Question regarding the minimum distance between valves and piping fittings

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This post was last edited by Bai Yunfan on 2011-9-22 06:00. The MOV valve (DN300 ball valve) used in the project always triggers a torque alarm when being closed under pressure; it stops at around 2% closure. The problems occurred quite frequently, so we invited the manufacturer to come to the site. The valves were manufactured in Italy, the actuators were from Germany, and the business side was handled by a company from the Netherlands; well, three technical experts showed up. The diagnosis results are as follows: 1. Stress may exist during valve installation, causing additional stress on the valve body, which in turn requires more torque for the closing process. Question: For valve installation, what is the allowable error between the two flanges? I checked EN 13840-4; it has an appendix, but it specifies three different levels. I’m not sure which one should be followed 2. The distance between the valve and the piping fittings (elbows, tees, etc., upstream and downstream) is too small, resulting in additional hydraulic forces. Question: Are there any relevant standards available for reference regarding the minimum distance between valves and piping? 3. Due to the aforementioned issues, the manufacturer recommends replacing it with an actuator with a higher torque. Question: For a DN300 ball valve with a maximum pressure of 36 kilograms before the valve, and a flow-limiting orifice plate downstream that allows a maximum flow rate of 1000 m3/hour, and given that the medium being transported is water with a density of 1000 kg/m3, what should be the output torque of the actuator required, theoretically? Thank you!