Lower Granite: Reliability, Resources and In-House Solutions

Story and Photos by Ranger Dawn Waldal   Each year, the Corps of Engineers does a routine outage for all eight locks on the Lower Snake and Columbia Rivers. Generally, the outages last no more than three weeks allowing for […]

Story and Photos by Ranger Dawn Waldal

 

Each year, the Corps of Engineers does a routine outage for all eight locks on the Lower Snake and Columbia Rivers.
Generally, the outages last no more than three weeks allowing for routine maintenance and inspection. This year was the first reoccurring extended outage that will be scheduled approximately every five years for 14 weeks to accommodate more complex maintenance and repair projects. Locks are scheduled to be out of service until mid-March.

During this years extended outage, Lower Granite’s upstream gate, which holds back Granite Lake during a lockage, had its synthetic fiber (Kevlar) rope cables replaced with a more durable plastic filled and coated (Tuff-Kote) steel wire ropes. When the dams were originally built in the 1970’s both Lower Granite and Little Goose had similar equipment that hoisted their upstream gates. Both had problems with the cables prematurely wearing out due to the tight bend radius and fatigue cracks.

So, in 1990 the Corps replaced the traditional steel wire ropes at both facilities, each employing a slightly different type of more flexible rope. Lower Granite received synthetic fiber ropes jacketed in a polyethylene plastic. Over time, a number of concerns arose as the ropes began to stretch, exposing fibers at the root. While this did not pose any direct issues, it did became increasingly worrisome as the ropes were not able to be magnetically tested for weaknesses as is possible with steel rope.

Most recently, as a precautionary measure and in an effort to buy down risk, the Corps of Engineers elected to replace the ropes with the same style that Little Goose received in 1990. Their plastic filled and coated steel wire ropes have had many years of successful reliability. To replace the ropes, it was necessary to disassemble the entire gear mechanism and remove each of the 6 discs and 5 cables from the drum, replace them with upgraded versions and put the discs, drum, cable and gear mechanism back together before re-installing it. Because the diameter of the new ropes is slightly different than the ones being replaced, new discs had to be machined for a proper fit. The dismantling and reassembly of the gear mechanism and rope lift was done by the Lower Granite Mechanical crew.

Mechanical crew lead, Matt Dinotto, oversaw mechanics Dave Sears and Frank Hudson as they wielded the giant gear used to turn the cable drum which operates the massive 86 ton, 27 foot high by 86 foot long upstream gate. Despite inclimate weather, lead mechanic Matt Dinotto guided his crew through the process as they carefully reinstalled the gigantic pieces of precision equipment.

Mechanical crew lead, Matt Dinotto, oversaw mechanics Dave Sears and Frank Hudson as they wielded the giant gear used to turn the cable drum which operates the massive 86 ton, 27 foot high by 86 foot long upstream gate.
Despite inclimate weather, lead mechanic Matt Dinotto guided his crew through the process as they carefully reinstalled the gigantic pieces of precision equipment.

Keeping the project in-house allowed the Corps to save considerable resources by utilizing talented Corps mechanics already on project. It was a cost effective operation that increased the reliability of the upstream gate and reduced the chance of cable failures that could have resulted in navigation lock shutdowns, revenue loss and inconvenience for not only the Corps, but barge operators, the agricultural industry and others that rely on the navigation locks for transport up and down the Columbia and Snake Rivers. As a whole, Corps navigational locks are known for their reliability.

Looking to the future, the Walla Walla District U.S. Corps of Engineers is already putting the wheels in motion for additional improvements to maintain that standard.
Some of the projects being planned for future extended outages include a district wide systematic replacement of the fill and drain valve structure including their operating linkages, as well as installation of computerized controls that will parallel existing systems and act as backups, reducing the chance of unplanned outages and maintaining navigational reliability.

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