Uniper SE is a major energy company servicing Europe and the U.S. A spin-off of German utility giant E.On, “Uniper” is a hybrid of the words “unique” and “performance”: and their newest method of inspection bears out their name. An inspection team using the collision-tolerant Elios operating inside the stack of a gas turbine was able to fly past baffles to perform an inspection in only an hour – saving 3 days of work and thousands of euros, all without a pause in production.
Uniper’s open cycle gas turbine stacks are huge – and hot. At 570 degrees Celsius – over 1000 degrees Fahrenheit – there is no question of human inspection while the turbine is operating, explains Mikael Nilsson, Uniper (Sydkraft Thermal Power AB) Maintenance Manager. The units act as stand-by reserve power plants and can be remotely activated at any time by the customer (Transmission Systems Operator). Inspections must take place at least every 3 years, and they must be carefully timed to take advantage of production downtime.
Traditionally, the inspection of the top half of the stack is performed by lowering workers into the space with a mobile crane: inspection requires extensive paperwork and a specialized work permit. The inspection itself takes about 30 minutes, but de-isolation and return to service take another hour. And that’s only half of the job: because of the baffles on the interior, the stack has to be inspected from the bottom up also. That requires 3 lost days of production to build scaffolding and perform the inspection.
It’s not only time consuming; it’s an expensive process. With 1 or 2 inspectors in the basket and another staff member to operate the crane, inspecting the top half of the stack alone can cost over $500 euros just in manpower. Inspecting the bottom of the stack is much more expensive – the scaffolding alone costs the company about $8000 euros.
Nilsson’s team used the Elios to fly inside the stack, flying past the baffles and inspecting the entire area in one mission. Using Elios, the team didn’t require the extensive paperwork and work permits required to send people into the stack, or approval from the customer since the unit was still available for dispatch. “We don’t even have to involve the customer at all,” says Nilsson. “And the customer appreciates that.”
The results of the mission speak for themselves. The cost of a 1-hour mission with Elios compared to almost 9,000 euros for a standard, 3-day inspection is another compelling advantage. Perhaps the major gain for the inspection team using Elios is in operations management. With a drone, managers can inspect before the outage – and be ready to fix any problems during the regularly scheduled downtime. “You can do much better planning,” says Nilsson.
Nilsson says that Uniper is more than pleased with the outcome. “They think it’s great that we reduce downtime and increase the availability,” he says. “We’ll definitely use drones more frequently.”