Start with the duty: isolation, control or preventing reverse flow. State medium composition, concentration, solids and the operating temperature range.
For every item include DN, PN or Class, maximum pressure, connection and flange standard. For replacements attach face-to-face dimensions, nameplate photos and a drawing.
List body and seal materials, actuation, supply, fail position, quantity, delivery city and documentation requirements separately. Mark missing parameters for clarification rather than guessing.