What is HAZID study and at what stage in the project is needed?
What kind of project IS it needed?
"HazID stands for hazard identification. It is more of a general risk analysis tool designed to alert management to threats and hazards as early in the process as possible"
HAZID is the first step in a project after the detail process design with all equipment has been done. All identified hazard must be recorded. The next step is the HAZOP (Hazardous Operations) which defines the risks. You may use the IEC 61882 or some risk trees like the one in the German norm VDI 2180. The risk rating is the input for the calculation of the SIL rating according IEC 61511. The output will be the SIL Level, the test cycle time and the requirements to design and build the SIL Loop. The whole loop must be build according the required SIL level. (From the sensor to the actors (the whole valve body).
If you reach SIL 4, you should reconsider the process design. SIL 4 appears mainly in the nuclear power industry
For Machinery you you can choose to the IEC 13849. Here you deal with PL (Performance Levels). It may be difficult to map the PL Levels to the SIL Levels.
A useful approach is
PL a = SIL 0
PL b/c = SIL 1
PL d = SIL 2
PL e = SIL 3