cableway safety and inspection common cableway problems
TRANSCRIPT
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Cableway Safety and Inspection
Common Cableway Problems
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Common Problems
• Loose backstays & main cable sag issues• A-frame towers• Footing/pedestal connections to A-frame• Mass anchors and U-bars• Freeboard• Hardware• Streambank erosion & slope stability• Design and as-built documentation
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Loose backstay cables
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Loose backstay cables
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Main Cable
Sag
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Sag• Systems designed to
current standards should use sag curve from Streamgaging Cableways (Note: not a 2% sag at all points on curves)
• Older systems should use sag curve from Circular 17 (Pierce, 1947), presented in Streamgaging Cableways
3% sag line
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A-frame towers
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Saddle Blocks
Saddle Blocks
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Sheaves/Saddle Blocks• Strength Efficiency
- Bending wire rope reduces its strength. To account for the effect of bend radius on wire rope strength when selecting a sheave or saddle block, use the table below:
• D/d ratio should be > 10 (Streamgaging Cableways)
• D/d ratio for a pipe A-frameand 1” cable is approximately6 (not within USGS standards)
Ratio D/dStrength Efficiency
Compared to Catalog Strength in %
40 95
30 93
20 91
15 89
10 86
8 83
6 79
4 75
2 65
1 50
D: diameter of sheave, saddle block, etc.
d: diameter of main cable
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CableCars
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Cable Cars
HIF Cars– Retrofits are required on all stand-up cars
(Nov 1997)(Retrofit kits are available from the HIF; part #2601030)
– Retrofits are required on all sit-down cars (Sept 2002)
(Retrofit kits are available from the HIF; part #2602010)
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Freeboard
DesignWaterSurface
• Freeboard unknown or documentation lacking• Not enough freeboard at 100-yr flood stage• Reference mark needed to indicate maximum stage for safe measurements
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Footing/pedestal connections toA-frame tower
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Footing/pedestal connections toA-frame tower
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Footing/pedestal connections toA-frame tower
A+
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Mass Anchors and U-bars
• Mass anchors– Many are undersized or actual dimensions
unknown– Submergence– Below grade causing cable to lay on ground
• U-bars– Many are undersized, oriented incorrectly, poorly
aligned, or placed at wrong angle– Often no auxiliary U-bars– Use quality U-bars
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Mass Anchors
• Undersized• Dimensions unknown• Poor below-grade construction• Built flush or below grade
U-bars
• Undersized• Bearing blocks• Poorly aligned• Auxiliary U-bars• Quality steel?
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Mass Anchors & U-bars
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Mass anchors & U-bars
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Mass Anchors & U-bars
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Mass Anchors & U-bars
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Standard Anchor Setup
• Main U-bar and turnbuckle sized to meet specs
• Two auxiliary U-bars sized to meet specs
(see Streamgaging Cableways for details on specifications for sizes and number of main and auxiliary U-bars)
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Hardware
Eyebolts Clips
Thimbles
Shackles
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Eyebolts• Forged, shoulder-type bolt• Bolts must be sized to meet
load (1” minimum; Streamgaging Cableways)
• ONLY 30% efficient at 45° angle!!!
Size In-line pull 30° pull 45° pull
(in.) (lbs.) (lbs.) (lbs.)
1/4 650 423 195
5/16 1,200 780 360
3/8 1,550 1,008 465
1/2 2,600 1,690 780
5/8 5,200 3,380 1,560
3/4 7,200 4,680 2,160
7/8 10,600 6,890 3,180
1 13,300 8,645 3,990
1-1/4 21,000 13,650 6,300
1-1/2 24,000 15,600 7,200
Working Load Limit
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Failed Eyebolts• Not shouldered; not forged
• Eye is welded shut
• Long shank; eye should be flush to bearing plate
• Undersized
• Placed horizontal not vertical
• Not-shouldered; not-forged
• Eye was welded to bolt
• Undersized
• (*** This eyebolt failed during a load test before reaching the 2,250 lb design load)
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Clips & Thimbles
•Thimble undersized•Clip too far from thimble
Good
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Clips
• Clips should be installed with saddle on “live” end of cable as shown:
• NEVER reuse clips; throw old clips away!!!• What if clips have been installed the wrong way?
– Leave original clips in place; install new clips, in the correct direction, in the spaces between the original clips
– Or if possible; remove clips, cut off “used” portion of cable and install new clips according to manufacturers directions (see Streamgaging Cableways)
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Clips-continued
• When installing new clips on a new cable:– Follow instructions in Streamgaging Cableways
• Install first (one base width from end) and last (as close to the loop as possible) clips and then install remaining clips equally spaced between the first two
• No standard spacing between clips; depends on turnback length
– Re-torque after first use and again after any larger than normal loads have been placed on the system
– If there is a need or you want to check torque during annual inspections, set torque wrench to one setting less than the required torque
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Other Hardware
Poor Seizing at Ends
Sockets
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Streambank Erosion
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Streambank Erosion
Pre-runoff
Post-runoff
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Streambank Erosion
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Slope Stability
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Maintenance
Paints & Coatings
Special Inspections
Unexpected Events
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Design and As-Built Documentation (Items Frequently Lacking)
• Mill certificates & material certifications• Make & model numbers of hardware• Receipts or design-file notes• Subsurface anchor and pedestal dimensions• Details of steel reinforcement used• Type of cement used in concrete mix• As-built drawings or sketches
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Did cableway pass inspection?
• Yes?• No?• Maybe?
Knowledge, judgment, communication