Computer hazops/‘Chazops

There has been much discussion on the apphcation of HAZOPs to computer-controlled systems (computer HAZOPs or CHAZOPs) 43 particular, defence standard DEF STAN 00-56 calls for HAZOPs in relation to both systems and sub-systems, but the only guide it was able to refer to originally was that for chemical process plant. This omission has now been remedied by the formulation and pubhcation of interim defence standard DEF STAN 00-58 Hazop studies on systems containing programmable electronics. ... 

For computer-controlled plant, it is also recommended that at least one Chazop or computer Hazop is carried out. This addresses the hazard potential of the software (and computer hardware) itself. As with the Hazop, the Chazop may also need to be revisited as a result of changes required during commissioning. 

The hazard study must look for potential hazards in the EUC operating with its basic process control system (BPCS). Generally, control system failures are seen as human operator errors, loop control faults or sequencing/interlock failures. However, it is also necessary for the hazard study to consider possible failure modes of any computer/PLC systems used in the BPCS or in supervisory control. This type of study falls within the scope of what are known as computer hazops or chazops . Section 3.13.3 contains some introductory notes on chazops. 

---