CALIBRATION GUIDE FOR GROUND-SPEED

CALIBRATION GUIDE FOR GROUND-SPEED
CALIBRATION GUIDE FOR GROUND-SPEEDCONTROLLED AND MANUALLY CONTROLLED
MATERIAL SPREADERS
February 2009
Prepared for
Clear Roads Technical Advisory Committee
Pooled Fund Project #TPF-5(092)
Prepared by
Blackburn and Associates
CALIBRATION GUIDE
PREFACE
This Calibration Guide is based upon information contained in a Clear Roads research report
entitled, “Calibration Accuracy of Manual and Ground-Speed-Controlled Salters.” Both the
Guide and related research were funded by the Wisconsin Department of Transportation
(WisDOT) and the United States Department of Transportation (USDOT) under the Clear Roads
pooled fund #TPF-5(092) and WisDOT Project #0092-06-21. The Clear Roads pooled funded
research program is an ongoing cooperative and comprehensive research activity that focuses on
field testing and evaluation of materials, methods, and equipment used in highway winter
maintenance.
The authors of this guide were Robert R. Blackburn, the Principal Investigator and Overall
Project Manager, Edward J. Fleege and Duane E. Amsler.
2
Table of Contents
PREFACE.................................................................................................................2
Table of Contents .....................................................................................................3
1. Introduction.........................................................................................................4
2. Background on Equipment Operations for Spreaders ...................................4
3. Background on Calibration ...............................................................................6
4. Equipment, Material, and Facilities Needed for Calibration and
Calibration Verification Testing......................................................................7
4.1 Equipment, Material, and Facilities Needed for Calibration ................................................ 7
4.1.1 Calibration of Dry Solid Material Spreaders ................................................................. 8
4.1.2 Calibration of Prewetting Systems............................................................................... 12
4.2 Equipment, Material, and Facilities Needed for Calibration Verification Testing............. 13
4.2.1 Verification Testing of Dry Solid Material Spreaders................................................. 13
4.2.2 Verification Testing of Prewetting Systems ................................................................ 13
5. Calibration in Closed-loop Mode of Operation ..............................................14
5.1 Preparation for Calibration ................................................................................................. 14
5.2 Calibration Check List ........................................................................................................ 16
5.3 Calibration According to Manufacturer’s Specifications ................................................... 17
5.4 Calibration Verification Tests............................................................................................. 18
5.5 Acceptance of Calibration Tests ......................................................................................... 19
6. Calibration in Open-loop Mode of Operation ...............................................21
6.1 Preparation for Calibration ................................................................................................. 21
6.2 Calibration Check List ........................................................................................................ 23
6.3 Calibration According to Manufacturer’s Specifications ................................................... 24
7. Calibration of Manually Controlled Salters....................................................26
7.1 Calibration According to Manufacturer’s Specifications ................................................... 26
7.2 Salt Institute Procedure ....................................................................................................... 26
8. Recommended Timing and Frequency of Calibration...................................27
9. Calibration Record Keeping .............................................................................27
REFERENCES.......................................................................................................28
APPENDIX A - CALIBRATION VERIFICATION TEST FORM .................29
APPENDIX B - SALT INSTITUTE PROCEDURES AND CHART USED
TO CALIBRATE SOLID MATERIAL SPREADERS WITH
MANUAL CONTROLLERS .........................................................................31
3
1. Introduction
The unprecedented high cost of diesel fuel and materials used for snow and ice control presents a
severe demand on the budgets for winter maintenance operations. Now more than ever, it is
imperative that snow and ice control operations need to be conducted in the most efficient and
cost-effective manner possible. Research results based upon operational experiences provide the
manager of snow and ice control operations with guidance on the appropriate chemical
application rates for a wide range of weather, traffic, and site conditions (1-3). However, this
guidance is of no value unless the material discharge rates from spreaders can be automatically
and accurately controlled.
Automatic control of material application rates used in highway winter maintenance operations is
achieved with ground-speed-oriented controllers. Currently, there are a wide variety of
controllers manufactured. Most ground-speed controllers used in the U.S. automatically adjust
hydraulic fluid flow in proportion to ground speed. A truck operator with an automatic controller
is able to maintain a constant application rate of material on the road without having to adjust the
valve opening to conform to the changing speed of the truck. To spread a constant amount of
material along a road segment, a truck operator needs only to select an application rate.
The installation of a controller in a spreader truck does not guarantee that the solid and liquid
discharge goals will be automatically and accurately achieved. The discharge goals depend not
only on how will the controller functions, but also on how will the controller interfaces with the
truck-spreader system. In order for spreader/controller combinations to optimally discharge solid
and prewetting material, their calibration settings need to accurate.
A study entitled, “Calibration Accuracy of Manual and Ground-Speed-Controlled Salters” was
conducted under the Clear Roads winter maintenance pooled funded project (4). The study
documented the accuracy of automated systems in delivering snow and ice control materials in
various combinations, with a focus on dry materials.
An important aspect of the calibration study was the development of procedures for the proper
calibration of spreader/controller combinations. Those procedures form the bases for the
calibration guide.
Following this information, the Guide is divided into eight additional sections plus two
appendixes. Section 2 describes the background on equipment operations for spreader. Section 3
presents the background on calibration. Section 4 describes the equipment needed for calibration.
Section 5 describes the procedures for calibration of spreader/controller combinations in closedloop mode of operations. Section 6 describes the procedures for calibration of spreader/controller
combinations in open-loop mode of operations. Section 7 describes the procedures for calibration
of manually controlled saltes. Section 8 provides the recommended timing and frequency of
calibration. Finally, Section 9 presents suggested calibration record keeping procedures.
2. Background on Equipment Operations for Spreaders
Dry materials for snow and ice control are generally applied to the roadway by means of either a
hopper-type spreader or a dump body with an under-tailgate spreader. Generally, hopper
spreaders are self-contained units mounted in or on the dump truck in winter, then removed and
stored in other seasons so that the trucks can be used for other maintenance work. These units
consist of a V-box body, discharge/feed conveyer, spinner disc, power drive, and other necessary
components. At the hopper’s base is a full-length feed system whose speed is controlled from
4
the truck cab. This feed system can either be a full-length belt, chain-drag belt, or a longitudinal
auger. These systems feed the granular material through an adjustable gate opening into a chute
where it falls onto a spinner that spreads it into the desired pattern across the road.
