Winter Maintenance Manual

Transcription

1 Winter Maintenance Manual Michael D. Evans Produced by Utah LTAP Center Utah State University 4111 Old Main Hill Logan UT

2 To order additional copies of this Winter Maintenance Manuals, please call the Utah LTAP Center at revised 08/2008

3 Contents Guide to Anti-Icing and Snow, Ice Control Strategies... 1 Basic Strategies... 2 Three Steps to Winter Storm Management... 2 Temperatures... 3 Pure Salt Concentration & Corresponding Specific Gravity... 4 Dilution of Solution... 4 Dillution of a Product... 5 Example Freezing Point of Magnesium Chloride Brine... 6 Quality Control... 7 Material Quality Control... 8 Dry Equivalents... 9 Pounds of Ice Melted Per Pound of Salt... 9 Salt Hydrometer Conversation Chart Mag Chloride Hydrometer Chart Pre-Wetting Percentage De-Icer (Salt) Remaining on Road After Traffic Post-Storm Benefits Keys to Success Effective Use of Plows Weather Information Sources Public Awareness T.A.P.E.R Application Rate Tables Product Selection... 22

4 Abstract Conversion Factors Conversion Factors (continued) Metric Conversion Factors Metric Conversion Factors (continued) Converstion Factors: Common Fractions to Decimal Numbers Perimeter, Area, & Value Formulae Product Considerations Spreader Calibration Procedure Winter Equipment PlowGuard & CurbGuard Installation Acknowledgements Our thanks to the following for their valuable help in creating this manual. Dale Keep, President Ice & SnowTechnologies (IST), LLC 2151 Granite Drive Walla Walla, Washington Lynn Bernhard, Methods Engineer Utah Department of Transportation Maintenance Division Front cover photo used with permission; copyright held by Michael D. Evans.

5 Guide to Anti-Icing and Snow, Ice Control Strategies Anti-icing is effective and cost efficient when correctly used and approached with realistic expectations Anti-icing should be first in a series of strategies for each winter storm Anti-icing is most cost effective on heavy frosts and freezing fogs Liquid chemicals are better than solids for anti-icing Crew training and a basic understanding of how deicers work is critical Sales personnel should not raise false expectations by over simplifying the use of deicer chemicals. It is extremely important that some sales staff do not continue to present their products as a panacea with a one-applicationrate-fits-all-conditions approach Decisions on snow and ice control strategies need to be based on total cost (with all things considered) rather than just the purchase price of a particular chemical. Page 1

6 Basic Strategies Anti-icing (Proactive) is a snow and ice control strategy for prevention of a strong bond between frozen precipitation or frost and a pavement surface by timely application of a chemical freezing point depressant. Deicing (Reactive) is an operation where a treatment of a deicer is applied to the top of an accumulation of snow, ice, or frost that is already bonded to the pavement surface. Three Steps to Winter Storm Management 1. Anti-ice Early 2. Managed Transition 3. Modified Standard Operations Page 2

7 Temperatures Effective. Effective Temperature is the lowest temperature in which the cost of the application is justified by the results obtained. Eutectic. Eutectic Temperature is the freeze point of a solution based on the percentage of chemical in the solution, and not the volume. Page 3

8 Pure Salt Concentration & Corresponding Specific Gravity As Measured by a Hydrometer at 15 C (59 F) Dilution of Solution As a chemical application takes on water the concentration of the solution dilutes and the Page 4

9 temperature at which it melts ice rises. This process is Dilution of Solution. Specifically, an ice control product will work until product dilution causes the freeze point of the brine to equal the pavement temperature. At this point, the material will stop melting and you may experience refreeze. How long an application will last depends on 4 factors and they explain why one application rate will not fit all storm events. The temperature and moisture of each storm event varies, therefore, the application amount needed to control each storm varies. Remember, the effectiveness of any deicing chemical is dependent on four factors: 1. Surface Temperature 2. Application Rate 3. Moisture present or received 4. Beginning concentration Dillution of a Product The dilution of a liquid product in a storage tank is not recommended and should not be done. The solution in the tank should represent the best solution for use. If less chemical is needed, then reduce the application rate. DO NOT DILLUTE PRODUCTS! THIS RAISES THE FREEZE POINT, LOWERS THE PERFORMANCE, AND REQURES HIGHER APPLICATION RATES FOR Page 5

10 SIMILAR RESULTS WHEN COMPARED TO THE NORMAL PRODUCT. Example Freezing Point of Magnesium Chloride Brine Page 6

11 Quality Control A good quality control program is essential to any reliable anti-ice/de-ice program. The potential for inconsistencies in delivered products will result in inconsistent performance. Without a good quality control program, performance results can differ even though applications and circumstances are the same. Knowing the specific gravity of a liquid chemical deicer and the associated information is the heart of a good quality control program. This information can be gathered in the field with a battery tester. Page 7

12 Material Quality Control It is critical that a chart showing concentration, specific gravity for that concentration and correlating freeze point for the liquid deicer product you are using be available. Multiply the weight of water times the specific gravity to determine the weight of the liquid deicer. (Magnesium Chloride example) 28% = specific gravity X 8.34 pound/gallon = pounds/gallon Field check liquid material can be accomplished by performing the following steps: 1. Get a sample and check the specific gravity of it with a hydrometer. 2. Reference the hydrometer reading to the correlating information on the chart. When possible, get certified weight slips on delivered load. With the weight slip and knowledge of the quantity delivered you can very quickly determine the quality of the product delivered. Assume you have ordered 5,000 gallons of 28% magnesium chloride. The weight of the load as verified by a certified weight slip is 51,000 pounds. 51,000 pounds/ 5,000 gallons = per gallon of weight /8.34 tells us that the specific gravity of this product is Checking the Page 8

13 chart, we find that this product is only 24% and clearly does not meet the 28% specification for the order. Dry Equivalents Remember that with liquid deicers, water is only a carrier. To determine dry chemical equivalents, again specifi c gravity and the weight of water comes into play. In the example, the 28% product weighed pounds per gallon with a specific gravity of Multiply the total weight per gallon times the concentration percentage (10.53 X.28 = 2.95 lbs.) to obtain the dry equivalent. In other words, for every gallon applied at this concentration, 2.95 pounds of chemical is applied, and 7.58 pounds of water is used as a carrier Pounds of Ice Melted Per Pound of Salt Page 9

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15 Salt Hydrometer Conversation Chart Page 11

16 Mag Chloride Hydrometer Chart Page 12

17 Pre-Wetting Pre-wetting (wetting the material at aplication) provides many benefits over traditional winter maintenance, as the following information demonstrates. Page 13

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19 Percentage De-Icer (Salt) Remaining on Road After Traffic Dry Salt Wet Salt 5 vehicles at 38 mph 30% 93% 100 vehicles at 38 mph 15% 80% Post-Storm Benefits Easy removal Less cleanup Reduced environmental impact High potential of reduced overall storm management cost Keys to Success Accurate Weather Information Proper Strategies Educated Product Selection Information-Based Application Methods Effective Use of Plows When anti-icing, plowing as a part of the strategy removes snow and loose ice on the road surface, which can cause excessive dilution of product applications and decrease its effectiveness. Plowing should be used to remove snow and loose ice Page 15

20 before anti-icing applications. If snow accumulates before or after applications, plowing directly before your next application will minimize product dilution. Anti-icing trucks should be equipped with front-end plows. Weather Information Sources NOAA - U.S. Weather Bureau Monthly norms of temperature and precipitation for multiple stations in each state. Wide geographical area, generalized forecast Very low cost Website: (search by city) General Weather Consultant Good mid to long range More detailed No on-site equipment Medium Cost Special Forecast Consultant Site specific Pavement temperatures RWIS used Medium cost Page 16

