Safe '09: Smooth Safety Integration
If setting up a 25-foot-high scaffold in an underground tunnel filled with expensive scientific equipment doesn't sound like carpentry, it's because SLAC Carpentry Shop staff are no ordinary carpenters. Not only have they fitted many a SLAC office with a new custom-made wooden desk, shelving unit or cabinet; they've also installed parking bollards, placed sandbags to prevent erosion, renovated bathrooms and laid tile. And that's just the short list. Even working in capacities well beyond traditional carpentry—addressing safety needs from excavation permits to elevated work surfaces to asbestos abatement—the men of the SLAC Carpentry Shop have made safety part of their craft, taking on unusual challenges with panache.
"They've had to deal with just about any hazard, so they know how to safely handle unique and complex situations," said Facilities Department head Liam Robinson. "We [at SLAC] talk a lot about integrating safety, and we're getting there. The carpentry shop is a powerful example that it can be done."
A tricky situation arose during the November linac downtime, when orders came for a long-delayed repair inside the accelerator tunnel in the Beam Switch Yard. A "dead leg," a capped-off pipe that had once carried low-conductivity water from the main line, had been slowly forming a leak. Operations workers needed to fix the pipe, but this particular leak was near the tunnel's 25-foot-high ceiling and above expensive undulator magnets. A ladder wouldn't be stable enough to reach the pipe, and it would have been impossible to construct a wooden platform around the equipment on the floor. In fact, it was a task that, up until recently, would have been difficult to complete safely.
About a year and a half ago, Facilities Safety Coordinator Jerry Pfefferkorn came up with the idea to buy a scaffolding kit and have the Carpentry Shop, with its solid safety record, become the team to erect it for other groups on site. Pfefferkorn worked with the shop to research different types of scaffolding. They selected a universal system that allowed them to construct safe work platforms with a minimum of hassle and in a variety of environments. It's ideal for a site like SLAC, where scaffolding must go up amid thickets of pipes and equipment. "It's basically a giant erector set for adults," said Carpentry Specialist Ryan Kuhn, who was the lead carpenter on the tunnel project. "You can even set it up on the side of a hill at a 45 degree angle." The carpenters went through a class on how to safely erect, use and dismantle scaffolding, and Pfefferkorn double-checks each construction and declares it safe to use. Now all operations workers can count on a safe place to stand, no matter where they are.
Thanks to Pfefferkorn's vision, the leak was safely accessible. However, maneuvering the scaffolding to the correct spot in the tunnel and setting it up still required planning. Working during the linac downtime, the carpenters and pipe workers had only a few days to get in and out. There would be little time for revision, so the plan needed to be perfect.
When faced with any job, Kuhn said, "we brainstorm each individual hazard we can think of." First was the matter of transporting three racks of heavy scaffolding a quarter mile along the tunnel from the nearest entrance. The carpenters could have carried the 100 individual pieces, which can be up to 10 feet long and twenty pounds in weight, but decided to drastically reduce the risk of trips, falls or sprains by coordinating with SLAC's rigging team. The riggers used an overhead crane that runs on a track along the tunnel ceiling to carry the racks to within twenty feet of the leaky pipe.
The accelerator tunnel in the Beam Switch Yard has two levels. The carpenters and scaffolding sections were now on a concrete platform 10 feet above the lower recess where the accelerator is housed. Some of the sections were needed in the recess, some on a catwalk above, for ease in constructing the scaffold. After setting up a temporary guardrail along the platform's edge, two men carefully passed the initial uprights and bracing down to two men in the recess. They then built a temporary bridge across the recess to the catwalk on the other side, and slid the rest of the pieces over. All wore personal protective equipment—hard hats, gloves, safety glasses, steel-toed boots and reflective vests—to further reduce any possible injuries.
As the carpenters built up the scaffolding, they set up chains and guardrails to prevent falls, built a guardrail-enclosed bridge from the catwalk to the scaffolding to facilitate access to the upper levels, and took special care with tools due to the equipment directly below them. But the crane, which had been such an aid, now posed an additional hazard. Above them was the crane's power line, an exposed electrical busbar that is usually safely out of reach. Working so near the ceiling, there was a risk of hitting the busbar with one of the long metal rails. "This was unlikely to happen but important to prevent," explained Carpentry Shop Supervisor Aidan Metzger. Since the crane was needed for other tasks during down time, it took close coordination with crane mechanic George Quilon to de-energize the crane and lock-and-tag it out every time the carpenters came into the tunnel to work.
Once the scaffolding was finished, Pfefferkorn, known for his keen and scrutinizing eye, came in to inspect the construction and certify it safe to use by the pipe workers. "He always adds something," said Metzger. "He finds one or two things to make [the work] safer."
Attention to detail has been a hallmark of the Carpentry Shop's work plans over the years. For Metzger and his crew it's as natural as designing a new desk or cabinet. "A safety plan is like your pattern," Metzger explained. "You have to think about the whole job before you make the first cut."