Replacement of the Cracked Rowland Man Winder Drum Shaft

Presented by: W.C. StemmetRowland Shaft Engineer

Contents1 Synopses2 Winder History3 Incident4 Analysis, planning and scheduling5 Actions prior to the replacement program6 Preparation work7 Safety8 Replacement over Christmas break9 Lessons learned10 Closure and Recognitions

Synopses

The daily safe transportation of our workforce to and from the underground levels is seen as just another activity in the mining cycle. This view changed when a crack was detected in the clutch spline of the Man Winder drum shaft.

The presentation:

Provides the framework and analysis that was used for the planning and scheduling of the temporary and permanent actions required to restore the defective drum shaft without affecting production.

It describes in detail the challenges faced, the technology and systems used to successfully conduct the repair.

Winder History

• Built by English Steel Corporation in 1929 for Rand Mines as a bi-cylindro-conical with a small drum diameter of 12ft and a large drum diameter of 24ft and a single clutch.

• Installed underground at Crown Mines at 16A shaft.

• In the early 1970’s it was relocated to Prieska as their man winder and retained in the bi-cylindro-conical form.

• Subsequently it was bought by Lonrho about 25 years ago and converted by Lebus Engineers to cylindrical drums and used as the kibble winder for sinking Western Plats 4 shaft.

• Currently in use as the men/material winder at Rowland Shaft Lonmin Platinum.

Incident

• During the weekly winder examination on 23 February 2006 an anomaly was detected in the winder drum shaft at the clutch spline.

• The affected area was thoroughly cleaned and investigated.• Metallock, Anglo Field Services and FFE Minerals-Vecor were

contacted to assist in the assessment of the failure. • A decision was taken to open the clutch area over the weekend

of 25 February 2006 to inspect the full extent of the crack. • The area on the shaft was marked to monitor any crack

propagation. • All clutching operations were suspended on the winder.

Cracked Shaft

Clutch outer line when fully engaged

Analysis, planning and scheduling

1. Metal stitching the cracked shaft

2. Machining out the cracked area

• FEA done on shaft

3. Replacing the drum shaft

Metal stitching the cracked shaft

175m

280mm

Metallock Industrial Services –Offered to gouge out the crack and weld it up in position.

Machining out the cracked area

Area targeted to be milled out in the shaft and replaced in the clutch slider

Finite Element Analysis of the Shaft (FEA)

• The FEA modelling was carried out on the shaft dovetail interface with the clutch slider using the maximum expected load from a single brake retarding a down going load.

• The FEA results show that there are no geometric modifications to the dovetail that will reduce the peak stresses on the cracked portion.

• The cracked dovetail is stressed at 74% more than the un-cracked face.

• The increase in stresses leads to high contact forces approaching yield on the cracked face.

Finite Element Analysis of ShaftA full length contact

367 MPa196 MPa

636 MPa340 MPa

Full face radius

193 MPa103 MPA

667 MPa357 MPa

Full face in contact

Average expected stresses over face.

Maximum stresses recorded / expected

Shaft results

Expected/normal clutch torque of 1.07 MNm

Finite Element Analysis of ShaftA partial face contact

667 MPa357 Mpa

1156 MPa619 MPa

Partial face radius

336 MPa180 MPa

1612 MPa863 MPa

Partial face in contact

Average stresses over

face.

MaximumStresses

Recorded / expectedShaft results

FEA Recommendations

• Leave the current cracked piece in place• Continue to monitor the crack in the shaft to see if the

crack propagated any further. • Daily and weekly visual examinations.• 2 Monthly stripping of the clutch with NDT and 3D

mapping of the area.• Review the current clutch design to determine if the

design is adequate for worst case braking operations. • Replace the cracked shaft and install a newly designed

clutch.

Replacing the Drum Shaft

• The used spare shaft in the store at Rowland Shaft was sent to FFE Minerals-Vecorwhere it was cleaned for inspection.

• A complete metal particle inspection, run out and ultrasonic test was carried out and the bearing and drum bush journals were machine polished and sized.

• Replacement was planned for the 2006 Christmas break

Actions prior to the replacement program

• Repair programme drawn up for 15 days.

• Christmas break was scheduled for 11 days.

• Retainers to keep machine shops open.

• Low bed access and road embargo.

• Craneage / Winder house roof.

• Motor and drum supports

• Drawings

Preparation work

• Additional overhead crane.

• Removal of drum and brake path bolts.

• Bolt manufacturing.

• Pre-fitting of spare bearings.

• Casting of drum bushes.

• Clutch design review.

• Lock nuts.

Safety

Man Hours Worked = 6084

LTI’s = 0

MTC’s = 0

Incident/Near miss = 1• Crane long travel motor failure

Scope of Work

•Refurbishment and delivery of the drum shaft.•Supply:

•A new set of bolts with final line bore machining done on site.•New drum bushes.

•Clutch thrust faces, thrust collar and monkey ring machined and refurbished.

•Strip winder, replace drum shaft and commission in12 days.

•Level 1 audit and dynamic tests.•Supply as built engineering drawings.•Design and manufacture new clutch.

Project

Winder before project

Shaft Delivery

19/12/2006

Bearings/Bolts Delivery

21/12/2006

Taking off the Ropes

Doubling down ropes and securing conveyances.

23/12/2006

Removing the drums and brake paths

Winder being stripped

Lifting out the old shaft

Where is the winder ??

Fitting the new shaft and bearings

Rebuilding the winder

Winder completely repaired05/01/2007

Lessons Learned

• To use all resources

• Necessity of drawings and plans

• Movement and distortion when dismantling old equipment

• Measurements and assumptions

Bolts inserted with Liquid Nitrogen on drums and brake paths

Lessons Learned

Frozen drum bolts on hubs

Clutch clamping on the drum shaft

Joint faces still open, bolts not

tight

To plan for possible Eskom power outages

Closure

Project finished 40 hours behind schedule due to the following delays:•Drum halves opened up and twisted on the joint flanges.

•Eskom power failure.•Old refurbished clutch not fitting on the new shaft.

Recognitions

• Lonmin Platinum Marikana Division• DME• The team• Shogun Construction• FFE Minerals-Vecor• Anglo Field Services• AMRE

Thank You

Any Questions

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