U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
202-366-4000
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
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| This report is an archived publication and may contain dated technical, contact, and link information |
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Publication Number: FHWA-HRT-05-153
Date: December 2006 |
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Long-Term Pavement Performance Program Falling Weight Deflectometer Maintenance ManualView PDF Version(1.63 Mb) PDF files can be viewed with the Acrobat® Reader® FOREWORDMany pavement engineers rely on falling weight deflectometer (FWD) technology. FWDs "thump" the pavement and record information related to its structural integrity. FWDs are often preferred over destructive methods of testing because they are much faster than destructive tests and do not entail the removal of pavement materials. In addition, the testing apparatus is easily transportable as a trailer or vehicle-mounted. The Federal Highway Administration’s (FHWA) Long-Term Pavement Performance (LTPP) program operates eight Dynatest® Model 8000 FWDs to collect load and deflection data on in-service pavement test sections across North America. LTPP has collected pavement deflection data in daily operations for 15 years, and in that time, the FWDs have had very little downtime. Continuous preventive maintenance is necessary to keep the complex hydraulic-electrical-mechanical FWDs operating under demanding conditions to collect high quality data and pass rigorous annual reference calibrations. The owner’s manual from the manufacturer provides guidance on most repairs, maintenance and troubleshooting; however, eventually FWDs require service beyond routine maintenance–in other words, the time comes for a complete overhaul. In spring 2003, the LTPP Southern Region support contractor overhauled one of the FWDs operated for the LTPP program. During the overhaul, the contractor documented the process photographically and described the process of disassembling and reassembling the FWD components and subcomponents. This document provides FWD owners, operators, and technicians information as a supplement to the Dynatest 8000 owner’s manual. Maintenance guidelines are based on continuous operation of FWDs. Less frequent operation may require adjusting maintenance frequency; however, the owner’s manual from the manufacturer should be followed. Gary L. Henderson Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation. This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. This report does not constitute a standard, specification, or regulation. Quality Assurance Statement The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. Technical Report Documentation Page
TABLE OF CONTENTSCHAPTER 1.
INTRODUCTION CHAPTER 2. FALLING WEIGHT
DEFLECTOMETER TRAILER CHAPTER 3.
SUBASSEMBLY CHAPTER 4. STRIKE PLATE, LOAD CELL,
RAISE/LOWER ASSEMBLY CHAPTER 5.
ELECTRONICS APPENDIX: SCHEDULED MAINTENANCE LOG LIST OF FIGURESFigure 1. Corrosion caused by battery Figure 2. Second battery ground connection Figure 3. Missing bolt drilled out, tapped, and replaced Figure 4. Stripped and sandblasted trailer ready to go to powder coat facility Figure 5. Rear view of trailer before powder coat was applied Figure 6. Front of newly powdered trailer Figure 7. Rear of newly powdered trailer Figure 8. Lower trailer covers Figure 9. Top trailer cover ("dog house") Figure 10. Front trailer cover Figure 11. Torsion axle and mounting plate Figure 12. Torsion tube housing Figure 13. Top view of torsion axle and shims Figure 15. Hydraulic hitch assembly and hand brake Figure 16. Mounted view of complete brake assembly Figure 17. Brake drum with adjusting slot Figure 18. Flexible brake lines Figure 19. Flexible brake line behind tire Figure 22. New axle wheel bearings and components Figure 23. Trailer brake and license plate lights and backup alarm Figure 24. Trailer turn signal and brake lights Figure 25. Freshly painted subassembly with joints reinforced Figure 26. Subassembly mounted on trailer Figure 27. FWD attached to tow vehicle Figure 28. Disconnect battery terminals Figure 29. Multisignal