The under-tailgate spreader is also a self-contained unit that slips into a dump body and is easily
removed and hooked up. These devices consist of a small hopper, an auger feed mechanism,
hydraulic drive system, and a spinner disc. Some truck bodies support a material distribution
spinner located behind the cab such that the distributed material is placed on the roadway in
advance of the drive wheels to provide additional traction.
The variables affecting dry material application rate are: 1) area of the gate opening on a hopper
box or the opening in the bottom of the tailgate hopper; 2) feed-belt or auger speed; 3) the
number of lanes being treated; and 4) truck speed. The gate opening and spread pattern are
generally not changed during spreading operations. Thus, to control the actual material
spreading rate, the speed of the feed belt or auger needs to be considered along with truck speed.
Automatic controllers use a truck-speed sensor for adjusting the opening of the hydraulic valve
that in turn controls the operating speed of the feed mechanism. Various types of truck-speed
sensors are available. Some are connected to the speedometer-cable while others measure the
rotation of the drive shaft or a wheel.
There are two types of automatic controllers: the open loop and the closed-loop system. Both
types require a speed sensor. The open-loop system monitors the truck speed and adjusts the
control valve to a predetermined setting to provide the correct belt or auger speed for the desired
spread rate. Any changes in the hydraulic system variables will result in an error in the belt or
auger speed.
The closed-loop system monitors both truck speed and belt or auger speed and adjusts the control
valve until a predetermined ratio value of belt or auger speed and truck speed is obtained. The
second speed sensor is needed to correct changes that occur during snow and ice control
operations such as wear of spreader equipment and variations in performance of the spreader’s
hydraulic fluid. Wear can change the calibration of the equipment. Also, the variable operating
temperature and aging of the spreader’s hydraulic capacity changes the operation of the belt,
auger, and spinner motors. The likelihood of a systematic error in delivery rate is greatly reduced
by the closed-loop system.
Following the anti-icing studies in the 90’s, there was an insurgence of interest in the use of
prewetted salt in snow and ice control. Prewetting equipment can be an integral part of the
spreader design or it can be a system that is added to an existing dry-material spreader. Either an
electric or hydraulic spray system is used in prewetting applications.
An electric spray system consists of a 12 VDC electric pump, in-cab controls, one or more
nozzles, hoses, spray tank(s) and necessary fittings. The cab controls are generally of two types.
The simple type has an on/off switch and a variable speed pump control for increasing or
decreasing the liquid chemical flow rate. This type of controller is generally not ground-speed
oriented. The other type of control monitors the amount of dry material being applied to the road
and automatically adjusts the liquid chemical flow rate to maintain a constant loading
(gallons/ton) ratio. This second type of controller can also monitor and display in the cab overall
total gallons of liquid pumped and tons of dry material spread per trip and for other periods of
time. This latter type of controller is generally equipped with its own conveyor/auger sensor.
5
Also, these controllers usually can be used in conjunction with any type of ground-speed control
system. Both types of liquid control systems operate independently of the spread width control.
A hydraulic spray system is usually in-line with the conveyor/auger motor so that the system
provides a constant relationship between the amount of liquid and dry material being spread.
The system includes a liquid spray pump, hydraulic motor, cab controls, nozzle kit, spray tanks
and necessary hoses and fittings. A small hydraulic motor is used generally to drive the liquid
chemical pump and is coupled in parallel with the conveyor/auger motor. An electrical solenoid
valve is connected to an on/off system switch in the cab. An adjustable flow regulator is
included to control the liquid chemical flow rate. Cab-mounted displays indicate the status of
various system components. The systems available generally have multiple spray nozzles.
3. Background on Calibration
Regardless of the type of spreader/controller used, it is extremely important to calibrate the
system to ensure that the desired quantity of material (dry solid and liquids for prewetting
systems) is actually being applied to the road. The most sophisticated controller is of little value
if an unknown amount of material is being spread. All spreader equipment should be calibrated
before winter operations begin. Even new spreader equipment delivered from the factory needs
to be calibrated. Periodic calibrations should also be conducted because changes in mechanical
linkages and components may occur and hydraulic systems perform differently as the season
progresses. Any radical deviations in the spreader output compared to the control settings, such
as running out of material before the route is completed or having excessive material remaining
after an operation, should be investigated. Finally, it is a good practice to recalibrate the
spreader equipment after any maintenance is performed on the spreader/truck system, including
changing hydraulic fluid and related filters.
Two methods are generally used to calibrate spreader equipment. One method involves
connecting a speed simulator to the control panel so that the controller senses that the truck is
traveling at a specified road speed. The second method involves jacking up the rear wheels so
that the truck can be run in place at a specified speed. (See Figure 3-1 for an example.) In both
methods, a timed volume, or weight, of discharged material is measured.
A less accurate third method for solid material
involves operating the truck over a measured
distance at a known constant speed and
determining the weight of material spread by
measuring the load weight before and after
spreading or capturing and weighing the
material dispensed over a known distance.
The variation in operating parameters over a
range of speeds makes it necessary to check
the spreader calibration over a number of
truck speeds.
A number of calibration procedures are
available to the users of dry and prewetted
Figure 3-1 Example of having the truck
solid material spreaders. These procedures are
jacked up to conduct drop tests in New York.
generally available from the spreader and
controller manufactures. The Salt Institute provides a calibration procedure for dry solid material
through its information data base (5).
6
The procedures for calibrating dry solid material spreaders are based generally on a catch or drop
(discharge) and weigh basis. The amount of material discharged during calibration varies from
manufacturer to manufacturer. The calibration procedures for prewetting liquid discharge are
based on a volumetric test and are marginal, at best. The basic problem with some calibration
procedures is that the user does not know if the calibration was performed satisfactorily, or at
least, as best as could be expected. Some manufacturers have tried to circumvent this problem by
recommending a calibration procedure that provides for “backing-into” or fine tuning the desired
output by adjusting the controller discharge constant.
The procedure given in this Guide for the calibration of spreader/controller combinations is
based on using the controller manufacturer’s direction together with a calibration verification
approach. This procedure augments the manufacturer’s recommendations with a check to verify
that the calibration was performed correctly, or at least, as best as could be expected considering
the limitations of the spreader/controller system.
