – d 4 ) x (Dh) x E
l
3
60"
36"
72"
84"
2" Schedule 10S
3" Schedule 40
3" Schedule 40 Pipe 1
1" Schedule 40
Pipe 3
Pipe 4
Pipe 2
F
1
=
.59(3.50 4 – 3.07 4 ) x .380 x 28,000,000
72
3
= 1,029lb
F
2
=
.59(2.375 4 – 2.07 4 ) x .380 x
28,000,000
60
3
= 391lb
F
3
=
.59(3.50
4
– 3.07
4
) x .380 x 28,000,000
84
3
= 648lb
F
4
=
.59(1.315
4
– 1.049
4
) x .380 x 28,000,000
36 3
= 239lb