Uphill / Downhill. Super Elevations. Wide-Width 2/15/2016. March 22-24, 2016 Nashville, TN

Transcription

1 Uphill / Downhill Wide-Width 1

2 Uphill Issue Loss of traction Downhill Issue Spills caused by truck rollaway Uphill Paving Obvious things Apply correct amount of tack Wait for tack to break 2

3 Uphill Paving Obvious things Separate paver from truck Self-propelled transfer device, or Windrow elevator Paver operates without stopping Less chance of wheel spin Uphill Paving Obvious things Control head of material Too much mix too much weight more chance of wheel spin Add auger and mainframe extensions when practical 3

4 Uphill Paving Obvious things Track pavers provide better traction -- either tread bar or smooth belt Wheel pavers more prone to spinning out Uphill Paving Truck Exchange Stop paver with hopper full of mix Provides material needed to move paver forward to contact next truck and continue without stopping 4

5 Uphill Paving Truck Exchange Next truck stops short of push rollers Leave 2-3 foot gap Apply truck brakes Uphill Paving Truck Exchange Tailgate still locked Break load to put pressure against the tailgate 5

6 Uphill Paving Truck Exchange Move paver ahead slowly to contact truck tires Release truck brakes Optional: truck moves forward slowly as paver moves forward Release tail gate immediately and raise bed more, if necessary Bring paver up to normal speed without stopping Uphill Paving Truck Exchange Pave out truck without stopping Gravity keeps truck against push rollers no braking needed 6

7 Uphill Paving Special techniques Ballast in tires for added weight on rear axle -- consult manufacturer for ballast options Broadcast HMA in front of tires for added traction on slick surfaces Uphill Paving Special techniques Front wheel assist option -- one bogie wheel driven per side All wheel drive option -- both bogie wheels are driven on each side 7

8 Uphill Paving Special techniques Activate screed assist (counterbalance) Transfer weight from screed to rear axle Improve traction Uphill Paving Screed Assist Check assist pressure before engaging Consult OMM for maximum pressure 8

9 Uphill Paving Special Techniques Enable Hill Hold feature, if available Brake stays engaged until -- propel system current exceeds valve cracking limit, or -- brake is engaged more than 2 seconds after propel lever is moved from Neutral position Prevents paver roll-back Downhill Paving Truck Brake Pressure Light brake pressure to maintain contact with push rollers Use optional calibrated hand lever to apply partial brakes Prevents rollaways 9

10 Downhill Paving Truck Hitch Popular option in some areas Positive connection between truck and paver Prevents rollaways Note: on steep grades, truck may pull paver Downhill Paving Spills in front of paver Be sure truck bed is empty before releasing Gravity pulls mix toward front of hopper Pave out most of mix in hopper in before stopping 10

11 Uphill / Downhill Rolling Pattern Uphill normal operation Both drums vibratory Uphill / Downhill Rolling Pattern Downhill roll static on steep grades Vibratory mode can cause washboard effect Need to verify effect on density May need additional passes 11

12 Uphill / Downhill Rolling Pattern Pneumatic roller good choice for uphill / downhill application May add passes in intermediate phase to help make up for less breakdown density Uphill / Downhill Paving Paving Speed Verify that paving speed and effective rolling speed are matched to uphill / downhill application May have to reduce paving speed if rollers make more passes 12

13 Uphill / Downhill Paving Paving Speed example 275 tons / hour 17-feet wide 3.0 uncompacted 75% efficiency rate Actual paving speed: 21 feet / minute Effective paving speed: 16 feet / minute Uphill / Downhill Paving Rolling Speed example 79-inch drums 2520 vpm frequency 3 repeat vibratory passes needed to get target density 9-pass pattern 80% efficiency rate Actual rolling speed: 194 fpm Effective speed: 16 fpm Matches paver speed 13

14 Uphill / Downhill Paving Rolling Speed example 79-inch drums 2520 vpm frequency 2 vibratory passes and 2 static passes needed to get target density 13-pass pattern on hills Actual rolling speed: 280 fpm Less than 10 impacts / foot Must reduce actual paving speed to 17 fpm on hills Uphill / Downhill Paving Checklist to Review with Crew Tack application Auger & mainframe extensions, if practical Truck exchange procedure Front wheel assist / all-wheel drive activated Screed assist pressure checked before activating Hill hold feature enabled Rolling patterns confirmed with QC team Paving speed and effective rolling speed confirmed 14

