Author Archive for knowledg

In order to comply with the requirements of MOC, whether because of regulations or because it makes good process safety sense, companies have set up elaborate systems that sometimes defeat the purpose.  The purpose of MOC is first, recognize that there is a change, and then determine if that change is safe.  Thus, a safety analysis is always required.  Should it always be a detailed safety analysis?  A full PHA with a team that includes a facilitator and scribe?

The answer is “no”.  The safety analysis should be commensurate with the complexity of the change.  Doing a detailed safety analysis every time takes away resources that could be used on other operations that have a higher risk, and that would make them safer.  For example, if you are going to change the driver of a pump to one with higher horsepower, the safety analysis could be made by a small group consisting of an experienced process engineer and a pump expert.  If the safety analysis shows a potential for significant impact on the process, then a more detailed study would be required.  On the other hand, if you are going to change the capacity, size or type of a process heat exchanger, the potential impacts are so many, that a detailed analysis should be performed.

The important aspect of a safety analysis is a factor that tends to be glossed over: the quality of the analysis.  I have reviewed dozens and a great many are left wanting. Review of the study by a technically competent member of the facility, that is not involved in the change (and especially doesn’t approve the change), goes a long way towards improving the quality of the safety analysis. This is what’s called peer review.

One last factor that typically doesn’t get included in the safety analysis is review of previous analyses.  Do you review your last 5-year PHA to identify potential impacts of the change?  Remember that a very detailed analysis was done at that time.  Do you review your past MOCs to see if you are modifying a past modification?  Are you unwittingly affecting a layer of protection that was put in place (and justified) in a past MOC?

As all these are time consuming activities, it pays to have an electronic PHA and an electronic MOC system.  Just make sure that they are easily searchable.