All on/off isolation valve standards are not created equal and cannot be applied unilaterally to all valves. This article references two types of valves: 1. Control valves, which are defined as manipulating a flowing fluid to keep process variables as close as possible to the desired set point; and 2. Isolation or shutoff valves, which have one primary function—to provide tight shutoff to ensure fluids don’t pass downstream.
There are several different standards organizations across process industries, some of the common ones are: API, ASME, ISO, MSS, EN, BS and JIS. Each of these standards will vary with defined criteria and many will defer to other standards for components of a valve’s design such as wall thickness, fire ratings, fugitive emissions or shutoff classifications, to name a few.