HAZOP

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How does SMS differ from HAZOP? What are the AS 2885 requirements for HAZOP studies on pipelines and pipeline facilities?

HAZOP and SMS are very different.

A HAZOP study looks mainly at whether variations in process conditions (pressure, temperature, flow, etc) can cause failure and is usually associated with process and control equipment. It does not involve much risk evaluation because potential failure modes are meant to be eliminated by design change. HAZOP for a pipeline system mainly applies to pipeline facilities such as scraper stations, MLVs, meter/regulator stations, etc.

The SMS looks at a completely different range of issues which in practice mostly apply to pipeline remote from facilities in locations where there is no process and control equipment but a whole lot of threats (mostly external) that can create damage and possibly failure. The SMS also includes the concepts of risk evaluation and ALARP for risks that cannot be eliminated.

To oversimplify somewhat, HAZOP is mostly focussed on what is going on inside the pipe (or equipment) and SMS is mostly focussed on things outside the pipe.

A HAZOP study is mandatory under AS 2885. There are only a few mentions of it in Part 6 but it remains an important part of pipeline safety management. The key requirement is in Clause 1.5.2 which requires that the process safety of the pipeline system be subject to HAZOP. The HAZOP process is long established and well-known the so the Standard provides no guidance on how to do it.

HAZOP is mentioned in Clauses 5.4.4 and 5.5.1 in the context of the detailed design SMS and the operational review SMS respectively. In both cases the essence of the requirement is that a valid and current HAZOP exists. That does not mean that it needs to be re-done for every operational review SMS, provided that there have been no changes to matters within its scope.

This blog post on HAZOP for pipelines was written many years ago but remains valid (apart from the reference to a superseded version of AS 2885.1): https://pipelinesoz.wordpress.com/2011/02/20/hazops/