Direction for obtaining the recommended calibration procedures from six controller
manufacturers can be obtained by visiting their web sites. The addresses if these sites are given
in Table 3-1
Table 3-1 Web Site Addresses for Six Controller Manufacturers
Spreader/Controller Manufacturer
URL Address
Cirus Controls
http://www.ciruscontrols.com/manuals
Component Technology
http://www.certifiedpower.com/cpi_comp_storm.aspx
Dickey-john
http://www.dickey-john.com
FORCE America *
http://www.forceamerica.com/
Muncie Power Products *
http://www.munciepower.com
Pengwyn
http://www.pengwyn.com/manuals.html
* Calibration protocols are not available from their web site. However, the procedures are available
electronically upon request.
Additional information on the six controller manufacturers’ recommendations can be obtained
form a recent Clear Roads study report (4). The user of this Guide should also contact the
highway agency’s fleet manager or controller manufacturer if any questions remain on how to
calibrate a specific system.
4. Equipment, Material, and Facilities Needed for Calibration and
Calibration Verification Testing
The items needed for calibration are described first followed by those needed for calibration
verification testing.
4.1 Equipment, Material, and Facilities Needed for Calibration
The equipment, material, and facilities needed for the calibration of spreader/controller systems
are varied and depend on the controller manufacturer’s requirements. However, some necessary,
and provisional, items can be identified that cover most of the requirements. These items are
divided into those needed for calibration of systems for distributing dry solid material and those
needed for calibration of prewetting systems.
7
4.1.1 Calibration of Dry Solid Material Spreaders
The items needed for this activity are:
•
A known road distance near the maintenance yard where the spreader truck’s odometer
and speedometer can be checked, if
necessary.
•
A truck speed simulator; or a way to
mechanically keep a constant vehicle
speed during a discharge test, such as with
a throttle, if equipped. A fan belt tensioner
and a stick might work in the absence of a
throttle. (Figure 4-1 shows a controller in a
truck cab with the speed simulator set for
20 mph, and application rates set for 403
lbs/mile and 9.95 gallons/ton.)
•
A hydraulic lift or hydraulic jacks to raise
the drive wheels off the ground if a
constant vehicle speed has to be Figure 4-1 Controller in a spreader truck
maintained mechanically. Front wheel cab with speed simulator display.
blocks need to be used if the rear axel
jacks are used. (Figure 4-2 shows a truck on a hydraulic lift and Figure 4-3 shows
hydraulic jacks used to raise the drive wheels off the ground.)
Figure 4-2 Spreader truck on a
hydraulic lift for drop tests.
Figure 4-3 Spreader truck’s rear wheels
raised off ground with hydraulic jacks.
•
A set of highway cones to warn people of rotating rear truck wheels when engaged as
shown in Figure 4-3.
•
About 5 – 6 cu. yd. of uniformly prepared solid material to be used that is stored under
cover and free of chunks with dimensions larger than the discharge gate or tailgate
opening. (See Figure 4-4.)
•
A mechanized loader bucket. (See Figures 4-4 and 4-5.)
8
Figure 4-4 Uniformly prepared solid
material under cover.
•
Figure 4-5 Mechanized loader bucker
used to load spreader truck.
A calibrated platform or commercial scale will need to be used for discharged solid
material weights of a thousand pounds or larger. (Figures 4-6 and 4-7 show a specially
designed large portable hopper with a load cell built and used by IDIT to catch and weigh
up to 2,000 pounds of discharge dry solid material during their spreader calibration
work.)
Figure 4-6 IDOT design and built large
hopper and load cell used in calibration
work.
•
•
•
Figure 4-7 IDOT’s large hopper and
load cell used in calibration work.
Alternatively, a calibrated weighing device would be needed that will accommodate 250
to 400 pounds of discharged solid material weight. (The device shown in Figures 4-6 and
4-7 could work equally well for this weight range.)
Several large plastic or metal containers could be used inplace of the IDOT unit for
catching up to 400 pounds of discharged solid material weight.
A single containment box could be used for catching up to 150 pounds of discharged dry
solid material. Figure 4-8 shows such a box being used to catch this amount of solid
discharged material. Figure 4-9 shows a portable scale being used to weigh an amount of
discharged dry solid material as shown in Figure 4-8.
9
Figure 4-8 Single containment box used to
collect up to 200 lbs of discharged dry
solid material.
Figure 4-9 Portable scale used to weigh
about 100 lbs of discharged dry solid
material.
•
Alternatively, a large plastic bucket inside a plastic 2’ x 3’ x 1’ deep or deeper mason tub
used for mixing mortar could be used for catching up to 150 pounds of discharged dry
solid material. Figure 4-10 shows such a combination of containers used for collecting
the smaller amounts of discharged solid material.
•
Several 5-gallon plastic buckets can be used for catching up to about 100 pounds of
discharged solid material. (See Figure 4-11.)
Figure 4-10 Large plastic tub inside a
mason tub for catching small amounts of
discharged solid material.
Figure 4-11 Plastic 5-gallon bucket used
for catching small amounts of discharged
solid material.
•
A dairy scale can be used for weighting each 5-gallon bucket containing the discharge
material as shown in Figure 4-12.
•
If a dairy scale is used for weighing, it needs to be calibrated first before use. This can be
done by recording the incremental weights of a 5-gallon bucket hanging from a scale with
one gallon of water added at a time until about four or five gallons of water are
accumulated. The empty weight of the 5-gallon container must be considered in this dairy
scale calibration process. (Figure 4-13 shows a 5-gallon plastic bucket hanging from the
dairy scale with three gallons of water in the bucket.)
10
Figure 4-12 Dairy scale used to weigh a
5-gollon plastic bucket with solid discharged
material.
Figure 4-13 A 5-gallon bucket containing
three gallons of water suspended from
a dairy scale.
•
The larger discharged weights can be
dumped directly onto the solid storage
pile without handling. (See Figure 4-14.)
•
The smaller discharge weights can be
dumped into the bucket of a high loader
for transfer to the solid storage pile.
•
A small tarp is needed to help retain the
smaller amounts of discharged solid
material. (See Figure 4-15)
•
Shovels, brooms, wheelbarrows, etc. are
also needed to help in collecting the
smaller discharged of weight of solid Figure 4-14 Large discharged weights of
material. (See Figure 4-15.)
dry solid material dumped directly on to
A stop watch, if necessary.(See Figure 4- the solid storage pile.
•
16)
11
Figure 4-15 Tarp with shovel, broom, and
wheelbarrow for collecting solid
discharged material.
•
A hand-held tachometer, if necessary.
