Mission accomplished

Abrasive tools meet the ultimate MRO challenge

by Phillip Benincaso and Jim Ballow

The U.S.S. Fairweather is a 35-year-old vessel once used by the National Oceanic and Atmospheric Agency to perform nautical charting missions. It had been out of service for 12 years but was recently recalled to active duty and required major maintenance and refurbishing work to put it back in ship shape form. The company that won the contract for the multi-million-dollar project was Cascade General Contractors of Portland, Ore. Its mission was to restore the Fairweather fully, from bow to stern, and return it to its original operations capability.

A major need in this vast undertaking was a complete overhaul of the ship’s hull, decks and other metal surfaces that had fallen into serious disrepair during its dozen years in mothballs.

Ship becomes shell
The first step in this scheduled 30-month project was a total gutting of all the ship’s fixtures and equipment. This called for the 85-man crew to cut out and remove everything from big bulkheads, compressors and heavy equipment to small items like cabinets, sinks and bunks. This operation is referred to as “rip and tear” work. The ship became literally a shell of its former self. After all the stripping and removal, things got down to the nitty gritty as work on the remaining skeleton began in earnest.

Welds everywhere
Individual refurbishing tasks were made easier and quicker by using the correct cutting, grinding and finishing tool for each specific job.

“We have many welds to do, as you can imagine, with the ship’s layout being completely reconfigured,” says Cascade General tool room manager Larry Eastman. “For instance, the berthing quarters are being moved aft from their original location in the bow, and other facilities are being similarly relocated. We are welding many new bulkheads, both 1/8- and 3/16-inch thick, into position. In some cases, we’re making two rooms out of one.

“Proper weld preparation is the key to weld integrity, so we are using flap discs to bevel the edges before the first pass on every weld. We use pipeliner files and rotary wheel brushes to clean out slag after the first pass and get it ready for the next weld pass. We find wheel and cup brushes and flap discs are also the best tools to vanish off all welds to smooth and for removing weld spatter.”

Down with downtime
Flap discs are the ideal tool for such applications because they come in a wide selection of grits, generally 24 to 120 grains per inch and in several grain types including aluminum oxide, zirconia and silicon carbide. This means the precise grit and grain type can be used for the specific metal being worked, whether it is iron, steel, carbon steel, stainless steel, aluminum, titanium or other exotic metals. This also means there is a great time savings from the old two-step method of first using a grinding wheel for rough work then changing to a finer sand disc for finishing and polishing. Flap discs actually go from rough grinding to fine finishing in one operation with a significant reduction in downtime.

Files and flapwheels
Files are also being used to work on pipe welding aboard the Fairweather. Its pipes are made of different metals, including iron and copper, and are of varying sizes up to 5 inches, so a wide selection of file types and sizes are needed for these changing applications. These include mill files, half-rounds and machinist files. Two-inch and 3-inch flap wheels mounted on power die grinders are also used in many situations to knock scale out of pipes.

When time is money and the ship has to be ready on schedule, it pays to have the right tool for each specific job.

Duty above, beyond the call
Eastman also points out that pipe-fitters are tough tool users. Even so, their files stood up well to the rough work.

“I’m not saying our files were abused, but it takes a good file to withstand the punishment these tools take,” he says. “In some cases, the slag was so hard to remove, workers would actually whack at it with the file like they were using a slag hammer.”

Burn spots disappear
Another common task on the ship was the removal of metal pins from the hull and bulkheads. The pins originally held up insulation, and when all that old material was cut out, dark spots were left by the cutting torches every place where the pins were originally welded.

Again, flap discs were the best tools to remove the burn spots and to restore the surface to smooth since they have the big advantage of being able to go from rough grinding to fine finishing in one step without changing discs. Other flap-disc applications included rust and scale removal and general maintenance cleanup work.

All hand tools on deck
As work on the Fairweather continues, almost every other abrasive hand tool will be called into service at some point: mounted points to polish out holes; non-wovens to polish surfaces; and rotary burrs of various shapes for beveling, chamfering, weld removal on light metals, deburring rough spots and working on brazed welds.

Each tool will be put to work on the job for which it’s best suited. This will have the Fairweather heading out to sea on schedule, shiny and new, and achieving its assigned missions.

Phillip Benincaso is a product support specialist and Jim Ballow is the marketing manager for PFERD, a manufacturer of abrasive tools. To learn more, call or visit www.pferd.com. 

 back to top                                       Back to Uptime archives