IGS ClearStream Chromium-6 Filtration for Safe HVTS Application

Introduction: Gas Turbine Corrosion

IGS was invited to apply HVTS cladding to mitigate high-temperature corrosion on a high efficiency, air-cooled gas turbine installed at a power & light facility in the United States.

High-Temperature Gas Turbine Corrosion

The turbine’s base metal spalling challenges were leading to premature failure of the blades and other downstream parts. This was increasing outage frequency and cost. Affected areas included the upper half CDC, upper half OTS, six upper and lower half diffusers, upper and lower inner barrel, lower half CDC combustion cans and five armway covers.

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Surface Preparation

The surface condition of the turbine components as received was consistent with the problem description provided by the asset owner. The surface exhibited corrosion and evidence of spallation due to high temperature exposure. No additional grinding was required as the initial blast application by IGS was sufficient surface preparation for HVTS application.

Ventilation and Filtration

In compliance with the IGS Hexavalent Chromium Exposure Control Plan, the company utilized radial fans with ClearStream filtration systems. The system features a HEPA filter in the upper and lower half enclosures providing adequate ventilation. Flexible ducting was run from the enclosures to the ventilation unit. The use of 30 filter units in the system ensured acceptable ventilation.

IGS completed all clean-up and material removal, placing spent blast media in labelled drums for disposal as agreed.

HVTS Application

The High Velocity Thermal Spray (HVTS) process included true high velocity application using IGS’s proprietary Metalspray® 3000 Low Stress application equipment. This cutting-edge technology allowed IGS to apply cladding with much greater density and decreased permeability, while keeping internal cladding stresses low.

In this process, IGS achieved the smallest possible thermal spray particle sizes and applied them in as dense a pattern as possible. This type of application increases the distance of pathways leading from the surface of the thermal spray to the substrate beneath. Permeation levels are eliminated and erosion resistance is increased.

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Future Projects

IGS engineers confirmed the viability of a full lower-half coating plan (focusing on the CDC and OTS).

CATEGORIES:

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Power
Thermal spray
Vessel/Tower

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