•
Hard hats, if necessary.
Figure 4-16 Suitable hand-held stop
watch.
4.1.2 Calibration of Prewetting Systems
The controller manufacturers are not in agreement on the items needed for the calibration of the
prewetting systems nor on the procedures for conducting the calibration. However, research
experience indicates that the calibration of the prewetting system should be conducted at the
same time as the calibration of the dry solid material spreader. Consequently, the items listed
below are those extra elements not included for the calibration of dry solid material spreaders.
•
Enough prewetting liquid chemical in the truck tank(s) to carry out the calibration tests
[tank(s) at least ½ full].
•
Adaptor hoses suited to capture the entire liquid chemical released from all the spray
nozzles during the calibration. (See Figure 4-17.)
Figure 4-17 Adaptor hose that fits over the
spray nozzle to capture the entire liquid
chemical discharged during calibration.
Figure 4-18 Containers for measuring the
volume of liquid discharged during
calibration.
12
•
A 5 – gallon plastic bucket for catching the liquid discharge. (See Figures 4-18 and 4-10,)
•
Several smaller graduated plastic containers for measuring volume of liquid discharged.
(See Figure 4-18)
•
A hydrometer for measuring the specific gravity of the prewetting liquid chemical, if
necessary.
•
A mechanism for returning the discharged liquid chemical to the tank(s) on the truck, or a
means to safely dispose of the discharged liquid.
4.2 Equipment, Material, and Facilities Needed for Calibration Verification Testing
Calibration verification testing is an integral part of the overall calibration process. It is based on
measuring small weights of solid discharges (in the neighborhood of 100 pounds) and small
volumes of liquid chemical discharges (in the neighborhood of 0.5 to 0.75 gallons).
Consequently, the additional equipment, material, and facilities needed for the calibration
verification testing are minimal compared to those items needed for calibration. As before, the
items needed for verification testing are divided into those needed for systems distributing dry
solid material and those needed for prewetting systems.
4.2.1 Verification Testing of Dry Solid Material Spreaders
The items needed for this activity are the same as those described under Section 4.1.1 with two
exceptions:
•
A calibrated weighing device that will accommodate up to 150 pounds of weight is the
only scale needed. The 250 to 400 pound capacity scale described in Section 4.1.1 could
be used: but a calibrated platform or commercial scale is not appropriate for this need.
•
Two stop watches for coordinating the solid discharge tests. (Similar to the one shown in
Figure 5-16.)
4.2.2 Verification Testing of Prewetting Systems
Three, 5-gallon plastic buckets are needed for conducting the liquid discharge tests. One bucket
is needed to collect the liquid from each test. The two other buckets are needed for temporarily
storing the total amount of liquid chemical discharged during the complete verification testing.
13
5. Calibration in Closed-loop Mode of Operation
This section of the Guide presents recommendations for the proper calibration of closed-loop
spreader/controller combinations. The recommendations presented are based upon the experience
gained from a calibration research project (4); from discussions and communication with the six
controller manufacturers involved with the study; and from the review of published and
unpublished literature.
The recommendations, which follow for the proper calibration of spreader/controller
combinations, are not intended to replace the procedures specified by the controller
manufacturer. Instead, the recommendations given in this Guide augment the manufacturers’
recommendations with additional checks and balances such that the system can be operated in
the field under the best possible control over material discharges. Many times, the limitations in
accurate solid material discharge over the range of truck speed – application rate combinations
used in the field have more to do with the hydraulic flow capacity of the spreader truck than with
the reliability of the controller. Similarly, the limitations observed in accurate liquid material
discharge have more to do with the liquid pump design than with the design of the controller.
5.1 Preparation for Calibration
Before starting the calibration procedure that is specified by the controller manufacturer, the
following items should be addressed:
1. Select dry, solid material for calibration that
is: representative of the bulk material,
uniform, relatively lump free, and free of
excessive moisture. (See Figure 5-1.)
2. Load the spreader truck to at least ½ full of
the selected dry material.
3. Load the spreader truck’s prewetting tanks,
if available, to at least ½ full of liquid
chemical used in the prewetting process.
Some controller manufacturers believe that Figure 5-1 Uniform bulk material
water can be used in place of liquid
chemicals during the calibration process,
however, this is not recommended.
4. 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. (See
Figure 5-2.)
5. For tailgate spreaders, verify that the truckbed can be raised to an operational
elevation and make sure that the auger can
be fully charged during the complete Figure 5-2 Selection of an appropriate
calibration process. (See Figures 5-3 and 5- single gate opening for range of
application rates to be used.
4)
14
Figure 5-3 Truck-bed raised to an
operational elevation for calibration.
Figure 5-4 Photo showing tailgate auger
fully charged during the calibration
process.
6. When calibrating the prewetting system, leave the spray nozzles in the discharge lines to
account for back-pressure conditions. (See Figure 5-5.)
(A)
(B)
Figure 5-5 Collection hoses placed over spray nozzles in the prewetting discharge lines.
7. Assemble the equipment identified in Section 4.1 that is needed for calibration.
8. Verify that the scales used to weigh the solid discharge material and the containers used
to measure the liquid discharge amount have been properly calibrated.
9. Verify that the truck’s speedometer has been properly calibrated and the speedometer
display agrees with the speed readout on the controller. (See Figure 5-6.)
10. Fill the truck’s hydraulic oil reservoirs to recommended capacity.
11. Verify that the truck’s hydraulic oil can be warmed to normal operational temperature
and that the temperature level can be held constant for the time required for calibration.
(See Figure 5-7)
15
Figure 5-6 Speed readout of 20 mph on
the controller in the truck cab.
Figure 5-7 Check the operational
temperature of the truck’s hydraulic oil.
12. Verify that the truck’s engine RPM can be held to at least 1500 RPM or to a spreading
RPM level during calibration.
13. Verify that the spreader’s conveyor or auger can be properly engaged during calibration.
The spinner assembly does not need to be engaged or in place during calibration
14. Verify that the proper control functions can be engaged during the calibration of the
prewetting system.
15. Finally, disengage any controller feature that is automatically built into the controller’s
operation that would cause a control valve to open to any position other than what is
dictated for a specific catch or drop test. This step is necessary to eliminate the possibly
of the control valve going to full open for a period of time after the start-up of the
discharge mechanism.
5.2 Calibration Check List
The following items are intended to serve as a reminder to the truck operator that the appropriate
functioning of the spreader/controller system has been checked and that the unit is ready for
calibration.
