zh - DAFRAM paper has been selected for Valve World Conference 2016 by the Steering Committee. Marco Sparisci (Lead Product Engineer, R&D Coordinator) presented how DAFRAM has approached the very crucial aspect of coatings for components of ball valves dedicated to severe service and very special applications.

Paper title:
Innovative experimental evaluation of hardcoatings for ball valves.

Abstract:
Over the last years, a thorough knowledge of coatings properties has become a key instrument for ball valves manufacturers to offer the best solution for each operating environment.

DAFRAM and 3P Engineering designed and built a special testing machine to collect reliable information about existing coatings behaviour and to test new solutions for ball valves.
In order to properly simulate the real working conditions of ball valves, kits (ball and seats) are cycled on the bench through a specified number of strokes.
The tightness of sealing surfaces is checked periodically during stroke cycling. Testing capabilities include also cycling in presence of abrasive particles (e.g. sand) and high temperature conditions (up to 650°C). Specifically designed postprocessor allows to collect and manage 2.5 kHz high frequency measurements on torque, position and pressure. Resulting graphs show very clearly coating behaviour during every single test cycle and over all the performed cycles. Torque measurement ensures static and dynamic friction coefficient evaluation by a proprietary mathematical method, while the tightness of sealing surfaces is expressed as suggested by International Standards for valve testing. So, conclusions about coating properties become easy to draw and to compare with other already tested coatings.
This test apparatus has been used by DAFRAM to benchmark commonly used hardfacings for valve trim components, also with several combinations of base materials. In addition, for specific Customer requests, unusual combinations of coating and base material have been tested at given process conditions.
Furthermore, the test bench shows its effectiveness in the development of new coating solutions for severe application on ball valves, i.e. high temperatures and abrasive service, or to optimize existing valve design by reducing operation friction between moving parts.

Author:
Marco Sparisci, Lead Product Engineer, DAFRAM SpA
Co-author:
Enrico Palmieri, R&D Engineer, 3P Engineering