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”)