1. Recommended amount of dry solid material loaded?
2. Recommended amount of liquid chemical loaded?
3. Correct gate opening for hopper-box or V-box spreader?
4. Truck-bed in correct elevated position for tailgate spreader?
5. Auger of tailgate spreader fully charged?
6. Can the hydraulic oil temperature be held at the correct level?
7. Can the truck’s engine RPM be held at the correct level?
8. All solid and liquid material discharge systems ready for engagement?
9. All controller features properly set?
10. All collection devices ready to receive material discharge amounts?
16
5.3 Calibration According to Manufacturer’s Specifications
Each controller manufacturer provides the user with a set of specific instructions for the
calibration of spreader/controller combinations. Directions for obtaining calibration
procedures for six controller manufacturers can be found from their Web sites given in Table
3-1. Although each manufacturer has specific procedures, certain fundamental generic steps
of the calibration process can be identified and are given below. The following steps are to be
taken after executing the calibration check list described in Section 5.2.
1. Remove the spinner assembly from the truck but keep the hydraulic hoses connected.
2. Warm the truck’s hydraulic oil to the specified operational temperature.
3. Discharge a small amount of solid and liquid chemical to make sure that the spreader’s
distribution mechanism is fully charged. Discard these amounts.
4. Select the calibration mode function on the controller for closed-loop operation. (See
Figure 5-8.)
5. Select the appropriate truck calibration
speed.
6. Set the truck’s engine RPM to the correct
level specified by the manufacturer.
7. Discharge and capture the appropriate
amount of solid and liquid chemical. (See
Figures 5-9 and 5-10 for examples.)
8. Abort the calibration test(s) if a
discontinuity in flow of either solid or
liquid material discharge is observed.
9. Measure the amounts of solid and liquid Figure 5-8 Photo of controller display
showing unit is in calibration mode.
chemical discharged satisfactorily.
10. Enter the values of the measured discharged amounts into the controller.
11. Record the various solid and liquid calibration factors obtained and used during the
calibration process.
12. Properly exit the calibration mode on the controller following the manufacturer’s
instructions.
17
Figure 5-9 Example of solid and liquid
materials being collected during drop
tests in Wisconsin.
Figure 5-10 Example of using a large
hopper with associated weight scale to
catch solid material during drop tests in
Iowa.
5.4 Calibration Verification Tests
The calibration verification procedure consists of running a very limited number of solid and
liquid discharge tests to check that the spreader/controller system is properly calibrated. The
recommended procedure amounts to running three discharge tests for each of four combinations
of variables, for a total of 12 tests. Each combination of variables consists of a specific value of
solid application rate, liquid application rate, and truck speed. The combinations of the
calibration verification test variables are given in Table 5-1, along with the test run discharge
times.
If, for some reason, the recommended 12 discharge tests are considered too many, then a
modified calibration verification procedure should be followed. The modified procedure amounts
to running three discharge tests for each of two combinations of variables, for a total of six tests.
The two combinations of variables should be selected from Table 5-1 and should span the winter
maintenance operating conditions most commonly used. As a suggestion, the conditions
associated with Test Variable Set Number 2 in Table 5-1 (300 lbs/mile solid application rate and
10 gal/ton liquid application rate) and with Test Variable Set Number 4 (600 lbs/mile and 15
gal/ton) could be used. Likewise, the conditions associated with Test Variable Set Numbers 1
and 3 could be used. The final selection of the two combinations of variables is left up to the
individual winter maintenance highway agency performing the calibration tests. It is important to
remember that three discharge tests still need to be conducted for each combination of variables
(set number) selected.
18
Table 5-1 Calibration Verification Test Variables
Solid
Liquid
Test Variable Application
Application
Set No.
Rate
Rate (gal/ton)
(lbs/mile)
1
200
10
2
300
10
3
500
15
4
600
15
Test Speed
(mph)
Test Run
Discharge
Time (sec)
25
25
20
20
73
49
36
30
The equipment needed for conducting the calibration verification tests is described in Section
4.2. Before conducting the calibration verification tests described next, disengage any controller
feature that would cause a control valve to open to any position other than what is dictated for a
specific catch or drop test. This step is necessary to eliminate the possibility of the control valve
going to full open for a period of time after the start-up of the discharge mechanism.
1. Conduct the 12 calibration verification tests or the modified six tests using the test
variable combinations and associated test run discharge times in Table 5-1.
2. Record the solid and liquid discharge amounts for each test and determine the arithmetic
average of both the solid and liquid discharge amounts for each test verification set
number. Forms for recording the calibration verification test results are given in
Appendix A for convenience. Form A is for recording data associated with running
discharge tests for combinations of variables described by Test Variables Sets Nos. 2 and
4 in Table 5-1. Form B is for recording data associated with running discharge tests for
combinations of variables described by Test Variable Sets Nos. 1 and 3. Form C is a
blank form for recording discharge test results for combinations of variables other than
those in Forms A and B.
5.5 Acceptance of Calibration Tests
1. Compare the arithmetic averages of the solid and liquid discharge amounts with the
respective theoretical and acceptable range values given in Table 5-2. The acceptable
ranges for both solid and liquid discharge amounts are based on ±4 percent of the
theoretical discharge amount. Properly calibrated spreader/controller systems operated in
the closed-loop mode of operation should produce average discharge amounts within the
acceptable ranges for the given discharge times. The acceptable ranges for both solid and
liquid discharge amounts are given also in the Calibration Verification Test Forms A and
B in Appendix A for convenience.
19
Table 5-2 Theoretical and Acceptable Range Values for Solid and Liquid
Verification Discharge Amounts
Dry Solid Material
Liquid Material
Test
Acceptable
Acceptable
Theoretical
Theoretical
Variable
Discharge
Discharge
Discharge
Discharge
Set No.
Range Amount
Range Amount
Amount (lbs)
Amount (gals)
(lbs)
(gals)
1
101.4
97.3 to 105.5
0.51
0.49 to 0.53
2
102.1
98.0 to 106.2
0.51
0.49 to 0.53
3
100.0
96.0 to 104.0
0.75
0.72 to 0.78
4
100.0
96.0 to 104.0
0.75
0.72 to 0.78
If Form C is utilized, the theoretical discharge values for the solid and liquid material can
be calculated for whatever combination of variables that are selected. The means of
calculating those values are given in Appendix E – “Procedure for Computing
Theoretical Solid and Liquid Discharge Amounts” of the Final Report entitled,
“Calibration Accuracy of Manual and Ground-Speed-Controlled Salter” (4).
