verification protocol for parking lot salt spreaders

verification protocol for parking lot salt spreaders
VERIFICATION
PROTOCOL FOR
PARKING LOT
SALT SPREADERS
SALT APPLICATION VERIFIED
EQUIPMENT (SAVE) PROGRAM
Robert Roszell / Program Director
3/8/2016
www.savesalt.ca
Table of Contents
Introduction ..................................................................................................................................... 2
Purpose of this Document ............................................................................................................... 2
How Salt Spreaders Work ............................................................................................................... 2
Spreader Types................................................................................................................................ 3
Manufacturer Specific Calibration .................................................................................................. 5
Qualified Personnel ......................................................................................................................... 5
Pre-requisites for Verification/Calibration ..................................................................................... 5
Required Equipment for Verification ............................................................................................. 5
Equations......................................................................................................................................... 5
Preparation for Verification ............................................................................................................ 6
Preparation for all spreaders ....................................................................................................... 6
Preparation for ground-speed controlled spreaders .................................................................... 6
Verification Procedure .................................................................................................................... 6
When to Calibrate/Verify................................................................................................................ 8
Introduction
For years, the snow and ice management industry has been pre-occupied with risks associated with
liability for slips, falls and other ice related accidents. These concerns, combined with a lack of tools to
effectively challenge slip and fall claims, has encouraged contractors to over-apply road salts on parking
lots and sidewalks. The application of salt in excess of what is needed drives up the price of winter
maintenance contracts, accelerates corrosion of building infrastructure and adversely impacts
neighbouring soils, vegetation and waterways.
Between 2012 and 2015, a consortium of provincial, municipal and non-governmental organizations,
coordinated through Landscape Ontario, have established scientifically defensible salt application rates
for parking lots, based on extensive monitoring by researchers at the University of Waterloo. These rates
show the potential for at least a 25% reduction over current rates, and are helping to provide the long
needed evidence for contractors to effectively challenge law suits and prove their due diligence. In order
to use the established rates, however, salt spreading equipment needs to be calibrated and verified to
ensure that target application rates verified through scientific testing are being achieved in practice.
Currently, operators of snow and ice management equipment for sidewalks and parking lots rarely, if at
all, calibrate their salt spreaders. Instead, operators use a combination of sight and experience as a
means of assessing whether ‘enough’ salt has been applied. How much is ‘enough’ is determined based
on the visible presence of salt on the road surface at a density that seems appropriate based on previous
experience. This method of assessment leads to highly subjective determinations of how much salt to
apply in a given situation – a problem that is compounded in most cases by the failure to use equipment
that automatically adjusts spreading rates to ground speed.
Purpose of this Document
The purpose of this calibration procedure is to provide guidance on how to verify salt spreader application
rates in order to ensure operators of spreading equipment are able to apply salt at application rates that
are appropriate for the condition and level of service being sought. By understanding and recording the
amount of salt being applied, contractors can better estimate their annual operational costs, apply salt
responsibly and offer evidence of due diligence when challenged.
How Salt Spreaders Work
The application rate of a spreader is affected by the speed of the truck, speed of the auger/conveyor,
area of gate opening and the speed of the spinner. The speed of the auger/conveyor determines how fast
the granular material is dropped onto the spinner through the area of the gate opening. The speed of the
spinner determines how wide the granular salt melting material is spread horizontally as it is dropped from
the moving vehicle; increasing the speed of the spinner will widen the spread of the dropped material and
reduce the density of application. To maintain the spreader at a constant application rate, the speed of
the auger/conveyor needs to increase when the speed of the truck and/ or spinner is increased.
Conversely, if the spinner speed is increased to widen the spread, the auger/conveyor speed needs to be
increased to maintain constant application rates.
Figure 1. Tailgate spreader.
Figure 2. Tailgate spreader showing auger and
underside of spinner.
Figure 3. V-box salter gate opening and conveyor
belt.
Figure 4. V-box spreader dropping salt onto spinner.
Spreader units have different levels of sophistication in feedback systems that control the auger/conveyor
and the spinner in relation to the speed of the truck and to each other. Currently, spinner settings are
usually disregarded during verification and are not integrated into the automatic feedback systems of
ground speed controlled spreaders. It is assumed that the speed of the spinner and thereby the width of
the spread would be set to salt/cover the width of highway lane(s) and, therefore, application rates are
appropriately considered in terms of pounds per lane distance. However, standard application rates for
parking lots are given in pounds per area, requiring that spinner settings be carefully considered in
verification procedures.
Spreader Types
There are three main types of spreaders used on private parking lots and sidewalks. In order of
sophistication in control settings and feedback systems, from lowest to highest, these are:

Manually controlled: auger and spinner speeds are controlled manually. Discharge rate from the
auger remains constant and does not change with speed; therefore, changes in the speed of the
truck will change the application rate.

