Marine Link
Friday, September 22, 2017

Built to Fit

August 18, 1999

When Foss Maritime Company decided to regear tug Iver Foss, the choice to go with Lufkin paid off, as the company's replacement gears had been designed to fit perfectly in the space vacated by the gears being replaced. Marine owners and operators, like Foss Maritime Company, have always faced steadily rising repair costs and replacement problems, as a result of aging propulsion drives. In fact, some manufacturers' units are no longer in production, and are not commercially available. Many non-Lufkin units require new equipment be installed, because access to parts and service can be difficult for some older or discontinued models; however, parts and service continue to be available for all Lufkin drives. As a result, Lufkin engineers have developed a cost-effective solution to these escalating expenses, while keeping downtime and installation costs to a minimum, by designing and manufacturing replacement units for existing non-Lufkin equipment. Foss Maritime Company's decision to regear its tug, Iver Foss, with two Lufkin RLS2100 drives was made easier because the RLS2100 has been designed to fit in the space previously occupied by two Cat 7271 propulsion gears, which were removed. One of the primary advantages of installing the RLS2100 was no structural modification to the vessel was required. The design fits in the existing foundation hole pattern and with the existing tail shaft coupling of the previous Cat 7271 units. Since Lufkin replacement models can be designed to be dimensionally interchangeable with the existing propulsion drives, Foss' downtime was greatly reduced, because the engine, gear foundation and tail shaft did not have to be disturbed - just realigned. When replacing existing equipment and regearing a vessel, Lufkin can make operational improvements to the original equipment. All Lufkin marine gearing meets ABS and other classification societies' standards. The RLS2100 marine gears are capable of transmitting 2,000 hp at 1,600 rpm, or 1,125 hp at 1,225 rpm, meeting ABS requirements at either power level. Also, the input shaft can be designed to bolt to the existing coupling flange, or preferably, a more modern coupling, which has been selected based on a torsional analysis. In this installation, Foss decided to use new couplings to improve the reliability of the new RLS2100 units. Lufkin has incorporated many cost-saving design features in the RLS2100. By designing the unit with rear-mounted hydraulic clutches, Lufkin ensures clutch maintenance can be performed easily without removing the unit cover or gear elements. Other features of the RLS2100 include average bearing lives in excess of 100,000 hours, and pinion bearing mounted in bearing carriers where room permits. These features enable Foss to extend time intervals between overhauls and reduce downtime to perform overhauls, which lowers total operating and maintenance costs. Of all Lufkin replacement drives, careful attention is taken to reduce installed space and weight as much as possible. Also, a conservative rating and design are incorporated to guarantee mechanical integrity and reliability. Then, internal thrust is balanced for high-operating efficiency and thermal stability. The RLS2100 has a full-capacity thrust bearing based on 60,000 lbs. thrust at 300 rpm propeller speed. Due to the extreme operating conditions and the need to maintain schedule integrity aboard Iver Foss, it is critical each component of the RLS2100 unit be manufactured incorporating proven design features to withstand the rigorous demands of marine service. By utilizing the latest 3-D solid modeling technology and sophisticated analytic capabilities, Lufkin can generate advanced designs that are proven before being manufactured. The designs can then be electronically transferred to the customer. Lufkin employs vertical integration and state-of-the-art technology such as carburizing gears to increase durability and torque capacity. As a pioneer in the application and development of CBN technology for high HP gearing, Lufkin is considered a leader in this area. CBN gear tooth finishing provides precision, noise reduction, decreased friction loss and scoring risk even at the high power levels required in marine service. As a result, Lufkin marine gearing consistently meets the AGMA Quality Class 13 Rating. Lufkin is an ISO 9001 company. Terry Orr is director of sales and marketing for the power transmission division of Lufkin Industries, Lufkin, Texas.
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