2. Redo the calibration according to the manufacturer’s specifications, if the results of the
calibration verification tests do not agree with the acceptable ranges of the discharge
amounts in Table 5-2. This activity might involve backing in, or “fine tuning”, the
calibration to obtain discharge results that agree, as best as possible, with the data in the
above table. It is very likely that the results of this approach will produce better
agreement for some combinations of test variables than others. This is because of the
system limitations. The main point here is to produce the best calibration possible for the
range of field operations expected.
3. Record the final calibration constants in a log for each spreader/controller combination.
20
6. Calibration in Open-loop Mode of Operation
This section of the Guide presents recommendations for the proper calibration of open-loop
spreader/controller combinations. The recommendations presented are based upon the experience
gained from a calibration research project (5); from discussions and communication with the six
controller manufacturers involved with the study; and from the review of published and
unpublished literature.
The recommendations, which follow for the proper calibration of spreader/controller
combinations, are not intended to replace the procedures specified by the controller
manufacturer. Instead, the recommendations given in this Guide augment the manufacturers’
recommendations with additional checks and balances such that the system can be operated in
the field under the best possible control over material discharges. Many times, the limitations in
accurate solid material discharge over the range of truck speed – application rate combinations
used in the field have more to do with the hydraulic flow capacity of the spreader truck than with
the reliability of the controller. Similarly, the limitations observed in accurate liquid material
discharge have more to do with the liquid pump design than with the design of the controller.
6.1 Preparation for Calibration
Before starting the calibration procedure that is specified by the controller manufacturer, the
following items should be addressed:
1. Select dry, solid material for calibration that is: representative of the bulk material,
uniform, relatively lump free, and free of excessive moisture. (See Figure 6-1.)
2. Load the spreader truck to at least ½ full of the selected dry material.
3. Load the spreader truck’s prewetting tanks, if available, to at least ½ full of liquid
chemical used in the prewetting process. Some controller manufacturers believe that water
can be used in place of liquid chemicals during the calibration process, however, this is
not recommended.
4. 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. (See Figure 62.)
Figure 6-1 Uniform bulk material.
Figure 6-2 Selection of an appropriate
single gate opening for range of application
rates to be used.
21
5. For tailgate spreaders, verify that the truck-bed can be raised to an operational elevation
and make sure that the auger can be fully charged during the complete calibration process.
(See Figures 6-3 and 6-4)
Figure 6-3 Truck-bed raised to an
operational elevation for calibration.
Figure 6-4 Photo showing tailgate auger
fully charged during the calibration
process.
6. When calibrating the prewetting system, leave the spray nozzles in the discharge lines to
account for back-pressure conditions. (See Figure 6-5.)
(A)
(B)
Figure 6-5 Collection hoses placed over spray nozzles in the prewetting discharge lines.
7. Assemble the equipment identified in Section 4.1 that is needed for calibration.
8. Verify that the scales used to weigh the solid discharge material and the containers used to
measure the liquid discharge amount have been properly calibrated.
9. Verify that the truck’s speedometer has been properly calibrated and the speedometer
display agrees with the speed readout on the controller. (See Figure 6-6.)
10. Fill the truck’s hydraulic oil reservoirs to recommended capacity.
22
11. Verify that the truck’s hydraulic oil can be warmed to normal operational temperature and
that the temperature level can be held constant for the time required for calibration. (See
Figure 6-7)
Figure 6-6 Speed readout of 20 mph on
the controller in the truck cab.
Figure 6-7 Check the operational
temperature of the truck’s hydraulic oil.
12. Verify that the truck’s engine RPM can be held to at least 1500 RPM or to a spreading
RPM level during calibration.
13. Verify that the spreader’s conveyor or auger can be properly engaged during calibration.
The spinner assembly does not need to be engaged or in place during calibration
14. Verify that the proper control functions can be engaged during the calibration of the
prewetting system.
15. Finally, disengage any controller feature that is automatically built into the controller’s
operation that would cause a control valve to open to any position other than what is
dictated for a specific catch or drop test. This step is necessary to eliminate the possibly of
the control valve going to full open for a period of time after the start-up of the discharge
mechanism.
6.2 Calibration Check List
The following items are intended to serve as a reminder to the truck operator that the appropriate
functioning of the spreader/controller system has been checked and that the unit is ready for
calibration.
1. Recommended amount of dry solid material loaded?
2. Recommended amount of liquid chemical loaded?
3. Correct gate opening for hopper-box or V-box spreader?
4. Truck-bed in correct elevated position for tailgate spreader?
5. Auger of tailgate spreader fully charged?
6. Can the hydraulic oil temperature be held at the correct level?
7. Can the truck’s engine RPM be held at the correct level?
8. All solid and liquid material discharge systems ready for engagement?
23
9. All controller features properly set?
10. All collection devices ready to receive material discharge amounts?
6.3 Calibration According to Manufacturer’s Specifications
Each controller manufacturer provides the user with a set of specific instructions for the
calibration of spreader/controller combinations. Directions for obtaining calibration procedures
for a number of controller manufacturers can be found from their Web sites given in Table 3-1.
Although each manufacturer has specific procedures, certain fundamental generic steps of the
calibration process can be identified and are given below. The following steps are to be taken
after executing the calibration check list described in Section 6.2.
1. Remove the spinner assembly from the truck, but keep the hydraulic hoses connected.
2. If a speed simulator is not available, block the front wheels and elevate the rear wheels
off the ground.
3. Warm the truck’s hydraulic oil to the specified operational temperature.
4. Discharge a small amount of solid and liquid chemical to make sure that the spreader’s
distribution mechanism is fully charged. Discard these amounts.
5. Select the calibration mode function on the controller for open-loop operation.
6. Select the appropriate truck calibration speed.
7. Set the truck’s engine RPM to the correct level specified by the manufacturer.
8. Select the solid discharge setting and the prewetting rate (if available) on the controller
according to the manufacturer’s specifications.
9. Discharge and capture the appropriate amount of solid and liquid chemical for either a
constant number of revolutions of an auger/conveyor shaft or for a specified time
interval. (See Figures 6-8 and 6-9 for examples.)
Figure 6-8 Example of solid and liquid
materials being collected during drop
tests in Wisconsin.