Ground speed – open loop: spinner speed is manually controlled but the auger/conveyor speed is
adjusted by a control valve to a predetermined setting based on the speed of the truck to keep
application rates consistent at varying speeds. This system is susceptible to error if the truck’s
speed is miscalculated or if there are changes to the hydraulics of the system.

Ground speed – closed loop: Auger speed is also monitored by a sensor and is adjusted to the
speed of the truck to comply with predetermined ratios between the two for consistent application
rates. Some manufacturers compensate for the spinner speed within their feedback system using
signal relays on the spinner.
Figure 5. Manual controls for auger and spinner
settings.
Figure 6. Interface for automatic settings of auger
and spinner speeds in ground speed controlled
spreader (© Robert Roszell 2016).
Figure 7. Interface for manual settings of auger and
spinner speeds in ground speed controlled spreader
(© Robert Roszell 2016).
Manually controlled spreaders (Figure 5) are currently the most common type of spreader used on private
parking lots in Ontario, but open and closed loop ground speed controllers are becoming increasingly
common (Figure 6, Figure 7). If the spreader only has manual controls, the verification procedure would
benchmark application rates associated with currently used settings and show what combination of auger
and spinner settings achieve standard low, medium and high application rates at frequently travelled
speeds. Ground speed controlled spreaders that are used with overriding manual settings may require
additional manufacturer specific calibration to verify the feedback system. Ground speed controlled
spreaders using desired application rates as input would be verified using this protocol and the contractor
would be informed whether further calibration, repairs and/or modifications are required for the purposes
of calibration.
Manufacturer Specific Calibration
Manufacturer-specific calibration ensures that all parts of the spreader system are working as they
should. New equipment should always be calibrated before first use. Hydraulic/ electric systems must be
verified to ensure that the preset ratios of truck speeds to auger speeds are accurate. Equipment
calibration must be conducted regularly as the age and wear of augers and spinners can significantly
affect their performance. Spreaders should also be calibrated after repairs, modifications or any changes
to the hydraulic system, and at a minimum once per year.
Qualified Personnel
Manufacturer specific calibration can be done by any qualified person but must be verified by an
authorized technician accredited through the SAVE program.
Pre-requisites for Verification/Calibration






