RXS900 Shot peener rehardens turbine compressor blades

Citation

(2008), "RXS900 Shot peener rehardens turbine compressor blades", Aircraft Engineering and Aerospace Technology, Vol. 80 No. 5. https://doi.org/10.1108/aeat.2008.12780eab.014

RXS900 Shot peener rehardens turbine compressor blades

Article Type: Aerospace technology From: Aircraft Engineering and Aerospace Technology: An International Journal, Volume 80, Issue 5

The latest Guyson glass bead peening system has recently been installed into a turbine repair centre for refurbishing turbine compressor blades for many of the major aero engine makers. Glass or ceramic bead is specified for peening, especially if there is any chance that ferrous dust contamination from metal media might result in rust.

Controlled shot peening is regularly being specified by the aerospace, automotive and nuclear industries to enhance component service life. It is a cold working process in which the surface of the component being processed is bombarded with small spherical blast media. Each piece of shot striking the surface of the component acts as a miniature peening hammer, deforming the component surface and causing a small indentation or dimple. The overlapping dimples develop a thin layer of metal in residual compressive stress at or near the surface.

Since nearly all fatigue and stress corrosion failures start at the surface of a part, the compressive stresses induced by shot peening can considerably increase component service life.

The Guyson peening equipment is used to re-harden the turbine blade surfaces after they have been used for a period of time and are due for scheduled maintenance, repair and overhaul. Peening takes place in a Guyson RXS900 blast cabinet equipped with an indexing rotating turntable fitted with six revolving work spindles, which index through the process area presenting the components accurately and for a strictly measured time in front of the blast guns. Blasting takes place at two of the six spindles. These are positively driven by a toothed belt, with proximity sensors closely monitoring spindle rotation to ensure very accurate blast coverage.

Twin vertical pneumatic sliding doors open and close automatically to allow the components to enter and exit the machine; this is interfaced with the indexing mechanism. The doors create a seal during the blasting operation to prevent media escaping to the workshop environment. Peening is achieved with eight model 900 blast guns fitted with boron carbide nozzles firing glass bead media; two guns in a fixed position and six mounted on a vertically traversing arm. Each blast gun is mounted on a fully adjustable support arm so that they can be positioned independently for angle of attack and stand off distance from the component.

As is expected on a system of this complexity, blast pressures, traversing gun travel, blast time, component rotation, media flow rates and all other process variables can be adjusted and monitored via an human machine interface.

After peening there is a degree of breakdown in blast media. This must be controlled and size integrity maintained by separating out undersize, broken bead, dust and debris with a media reclamation cyclone. This is complemented with a twin deck vibratory sieve separator, the upper deck removing oversize particles and the lower deck sieving out good quality blast media of the correct size which is returned to the media storage hopper. The combination of cyclone and vibratory sieve unit offers an extremely efficient media reclamation system and ensures only good quality media is fed back to the blast nozzle.

The dust-laden air from the cyclone is drawn through the dust collector by the fan with the airflow being controlled by an adjustable butterfly valve. Initial pre-separation takes place as heavier particles are deflected downwards towards the hopper and dust collector bin. Finer dust is carried up to the filter elements where it is retained on the outer surface. The cleaned air passes through the filter elements into the fan chamber, where it is exhausted; each filter element is cleaned in sequence using a reverse jet of compressed air.

For furhter details please contact: Guyson International, Tel.: +44 (0)1756 799911, Fax: +44 (0)1756 790213.