Contribution of permit to work to process safety accident in the chemical process industry

Abstract

Permit to Work (PTW) is the Technical Measurement Document required to control work such as maintenance, inspection, modification and non-routine high risk activities to prevent a major accident. It is one of the elements of the Process Safety Management (PSM). The current issue of the chemical process industry (CPI) is that the accident rate has not decreased even though PSM has been widely implemented in the developed country. Statistics on the accident cases published by Chemical Safety and Hazard Investigation Board (US), European Major Accident Reporting System and Failure Knowledge Database (Japan) has revealed that PTW has significance contribution to the occurrence of accidents and is worthwhile to be studied in details. Failure in complying with PTW system has caused major accidents cases, such as Motiva Enterprise LLC (2001), Phillips Pasadena (1989) and Piper Alpha Platform (1988). Another reason for studying PTW, being that the trend of its percentage of contribution to process accident rate is not decreasing over the past two decades even though there are shared information and feedback available. In the chemical process industry, there are various types of PTW namely Hot Work, Confined Space Entry, Line breaking & vessel opening and others. Each has its own function and the percentage contribution of each PTW type is determined using data mining approach. This study is focusing on the identification of main factors of PTWrelated accidents which are classified under organisation, human factors, communication, competency, procedure, supervision, tools and equipment and etc. The percentage contribution of each main factor is determined and the results are presented for sharing and learning purposes.