The Siemens Industrial Turbomachinery AB factory in Finspang, Sweden, is one of the leading suppliers of steam turbines to the solar energy industry worldwide. In fact, two out of every four steam turbines made there will be used in the solar industry.
A steam turbine is a device that extracts thermal energy from pressurized steam and converts it into rotary motion to drive a generator that, in turn, makes electricity. At solar power plants, solar energy is used to make steam to power the turbine. Once powered, the turbine operates under enormous pressures and temperatures to drive the generator.
Workers at the Siemens factory assemble steam turbines, as well as gas turbines, from machined steel parts. Besides so-lar power plants, these turbines are used in steel plants, biomass, and oil and gas facilities.
Historically, Siemens has used tab washers to secure bolts at turbine joints. After installation, these washers were manu-ally folded over the bolts to prevent them from moving. The process is labor-intensive and expensive—but crucial, as a turbine is expected to have a service life upwards of 30 years.
Looking to lower costs and increase productivity, Siemens now uses safety washers made by Nord-Lock International AB to secure the bolts. Each washer consists of a top and bottom that, during bolt tightening, interlock to create tension and positively lock the bolt in place.
Tension develops because the cam angle of the washer is larger than the thread pitch of the bolt. In essence, the bolt self locks and remains that way even when subjected to extreme vibration or dynamic loads.
Martin Lindback, who works in the research and development department at Siemens Industrial Turbomachinery, says the safety washers cost 80 percent less than tab washers and reduce installation time by 95 percent.
Lindback also notes several other advantages of the safety washers. One is they can be reused, unlike tab washers. The safety washers are easier to service both in the plant and on customer sites. Also, they increase safety by eliminating the risk of bolts loosening. Finally, they are coated with zinc flake, which makes them corrosion-resistant.
“It is amazing how such a little thing can be so beneficial,” says Lindback.
Recently, assemblers at the Finspang factory completed construction of a 123-megawatt, SST-900 steam turbine for BrightSource Energy Inc.’s Ivanpah Solar Complex in Southern California. BrightSource will use the SST-900 to help generate up to 900 megawatts of solar power, which will be sold to California utility company Pacific Gas and Electric. The steam turbine is designed to handle the load swings and frequent starting and stopping that is characteristic of solar energy generation.
In November 2010, the plant began using the safety washers to assemble Siemens’ new SGT-750 industrial gas turbine. With a capacity of 37 megawatts, the SGT-750 is a versatile machine that can be employed for power generation and as a mechanical drive.
For more information on safety washers, call 877-799-1097 or visit www.nord-lock.com.