When someone says “What is your basis of safety going to be?”, in an engineering context, how would you reply? And what is “ALARP”?
As a process engineer for many years, I was unaware of this concept. It wasn’t until starting to work in process safety that I started to join the dots.
The concept of a “basis of safety” can be hard to explain, and even harder to prove in some cases. From our work carrying out DSEAR Risk Assessments across many industries, here’s our insight into what constitutes a basis of safety and some key examples.
When carrying out a risk assessment such as DSEAR, the client has to be able to demonstrate that they are keeping personnel safe, in line with ALARP principles.
To do this, as the risk assessors, we need to identify HOW people will be kept safe, by showing HOW either a fire or explosion will be prevented or mitigated.
Basis of Safety Options
We therefore describe there being two types of basis of safety we can use:
- Preventative Basis of Safety
- Mitigative Basis of Safety
Some examples of these could be:
Preventative:
- Avoidance of a flammable atmosphere (e.g. by inertion, high ventilation, using an alternative material, making the material non flammable etc.)
- Avoidance of ignition sources (harder than it sounds when there are so many to consider)
- Control of ignition sources (easier to do, by e.g. using suitably rated equipment which should not become an ignition sources if maintained and operated correctly).
Mitigative:
- Safe venting of explosions (to a safe location, or with safe venting equipment such as flameless vents)
- Explosion suppression (potentially expensive and complex solution)
- Exclusion of personnel from the area (this could be hard to prove).
Once the most suitable basis of safety has been chosen, then all the safeguards needed to achieve this need to be in place.
Recommendations and ALARP
This is where recommendations come in. If there are gaps in protection layers which means a basis of safety has not been achieved to an ALARP level, then we can make recommendations to plug these gaps with improvements.
For example, if we have a dust collector, with an explosion panel fitted, and the intended basis of safety is “safe venting of explosions”, there might need to be a recommendation to:
- Ensure explosion panel is suitably ATEX rated and maintained.
- Ensure explosion panel does not vent into an occupied area.
The equipment may already have the means to provide the basis of safety, but it may not quite be there in terms of a reliable and ALARP level.
So next time someone asks what your basis of safety is going to be, just think “should we preventing this, or mitigating this?”. Preventative is always preferrable in line with the hierarchy of inherent safety, but is often not possible.