What is the sequence for installing the valves and check valves on the boiler feedwater and circulating water pump outlet pipes? ? ?

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1. Regarding the outlet pipeline of the circulation pump: the correct sequence should be pump outlet → slowly opening and closing check valve → butterfly valve (this arrangement is said to facilitate maintenance and replacement of the check valve), or pump outlet → butterfly valve → slowly opening and closing check valve (this arrangement is said to protect the butterfly valve from water hammer). I: 2. In our company, due to different manufacturers, the installation sequence of check valves and other valves on the outlet pipelines of the circulation pumps in various systems also varies. III. I would like to ask the experts: Are there any national standards GB that specify this? What is the correct order of installation? There seems to be disagreement regarding the proper installation order of the shut-off valves and check valves in the water inlet pipeline of waste heat boilers as well ? ? ?