Current through Register Vol. 49, No. 6, March 15, 2024
PURPOSE: This rule covers installation requirements
for pitless scales.
(1) This
rule shall apply to the installation of vehicle, axle-load and livestock scales
of pit-less full electronic or mechanical and self-contained electronic or
mechanical design being installed in one (1) permanent location for more than
one hundred eighty (180) days.
(A) A pitless
scale may be installed in a pit; however, all pit requirements of
2 CSR
90-21.030 must be met.
(2) All scales represented as complying with
this rule shall meet all of the standards specified and all applicable
specifications and performance requirements of the current edition of
National Institute of Standards and Technology (NIST) Handbook 44,
Specifications, Tolerances, and Other Technical Requirements for Weighing and
Measuring Devices.
(3)
Whenever the provisions of this rule call for the use of reinforced concrete,
the concrete shall be of grade and reinforced in the manner consistent with the
guidelines established by the American Concrete Institute.
(4) A suitable foundation must be provided
for the scale to rest on. This foundation should meet the following minimum
requirements:
(A) Adequate bearing area to
match piers to existing soil bearing capabilities stabilized at the desired
grade (elevation) to support at least three thousand (3000) pounds per square
foot in pier locations;
(B) The
scale foundations installer shall be responsible for determining whether or not
soil characteristics meet the requirements of subsections (4)(A) for a
particular design, by employing a penetrometer or plate-bearing test using
proper American Society of Testing and Materials (ASTM) guidelines. If soil
conditions do not meet those requirements, the installer shall notify the
owner; and the owner shall arrange for spread footing design modifications to
suit the existing soil conditions;
(C) The scale may be installed above the
ground; however, the installation should be such that surface water will drain
away from the scale area; and
(D)
Access to critical scale parts must be provided to permit proper inspection,
servicing and cleaning.
(5) Piers.
(A) Piers shall be of reinforced concrete
poured to the depth of the local frost line but not less than three feet
(3').
(B) All piers must be
interlocked by a solid reinforced concrete slab with a minimum thickness of six
inches (6"). This slab may be below the top of the piers to promote access and
cleanout; or by reinforced concrete sides with a minimum thickness of twelve
inches (12") and the same depth as the piers in which case the horizontal area
between the piers will be of concrete with a minimum thickness of three inches
(3"), not necessarily tied to the piers or in the same plan, to promote
cleanliness.
(C) Piers must support
the combined loads applied by the weight of the scale, the weighbridge, plus
the maximum anticipated load on the scale and must distribute these loads
evenly over the underlying ground so that any settlement of the structure shall
be as little as possible and that settlement shall be uniform throughout the
structure.
(D) Reinforcing should
extend the entire width of the piers and be of a minimum schedule consistent
with the American Concrete Guidelines.
(E) Anchor bolts for check stands and load
cell stands shall be of the embedded type or thunderstuds if installed in
accordance with good engineering practice to assure that those working parts of
the scale remain securely anchored during normal and reasonable use of the
scale.
(6) On scales
with a mechanical indicating element, the element shall be mounted on a firm
foundation which is adequate to prevent deflection or vibration.
(7) Approaches to Pit Type Scales.
(A) Vehicle Scales. On the entrance and exit
ends of a vehicle scale there shall be a straight approach a) the width at
least the width of the platform, b) the length at least one-half (1/2) the
length of the platform but not required to be more than forty feet (40'), and
c) not less than ten feet (10') of any approach adjacent to the platform shall
be constructed of concrete or similar durable material to ensure that this
portion remains smooth and level and in the same plane as the platform.
However, grating of sufficient strength to withstand all loads equal to the
concentrated load capacity of the scale may be installed in this portion. Any
slope in the remaining portion of the approach shall ensure ease of vehicle
access, ease for testing purposes, and drainage away from the scale.
(B) Axle-Load Scales. At each end of an
axle-load scale there shall be a straight paved approach in the same plane as
the platform.
The approaches shall be the same width as the platform and of
sufficient length to insure the level positioning of vehicles during weight
determinations.
(C)
Livestock Scales. Approaches shall be of reinforced concrete. On at least one
(1) entrance there shall be a ten-foot (10') approach at least as wide as the
gate with a minimum gate width of four and one-half feet (4 1/2'), accessible
for movement of test weights to the scale platform. This approach may be on an
incline from the scale platform, but not such that would hamper the movement of
test weights onto the scale platform.
1.
Livestock scales installed prior to July 1, 1998, shall be exempt from the
requirements of subsection (7)(C) of this rule.
(D) Railroad Track Scales. Approach rails
must be installed in accordance with requirements as outlined in the
AAR Scale Handbook.
(8) The lever fulcrum stands or load cell
stands shall be so designed, constructed and installed that under any practical
conditions of loading, the resultant force through the bearings or load cell(s)
will fall within the middle third of the length and width of the
base.
(9) Means shall be provided
to restrict motion of the weighbridge or platform, not to exceed one-quarter
inch (1/4") in any horizontal direction unless the manufacturer proves this
unnecessary for a particular design.
(10) Electronic, hydraulic and mechanical
indicating elements, where used, shall be installed in a location and in a
manner to assure continuous accurate performance under all ambient
conditions.
(11) Load cells
employed in vehicle scales shall meet the following minimum standards.
(A) The output characteristics of the load
cells shall be such that they will not cause the systems performance to vary
beyond allowable tolerances; and
(B) Each individual load cell shall be
capable of withstanding loads equal to one hundred fifty percent (150%) of its
rated capacity without change in span calibration. Each load cell support
structure shall be capable of withstanding loads equal to three hundred percent
(300%) of the rated capacity of the cell without physical failure of the
structure.
(12) All
cabling between load cells, junction boxes and electronic instrumentation shall
be shielded and grounded as recommended by the original scale manufacturer. The
ground shall be a copper clad rod which, whenever possible, shall be driven to
a depth of the water table. Connection between the ground rod and the common
ground points of the system shall be made with heavy copper wire of No. 10
gauge or larger. All cables shall be insulated with materials having good
nonhygroscopic qualities and stable capacitance between conductors. All cable
connections, as well as the cell itself, shall be properly protected against
moisture penetration. Load cell cables physically shall be separated from power
cables and never shall be run in the same conduit.
(13) The power source for the electronic
instrumentation shall be free from harmonics and electrical noise transients.
(A) The power source shall be on a separate
circuit back to the distribution transformer with no other loads connected,
unless it can be demonstrated that the other live loads will not affect the
accuracy of the instrumentation.
(B) One (1) side of the power source should
be at ground potential.
(14) Individual requirements of sections (12)
and (13) may be waived if the manufacturer or installer demonstrates other
means of providing adequate protection against moisture, radio frequency
interference (R.F.I.), lightning and power surges.
(15) Pitless scales installed prior to April
11, 1985, shall be exempted from the requirements of this rule.
(16) Requirements of section
413.175,
RSMo must be met prior to the actual installation of devices covered in this
rule. Following installation, any device covered in this rule must be
calibrated and placed in service by a registered Missouri scale serviceman or
officially examined by Missouri Weights and Measures Division before the device
can be used in commercial service.
(17) If any provision of these rules is
declared invalid, the validity of the remainder of these rules shall not be
affected.
*Original authority: 413.065, RSMo 1983, amended 1993,
1994, 1995.
