Emery and Riverside Generating Stations, owned and operated by Alliant Energy

Safety is Alliant Energy’s top priority. Maintaining a safe work environment during outages can be challenging, particularly so when work inside the gas-turbine enclosure is required. It presents fall and trip hazards above the engine, and a concrete floor. Also, as the condition of the gas turbine (GT) and its related equipment is revealed, outage scope can change dramatically, making it difficult to predict what hazards will exist when, and how to mitigate them proactively.

The perfect solution to this outage safety challenge would be to make it impossible for anyone to get hurt inside the enclosure. An innovative rail and lanyard safety solution developed by Alliant Energy, in conjunction with Hy-Safe Technology, contributes significantly to the achievement of this goal.

Fall hazards typically are tackled using one of these two protection methods: a fall-arrest system or a fall-restraint system. The former protects an individual by limiting the fall distance and absorbing the shock of the fall; the latter prevents an individual from falling in the first place, by limiting the technician’s travel to a safe distance away from fall hazards. Inside an enclosure, technicians typically work on many areas of the engine, making fall-restraint systems physically impractical.

Fall-arrest systems require load-bearing tie-off points, sometimes two per person so personnel are secure at all times as they move around. Also, to maintain a high level of productivity, multiple technicians generally work on the GT concurrently. This is challenging because the enclosure doesn’t provide many secure tie-off points. Bear in mind that once the enclosure roof is removed, the load-bearing capability of its sides is greatly diminished, eliminating their value as an effective foundation for tie-off points. The disassembly work itself eliminates some other tie-off points.

Alliant Energy looked for scaffolding/tie-off alternatives to resolve the unique fall hazards presented by enclosure work. The Hy-Safe solution consists of retractable lanyards underneath an engineered rail (Fig 1), shown in use in Fig 2. Fig 3 shows two rails mounted under an I-beam (a/k/a trolley); three retractable lanyards can be installed on each of the rails.

This highly engineered system is designed specifically for fall protection, not for lifting, and is centered over the turbine. Up to six technicians can connect these lanyards to the D-rings on the backs of their harnesses; a breaking mechanism in each lanyard effectively, and independently, arrests any fall that might be experienced. Once the enclosure roof is removed, the existing crane is replaced with the trolley; the crane is reinstalled just prior to roof replacement.

Results. The rail and lanyard solution has proven safe and efficient, and capable of use in any of the company’s GT enclosures. It offers these benefits over traditional scaffolding/tie-off alternatives:

• Improves fall protection from a static and reliable anchor point. This practically eliminates trips and fall hazards, provides continuous protection as hazards evolve during an outage, and eliminates the need to reconfigure scaffolding and tie-off points for complete enclosure protection.

• Creates the following productivity, time, and cost improvements:

  • Technicians have the flexibility to do their jobs using safe techniques and positions.

  • Multiple technicans can work around each other easily and productively.

  • Two mechanics can install or remove the trolley in less than an hour.

  • Direct financial benefits are estimated at up to the mid-five-figures per outage over alternatives.

  • The time saving increases unit availability and lowers replacement power costs.

• Allows flexibility for a variety of work, including borescope, combustion, hot-gas-path, and major inspections.

Use of the rail and lanyard system received positive comments from technicians. One remarked, “Best I have ever used. None of the millwrights complained about it at all.” Another said there was a steep learning curve, but once the system was in place, it “worked very well and allowed multiple people to be working at heights safely, and it allowed for access along the entire length of the unit with minimal restriction.”