Inspection and repair on Renk SHSI 3S 1000 gearbox

Scope of work:

We performed an inspection and repair on a gearbox Renk gearbox SHSI 3S 1000.

The conversion operations consists of:

• Disassembly
• A large opening was cut out of the wall between the engine room and the pump room
• A special lifting frame was welded in place to lift off the gearbox top cover and the output shaft
• All piping, coolers, and electric connections were removed by the crew onboard
• The axial thrust pads were removed from the gearbox before lifting the top cover
• The torn motor including its gearbox was removed from the gearbox top casing to gain lifting height
• Top cover of the gearbox was lifted off with four chain blocks and moved towards the pump room
• The output shaft was removed and transported to the workshop of Gearbox Services in Oud Beijerland
• All three gears, both bearings and the thrust collar were removed from the shaft


Inspections on board
• It was decided not to remove the input shaft from the lower gearbox casing. Instead the bearings are visually inspected with the help of a videoscopic camera. No defects other than dirt in some of the bearings was found. The dirt was flushed out with diesel oil by the crew on board
• The thrust bearing clearance of the output shaft was checked. The clearance was 0.65 mm. The manual specifies a clearance between 0.50 and 0.70 mm. The maximum allowable clearance specified is 1.00 mm
• All thrust pads were cleaned. Hard imbedded particles were removed with a scraper. No cracks or serious problems were found


Fabrication and assembly of new gearbox output shaft
• Pre-machining of raw material
• Hardening and tempering
• Testing of mechanical material properties
• Machining to actual size of non-critical diameters
• Machining of sand pump impeller thread
• Machining of oil holes in center of shaft
• Machining of keyways and thread holes
• Machining and fitting of tapered diameters
• Assembly of gears, bearings and thrust collar
• Transport back to vessel


Installation of output shaft on board
• All parts were thoroughly cleaned before assembly. Remains of old liquid gasket were removed. An oil stone was used to verify the flatness of the gearbox split line.
• The output shaft was installed in the gearbox. Backlash of the gears and the correct position of the bearings was verified
• Two axial pads were installed in the lower casing to ensure the correct axial position of the output shaft
• Top casing was installed. Loctite silicone blue sealant was used between the split line
• Bolts were pneumatically tightened with a suitable impact hammer
• The remaining axial pads were installed
• Torn motor including gearbox was installed and aligned with an alignment laser
• Gearbox was filled with 1300 liters of ISO VG 100 lubrication oil
Testing
• Electric stand by pump was started to check for any oil leaks. No leaks were observed
• Dredge pump was started and tested with water only for 2 hours. No abnormal temperatures or sound was observed
• Dredge pump was tested during dredging for 2 hours (low speed). No abnormal temperatures or sound was observed. Maximum casing temperature was 50 degrees Celsius. Lubrication oil reached a maximum temperature of 48 degrees Celsius. Oil pressure was 2.6 bars.
• Dredge pump was tested in medium and high speed during rainbowing for 10 minutes in each gear. No abnormal temperatures or sound was observed
• Inspection covers were opened and the loaded contact pattern was checked by the wear of the earlier applied red lacquer. Only the low speed and medium speed gears could be inspected. The high speed gear did not show any wear of the red lacquer. Both the low speed gear and the medium gear showed a contact pattern of approximately 70 % of the total tooth face width