Cableway Safety and Inspection

Common Cableway Problems

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

Loose backstay cables

Loose backstay cables

Main Cable

Sag

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

A-frame towers

Saddle Blocks

Saddle Blocks

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

CableCars

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)

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

Footing/pedestal connections toA-frame tower

Footing/pedestal connections toA-frame tower

Footing/pedestal connections toA-frame tower

A+

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

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?

Mass Anchors & U-bars

Mass anchors & U-bars

Mass Anchors & U-bars

Mass Anchors & U-bars

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)

Hardware

Eyebolts Clips

Thimbles

Shackles

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

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 & Thimbles

•Thimble undersized•Clip too far from thimble

Good

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 Hardware

Poor Seizing at Ends

Sockets

Streambank Erosion

Streambank Erosion

Pre-runoff

Post-runoff

Streambank Erosion

Slope Stability

Maintenance

Paints & Coatings

Special Inspections

Unexpected Events

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

Did cableway pass inspection?

• Yes?• No?• Maybe?

Knowledge, judgment, communication