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11/30/2018

Methods for Checking/Auditing Pipe Flanges, Pressurized Connections and Other Critical Joints

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Summary:
Improper torque of high-pressure vessels can be attributed to safety incidents that cause financial loss, loss of property and even loss of life. The more volatile and dangerous the substance the more critical it is to take precautions to ensure flanges and bolts have been properly torqued and most importantly, properly audited.


The Clean Air Act requires refineries to develop and implement a Leak Detection and Repair (LDAR) program to control fugitive emissions. Fugitive emissions occur from valves, pumps, compressors, pressure relief valves, flanges, connectors and other piping components.  A study conducted by the Pressure Vessel Research Council (PVRC) in the USA indicated that a significant percentage of flange joint failures resulting in leaks were due to loose bolts.


Improper torque of high-pressure vessels can be attributed to safety incidents that cause financial loss, loss of property and even loss of life.  The more volatile and dangerous the substance the more critical it is to take precautions to ensure flanges and bolts have been properly torqued and most importantly, properly audited.


Given the ever more challenging environmental, legislative and economic demands facing plant operators, while always striving to ensure maximum operational efficiency, joint integrity must be seen as a crucial element of any maintenance program. Effective management of critical pressure-containing joints can reap rewards in terms of cost-savings and operational efficiency, not to mention removing risk.


In Arita, Wakayama Japan a leakage and fire of naphtha and hydrogen was attributed to uneven tightening torque of five to twenty-five bolts at the inlet flange of the reactor, where a "creep" phenomenon caused them to loosen.


Numerous incidents of leakage are recorded by the International Occupational Safety and Health Information Centre (CISDOC) and published as a Hazardous Installations Directorate to assist inspectors in assessing and inspecting accidents.