Project: Coated Valves

Over the last years several SME and laboratories around the globe have put a lot of effort into developing types of crud oil and crud gas valves which are used extensively in high-pressure applications of industrial piping, pressure vessels, pipelines, risers and associated equipment. Although the working principal of these valves cannot be described as complicated, there are quite a few work related problems, which must be considered though the simulation and design of their CO parts. One of the crucial factors describing a valves quality, is the leak rate dependency of its’ seating, since most elastomeric-metal seatings show a very low life span._x000D_Even though the work loads of the valves during the opening-closing phase cause certain damage to the elastomeric seating, they are not the CO wear factor of the valve. The large pressure drop across the valve, causes an instant and very high temperature field, in some cases from -150¿C to 50¿C, deteriorating the mechanical resistance of the spheres’ material. Moreover the abrasion of the sphere and in particular of the seating is accelerated by the high speed impact of the gas or oil impurities (˜5µm), which in some cases get jammed between the sphere and the seating causing additional wear to both._x000D_As a result of the severe abrasion of the elastomeric seating the implementation of metal-to-metal contact type flanges will be investigated. This type of seating will allow the further enhancement of the mechanical properties, thermal- and strength wise, through the application of properly selected coating on the spheres’ and the seatings’ surface respectively. The new metal-to-metal valves will be designed to accommodate higher-capacity applications, providing a Class VI seat leakage with shutoffs to 200 psi and will prolong the valves life span in comparison to the corresponding elastomeric-metal seated ones. Metal-to-metal seating will eliminate the need for elastomeric seals or piston rings, which incur costly COtenance downtime._x000D_During the first phase an extensive flow simulation of the valve will be conducted. Generally, the calculations to be performed can be separated into a design step and the proof of sufficient tightness and strength of flange, bolts and gasket for the various operating conditions according to the chosen bolting method. This will allow to determine not only a design providing lower opening-closing forces of the valve due to reduced friction, but also to establish an adequate gas- or oil-proof sealing of the valve. This sealing will most likely be achieved through a labyrinth-like metal-to-metal seating which will gradually deteriorate the pressure distribution along the achieved contact zone, providing a Class VI seat leakage. The properties of all components (flanges, seating etc.) and its influence on the mechanical behavior of the entire system is considered. Beside the influence caused by thermal effects and pressure variations, the impurities abrasive behavior on the sphere as well as the seating must be regarded._x000D_The project will consider valves with sizes ranging from 4 to 8 inches and sphere materials that include cast iron, carbon steel and stainless steel. The superficial improvement of base materials is imperative. The evolution of Physical Vapor Deposition (PVD) technologies facilitates the development of improved coating material, i.e. enhanced insulating films can be produced by means of High Ionization Sputtering process technology. In the frame of the project the application of such technologies will result to an increased loading capacity of the various mechanical parts. Moreover, the chemical stability, the oxidation resistance and the thermal conductivity of the sphere and seating will be significantly improved by means of appropriate coating selection. Investigations will be focused on the correlation between the coating adhesion and the mechanical or chemical pre-treatment through the deposition of a bonding-layer for each material. Thus, optimum treatments can be applied for each substrate-coating combination, leading to superior film adhesion._x000D_The deposition of appropriate coatings on the mechanical parts will contribute to low friction movement across the valve plug at all levels of opening, thereby reducing the thrust required to open or close the valve. This reduces the actuator force the valve requires so that a smaller, lower-cost actuator can be used, whether it is pneumatic, spring and diaphragm, electric or hydraulic._x000D_The final step of the project will be to design and construct an appropriate test station, which will allow determining the life span of a valve for pre-described conditions including gas or oil transfer, pressure control, temperature adjustment, impurity size selection. In this way the durability of the valve can be compared to the initial valve model, but furthermore to competitive valves allowing the extraction of a confident conclusion concerning the quality of the final product.

Acronym COVA (Reference Number: 4389)
Duration 01/09/2008 - 01/09/2010
Project Topic A new type of metal-to-metal crud oil/gas valve will be developed. The innovation of the valve lies in the labyrinth like seating of the sphere as well as the specially developed coatings for the seating and sphere respectively.
Project Results
(after finalisation)
The CO result of the project is a hard, protective DLC-coating with low friction and smooth surface for tribological applications.
Network Eurostars
Call Eurostars Cut-Off 1

Project partner

Number Name Role Country
4 ENIMEX S.A. Coordinator Greece
4 Fraunhofer Gesellschaft zur Förderung der angewandten Forschung e. V. Partner Germany
4 CEntre for Research and Technology Hellas Partner Greece
4 CemeCon AG Partner Germany