Optimization of stuffing box stem seals in Fittings as far as Function and Emission Behavior through Surface Coating is concerned
Project Number 369
For sealing movable spindles in the covering or casing implementation of valves so-called stuffing boxes are used with packings. Objective of this research project is to optimize the valve stem seals in valves by surface coating and treatment to ensure reduced wear-and application-oriented function, thereby increasing the reliability and availability of these components. The optimization of the stem surface for corrosion resistance, wear resistance and low friction in the stuffing box using modern surface coating technology has this highly innovative character. In addition to the design and calculation of suitable valves there are issues of material selection, quality and the topography of surfaces in the forefront of this project.
The points concerned are basic oriented (determination of the frictional behavior of surface and spindle pack), product oriented (optimization of the spindle surface) and
process oriented (and application development, testing and possibly modification of modification and optimization of coating processes).
Work Package 1: optimizing the spindle surface for high wear resistance, high sealing quality and low friction in the stuffing box for use at temperatures up to 400° C. Modern surface coating and treatment process, eg HVOF-PVD double coatings should be tested and optimized.
Work Package 2: Use of modern materials for spindles out of the area of industrial fittings. These materials are both new as well as already having been successfully tested for coating processes for their suitability and evaluated in accordance. The choice of spindle materials is aimed at a practical application of the project results.
Work Package 3: Studies on the corrosion resistance of spindle and fittings materials from stainless steels. The focus of the proposed research is the investigation of corrosion effects from the area of the seal (graphite, corrosive anions), which may result as described above in the case of passive stainless steels to local corrosion.
Work Package 4: The main objective of this work package is to investigate the friction and sealing behaviour of coated valve spindles in media usual in power plants such as hot water and steam in a closed water cycle.
Work Package 5: Structural mechanical and metallurgical characterization of the coatings with the involvement of the previous project considered spindle variants.
Work Package 6: characterization of the surface structure by surface microtopography and correlation with the friction behavior.
Work Package 7: analysis of the mechanisms of the observed different course of friction force and the transient behavior of the stick in the sliding friction. With advanced studies the question should be addressed of what mechanisms are responsible for these different courses of friction force.
The project is supervised by the Working Panel Pipe Systems, Valves and Pressure Vessels. The research project is funded by the German Federal Ministry of Economics and Technology via the AiF (AiF project no. 17222 N).