Bearings and Seals: Applying the Latest Technologies
Featured in HydroWorld | June 2011
By Elizabeth A. Ingram
Bearings and seals have important jobs to fulfill on various pieces of equipment at hydroelectric facilities, including gates and turbines. Bearings can minimize friction and corrosion, keep the shaft aligned, and eliminate the need for grease. Seals can protect against the intrusion of water and dirt and minimize leakage.
The applications on the following pages showcase innovative materials and approaches designed to provide for reliable long-term operation while minimizing wear and leakage. As a result, the hydro project owners have gained confidence in the operation of their facilities and, in many cases, saved money and/or time.
Installing self-lubricating bearings on miter gates
The downstream navigation lock gates at the 1,780-MW The Dalles Dam project were showing signs of wear. These two miter gates, which began operating in 1957, allow for passage of marine traffic on the Columbia River in Oregon.
In September 2009, U.S. Army Corps of Engineers personnel noticed issues of wear, based on readings from the gate stress and strain monitors. Inspection of the gates revealed that two did not make any contact when closed and the overall load was being transferred to the pintle areas. This resulted in cracking through the skin plate and end post. Emergency repairs were performed to keep the gates operating while the Corps began design and engineering work to replace all the gates.
The new gates are 52 feet wide by 106 feet high and weight about 750,000 pounds. For the rotating parts, the Corps specified self-lubricated bushings and thrust plates to eliminate grease and any concerns about corrosion. Columbia Industrial Products (CIP) manufactured CIP Hydro Bearings for the gudgeon pin upper bushing, operating arm bushings, eye bar bushings, flange bushings, and thrust washers. CIP Hydro is a laminated composite material, says Jessica Leamen with CIP. This material is a medium-weave polytetrafluoroethylene and polyester fabric blend. The addition of solid lubricants to the resin reduces friction, extends wear life, and improves performance in wet and dry applications, she says.
To address the Corps’ concern with corrosion in the application, the bearings were designed with a glue-fit installation method. The glue acts as a protection paint for the housing and eliminates the concern with water seeping into the surface between the housing and bearing, Leamen says. The glue-fit process also allows for tighter running clearances and overall dimensions that are similar to the original bearing design. Design with this method eliminates the tolerances of the house and the press/interference fit between the inner diameter of the housing and the outer diameter of the bearing. The internal diameter of the bearing remains unchanged and can more accurately operate based on the final machined tolerances of the composite, therefore accomplishing tighter running clearances.
CIP had previously used this installation method during replacement of the tainter gates at 40-MW Foster Dam.
Installation was completed in March 2011.