My problem is that the piping engineer asked me the following data for a number of non-return valves:- The min. and max. flowrates- The min. and max. operating pressures- The min. operating temperature- The minimum pressure drop (for opening).1/ Does the min. flowrate correspond to the min. operating flowrate or the min. flowrate for full lift?2/ What is the purpose of min. pressure? Can i consider the atmospheric pressure (0 barg) or the full vacuum pressure (-1 barg) which could occur during start-up, shut-down or maintenance?3/ What is the purpose and how to calculate the min. pressure drop? are there some typical values by type of valve?If you have interesting references, please feel free to share.1. min. operating flow rate2. this question is for the mechanical design of valves. therefore you should give him/her the most severe condition. Then valve vendor will consider it.3. Why did piping guy mention "(for opening)"? If he wants the min. pressure drop for opening, that is for the cracking pressure, which is the minimum required pressure for valve opening.I guess this valve is not normal check valve.....right?

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