The Proprietary Proven Solution for Gas Turbine Exhaust Silencing
Concern about the lack of stability of refractory ceramic fibre used in dynamic silencing applications and the consequential expulsion of RCF material into the environment have been key drivers in the selection of basalt fibrous material as the preferred replacement for RCF materials. In late 2002, following a thorough test programme to establish suitability for purpose, General Electric Power Systems specified Lancaster GTB Gas Turbine Basalt as the successor to RCF in gas turbine exhaust silencers. Approved and used by the leading turbine manufactures, GTB has become the industry benchmark for “fit-for-purpose” GT exhaust silencer infill. Industry-wide awareness of the acceptability of GTB as the successor to RCF has created an increase in demand for “Gas Turbine Basalt” material, providing some motivation to the perception that fibrous materials produced from basalt rock will be generically equivalent to Lancaster’s GTB Gas Turbine Basalt. This is not the case, as indicated below.
The Gas Turbine Exhaust Silencer Environment
The gas turbine exhaust environment places a unique combination of stresses upon fibrous materials used in silencers and ducts. The hot exhaust efflux has an air-rich composition, creating a highly oxidative environment within ducts, silencers and stacks. This causes mineral fibre containing oxidisable iron to transform into a red/brown powder at temperatures as low as 208’C. This does not happen with GTB Gas Turbine Basalt.
The highly dynamic gas flow produces thermal imbalance, turbulence and pronounced vibrations at discrete frequencies. Locational stability under such conditions can only be maintained by using high-diameter fibres at relatively high density. GTB Gas Turbine Basalt is specifically manufactured to achieve this requirement.
The combination of the above effects will results in the rapid failure of unsuitable materials.
Basalt Deposits Are Not All The Same
Basalt deposits occur naturally as a result of volcanic activity. Differences in compositions, together with the effects of weathering over many years, mean that many basalt deposits are not chemically suitable for production of “Gas Turbine Basalt” materials. Thorough research has been undertaken by Lancaster to identify the most suitable basalt source rock. Following the analysis of many source rock samples from the U.K., South America, Europe, and the Middle East, a deposit in Scotland was clearly identifiable as being the most suitable for the production of Lancaster’s GTB Gas Turbine Basalt.
Importance of the Manufacturing Process
The oxidising nature of the melting process operated by Lancaster is essential in maintaining the favourable chemistry of the source rock for GTB Gas Turbine Basalt. Similarly, the process parameters ensure the production of high-diameter fibres that not only provide the correct flow resistivity at a density that ensures locational stability, but also enable the GTB material to remain unclassified under the EU Directive on Man Made Vitreous Fibres (EU DG 97/69EC, 67/548/EEC MMVF AMENDMENT).
The Proven Solution
- Unique level of experience – 25 years of field operations.
- Unique endorsement – Specified by GE, approved by all turbine manufactures.
- Unique track record – No failures due to infill loss.
- Unique portfolio of machine types and applications.
