Transcript Document
Prestudy Paver Training Wardenburg 17-18 February 2009 Dipl.-Ing. (FH) Volker Behrens [email protected] Dipl.-Kfm. Roland Egervari [email protected] 1 Introductory questions Describe the main part of the paver and the material distribution process. Give a short definition for the floating screed principle. – Which factors influence the floating property of the screed? – Define the purpose of the screed load – unload systems – What is the purpose of the tamper? Why do we need vibration in the screed bottom plates? – How do we define „angle of attack“? Specify at least 3 USP‘s for the new Dynapac VB510/600 screeds. Levelling – What is the difference between a GRADE and SLOPE controller? – What does the expression „modular“ means in connection with the MOBAMatic levelling system? Name 3 major differences between Dynapac and Svedala Demag pavers Define the Compactasphalt® method and its advantages 2 Paving in general – Main parts of the paver Canopy Foldable hopper Engine hood Remote control and screed operator position Conveyor Screed Crawler direct drive Push roller Crawler Levelling arm 3 Material – Conveying and Distribution – Material Flow 1. A lorry or other kind of feed vehicle dumps the material mix in the hopper. 2. The conveyor belts transport the mix to the rear wall of paver. 3. One auger for each side distributes the material mix across to the paving direction in front of the screed to the complete paving width. 4. Paving speed, paving width and thickness are fundamental factors of the required material quantity. Sensors at the rear wall in top of the conveyor belt and the auger take care of a controlled, continuous material flow. The bulk in front of the screed is significantly responsible for a constant result. The head of the material in front of the screed must be constant. 4 Material – Conveying and Distribution – Material Supply 5 Screed – Free Floating Screed G Z a W A A = Buoyancy (upward force from the asphalt) G = Weight of the screed W = Resistance from the head of the material W1= Friction between the screed plate and the material Z = Traction power The angle between the bottom plate of the screed and the surface being paved is known as the angle of attack. A number of forces act on the screed, The force Z is the tractor unit moving the screed forward and the forces W and W1 are the resistance from the head of material and the friction between screed plate and the asphalt respectively. G is the weight of the screed and A is the upward force from the asphalt. A depends on the angle of attack (a) and the speed of the paver. The layer thickness is determined by adjusting the tow-point on the tractor unit. Screed – Free Floating Screed Forces that influence the balance of the screed: The screed rises if: • the head of material increases • the speed of the tractor increases • the material temperature drops Material bulk in front of screed to high. The screed settles if: • the head of the material decreases • the speed of the tractor unit decreases • the material temperature increases The height of the screed remains constant only if all forces acting on the screed are in equilibrium. Material bulk in front of screed to low. Auger correct adjusted and material bulk in front of screed optimal. 7 7 Screed - Screed Control Screed STOP – LOAD – UNLOAD systems Screed stop system This system automatically locks the screed lift arms when the paver stops during a paving operation. Screed unload system This system prevents the screed from sinking into the material by laying of extremely soft materials or by traction problems (controlled by an adjustable hydraulic pressure on the screed lifting cylinder). The screed side arms are attached to the hydraulic levelling cylinders which control the level of the screed. The tow-point position affecting the layer thickness. Screed load system The system provides additional load to the screed and enables it to maintain the desired level after a long stoppage (controlled by an adjustable hydraulic pressure on the screed lifting cylinder). The screed lifting cylinder are not active during the normal paving procedure. Only in function by screed „load & unload“ control. 8 Screed – Tamper & Vibration Vibration •Compaction effect •Reduces the friction between screed plate and asphalt mix •Screed floats more easily over the material •Bitumen raises to the asphalt surface providing additional lubrication enhancing the surface structure The tamper facilitates the flow of material underneath the screed plate. The tamping mechanism uses a vertical, high-amplitude movement at comparatively low frequencies. 9 Screeds New: VB 510T(V) / EB 51 New: VB 600T(V) / EB 60 1. Low height of construction Better view in the auger section (head of material) 2. Unique, patented telescopic system 3. 380 mm screed bottom plate depth 4. Excentric lever for the adjustment of the angle of attack (next slide) 5. Quick height adjustment for the hydraulically extendable parts 10 Screed - Free Floating Screed Quick adjustment Layer thicknesses : Position I : < 7 cm Position II: < 7 cm – 14 cm Position III: > 14 cm The angle between bottom plate of screed and sub base is called “angle of attack”. By changing of the position from quick adjustment lever, the angle of attack will be increased or decreased. 11 Levelling – Automatic Levelling System A grade controller, working off a reference surface, automatically maintains the height of the screed and the layer thickness for the material • Modular construction • Regulator automatically recognises the connected sensor The slope controller maintains the specified left and right-hand cross-slope of the mat during the laying procedure. It detects any deviations of the screed from a pre-set cross-slope and generates the necessary signals to restore the original setting. Laser Sender LS-250 Digital Remote Control Ultra-Sonic Sensor SONIC-SKI Rotary Sensor DIGI ROTARY Slope Sensor DIGI-SLOPE Laser Scanner RSS 3-D Levelling Control System 12 Levelling – Automatic Levelling System Slope Sensor The slope controller maintains the specified left and right-hand cross-slope of the mat during the laying procedure. It detects any deviations of the screed from a pre-set cross-slope and generates the necessary signals to restore the original settings. 13 Brand specific features / Dual branding 14 Brand specific features / Dual branding Auger drive Auger drive 15 Brand specific features / Dual branding Delta crawler crawler 16 Brand specific features / Dual branding Hopper design Hopper design 17 Brand specific features / Dual branding Canopy type Canopy type 18 Compactasphalt - Definition The method was developed in cooperation with the company Hermann Kirchner GmbH & Co. in Bad Hersfeld and Prof. Dr.-Ing. Elk Richter from the University of Applied Sciences in Erfurt, to reliably achieve paving a thin wearing course with high compaction. According to the German fact sheet MKA, the Compactasphalt method allows the laying of the wearing and binder course in one single process hot on hot, whereas the binder course is highly pre-compacted and the rolling process of both layers is carried out in one single operation. Due to the modular design of the paver unit, no heavy vehicle has to pass over the hot binder course. 19 Compactasphalt - Advantages Halved construction time Cost savings due to halving of the expensive wearing course Excellent interlocking of the courses Extended time for compaction – By increasing the laying thickness from 4 cm to 12 cm, the compaction time is extended 7 times! Certified laying process according to the German Rule compendium „ZTV Asphalt-StB 07“ Asphalt laying at 0°C is possible 20 Driven by innovation – committed to customer performance 21