15 Terminology Crown section: opposing slopes either side of C/L Level Section: no slope upper side; same slope lower side Tangent runoff: distance between crown section and level section is a gradual change in profile 15

16 Terminology Super elevation: no crown and maximum slope Super elevation runoff : distance between level section and super elevation is a gradual change in profile Maximum slope determined by distance from crown section to super elevation Cross Section View Identifies profile by station Identifies profile by lane Can set up to pave one lane at a time, or Can pave full width on narrower structures 16

17 Before Paving Verify slopes are clearly marked for screed operator Readable from 50 feet Before Paving Check slopes in multiple locations Compare measured slope to plan at grade stakes Note amount of correction needed, if any 17

18 Before Paving Calculate thickness changes 1% Slope correction = 1/8 depth change per foot 1% Slope correction across 12-foot lane = 1.5 of depth change Before Paving Notify inspector or engineer if paver will be making profile corrections Discuss the effect of slope corrections on yield Determine how much slope tolerance is acceptable 18

19 Before Paving Choose set-up that makes most sense a. grade control both sides if profile is correct b. grade control and auto slope for small corrections c. grade control and manual slope for large corrections If Profile Is Correct Grade control both sides will reproduce existing profile Best control of yield Best ride quality 19

20 Small Profile Corrections Grade control one side -- manual with screws -- auto with one sensor -- turn off avg. ski or configure to use one sensor Auto slope control opposite side Auto Slope Control Operator slowly dials in slopes shown on grade stakes Slope control makes rapid changes Tow point may move large distance Be prepared to buy back cylinder 20

21 Tow point at top of cylinder stroke Turn crank to increase thickness Still in Auto Slope Control Tow point will start to move down in response to manual depth increase Stop turning screw when tow point position is acceptable Tow point at bottom of stroke Turn crank to decrease thickness Still in Auto Slope Control Tow point will start to move up in response to manual depth decrease Stop turning screw when tow point position is acceptable 21

22 Large Profile Corrections Grade control one side -- manual with screws -- auto with one sensor -- turn off avg. ski or configure to use one sensor Manual slope control opposite side Measured Value Manual Slope Corrections Select slope sensor Calibrate measured slope value (Survey mode for Topcon System 5) Remain in MANUAL mode Control measured value within tolerance through depth cranks 22

23 To Increase Slope Turn screw in direction of thickness decrease Watch measured slope value on display To Decrease Slope Turn screw in direction of thickness increase Watch measured slope value on display Disadvantage: slope changes occur slowly in manual mode Advantage: tow point never runs out of stroke 23

24 Paving two lanes Only possible if road can be closed Requires good planning and communication for crewmembers Requires lots of communication to residents and businesses Paving Two Lanes Plan how to get trucks in front of paver Avoid long back-ups if possible Select adequate turn-around locations Give truck drivers clear instructions 24

25 Paving Two Lanes Add as much auger and tunnel extension as practical 10 feet Paving Two Lanes Try to avoid paving width changes Impractical to install extensions Nearly impossible to control feeder system properly at wide width without auger and tunnel extensions 19 feet 25

26 Paving Two Lanes More complicated than paving lane by lane Need to do some math Paving Two Lanes Crown section is simple With screed in the air, install required crown Verify crown after take-off 26

27 Tangent Runoff Calculating Tangent Runoff 1. Subtract slopes on either side of CL and divide by = 2, 2/2 = 1 2. Change crown gradually to 1% during tangent runoff 3. Add slopes on either side of C/L and divide by = 2, 2/2 = 1 4. Gradually add 1% left to right slope during tangent runoff 5. Left lane will be flat. Right lane will be 2% L-R slope at station Crown Section Calculating Super Elevation Runoff 1. Subtract slopes on either side of CL and divide by = 0, 0/2 = 0 2. Change crown gradually to 0% during super elevation runoff 3. Add slopes on either side of C/L and divide by = 4, 4/2 = 2 4. Gradually change to 2% left to right slope during first part of super elevation runoff. 5. Screed will be flat. 2% L-R slope at station Super Elevation Runoff 27

