Inherent Safety: Minimize
We continue our series of posts on the topic of Safety in Design. The first six posts were,
The principles of inherent safety vary from organization to organization, but most descriptions of the topic are structured around the following five elements.
Eliminate
Substitute
Minimize
Moderate
Simplify
In this post we consider the third item in the above list: Minimize.
The third step in the Inherent Safety hierarchy is Minimization. Usually, this step involves reducing the quantity or concentration of hazardous substances used in a process.
This philosophy comes in part from the Bhopal tragedy that resulted in so many fatalities. That facility stored large quantities of the intermediate compound methyl isocyanate. Had this inventory been reduced ― a technically feasible solution ― the consequences of the event would have been much less severe.
Representative Minimization questions include the following:
Can inventories of hazardous chemicals be reduced, possibly through the use of Just in Time management techniques?
Can the length of piping containing hazardous materials be reduced?
Can hazardous chemicals be transferred by pipeline rather than by truck or train?
It may be possible to artificially reduce inventories of hazardous materials at a site by requiring the manufacturer of those chemicals to implement Just-in-Time techniques, as discussed in Chapter 1. In such situations it is important to ensure that the manufacturer’s safety standards are acceptable.
There is one situation where minimization may not be appropriate, and that is to do with adding over-capacity to equipment. Although the design engineers aim to reduce the size of equipment so as to reduce costs, some over-design can help take care of operational upsets and changes in performance. For example, adding extra tubes to a heat exchanger may help handle temperature surges and may reduce the interval between exchanger cleanings, thus reducing the exposure of maintenance personnel.