connection to control box Figure 30. Reinforced weld on top of subassembly Figure 31. Reinforced weld on bottom of subassembly Figure 32. Guide locations on a subassembly Figure 33. Drop weight assembly Figure 34. Placement of glide ring, bottom view of weight package Figure 35. Closeup view of glide ring Figure 36. Roller guides mounted to drop plate Figure 37. Buffer pads and drop plate in position Figure 39. Weights on the drop weight assembly Figure 40. Hydraulic pump, motor, and fluid tank Figure 43. Brushes and retainer Figure 44. Manifold block and A/B valve mounted to hydraulic pump Figure 45. Components of the A/B valve and manifold block Figure 46. PS1 and PS2 switches Figure 47. Threads on the PS1/PS2 switch Figure 48. Solenoid mounted to hydraulic motor Figure 49. Wiring for Motor and Solenoid Figure 50. Electrical wiring for the hydraulic motor Figure 51. Main cylinder components Figure 52. Center cylinder and components Figure 55. Main cylinder gland and components Figure 56. Assembled main cylinder gland Figure 57. Catch flange, release piston, and plunger shaft Figure 58. Top view of catch flange Figure 59. Assembled catch flange and release piston (bottom view) Figure 60. Assembled catch flange and release piston (top view) Figure 61. Center cylinder and gland Figure 63. Assembled main cylinder Figure 64. O-ring installed in the main cylinder Figure 65. Main cylinder attached to strike plate Figure 66. Upper catch shell and interior components Figure 69. Placement of the guide pins Figure 70. Ball bearings in place on the inner body Figure 71. Inner body set in place Figure 72. Inner body and hex bolts Figure 73. Inner catch top cover installed Figure 74. Outer shell, top down, with interior components exposed Figure 75. Interior of catch assembly with compression springs Figure 77. Outer shell with inner ring in position Figure 78. Inner ring in position inside the outer shell Figure 79. Insert outer flange Figure 80. Guide flange and spring Figure 82. Attach the upper catch Figure 85. Complete upper catch assembly with cover Figure 86. Side cylinder and components Figure 87. Mounted side cylinder Figure 88. Front side cylinder, looking up, from under FWD Figure 89. Rear side cylinder looking up from under FWD Figure 90. Load cell mounted to the strike plate Figure 92. Bottom view of load cell swivel and retaining bracket on strike plate Figure 93. Load plate (base down) Figure 94. Load plate with mounting brackets Figure 95. Load cell with brackets mounted Figure 96. Mounting brackets and lock flange attached to strike plate Figure 97. Strike plate with attached load cell and pad (shown inverted) Figure 98. Adhesive applied to PVC disk Figure 99. Raise/lower bar guide location before assembly(rear) Figure 100. Raise/lower bar guide during assembly Figure 101. Raise/lower bar guide in location Figure 103. Center lift nut and attaching bolts Figure 104. Closeup of cable connection Figure 105. Raise/lower bar, guide rod, and attaching cable Figure 108. Mounted geophone holders to raise/lower bar Figure 109. Completed assembly of raise/lower bar Figure 110. Rear view of raise/lower assembly Figure 111. Geophone holder components Figure 112. Assembled geophone holder Figure 113. Geophone components Figure 114. Ground ring and geophone Figure 115. Mounted ground ring Figure 116. New geophone cable Figure 118. Attached ground lug Figure 119. Geophone cable soldered to geophone Figure 120. Silicone-filled housing Figure 121. Base cover on housing Figure 122. Geophone with base plate attached Figure 124. Completely assembled geophone Figure 125. Raw cable and DIN plug housing Figure 126. Internal view of the DIN plug Figure 127. Completed DIN plug Figure 128. Four types of proximity switches Figure 129. Electronics connection box Figure 131. Rear view of vertically mounted system processor Figure 132. Vehicle-mounted proximity switches Figure 133. Vehicle charge plug Figure 134. Trailer-to-vehicle charge plug Figure 135. Power control box (board behind front panel) Figure 136. Trailer fuse block Figure 137. Electronics battery inside the vehicle LIST OF TABLESFHWA-HRT-05-153
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