Figure 6-9 Example of conducting drop
test with an open-loop controller in Ohio.
10. Abort the calibration test(s) if a discontinuity in flow of either solid or liquid material
discharge is observed.
24
11. the calculated discharge amounts and calibration Measure the amounts of solid and liquid
chemical discharged satisfactorily.
12. Repeat Steps 8 through 11 for either the required number of times or for the next setting
on the solid discharge knob.
13. Calculate either an average pounds/revolution (lbs/rev) from the number of tests or a
spreader constant by differencing the discharge amounts using two successive discharge
knob settings.
14. Calculate the solid application rate (lbs/mile) for various control settings using average
lbs/rev value and measured rev/min for each setting using a tachometer. (See Figure 610.)
15. Contact the manufacturer to determine
how to adjust the prewetting constant,
if necessary.
16. Enter the values of constants into the
controller.
17. Record the various solid and liquid
calibration factors obtained and used
during the calibration process.
18. Properly exit the calibration mode on
the
controller
following
the
manufacturer’s instructions.
Figure 6-10 Measurement of revolutions of
an auger/conveyor shaft for various control
settings using a hand-held tachometer.
6.4 Use of Calibration Verification Tests Results to Back-in the Calibration Factor
Research results have demonstrated that the spreader/controller systems operated in an open-loop
mode, in general, can not be expected to achieve the same control over discharge rates as the
closed-loop system. However, it is very likely that fine tuning the open-loop system with the
calibration verification test results will produce better agreement for some combinations of test
variables. Again, the main objective of running the calibration verification tests is to produce the
best calibration possible for the range of field operations expected.
1. Conduct the calibration verification tests of the open-loop system following the
procedures described in Sections 5.4 and 5.5.
2. Record the final calibration constants in a log for each spreader/controller combination.
25
7. Calibration of Manually Controlled Salters
The calibration of ground-speed controlled systems that are operated in a manual mode should be
conducted following the controller manufacturer’s recommendations after certain preparatory
steps are taken. These preparatory steps are the same as are used for the calibration of groundspeed controlled units operated in a closed-loop or open-loop mode. (See Sections 6.1 and 7.1 for
details.)
The calibration check list for manually controlled systems is the same as those used for the
calibration of ground-speed controlled units operated in a closed-loop or open-loop mode. (See
Sections 6.2 and 7.2 for details.)
7.1 Calibration According to Manufacturer’s Specifications
The procedures used to calibrate ground-speed controllers that are operated in a manual mode are
somewhat unique to each manufacturer. However, it is noteworthy to describe the calibration
procedure used by a manufacturer as one example.
1. The calibration approach amounted to selecting a truck speed, say 30 mph, and an
application rate of 200 lbs/mile. Several catch tests were run for 60 sec while adjusting
the knob setting on the application rate until a constant discharge weight of 100 lbs was
obtained. This approach produced the appropriate calibration constant (lbs/pulse or
lbs/revolution) within the controller.
2. The catch tests were repeated, as a check, using the same truck speed of 30 mph, but an
application rate of 400 lbs/mile and 30 sec run times. The second catch tests, were
performed while adjusting the knob setting on the application rate until a consistent
discharge weight of 100 lbs was obtained. The second catch tests produced a calibration
constant in the controller that agreed with the constant obtained from the first catch tests.
3. The detents on the control knob provided application rates that were tied to the
calibration rate of 200 lbs/mile at 30 mph truck speed.
4. The procedure would need to be repeated if a different truck speed and/or discharge gate
opening were selected.
7.2 Salt Institute Procedure
The calibration of controllers that are designed only for manual modes of operation can be most
readily accomplished by using a procedure specified in the Salt Institute’s Snowfighters Training
Program(6). That procedure is reproduced in Appendix D and is summarized below.
The calibration of manually controlled spreaders according to the Salt Institute’s procedure is
accomplished by simply calculating the pounds per mile that are discharged at various spreader
control settings and truck speeds. This is achieved by first counting the number of auger or
conveyor shaft revolution per minute, measuring the material discharged in one revolution,
multiplying the two quantities together, and then finally multiplying the discharge rate by the
minutes it takes to travel one mile at a given speed. This procedure produces a calibration chart
that provides a range of discharge (application) rates that are individually tied to specific truck
speeds for a given control setting.
26
Checks of several discharge rates/control settings should be performed to verify that the
calibration of the manually controlled system was performed correctly. For hopper-box
spreaders, the system needs to be calibrated for specific gate openings. For tailgate spreaders, the
truck-bed needs to be raised to an operational elevation and the auger needs to be fully charged
throughout the complete calibration process.
Finally, the calibration chart(s) for each spreader/controller combination operated in a manual
mode needs to be recorded in a log and displayed in the truck cab for the operator’s use.
8. Recommended Timing and Frequency of Calibration
It is extremely important to maintain spreader/controller systems in good working order and to
ensure that the units are calibrated to the best possible extent. A well maintained and calibrated
spreader/controller system will return benefits to the highway agency in terms of material and
manpower cost savings.
The recommended timing and frequency of the system calibration are addressed in varying
degrees by the controller manufacturers. The recommendations given below, attempt to unify the
approach towards proper calibration. This approach is based on research experience and
discussions with field winter maintenance personnel and representatives of controller
manufacturers.
Spreader/controller systems should be calibrated/recalibrated under the following conditions:
• When the spreader/controller unit is first put into service.
• Annually, before snow and ice control operations begin.
• After major maintenance of the spreader truck is performed and after truck hydraulic fluid
and filters are replaced.
• After the controller unit is repaired or when the speed (truck or belt/auger) sensors are
replaced.
• After new snow and ice control material is delivered to the maintenance garage location.
9. Calibration Record Keeping
The maintaining of the calibration history of individual spreader/controller combinations is just
as important as the timing and frequency of the calibration of these units. It is through this
consistent record keeping that light is shed on potential problems, not only with the controller
and related sensors, but also with the spreader truck on which the controller is installed.
Procedures should be established for maintaining calibration records at the maintenance garage
level for each spreader/controller combination along with the equipment maintenance and repair
histories. A review of the calibration constants recorded over time for each spreader/controller
system will help identify equipment problems that need corrective action.
