Cableway Safety Cableway Safety An overview of common problems and issues regarding current USGS cableway systems.

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”)