Issues related to binder distributors

Trevor Distin

Background

• ± 75 calibrated binder distributors operational in the RSA

• Spray approximately ± 100, 000, 000 litres of binders per anum viz ± 80 million m2

• Increased use of modified binder seals under high traffic conditions

• Shift from spraying emulsions and hot bitumen to more viscous PMB’s and Bitumen Rubber

Overview of issues

1. Various methods being used to determine transverse distribution

2. Spray tolerances3. Validity period for sprayer

calibration certificates4. Protocol for flushing and

testing spray bars on-site

Binder Sprayer Specifications

• TMH 2 (1979) – Spraying performance of binder

distributors• TRH 3 (1998) Appendix J

– Calibration of transverse distribution of spray bar in the field

• COLTO section 4300-15– Spray rate tolerances

Transverse distribution of spray bar - fixed pit facility

Requirements of TMH 2

• Not more than 5% of individual values may differ more than 18% from mean

• Divide spray bar into three sections: Mean of side sections may not differ more than 5% from mean of middle

• Mean of volume collected in any 4 adjacent trays may not differ from mean by more than 10%

Typical transverse distribution(TMH 2)

- 25

- 20

- 15

- 10

- 5

0

5

10

15

20

Transverse distribution of spray bar - in the field

• Known as ‘bakkie’ test• 3 nozzles per trough• 42 nozzles = 14 ‘bakkies’• Different methods being used to

interpret results

‘Bakkie’ test

Method 1• Highest value is 100%• All other values may not be

less than 95%

Method 2• ± 5% deviation allowed from

mean Method 3• Difference between adjacent

troughs may not be more than 5%

Method 4• Results divided into three sets:

Left wing, right wing and centre bar

• Mean of each section may not differ by more than 5% from overall mean

Method 5 (TRH 3)• One container under each

extension• Two containers under main bar• Containers may not differ from

each other more than 5%

“Bakkie” Test(3 nozzles per trough)

- 15

- 10

- 5

0

5

10

1 2 3 4 5 6 7 8 9 10 11 12 13 14

trough number

% d

evia

tion

Spraying Tolerances

RSA±0,06 l/m2 (all binders)

±5% (bitumen rubber)

COLTO section 4300-15

Australia±0,10 l/m2

(conventional)

±0,15 l/m2 (PMB’s)

±0,20 l/m2 (bit rubber)

Factors effecting accuracy of spray reading

• Accuracy of dipstick – 50 litre graduations (±5mm)

• Length of spray– 50 l @ 0.06 l/m2 = 915 l

• Expansion of dipstick– 5 mm of expansion @ 200 °C

• Expansion/contraction of product– On 20 kl 228 l difference on diff 10°C

• Viscosity of product

Viscosity influences

• Machine is calibrated with a Newtonian oil with a viscosity of 40 - 100 cSt @ 40 °C

• PMB is non-Newtonian and sprayed at 200 °C with a viscosity of 150 - 200 cSt

Calibration of sprayers

• 3 Provincial testing facilities– Pretoria– Pietermaritzberg– Port Elizabeth

• Validity period of calibration certificate– 12 months for Provinces– 6 months for SANRAL

Cost of calibration

Time related costs– Preparation– Travel– Testing

Travel – R7 per km– Accommodation

Testing fee

TOTAL

• R30,000– 2 days– 2 days– 1 day

• R11,500– 1500 km– 2 nites

• R2,700

• R44,200

Way forward?

Appoint a task team to:– Investigate appropriate validity period for

calibration certificate– Develop a rational method for the ‘bakkie’

test– Investigate spray tolerances for modified

binders– Develop a protocol for flushing and testing

spray bars on-site in line with HSE requirements

Proposed task team

Client– Gautrans– KZN– SANRAL

Consultants– Wouter Schreuder– Russel Clayton– Douglas Judd

Contractors– Nico Wilcox– Philip Kuun– Charlie Backlund

Applicators– Densil Sadler– Kevin Spence– Kobus Louw