Abstract
Modern processing plants use a variety of control loop networks to deliver a finished product to the market. Such control loops, like control valves, are designed to keep process variables such as pressure, temperature, speed, flow, etc. within the appropriate operating range and to ensure a quality product is produced. All control valves have a bypass so that production can proceed if maintenance is needed for the control valve as part of the control loop. The important point is that in both operation and maintenance situations, the bypass valve and the control valve should have approximately the same flow capacity to provide nearly the same amount of pressure. This paper presents a case study in seawater service on the selection of manual bypass valves for a 16″ control valve in class 150 and titanium material. A 16″ butterfly valve of class 150 was chosen for the control valve bypass, which provided a much higher flow capacity than the control valve. In this paper, four solutions are recommended to achieve the same coefficient value (Cv) for the control and bypass valve. Using the reduced size butterfly valve could be the cheapest and best solution. On the other hand, selecting the same control valve for bypass line is the most expensive but maybe the most reliable solution. Using a flow orifice for throttling could be ranked as the second expensive option and the second reliable one. Selection of butterfly valve for throttling is the second cheapest option, but it has the least reliability. Different parameters such as space and weight saving, cost as well as reliability have been considered in evaluation of different solutions.
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I would like to express my gratitude to my partner, Ms. Tamara Zhunussova, for her great support.
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Article Highlights
• Modern processing plants use many networks of control loops to produce and deliver a product to the market.
• Too high flow passing through the bypass valve can jeopardize the process system and increase the bypass valve internals, resulting in wearing and cavitation.
• The bypass of a control valve should have almost the same flow capacity as the control valve to avoid process problems.
• There are several ways to solve the high flow capacity from the bypass of the control valve such as reducing the size of the bypass valve, using flow orifice after the bypass valve, choosing a globe valve for bypass valve, etc.
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Sotoodeh, K. Challenges Associated with the Bypass Valves of Control Valves in a Seawater Service. J. Marine. Sci. Appl. 19, 127–132 (2020). https://doi.org/10.1007/s11804-020-00132-8
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DOI: https://doi.org/10.1007/s11804-020-00132-8