Taboão da Serra, Brazil
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De Souza L Cuadros M.A.,IFES Instituto Federal Do Espirito Santo | Munaro C.J.,Ferrari | Munareto S.,IFES Instituto Federal Do Espirito Santo
Proceedings of the IEEE International Conference on Industrial Technology | Year: 2010

Stiction is a common cause of loop performance deterioration. The presence of stiction in the spring-diaphragm type valve is the most frequently found valve problem in the process industry. Methods have been proposed fitting an ellipse to the PV-OP plot and the maximum width of the ellipse is reported as "apparent stiction". An improvement on these methods is here proposed for situations where the PV-OP plot is similar to a parallelogram, resulting in a better estimation of stiction. The application of this quantification algorithm together with the cross-correlation detection method to several examples is used to demonstrate the superiority of the proposed approach. ©2010 IEEE.

David F.F.,Ifmg Instituto Federal Of Minas Gerais | David S.F.,IFES Instituto Federal do Espirito Santo | Lira Silveira L.,Federal University of Pernambuco | Ferreira R.A.S.,Federal University of Pernambuco
Materials Science Forum | Year: 2016

The reinforcing wire production CA-60 is highly relevant due to its wide application in concrete products (welded wire mesh and truss girder), driven by growing demand for products of the construction area. One of the properties required by ABNT/NBR 7480/07 is the yield stress (σe), which has a direct effect on the maximum load that the structural component may be subjected in service. The addition of steel wire temperature during cold rolling increases the σe and reduces the ductility due to the aging phenomenon. These variations occur due to the formation of solute atoms atmosphere around the dislocations. The purpose of this paper is to study the behavior of σe during heat treatment of static aging at 100 °C in the wire CA-60 steel made from the niobium microalloyed steel equivalent ASTM A913 and the equivalent ASTM 1013 steel. As a result the wire carbon steel 1013 showed the same variation of σe during static aging of niobium microalloyed steel A913. This phenomenon was justified because of the increased level of pro-eutectoid ferrite and grain size in the carbon steel 1013. © 2016 Trans Tech Publications, Switzerland.

de Souza L. Cuadros M.A.,IFES Instituto Federal do Espirito Santo | Munaro C.J.,Ferrari | Munareto S.,IFES Instituto Federal do Espirito Santo
Computers and Chemical Engineering | Year: 2012

The oscillations caused by static friction (stiction) in control valves cause losses in quality and expense of raw materials. The effects of friction can be reduced through compensation techniques, until the maintenance of the valve is made in the next programmed plant shutdown. In this work, a well-known stiction compensation method that reduces variability both at process variable and valve stem movement is revisited. Limitations of this method are overcome through two proposed methods using a similar approach. The effectiveness of the proposed compensators is demonstrated using simulation examples and a flow control loop in a pilot plant. © 2011 Elsevier Ltd.

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