Rice Lake Combination System - Precision Loads On-Board Weighing Systems - Manual (Page 62)

58 Precision Loads On-Board Weighing Installation & Service Manual
6.0 Appendix
6.1 Bolt Torque Values
For secure and accurate scale system operation, ensure that all load sensor mounting bolts and locating bolts are
correctly tightened to torque specifications. Torque values can vary significantly depending on the lubrication of
the bolt threads. The following values shown are based on clean, new threads in as received condition, without
additional lubrication. Rice Lake Weighing Systems recommends the use of a thread lubricant such as Loctite 767
or equivalent to prevent the seizing of threads over a long period of time. If replacing any load sensor bolts, use
only plated SAE Grade 8 (or ISO/DIN 10.9) specification bolts and Grade C lock nuts. Use only new bolts and lock
nuts.
Table 6-1. Load Sensor Locating and Mounting Bolts
Bolt Size Part Number
Required
Torque
1-1/4" -12UNF x 2.50L PL9000-13C 1000 lb fft 1355 Nm
1-1/8" -12UNF x 3.25L PL9000-26C 1000 lb fft 1355 Nm
1" -14UNF x 1.50L PL9000-22A 760-840 lb fft 1085 Nm
1" -14UNF x 2.00L PL9000-22C 760-840 lb fft 1085 Nm
1" -14UNF x 4.50L PL9000-22D 760-840 lb fft 1085 Nm
3/4" -16UNF x 1.50L PL9000-17C 380-420 lb fft 542 Nm
3/4" -16UNF x 2.00L PL9000-17D 380-420 lb fft 542 Nm
Bolts for Spring Mounts Tighten Spring Bolts so that each Body Spring is
compressed by approximately 1/4 inch (7 mm)
Note
For Model PL9000-13 and PL9000-22 load cells, it is important to be cautious for the possibility of bolts being
bottomed-out in the load cell "ears". These model load cells, and models of other manufacturers, have "ears"
which extend the bolting surface out over the main beam of the load cell body, and if bolts in these ear
sections bottom-out onto the main beam of the cell, mechanical bending will be restricted, resulting in poor weighing
results and possible damage to the cell. Use a flat blade tool to slide into the slotted area of each load cell ear to make
sure there is at least 1/8" (3 mm) gap between the main beam and the bottom of the load cell bolt.
Bolt thread depth. The installer must always ensure that there is both sufficient thread depth of all bolts which screw into
load cells and bearing plates, and ALSO that these bolts cannot bottom out in the load cell or bearing plate. Sufficient
thread depth is achieved when the depth of the bolt into the load cell or bearing plate threaded holes is equal to or greater
than the diameter of the bolt.
A bolt which bottoms-out in a load cell or bearing plate is too long and will result in a hazardous operating
condition. Also, when mounting load cell models with "ears", the installer must ensure that bolts threaded into the
ears cannot bottom out against the load cell body under any condition, as this will affect both accuracy and safety
of the installation.
In order to minimize the potential for these hazards, the following precautionary steps should be taken. It must be
noted that the sole responsibility to ensure these measures are strictly controlled at all times remains with the
installer.
Measure the thickness of the bracket/trunnion material, and add the thickness of the washer (typically 0.125" or 3.5
mm), and nominal thread depth of 0.875" (22 mm). Subtract the length of the bolt. Any length exceeding the above
sum may result in bottoming out of the bolt and a hazardous operating condition. Any length less than this sum
may not provide sufficient thread engagement.
Note
Standard bolt sizes for the 1"-14THD bolts used with PL9000-22 load cells are 1.50" Long (33mm), 2.00" Long
(51mm) and 2.50" Long (64mm). Other length requirements may necessitate custom-sized bolt lengths.
6.2 Spring Bolt Mountings
The mounting of on-board load cells in rigid straight truck applications such as refuse packer bodies, rigid tanker
mounts, etc. typically require the installer to provide stress relief of the body in the load cell installation. Stress
relief is necessary in preventing possible damage to the body or other structural members. For these applications,
RLWS provides specifically-manufactured body coil springs and extended bolts, in two types, depending on the
model of load cell being used.