How to make hazardous areas safer without any increase in costs

Introduction

Hazardous Areas are typically found in large facilities like oil and offshore oil & gas platforms, oil refineries, chemical processing plants, tank farms, supertankers, other ships that carry petrochemical cargo and even places like grain silos, which have the risk of explosion or fire due to explosive mixtures of vapors or dusts. Hazardous Areas are also referred to as "Classified Locations" in North America.

This article is a short guide to how these areas can be made safer, without any increase in costs.

How are areas classified?

Hazardous Areas in a typical facility are classified on two aspects. One is the probability of a flammable, or explosive mixture (this includes dusts too), being present in that area and secondly, the type of the material being present. Hence classification entails specifying the area (known as Area Classification) as well as the material (Material Classification). A third parameter, temperature is also important and Temperature classification, is also done. An equipment then, carries a marking that shows the Area, Material and Temperature classification, for which it can be installed safely, i.e. without the risk of explosion hazard.

Area Classification is not a permanent thing

Most area classification studies, are done during the design stage. This is not always followed up with periodic audits of whether the previous area classification still holds good or not (say due to plant modifications, change of processes, usage of different raw materials, addition of facilities and so on).

Sometimes, the basis of the area classification itself, is not understood by the people who actually operate the plant, resulting in the original design being no longer valid. This is not a one-off possibility, it happens many times. Unfortunately it may also result in a disaster.

Actual Case Study

The US Chemical Safety Board recently posted a few videos of investigations regarding actual disasters related to chemical plants on its own website, as well as YouTube. One of these videos relates to the explosion at a paint & ink manufacturing facility at Danversport, Massachusetts. If you watch the video, posted below, you will realize that the root cause of the accident, seems to be inadequate ventilation. Apparently, the original design engineers had built in the forced ventilation to reduce the area classification from say Division 1 to Division 2 or possibly from Division 2 to Safe (the latter seems more likely). This "safe area" classification will no longer hold true, if the ventilation is switched off. However, these key facts were not communicated to anybody. Of course all of this is conjecture, but perhaps you can view the video and draw your own conclusions.