27
REFERENCES
1. Ketchan, S., L. David Minsk, R.R. Blackburn, E.J. Fleege, “Manual of Practice for an
Effective Anti-Icing Program: A Guide for Highway Winter Maintenance Personnel,” Report
No. FHWA-RD-95-202, Federal Highway Administration, Washington, D.C., June 1996,
http://www.fhwa.dot.gov/reports/mopeap/eapcov.htm
1. “Guide for Snow and Ice Control,” American Association of State Highway and
Transportation Officials, Washington, D.C., 1999
2. NCHRP Report 526, Snow and Ice Control: Guidelines for Materials and Methods, 2004
Web site: trb.org/publications/nchrp/nchrp_rpt_526.pdf
3. Blackburn, R.R., E.J. McGrane, C.C. Chappelow, D. W. Harwood, and E.J. Fleege,
“Development of Anti-Icing Technology”, Report No. SHRP-H-385, Strategic Highway
Research Program, National Research Council, Washington, D.C., 1994
4. Blackburn, R.R., E.J. Fleege, and D.E. Amsler, “Calibration Accuracy of Manual and
Ground-Speed-Controlled Salters,” Clear Roads Pooled Fund #TPF-5(092), Final Report,
2008.
5. The Snow Fighters Handbook and Snow Fighters Training Program, Salt Institute web site:
http://www.saltinstitute.org/snowfighting/index
28
APPENDIX A
CALIBRATION VERIFICATION TEST FORM
29
Calibration Verification Test Form
Location: _____________________________
Spreader Type? Hopper-box or Tailgate
Gate Opening: ____
Spreader Controller: ______________________ Firmware Version: ______
Truck No.: _____________ Model: ______________
1
2
3
Average
500
500
500
1
2
3
Average
600
600
600
0.507
0.507
0.507
97.3 to 105.5
10
10
10
25
25
25
49
49
49
102.1
102.1
102.1
0.49 to 0.53
0.510
0.510
0.510
98.0 to 106.2
15
15
15
20
20
20
36
36
36
100.0
100.0
100.0
0.49 to 0.53
0.75
0.75
0.75
96.0 to 104.0
15
15
15
20
20
20
30
30
30
100.0
100.0
100.0
0.72 to 0.78
0.75
0.75
0.75
96.0 to104.0
30
Acceptable
Discharge Range
Amount (gal)
300
300
300
Theoretical Liquid
Discharge (gal)
1
2
3
Average
101.4
101.4
101.4
Test Liquid
Discharge (gal)
73
73
73
Year: ____________
Liquid Discharge
Acceptable
Discharge Range
Amount (lbs)
25
25
25
Theoretical Solid
Discharge (lbs)
10
10
10
Controller Recorded
Solid Discharge (lbs)
Test Time (sec)
200
200
200
Test Solid Discharge
(lbs)
Set Simulated Truck
Speed (mph)
1
2
3
Average
Item
Set Prewetting Rate
(gal/ton)
Solid Discharge
Set Application Rate
(lbs/mile)
Settings for Verification Tests
Controller Recorded
Liquid Discharge
(gal)
Date: ____________________________
0.72 to 0.78
APPENDIX B
SALT INSTITUTE PROCEDURES AND CHART USED
TO CALIBRATE SOLID MATERIAL SPREADERS
WITH MANUAL CONTROLLERS
CALIBRATION CHART (US)
Agency:
Location:
Truck No:
Date:
Spreader No:
By:
Gate Opening
(inches)
DISCHARGE RATE (pounds discharged per mile)
(Hopper Type Spreaders)
A
Control
Setting
B
Shaft RPM
(Loaded)
C
Discharge per Discharge per
Revolution
Minute (lb)
(pounds)
(A x B)
TRAVEL SPEED AND COMPUTATION MULTIPLIER ( )
5 mph
(x 12.00)
10 mph
(x 6.00)
15 mph
(x 4.00)
20 mp h
(x 3.00)
-
25 mph
(x 2.40)
30 mph
(x 2.00)
35 mph
(x 1.71)
40 mph
(x 1.50)
45 mp h
(x 1.33)
1
-
-
-
-
-
-
-
2
-
-
-
-
-
-
-
-
-
-
3
-
-
-
-
-
-
-
-
-
-
4
-
-
-
-
-
-
-
-
-
-
5
-
-
-
-
-
-
-
-
-
-
6
-
-
-
-
-
-
-
-
-
-
7
-
-
-
-
-
-
-
-
-
-
8
-
-
-
-
-
-
-
-
-
-
9
-
-
-
-
-
-
-
-
-
-
10
-
-
-
-
-
-
-
-
-
-
11
-
-
-
-
-
-
-
-
-
-
THE ACTUAL APPLICATION RATE (POUNDS PER LANE MILE) ON THE HIGHWAY
IS THE DISCHARGE RATE DIVIDED BY THE NUMBER OF LANES BEING TREATED
SPREADER CALIBRATION PROCEDURE
Calibration is simply calculating the pounds per mile discharged for each control setting at various travel speeds by first counting the number of auger or conveyor
shaft revolutions per minute, measuring the weight of salt discharged in one revolution, then multiply the two to obtain discharge per minute, and finally multiplying
the discharge per minute by the time it takes to travel 1 mile. Most spreaders have multiple gate openings; so you must calibrate for specific gate openings.
Equipment needed:
1. Scale to weigh salt
2. Salt collection device
3. Marking device
4. Watch with second hand
Calibration steps:
1. Remove, by-pass or turn off spinner.
2. Warm truck’s hydraulic oil to normal operating temperature with spreader system running.
3. Put partial load of salt on truck.
4. Mark shaft end of auger or conveyor.
5. Dump salt on auger.
6. Rev truck engine to operating RPM.
7. Count number of shaft revolutions per minute at each spreader control setting, record.
8. Collect salt discharged for one revolution, weigh it and deduct the weight of the container. (For greater accuracy, collect salt for several revolutions and divide
by that number of revolutions to get the weight for one revolution.)
9. Multiply Column A by Column B to get Column C; then multiply Column C by the number of minutes to travel one mile ( ) at various truck speeds to get
pounds Discharged per mile.*
#################################################################################################################################
CALIBRATION OF AUTOMATIC CONTROLS
Automatic controls may be calibrated using the following steps:
1. Remove, by-pass or turn of spinner.
2. Set control on given number.
3. Tie sack or heavy canvas under spreader discharge area.
4. Mark specific distance on a highway or other paved area, such as 1000 ft. .
5. Drive that distance with spreader operating.
6. Weigh salt collected.
32
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertisement