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Publication Number: FHWA-HRT-05-153
Date: December 2006

Long-Term Pavement Performance Program Falling Weight Deflectometer Maintenance Manual

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FOREWORD

Many 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
Director, Office of Infrastructure Research
and Development

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

1. Report No.

FHWA-HRT-05-153

2. Government Accession No.

N/A

3. Recipient’s Catalog No.

N/A

4. Title and Subtitle

Long-Term Pavement Performance Program
Falling Weight Deflectometer Maintenance Manual

5. Report Date

December 2006

6. Performing Organization Code

N/A

7. Author(s)

Robin Belt, Tyler Morrison, Eric Weaver

8. Performing Organization Report No.

N/A

9. Performing Organization Name and Address

Fugro Consultants, LP
8613 Cross Park Drive
Austin, TX 78754

10. Work Unit No. (TRAIS)

N/A

11. Contract or Grant No.

DTFH61-01-C-00087

13. Type of Report and Period Covered

Final – Spring 2003

12. Sponsoring Agency Name and Address

Office of Infrastructure R&D
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101 2296

14. Sponsoring Agency’s Code

15. Supplementary Notes

Contracting Officer’s Technical Representative: Jack Springer, PE, HRDI-13

16. Abstract

The Federal Highway Administration’s (FHWA) Long-Term Pavement Performance (LTPP) program operates eight Dynatest Model 8000 FWDs to collect 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-electricalmechanical 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 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.

17. Key Words

Falling weight deflectometer, FWD, pavement deflection, maintenance, Dynatest, pavement testing equipment

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service; Springfield, VA 22161

19. Security Classification (of this report)

Unclassified

20. Security Classification (of this page)

Unclassified

21. No. of Pages

88

22. Price

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized (art. 5/94)
   

Metric Conversion Chart


TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION
     Background
     Organization

CHAPTER 2. FALLING WEIGHT DEFLECTOMETER TRAILER
     Trailer Frame
     Accessories
     Torsion Axles
     Hydraulic Brake System
     Tires And Wheels
     Trailer Lights

CHAPTER 3. SUBASSEMBLY
     Subassembly Maintenance
          Guide Profiles
          Drop Weight Assembly
     Hydraulic System
          Main Cylinder
          Center Cylinder
          Main Cylinder Gland
          Catch Flange and Plunger Piston
          Bench Assembly Method
          Upper Catch Assembly
     Side Cylinders

CHAPTER 4. STRIKE PLATE, LOAD CELL, RAISE/LOWER ASSEMBLY
     Strike Plate
     Load Cell
     Raise/Lower Bar
     Geophone Holder

CHAPTER 5. ELECTRONICS
     Proximity switches
     Electrical Connection Box
     System Processor
     DMI Proximity Switch
     Vehicle Charge Plug Connection
     Power Control Board
     Fuse Blocks
     Electronics Battery

CHAPTER 6. CONCLUSION

APPENDIX: SCHEDULED MAINTENANCE LOG


LIST OF FIGURES

Figure 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 14. Trailer tires

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 20. Rigid brake lines

Figure 21. Brake drum

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 38. Lift collar

Figure 39. Weights on the drop weight assembly

Figure 40. Hydraulic pump, motor, and fluid tank

Figure 41. Hydraulic pump

Figure 42. Hydraulic motor

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 53. Center cylinder

Figure 54. Oil hole port

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 62. Inner tube

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 67. Upper catch shell

Figure 68. Inner body

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 76. Inner ring

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 81. Upper catch

Figure 82. Attach the upper catch

Figure 83. Align top cover

Figure 84. Tighten all bolts

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 91. 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 102. Raise/lower bar

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 106. Raise/lower cover

Figure 107. Attached 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 117. Separated wire

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 123. Attached magnet

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 130. System processor

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 TABLES

Table 1. Truth Table for Hydraulic System Operation

FHWA-HRT-05-153

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The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT).
The Federal Highway Administration (FHWA) is a part of the U.S. Department of Transportation and is headquartered in Washington, D.C., with field offices across the United States. is a major agency of the U.S. Department of Transportation (DOT). Provide leadership and technology for the delivery of long life pavements that meet our customers needs and are safe, cost effective, and can be effectively maintained. Federal Highway Administration's (FHWA) R&T Web site portal, which provides access to or information about the Agency’s R&T program, projects, partnerships, publications, and results.
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