Pump & Valve Wear Behaviour
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Technox® ceramics are now used with increasing frequency in pump and valve applications. This increase in use results from the excellent erosive wear resistance of Technox® zirconia providing longer life and cost savings. This data sheet attempts to explain the mechanics of erosive wear behaviour and provide independent, third party, data about the comparative performance of Technox® against other materials.
The process of erosive wear occurs by the impact of particles upon a surface with a resultant loss of material due to fracture, spalling and/or abrasive wear of the impacted surface.
Erosive wear can occur in both metals and ceramics. However, due to their high hardness, ceramics are generally more resistant to erosive wear. Yet there are significant differences between the two classes of material: with a metal (which displays ductile deformation behaviour) the impact of abrasive particles at 90° to the horizontal is less damaging than more acute impact angles, but with ceramics, where the deformation mode tends towards brittle fracture, 90o impacts cause the most damage.
Recent experimental evidence for ceramic materials has shown that although hardness is an important parameter in controlling erosive wear, of greater importance is the ratio of hardness/toughness. In simple terms one can interpret these results as follows:
1. A hard but brittle ceramic will resist indentation by a hard indenter, but the surrounding “brittle” surface may crack, leading to the removal of a significant amount of material, and hence significant wear.
2. A softer but tougher ceramic may display higher indentation damage, but the toughness of the material will avoid any surface cracking and hence the removal of large amounts of surface material, thus reducing wear.
These theories have now been tested by experiment as detailed below. The aim of this work was to monitor the performance of several candidate materials for pumping applications.
Erosive wear test data
Rods of the candidate materials and coatings (10 mm diameter, 30 mm long) were placed in the outlet stream of a high pressure water jet under the conditions indicated. The volume loss of each material was measured as a relative % of the volume loss from a stainless steel 316 control pin, i.e. the lower the value the more wear resistant the material. The obvious conclusion to be drawn from these results is that Technox 2000® displays excellent wear performance under conditions of both erosive and erosive/corrosive wear. The wear performance of the zirconia being some 5-18 times better than that of the Tungsten Carbide 6% Cobalt materials.
In addition to the excellent erosive wear resistance Technox® ceramics also display excellent cavitation resistance. The uniform and homogeneous microstructure, coupled with high densities and corrosion resistance promote low material loss during turbulent flow conditions. A factor which affects cavitation resistance is the quality of surface finish. High degrees of polish lengthen the period before cavitation erosion begins.
Technox® ceramics have a well established pedigree in many oil-field and down-hole installations throughout the world. Typical applications include: Plug stems and valve seats, choke trims, choke beans, movable orifice valves, gate valve seats, ball valves and seats, mud pump nozzles and turbo drill components.
One outstanding recent achievement was the production of a solid swash-plate pump body (approx. Æ100 mm) and pistons for use by British Gas in sea bed control systems. Running at 100 bar and with only a 1mm particulate filter, the pump has already performed for over 2000 hours and is still going – out performing the steel equivalent by 1960 hours.
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- Extrusion Dies – Technox 500
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- Pump & Valve Wear Behaviour
- Solid Handling Wear Parts
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