STP 219-10
Standard Test
Procedures Manual
1.
Section:
MISCELLANEOUS PROCEDURES
Subject:
PORTABLE SCALE INSPECTION
SCOPE
1.1.
Description of Test
This test method describes the procedure for inspecting a contractor’s portable scale to
ensure its accuracy.
1.2.
Application of Test
The ministry staff will inspect the scale and confirm that the scale is functioning within
the tolerances outlined in this test procedure.
The annual certification shall be arranged by the contractor to be performed by private
scale inspectors using the 10 tonne method.
For inspection/check tests, the Contractor will supply two (2) tonnes of approved test
weights.
1.3.
Definitions
Scale house – the building that houses the indicating elements of the scale and serves as
the scale operator's office.
Scale platform – the load receiving platform.
Beam stand – the stand on which all the indicating elements of the scale are mounted.
Weigh beam – the main beam whose motion denotes the balance condition of the scale.
Steel yard connecting rod – the rod that connects the weigh beam to a system of levers
and to which the scale platform is mounted.
Pivots and bearings – support the weigh beam on the beam stand and the scale platform
onto a system of levers.
Date: 2011 02 01
Page: 1 of 8
Standard Test Procedures Manual
Section:
STP 219-10
Subject:
MISCELLANEOUS PROCEDURES
PORTABLE SCALE INSPECTION
Poises – weights which, when properly manipulated on the weigh beam will indicate the
weight of the load applied to the scale platform.
Balancing ball – an adjustable weight which is used to make fine adjustment to bring the
weigh beam to a balance condition.
Counter balance hanger – large weights, when applied, bring the weigh beam to a balance
condition.
Antifriction plates – used to limit the side play or movement of the pivots on their
bearings.
Bumper bolts – used to limit the horizontal displacement in any direction of the scale
platform.
Trig loop – used to indicate the amount of movement or oscillation of the weigh beam
above and below a balanced condition.
2.
APPARATUS AND MATERIALS
2.1. Scale House
The scale house must be weather proof and be equipped with adequate lighting, heating,
hand rails, safe steps, a door exiting away from the platform and an unobstructed view of
the scale.
3.
PROCEDURE
3.1. Inspection List
Ensure the certification sticker date is less than one year old.
Scale
Component
Beam Stand
Steel Yard
Connecting Rod
Date: 2011 02 01
Inspection List
Ensure the beam stand is rigidly
supported to prevent deflections
when a loaded vehicle drives onto
the scale platform.
Ensure the rod is plumb and has
ample clearance to avoid friction
where it passes through the scale
house floor.
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Standard Test Procedures Manual
Section:
STP 219-10
Subject:
MISCELLANEOUS PROCEDURES
Weigh Beam
Balancing Ball
Counter Balance
Hanger
Scale Platform
Scale Pit
Date: 2011 02 01
PORTABLE SCALE INSPECTION
Inspect pivots and bearing for
cleanliness, wear and freedom
from rust.
Inspect missing anti-friction
plates or dust caps.
Check the beam notches for
cleanliness and wear.
Check the weight indication for
legibility.
Ensure that the poise latch is
positively engaged in the beam.
Ensure the ball is secured in
position when the beam is
brought to a balanced condition.
Ensure the hangers have no loose
material or easily removable
weights hanging on them.
Ensure the platform has a free
floating movement with ample
clearance at the ends and sides.
Ensure the platform is structurally
sound and does not allow
displaced material from falling
into pit and packing about the
moving parts.
Ensure the end walls or
abutments are adequately
supported to prevent binding of
the platform.
Ensure the approach ramps are
straight and level for at least the
length of the longest vehicle to be
weighed.
Ensure the platform is cleared of
any debris or foreign matter that
might adhere to the test weights
or otherwise be removed during
the tests.
Ensure the scale supports have
stable soil condition to withstand
the pressures when a load is being
weighed.
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Standard Test Procedures Manual
Section:
STP 219-10
Subject:
MISCELLANEOUS PROCEDURES
Lever System
Bumper Bolts
3.2.
PORTABLE SCALE INSPECTION
Ensure the foundation is stable to
ensure the scale remains level at
all times.
Ensure adequate drainage of the
pit.
Examine the levers for alignment,
binding, plumb and condition.
Ensure proper clearance and
alignment of the bumper bolts.
Zero Balance Test
Procedure
Place all poises at their zero
indications.
Bring the beam to balance using
only the balancing ball or by
applying weights to the counter
balance hanger.
The beam will be in a balance
state when it comes to rest at a
point midway in the trig loop.
3.3.
Limits of Error
0.2% of the known test load or
one minimum scale graduation
whichever is greater.
Load Discrimination (Sensitivity) Test
Procedure
The scale is zero balanced with
zero load on platform.