28 Completing Super Elevation Runoff 1. Flat screed no crown 2. Gradually change slope to 4% L-R at station Gradually change slope to 6% L-R at station Maintain maximum slope of 6% for length of super elevation 5. Reverse steps to resume crown section at end of super elevation Super Elevation Runoff Special Techniques Align trucks to high side of hopper Minimize hopper load imbalance Minimize spills caused by dragging mix out of hopper 28

29 Super Elevation Paving Checklist to Review with Crew All profiles clearly marked for crew Slopes checked before paving Slopes corrected, if necessary, before paving Thickness changes calculated based on slope corrections Inspector informed of possible yield variations Set up auto or manual control to match application requirements Add extensions for two-lane paving Provide calculations for runoff changes when two-lane paving Discuss how to align trucks Wide-Width Paving 29

30 Wide-width Paving Variable Width Find widest section -- flat screed or sloped extension? -- set up balanced extensions whenever possible Wide-width Paving Variable Width Add necessary screed extensions Check angle of attack and flatness Install screed heat plug-in 30

31 Wide-width Paving Variable Width Find narrowest section -- What is minimum extension width? Wide-width Paving Variable Width Add maximum allowable auger extensions Add maximum allowable mainframe extensions 31

32 Wide-width Paving Variable Width Be prepared to shovel mix out to end gate at widest width Be prepared to shovel trapped mix when extension retracted for narrower width Wide-Width Paving Variable Width Position mechanical feed sensor Paddle 18 from end of auger shaft at 45 degree angle 18 32

33 Wide-Width Paving Variable Width Aim sonic feeder sensor at material moving off front of the auger shaft 18 from target Wide-Width Paving Variable Width Feeder system runs full speed when sonic sensor more than 30 from target Head of material erratic Throwing aggregate to create segregation stripe 33

34 Wide-Width Paving Variable Width Still rolling forward around mainframe extension Stripe moving toward edge of mat Need to re-aim sonic sensor when paving width changes Wide-width Paving 2 Fixed Wide Width Install wide-width kit for extra auger and mainframe extension Lower brace (1) attaches to tractor and mainframe extensions Upper brace (2) attaches to auger bearing support 1 34

35 Wide-width Paving 2 1 Fixed Wide Width Auger bearing support (1) attaches to end of mainframe extension Provides guide for outer auger bearing hanger (2) 4-foot auger extension still free to move vertically Wide-width Paving Fixed Wide Width 4 (1,2 m) mainframe extension added Always cover auger extensions Helps guide mix out to end gate 35

36 Wide Width Paving 12 (30 cm) Fixed Wide Width Auger extension -- last auger segment 12 to 24 from end gate Mainframe extension -- must cover length of auger extension Maintain head of material at half an auger all the way out Wide-width Paving Averaging Ski Installation Non-contact ski Outside paving width -- joint match application -- need long scissor arm mounting hardware -- fold rear section over new mat for best averaging 36

37 Wide-width Paving Averaging Ski Installation Non-contact ski Inside paving width -- short mounting hardware -- check clearance over screed extension -- check for interference from head of material in front of extension Wide-width Paving Averaging Ski Installation Mechanical ski Inside paving width -- Fore N Aft Leveler -- no limitations 37

38 Wide-width Paving Averaging Ski Installation Mechanical ski Outside paving width foot outboard Leveler -- superior averaging -- limited reach in this application; need extra long front guide bar Wide-width Paving What Not To Do Excessive head of material Averaging ski improperly installed Feeder sensor in wrong position 38

39 Wide-Width Paving Checklist to Review with Crew Confirmed maximum paving width (variable width) Confirmed minimum paving width (variable width) Installed necessary bolt-on screed extensions Installed maximum allowable auger and mainframe extensions Reviewed feeder sensor position(s) Installed wide-width kit (fixed width paving) Reviewed grade control set-up inside paving width Reviewed grade control set-up outside paving width 4 Thanks for your Participation Please complete the evaluation to provide your feedback on this session and suggest topics for future events. Remember to mark these upcoming events on your calendar! March 7-11,