What are the principles for classifying instrumentation equipment into A, B, and C?

We are working on that as well; we’re creating a scoring system, but the main factor considered is the level of importance – items that can affect the entire factory’s production are classified as Category A, those that affect workshop production are classified as Category B, and the rest are classified as Category C, and so on

Our classification principle is as follows: those related to measurement, energy consumption calculation, and safety monitoring (interlock) are classified as Category A； Generally, process parameter monitoring falls under Category B ； Other instrument equipment is classified as Category C ；

Our company currently has the rule that systems such as DCS, SIS, and ITCC are classified as Category A； Items such as interlocks, control instruments, special control valves (unit anti-surge valves, slide valves, shut-off valves), detectors for flammable and toxic gases, radiation instruments, fire alarm systems, and industrial television systems fall under Category B ； The others are classified as Category C.

Our classification is as follows, for your reference to determine its suitability: Categories A, B, and C. Measurement equipment includes measurement standards and auxiliary devices, as well as equipment and software used for inspection. Measurement standards are divided into the company’s highest measurement standards and those for operational use ； Measurement equipment is managed in three categories: A, B, and C. Class A: The highest calibration standard of a company; calibration standards used for value transfer ； Equipment for trade settlement, security protection, and environmental monitoring is included in the **list of equipment subject to mandatory inspection**. Category B: Used at process-critical inspection points, where there are certain requirements for the accuracy and reliability of the measurement data; measurement equipment with high reliability ； Measurement equipment used for quality inspection (except for Category A) ； Measurement equipment used for cost accounting. Category C: Generally refers to low-value, consumable measurement equipment ； Indicating measuring equipment with stable performance and high reliability, which is not used frequently, whose values do not change easily, cannot be disassembled easily, and for which no strict accuracy requirements apply ； **The metrology administrative department explicitly permits measuring equipment that is designed for single-use or requires a validity period management.

There are relevant guidance documents for the classification and definition of measuring instruments, which is very helpful for a company to establish a standard management system