Spreader must have been previously calibrated (if applicable)
Equipment must be no older than 7 years
Contractor must be licensed and insured
Spreader must be installed securely to the truck chassis and in working order
Must be able to turn off or remove the spinner (i.e., for drop test)
All of the snow melt material must flow directly onto the spinner
Required Equipment for Verification
1. Drop test box with dimensions of: 70 X 70 X 20.4 cm (bottom not required). The test box has a volume
3
of 0.1 m .
2. Stop watch
3. Tape measure
4. S.A.V.E. program initial settings form and work sheet
Equations
The salt application rate is affected by the gate opening, conveyor or auger speed, spread width of the
the spinner, and truck speed. The following equations are used to determine spreader application rates
while keeping the gate opening constant:
Salt flow rate (Kg/ sec) = weight of salt in the filled box (Kg) / time to fill box (sec)
3
where the weight of salt is determined based on the box capacity of 0.1 m and the density of salt being
3
used (Sodium chloride is 1.30 metric tonne/ m , as per OPSS 2502)
2
Area covered (m / sec) = speed (m/ sec) X spread width(m)
2
2
Spreader application rate (Kg/ 100m ) = (salt flow rate (Kg/ sec) / area covered (m / sec))*100
Preparation for Verification
Preparation for all spreaders
1. Select dry, solid material for calibration that is representative of the bulk material,
uniform in size, relatively lump free, and free of excessive moisture.
2. Load the spreader truck to at least ½ full of the selected dry material.
3. For hopper-box or V-box spreaders, select a single gate opening that will accommodate
a full range of solid material application rates to be used during operations. The size of the opening
should be kept constant during the test and for operations thereafter.
4. For tailgate spreaders, verify that the truck bed can be raised to an operational elevation and make
sure that the auger/conveyor can be fully charged with salt during the complete calibration process.
5. Ensure that the truck’s hydraulic temperature has been given time to warm up prior to beginning
verification.
Preparation for ground-speed controlled spreaders
If the spreader is a ground speed controlled system (open or closed) it must be put into simulated speed
control, either through the existing cab interface or by an external electronic speed simulation device, to
accurately verify the amount being spread. Alternatively, if it can be accomplished safely, the truck can be
jacked to lift the drive wheels and allow them to spin at the desired speed. If simulating the speed cannot
be achieved by any means, the truck’s controls can be placed into manual operating mode and
verification can be completed as it would for a manually controlled spreader. The interfaces of some
ground speed controlled spreaders display the manual auger and spinner setting values for the selected
application rate during regular operations in automatic mode. These manual values can be used to verify
their corresponding application rates but this protocol will not be able to verify the system that is utilized to
provide feedback signals between the speed of the truck, auger, and/or spinner of ground speed
controlled spreaders if speed is not simulated. If application rates to be verified are given in kg/lane
2
distance, the width of the lane should be used to convert the application rates to kg/ 100m ).
Verification Procedure
Step 1: Collect and record user information into the SAVE worksheet
Begin by recording existing information of the spreader system and truck onto the SAVE worksheet. The
information should include:
a)
b)
c)
d)
Company’s name, address, phone number, and contact person
make and model of the spreader, hydraulic or electric?
year manufactured
current auger gate opening size(both height/ width of opening and any notches or holes being
used for referencing)
e) make, model, year, and license plate of the truck
f) usual speeds at which truck operates during spreading (may have more than one speed)
g) currently used controller settings for auger and spinner
Commonly used settings will be tested first to benchmark the existing settings and will guide the verifier in
determining the range of spreader and auger settings to be tested to reach the target spread rates.
Step 2: Measure spreader width
During testing, the truck’s engine speed should be kept at the usual operating RPM. Run the auger and
spinner on the setting most often used by the client. Observe where the majority of the salt lands and the
extent of the spread. Record the measurement approximately 10-12 inches less than the furthest material
thrown, which is considered to be the overlap zone when spreading in parking lots. Measure the width
with a tape measure and record it along with the spinner setting used.
Figure 8. Measurement of the width of salt spread for selected spinner setting.
The standard widths used during spreading are 3.05 m (10 ft), 6.1 m (20 ft), and 9.14 m (30 ft). Gauge
whether the most often used spinner setting produces a spread width similar to the standards and test
higher and lower spinner settings to satisfy the standard range of widths. Enter the tested spinner settings
and corresponding measured spread widths into the SAVE worksheet.
Step 3: Measure auger salt discharge rate
Remove or turn off the spinner assembly (by controls or by disconnecting hoses) on the truck. If the
spinner cannot be turned off or removed, calibration cannot proceed using this protocol. Discharge a
small amount of solids to make sure that the spreader’s distribution mechanism is fully charged. Discard
these amounts. Set up the drop test box below the auger exit orifice to capture the solids. Turn on the
auger at the setting that is most often used and measure the time it takes to fill up the standard drop test
box using a stop watch. Safely even the distribution of the salt falling into the test box as it fills to the top
(Figure 10). Once filled, record in the SAVE worksheet the time in seconds it took to fill and the auger
setting used. Transferring these values into the Excel worksheet will automatically update cells to give
2
calculated spread rates (kg/ 100 m ) for the auger setting tested in combination with the different spinner
settings. Compare calculated spread rates for each spinner setting and continue to alter auger settings
until desired standard application rates are reached. Empty the test box and repeat the auger test with the
new setting.
Figure 9. Timing drop test until test box is filled
(© Robert Roszell 2016).
Figure 10. Ensure salt fills evenly into the test box
during auger drop test.
Step 4: Determine optimal settings for standard low, medium, and high application rates (5, 10, 15
2
lb/ 1000 ft )
Once all the spread widths and drop test times have been recorded, transferring the values to the Excel
worksheet will automatically highlight the closest calculated spread rates to the low, medium, and high
application rates for each user entered speed. Use the chart to identify the auger and spinner setting that
will produce these rates and record it in the “optimal settings” section. The entire chart or just the optimal
settings can be printed and must be placed in a visible location in the cab for the operator’s reference.
The cab chart displaying the required auger and spinner settings based on desired salt application rates
is unique to the tested spreader and truck combination and is deemed valid only for the verified
combination. Should the spreader be moved to another truck, the spreader will need to be re-verified for
the new spreader- truck combination and a new cab chart will be produced to reflect the change. The
chart shall be clearly displayed next to the spreader controls or with a copy of the calibration sheet and
placed on the vehicle instrument panel in full view.
When to Calibrate/Verify
The verification is only valid for the tested spreader/controller unit and for the tested combination of
spreader/controller and truck. If the controller unit is repaired/ replaced or when speed sensors for the
truck or auger/conveyor are replaced, the unit must be recalibrated and verified. Verification followed by
manufacturer specific calibration/recalibration (if necessary) are to occur (i) annually prior to the winter
maintenance seasons, (ii) after major maintenance of the spreader truck, including replacement of
hydraulic fluid or filters, and (iii) before using newly delivered snow and ice control material.
SAVE Program
Salt Spreader Verification Worksheet
Company
Address
City
Province
Phone Number
Email
Website
Calibration Date
Truck Make
Truck Model
Truck Year
License Plate
Spreader Make
Spreader Model
Spreader Year
Hydraulic or Electric Controls
Gate opening height (cm)
Gate opening width (cm)
Gate opening area (cm2)
Auger
Setting
Gate Opening
(mm)
Time to Fill
Box (sec)
Spinner
Setting
www.savesalt.ca
Spread
Width (ft)
Spread
Width (m)
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