21 Weather Websites (search by city) Public Awareness Liquid Anti-icing is a relatively new practice compared to traditional salting and sanding. Because the driving public sees the activities that maintain roads during storms, it is important that they are educated regarding new winter practices. Imagine the reaction of an uninformed citizen that sees maintenance personnel applying what appears to be water to a cold road. Reactions could include, apprehension, curiosity, outrage or even fear. To pro-actively remedy this educate the public through print media, television, and radio. Allow the local news to cover a story on the new practices and the benefits it will provide the public. A little up-front attention will save you from a lot of grief and phone calls. Page 17

22 T. A. P. E. R. A Method for Implementation T. A. P. E. R. Temperature: How cold did it get since my last application? Application: What is my rate of application? Product: What product am I using? Event: What kind of storm event? Amount/type of precipitation? Results: What were the results? Why? What should be changed? Your level of service goal should drive road maintenance activities. There is no cure-all application rate for any deicing chemical. As with any deicer product or tool the effectiveness and efficiency of use comes from experience. The T. A. P. E. R. Log system is an easy method to track your experiences, and establish application guidelines that meet your needs. TAPER is an easy way to track actions and results. Remember, no one application rate fits all storm events. Page 18

23 Application Rate Tables Information gathered from the TAPER logs can be summarized into application rates for your area. Page 19

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25 Use the data from the TAPER Log, in chart form, to set the application rate for the forecasted precipitation (as shown below). Numbers are used to demonstrate the system, and are not necessarily accurate application rates. Remember, application rates will vary with surface temperature, moisture, and beginning concentration. Page 21

26 Product Selection Material that gets the job done. Material that operates within a specific temperature range. Material that works fast. Material that is safe to the environment: humans and animals; rass, trees, shrubs, etc.; reduced corrosion. Material that is effective and economical when total cost of use is considered. Material that is easy to handle: not harmful; not an irritant. For further information: Manual of Practice for an Effective Anti-icing Program: A Guide For Highway Winter Maintenance Personnel Page 22

27 Abstract Highway anti-icing is the snow and ice control practice of preventing the formation or development of bonded snow and ice by timely applications of a chemical freezing-point depressant. It provides a maintenance manager with two major capabilities: the capability for maintaining roads in the best conditions possible during a winter storm, and the capability to do so in an efficient manner. As a consequence, anti-icing has the potential to provide the benefit of increased traffic safety at the lowest cost. However, to achieve this benefit the maintenance manager must adopt a systematic approach to snow and ice control and must ensure that the performance of the operations is consistent with the objective of preventing the formation or development of bonded snow and ice. Such an approach requires use of considerable judgment in making decisions, requires that available information sources be utilized methodically, and requires that the operations be anticipatory or prompt in nature. An additional reference would be Snow & Ice Control Chemicals Practices & Theories (by Dale Keep). This manual provides information for successful implementation of an effective highway anti-icing program. It is written to guide the maintenance manager in developing a systematic Page 23

28 and efficient practice for maintaining roads in the best conditions possible during a winter storm. It describes the significant factors that should be understood and must be addressed in an anti-icing program, with the recognition that the development of the program must be based on the specific needs of the site or region within its reach. The manual includes recommendations for anti-icing practices and guidance for conducting anti-icing operations during specific precipitation and weather events. Page 24

29 Conversion Factors Page 25

30 Conversion Factors (continued) Page 26

31 Metric Conversion Factors Page 27

32 Metric Conversion Factors (continued) Page 28

33 Conversion Factors: Common Fractions To Decimal Numbers Page 29

34 Perimeter, Area, & Value Formulae Page 30

35 Product Considerations Page 31

36 Spreader Calibration Procedure Calibration is simply calculating. Page 32

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42 Winter Equipment PlowGuard & CurbGuard Installation Bolts Torque bolts to 200 ft./lbs. Nuts Use S.A.E. Grade 8 Nuts. No Lock Washers Lock washers gouge the backside of the snowplow moldboard because the washer is harder than the moldboard. These hardened lock washers act as a cutting tool, causing unwanted metal shards on the moldboard where the nut is to seat. No matter how hard you tighten the nut, these metal shards will flatten under use, causing the nut to loosen on the bolt and eventually shear the bolt under use. Use a hardened lock nut to alleviate this condition. If using standard Grade 8 nuts, double nut. Page 38

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