Piano wires are made in a manner that allows them to remain in tune when they are properly tightened. Because of the way they are made, they can also be used as tools when alignment is required, such as during the replacement or cleaning of the rotors in large industrial steam turbines. Because the inner workings of turbines are set to exacting standards, they must be reassembled correctly; to do this, many companies use a "tightwire alignment kit," that provides specialised brackets and a 0.016-inch piano wire.
Most piano wire rotor alignment kits come with brackets. The brackets that are used with tightwire alignment kits are an imperative part of the assembly process in a steam turbine because they begin the alignment process before any of the inner components are placed on the turbine's rotary bore. The brackets are fastened onto each end of the steam turbine's casing and positioned directly at the centre of the turbine bore.
The placement of these brackets is crucial and pertains to the exact nature of the turbines. If the rotary components of the turbines are not aligned properly through the use of the brackets, they can make contact with different seals and stationary elements of the turbine bore's interior, which can destroy both the rotor and the turbine seals. This would require an expensive and time consuming fix.
Using the Piano Wire
Once the bracket is in place, the piano wire is run through the bracket at one end of the turbine bore and secured to the bracket. It is then run directly through the bracket at the other end of the turbine bore, creating a straight-lined guide through the exact centre of the turbine bore. The piano wire is then weighted on the end that isn't secured to the bracket so that it's pulled taut and shows no kinks or bends.
Centring the Wire
Making sure that the piano wire is centred perfectly through the expanse of the turbine bore is crucial because the wire acts as the guide for all of the rotors and diaphragms that are to be centred throughout the turbine. To ensure correct alignment, each bracket that the wire is run through is equipped with winding equipment as well as precision micrometers. This allows for the cord winding and tightness of the wire to be adjusted according to the turbine's bore centre.