May I ask under what circumstances is a handwheel necessary for a control valve? Are there any regulations specifying that it must be installed in certain situations?

I. Rationale for not including a handwheel: According to Article 11.9.7 of the \"Specifications for the Selection and Design of Automated Instruments\" (HG/T 20507-2014), the installation of a handwheel mechanism shall meet the following requirements: 1. A handwheel mechanism shall be provided for control valves that do not have a bypass system. 2. The process production safety interlock for controlling the emergency shut-off valve shall not be equipped with a handwheel mechanism. 3. Handwheels should not be used for the mechanical positioning of valves. Additional note: This item was copied from abroad and is primarily aimed at production equipment. II. Basis for including handwheels: Basis 1: According to Article 9.1.12 of the \"Code for Design of Oil Depots\" (GB 50074-2014), valves installed on process pipelines should be steel valves. The selected electric or pneumatic valve should have a manual operation function. For valves with a nominal diameter of 600 mm or less, the time required to manually close the valve should not exceed 15 minutes ； For valves with a nominal diameter greater than 600 mm, the time required to manually close the valve should not exceed 20 minutes. Explanation of the provision: 9.1.12 Steel valves have superior properties such as tensile strength and toughness compared to cast iron valves. The use of steel valves is much safer in preventing valve freezing, cracking, water hammer, and other external mechanical damages compared to cast iron valves. To ensure safety, steel valves are now widely used in pipelines for flammable and combustible liquids in the petrochemical industry. In terms of price, steel valves are not much more expensive than cast iron valves. In light of this, this provision stipulates that \"valves on process pipelines shall be steel valves.\" One of the lessons learned from a oil depot fire that occurred in 2010 was that, after the power supply system was damaged, the electric valves installed on the pipelines for inflowing and outflowing oil in the storage tanks could not be shut down manually quickly, which led to an expansion of the scale of the accident. The time limit specified for manually shutting down the valves is intended to prevent similar situations from occurring.