Post on 17-Dec-2015
Cableway Cableway SafetySafety
An overview of common problems and issues regarding current USGS cableway systems.
Common Problems
• Freeboard
• Anchors and U-bars
• Sag
• System hardware
Freeboard• Not enough freeboard during high flows
– Should have 10’ to 15’ between bottom of loaded cable and water level during 100-year flood (Streamgaging Cableways)
– Place notice in the gage house stating max usable stage(max usable stage = bottom of loaded cable – 10 ft)
Anchors and U-bars
• Anchors– Many are undersized or don’t know actual dimensions
– Fortunately, most are not in areas where submergence is possible
• U-bars– Many are undersized, placed in wrong direction or placed
at wrong angle
– Often no auxiliary U-bars
– Recommend getting all U-bars through the HIF• Quality assurance
• X-rayed to verify structural integrity
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)
Sag• Systems designed to
current standards should use sag curve from Streamgaging Cableways (Note: not a 2% sag curve)
• Older systems should use sag curve from Circular 17 (Pierce, 1947), presented in Streamgaging Cableways
3% sag line
System Hardware
• Sheaves
• Saddle blocks
• Eyebolts
• Clips
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
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
Backstay Tension Calculations
*** A 1-inch shouldered eyebolt pulled at a 45° angle
is rated for a working load of 3,990 lbs
• Forces exerted on backstay cables vary for different angels
• Values were obtained from Sverdrup Technologies report; Sverdrup performed the engineering analysis for current USGS cableway systems
Assumptions: 1" EEIP cable Cable weight: 1.85 lb/ft300' clear span Design load: 2,250 lbsRolling sheaves
Sverdrup Technologies -- cable tension multipliers (approximate):2% sag: 6.53% sag: 5.0
Main Cable Tensions: (total load on cable times multiplier)2% sag: 18,250 lbs3% sag: 14,000 lbs
Sverdrup Technologies -- tensionBS / tensionMC (approximate):30° BS: 0.2045° BS: 0.45
Backstay Cable Tensions: (ratio of main cable tension)2% sag 3% sag
30° BS: 3,650 lbs 2,800 lbs45° BS: 8,200 lbs 6,300 lbs ***
(total cable load includes cable weight)
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)
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)
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
Other Issues• 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)
– Non-HIF Cars• Currently working on a plan for testing non-HIF cars for
compliance
• Load Testing– Consult Regional Cableway Specialist before deciding
to load test a structure
Inspection Checklist
• Official Western Region inspection checklist (WR Policy Memo – July 18, 2002)
http://1stop.usgs.gov/Safety/Topic/checklists/cableway_inspection_checklist.pdf
• This checklist should be used by all Western Region Districts for future annual inspections
• Take note of the “Inspection Results” box(at the end of the inspection, determine whether or not the structure is SAFE to use)
• UNSAFE cableways must be condemned and removed from service until repaired (WR Policy Memo – June 14, 2002)(includes being locked with a non-USGS lock or having the cable car removed immediately following the inspection; include a sign: “Removed from Service”)