According to the current state of technological development of functional safety in China and the current functional safety standards for process control industry, there is currently no mandatory standard. There are some mandatory standards in terms of machine safety.

The principles and specifications for the design of safety-related systems, as pointed out in the "Code for the Design of Petrochemical Safety Instrumentation Systems":

(1) The logic operator of the safety instrument system can be composed of a relay system or a programmable electronic system, or it can be composed of a mixture thereof.

(2) Level 2 and level 3 safety instrumented systems should use redundant or fault-tolerant logical operators.

(3) Process interfaces include input and output cards, sequential event input cards, power distributors, safety barriers, switches, relays and other related equipment.

(4) The sensors and final actuators connected to the input and output cards should be designed to be fail-safe, that is, Fail-safe, that is, the requirements for fail-safe.

The safety integrity level is an overall assessment of the entire safety circuit. Obviously, even the related devices on the circuit link, such as relays, also require Fail-safe design requirements.

At the same time, in the report shared by some design institute experts, the SIS design principles introduced also proposed that [SIS logic controller] should obtain the functional safety of the national authoritative certification body.

The relay used in the safety circuit of the above safety-related system, regardless of whether it is used in the relay system or the associated device in the process interface in the circuit, from the perspective of design reliability and safety protection, has a self-diagnosis function and diagnostic coverage Safety relays with high probability of failure, low probability of failure and authoritative certification are better choices.