richard jordan
TRANSCRIPT
Insert the title of your presentation herePresented by Name HereJob Title - Date
Reducing spread rates to save saltPresented by Richard JordanPrincipal Researcher – 24 March 2010
Factors affecting required spread rate
Page 2
Initial salt distribution
Amount of salt in solution at road surface- Rate of dissolution
- Trafficking
Amount of water present- Drainage
- Trafficking
Forecast road surface temperature
Page 3
Spreading direction
LV Lane 1 Lane 2 Lane 3 RM RVHS
42
9 10 11 12 13 14
27 2825 26
4 5
39 40 41
6 7 8
14m
28m
15 16
29 30
18 19 20
32 33 34
21
Strip 1
Strip 2
Strip 3
0m
17
31
1 2 3
35 36
22 23 24
37 38
0 5 8.6 12.2 15.8
Position across carriageway (m)
Salt distribution and salt loss trials
Poor distribution profile and high wastage
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Spreader direction
0
10
20
30
40
0 4 8 12 16
Spread salt (g/m2
)
Position across carriageway (m)
Dry salting at 20g/m²
Strip 1
Strip 2
Strip 3
Average
Verge Lane 1 Lane 2 Verge
Dry, pre-wetted and treated salt
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Spreader direction
0
10
20
30
40
50
0 2 4 6 8 10
Spread Salt (g/m²
)
Position across carriageway (m)
Salt 1
Salt 2
Salt 3
Verge Lane 1 Lane 2 Verge
Reasonable distribution with little wastage
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7.7
Spreader direction
0
5
10
15
20
0 4 8 12 16
Spread salt (g/m2
)
Position across carriageway (m)
Prewetted salting at 10g/m²Strip 1
Strip 2
Strip 3
Average
Verge Lane 1 Lane 2 Verge
What can be achieved with correct settings for de-icer
0
5
10
15
20
0 5 10 15 20
Spread salt (g/m²)
Position across carriageway (m)
Prewetted salting at 20g/m2
Strip 1
Strip 2Strip 3Average
HS Lane 1 Lane 2 Lane 3
15.4
7.7
Page 7
Dry salt
Page 8
Pre-wetted salt
Dry salt:Brine 70:30 by weight
Brine concentration: 23%
Page 9
Factors to consider
Page 10
Moisture content of salt should be controlled – preferred range 1.5 to 3.5%
Salt distribution becomes less consistent the more moisture content increases above 4%
Spreader settings must be optimised for the de-icer to be spread
Salt loss is higher for dry salt than for pre-wetted salt and treated salt
Initial salt distribution can be more uniform with pre-wetted salt and treated salt
Effect of salt distribution and salt loss on spread rate
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Target salt at forecast conditions
(g/m2)
Minimum initial
dosage relative to nominal
spread rate
Salt remaining
after trafficking
Required nominal
spread rate (g/m2)
Salt saving
5.0 80% 40% 15.6
5.0 85% 45% 13.1 17%
5.0 90% 50% 11.1 29%
Surface state definitions (from Raukola et al, 1993)
Definition Water (g/m2)
Water film thickness
(mm)Description
Little moist 5 – 20 0.005 – 0.02 Detectably dark road surface
Moist 20 – 50 0.02 – 0.05 Clearly dark road surface
Wet 50 – 200 0.05 – 0.20 Spray phenomenon starts
Very wet 200 – 400 0.20 – 0.40 Small drops of water in the air
Flowing >400 >0.40 Flow according to gradient, splash
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Proposed spread rates (1)
Weather and road conditions
Old dry salting spread
rate (g/m2)
New dry salting spread
rate (g/m2)
New pre-wetted salting
Spread rate
(g/m2)
Salt content (g/m2)
Frost or forecast frostRST at or above -2˚C 10 8 8 6.2
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Proposed spread rates (2)
Weather and road conditions
Old dry salting spread
rate (g/m2)
New dry salting spread
rate (g/m2)
New pre-wetted salting
Spread rate
(g/m2)
Salt content (g/m2)
Frost or forecast frost RST below - 2oC and above - 5oC and dry or damp road conditions (50% more if damp and lightly trafficked) 20
10 9 6.9
Frost or forecast frost RST below - 2oC and above - 5oC and wet road conditions (50% more if lightly trafficked)
16 15 11.5
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Conclusions
For precautionary treatments
There is potential to reduce salt usage by reducing spread rates
The amount spread rates can be reduced safely is dependent on the initial salt distribution
To achieve a uniform salt distribution, spreaders must be set up for the salt being spread
Salt must be stored carefully if it is to be spread consistently
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National Winter Service Research Group
Best Practice Guidance
Performance requirements for spreaders
Spreader calibration procedures
Controlling moisture content variations to optimise performance
Salting technology – dry, pre-wet, treated
Salt and cost saving measures
Route selection
Road weather information systems
Information needs for short, medium and long term decisions
Page 16
Page 17
Thank you
Reducing spread rates to save salt
Snow Summit 2010
Presented by Richard JordanPrincipal Researcher – 24 March 2010
Tel: 01344 770828Email: [email protected]