SOPs are mandatory for product-related processes, and operator manuals cannot replace them. Manufacturers' operating manuals offer general information for using and maintaining equipment that may be suitable for many purposes, including your applications. Manuals do not identify use of the equipment within your facility, nor do they say who is responsible for processes and who carries them out. Further, manuals are not controlled documents subject to periodic review and revision and thus may not remain current to your needs. Your SOPs, through your change control process, will reflect any improvements you make to your processes over time.