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Issues related to binder distributors

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

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Issues related to binder distributors

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  1. Issues related to binder distributors Trevor Distin

  2. 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

  3. Overview of issues • Various methods being used to determine transverse distribution • Spray tolerances • Validity period for sprayer calibration certificates • Protocol for flushing and testing spray bars on-site

  4. 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

  5. Transverse distribution of spray bar - fixed pit facility

  6. 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%

  7. Typical transverse distribution(TMH 2)

  8. 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

  9. ‘Bakkie’ test

  10. 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%

  11. 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%

  12. “Bakkie” Test(3 nozzles per trough)

  13. 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) Spraying Tolerances

  14. 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

  15. 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

  16. Calibration of sprayers • 3 Provincial testing facilities • Pretoria • Pietermaritzberg • Port Elizabeth • Validity period of calibration certificate • 12 months for Provinces • 6 months for SANRAL

  17. 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 Cost of calibration

  18. 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

  19. 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 Proposed task team

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