Risk assessments

A risk assessment names a hazard, who or what it can harm, what is already in place to control it, and what still has to be done. It covers the life of the work: construction, commissioning, operation, and maintenance. Entry to a digester, disconnection of a hose on a gas line, isolation of a high-voltage breaker, and sampling a wastewater pit are different jobs. Each one needs its own look. A single line that says "biogas plant" is not an assessment.

The record is a register. Each line has the hazard, the consequence if the control fails, the controls that exist, and the action still open, with a person and a date. Likelihood and consequence are both written down, so that a rare event with a fatal outcome is not scored as trivial. The register is revised when the feedstock, the layout, or the equipment changes. It is the document a supervisor uses to brief a job.

It does not replace a site safety assessment of the plot, and it does not replace a HAZOP of the process design. Those answer different questions. An action that moves a unit, a road, or a control room goes back to the site assessment. An action that is a deviation of flow, pressure, temperature, or composition, found on the drawings, belongs in the HAZOP. An action that adds or changes a trip, a valve, or a screen goes to automation and into operator training, so the control named on the register is the control the shift actually has.