search.noResults

search.searching

note.createNoteMessage

search.noResults

search.searching

orderForm.title

orderForm.productCode
orderForm.description
orderForm.quantity
orderForm.itemPrice
orderForm.price
orderForm.totalPrice
orderForm.deliveryDetails.billingAddress
orderForm.deliveryDetails.deliveryAddress
orderForm.noItems
FEATURE GEARS & GEARBOXES


Rapid gearbox repair resolves design faults for steel mill


Keeping downtime to a minimum requires a combination of in-house engineering skills and a partnership with a well-resourced, specialist repair provider. This became evident for one steel mill when a bearing failure caused a production line to stop and an urgent repair was required. Calling on Sulzer engineers, the plant initiated a round-the-clock repair that minimised downtime and delivered a cost effective and long-lasting solution


D


ealing with enclosed pieces of equipment, such as pumps and


gearboxes, can often reveal unexpected damage. What may appear as a simple repair can quickly develop into a much larger concern once the covers have been removed, and the initial investigations are carried out. The extent of the issues found may be beyond the technical capabilities of a customer’s in-house maintenance department. In such situations, entrusting the repair to a multi-disciplined maintenance provider may be the most cost-effective solution. In this particular case, a 15-shaft


gearbox on a steel coil levelling line, had suffered from a failed bearing, and the maintenance manager asked a Sulzer engineer to attend the site to discuss possible options. Sulzer took delivery of the gearbox at 2:00am the next morning and the process of disassembly and detailed inspection began. With all of the securing bolts removed, the casing was difficult to open; this was potentially a problem caused by excessive sealant use. In fact, it appeared the sealant may have also blocked the oil galleries lubricating the shaft bearings and was a likely contributing factor to the bearing failure. As the inspection progressed, the


customer was informed on all of the findings which were likely to have contributed in the failure of the gearbox. The bearings themselves varied in dimensions, despite their critical need to be identical. This discrepancy in the dimensions had a knock-on effect to the spacers on each shaft, as they too were


24 FEBRUARY 2017 | DESIGN SOLUTIONS


all different. Aneil Hanafiah, mechanical engineer,


explains: “It soon became apparent that the gearbox was an original design that had been copied. We measured several dimensions repeatedly because they seemed to be so far out from what we were expecting. We invited the customer to come and inspect the various components in order to gain a better understanding of the scale of the repair.” Almost every component within the gearbox had to be remanufactured or repaired in some form, either due to poor original manufacturing, or through wear caused by inaccurate assembly. Even the keyways on the shafts that held the gears in position were off-centre both radially and axially. This would soon be resolved by enlarging the keyways so that the new position could be aligned on each shaft. The new keys were manufactured so that the gears could be relocated into the correct positions. With lubrication supplies to the


bearings being critical to the smooth running of the gearbox, the misalignment of the oil galleries in the bearings was the next problem area to resolve. Again, these were re-machined and positioned in the correct location so that the new, quality bearings would now have sufficient lubrication. Several of the shafts were repaired using a wire thermal spray process and then machined back to the design tolerance for a perfect fit. Two shafts were beyond repair and so the machine shop manufactured new components as replacements.


On the positive side, the original gears


were inspected with a penetrating dye and all were found to be undamaged. Some minor wear was found and refurbished before they were reassembled into the gearbox. The robustness of the gears appeared in direct contrast to the rest of the gearbox, leading the engineers to question if the gearbox had originally been manufactured in parts, in separate locations, prior to original assembly. Throughout the repair project, the customer was regularly updated on progress and despite the considerably broadened scope, the deadline for completion was still met. All of the damage was repaired and all components were manufactured to best engineering practices, which significantly improves the durability of the gearbox. Hanafiah concludes: “This particular


example illustrates the potential for a relatively simple repair to escalate into something much more complex. It also shows how the purchase of what could be imitation products without knowledge can sometimes lead to additional maintenance costs. These will often far outweigh the initial low cost benefit. Now termed as the total cost of ownership (TCO), this approach takes into account the long term implications of running and maintenance costs and gives us a more realistic value to high quality equipment and repairs.”


Sulzer www.sulzer.com





Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64