Apply a known weight to the
platform. The weight must not be
greater than (a) one half the
in-service limit of error of the
scale at capacity of the scale or
(b) twice the finest weigh beam
graduation, whichever is less to
cause the beam to move from a
position of zero balance to a
position of rest at the limits of its
travel. E.g.: a scale of 50 000
kilograms capacity with a
Date: 2011 02 01
Limits of Error
2 minimum graduations on
weigh beam or 0.2% of scale
capacity whichever is less.
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Standard Test Procedures Manual
Section:
STP 219-10
Subject:
MISCELLANEOUS PROCEDURES
PORTABLE SCALE INSPECTION
minimum graduation of 5
kilograms would be required to
be sensitive to 10 kilograms.
3.4.
Preliminary Two Section Scale Test
Procedure
A loaded vehicle whose gross
weight is at least half the scale
capacity is driven onto the
platform; with the front wheels
located over the main bearings at
the opposite end.
The load is balanced out by the
poises and the indication noted.
Remove the vehicle.
Return all poises to zero.
Note and correct any change
from a zero balanced condition.
Any change to zero balance
greater than 0.1% is evidence of a
malfunction in the lever system
or a faulty installation.
Reverse vehicle and drive onto
platform.
Note the weight indication.
3.5.
Limits of Error
0.2% of the average indicated
weight. E.g.: If the average of
indicated weights was 25 000
kilograms then a difference
greater than 50 kilograms
would not be allowed.
Preliminary Four Section Scale Test
Procedure
Follow the same procedure
described for the two section
scale test except that the loaded
vehicle will be driven onto the
scale platform from the opposite
direction with the rear axle
centered over each section or pair
of main bearings in turn.
Date: 2011 02 01
Limits of Error
Apply the same limits
described for the two section
scale test.
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Standard Test Procedures Manual
Section:
STP 219-10
Subject:
MISCELLANEOUS PROCEDURES
3.6.
Weight Test
Procedure
Zero balance the scale.
Apply the 2 000 kg test weights.
Record readings as weight is
applied until all weights are
applied.
3.7.
PORTABLE SCALE INSPECTION
Limits of Error
0.2% of applied test weight or
one minimum scale gradation
whichever is greater.
Strain Test
Procedure
A loaded vehicle with a load
value of at least the maximum
load ordinarily weighed on the
scale is required for the strain
test.
Place the loaded vehicle on the
scale.
Carefully weigh and record
reading.
Place all available test weights
evenly over the remainder of the
platform in 500 kilogram
increments.
Record readings as weights are
placed on the platform.
Test for load discrimination
under full load by adding or
removing small weights. The
same rule applies as at zero load.
While the scale is under load,
check as many poise
combinations as possible to
indicate the weight. Watch for
notches that appear to be worn.
Remove weights and vehicle.
Check zero balance once again.
Date: 2011 02 01
Limits of Error
0.2% of known test load or one
scale graduation whichever is
the greater.
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Standard Test Procedures Manual
Section:
MISCELLANEOUS PROCEDURES
4.
STP 219-10
Subject:
PORTABLE SCALE INSPECTION
RESULTS AND CALCULATIONS
4.1. Report of Results
Complete the entire Scale Accuracy Inspection form. Distribute to:
one copy to contractor;
place one copy in the scale house; and
retain one copy.
5.
ADDED INFORMATION
5.1.
Any change to zero balance greater than 0.1% is evidence of a malfunction in the lever
system or a faulty installation. Recommend that the scale be inspected by a qualified scale
mechanic.
5.2.
If the Preliminary Section Test indicated one section of a three or more section scale was
inconsistent with the rest, it would be advisable to re-apply the test weights to this section as
well as one of the other sections.
5.3. References
Standard Specifications Manual 1800-2, Scales and Scale House.
Date: 2011 02 01
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SCALE ACCURACY INSPECTION
CONTRACT NO.
HWY.
Contractor
DATE
Directions
How long at this location?
Make of Scale
Min. Grad.
Portable Truck Scale
Serial No.
Portable Hopper Scale
Capacity
Gravel/Raw Materials
SECTION TEST (Truck Scales)
1
2
Asphalt/Processed Materials
CORNER TEST (Hopper Scales)
3
4
5
_
2
3
_
1
4
WEIGHT TEST
Satisfactory
Unsatisfactory
Test Weights Applied
Drainage
Scale Indication
Approaches
Error
Base Timbers
% Error (Error ¸ Test Weight)
Moving Parts Clear & Level
STRAIN LOAD TEST
Ends of Deck-clear
Indicated Vehicle Weight
Beam Condition, Clearance
Plus Test Weights
Beam House Installation
Scale Should Indicate
Sensitivity Zero
Actual Scale Indication
Sensitivity Full Load
Error
% Error (Error / Test Weight)
REMARKS:
Inspected by:
Signature
Phone number
Date
Date: 2011 02 01
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