Are we too comfortable with existing standards?

摘要

I recently read about Robert Frith in an article by Michael Abrams, an independent writer. Frith is a mechanical engineer and Founding Director of FE Consultants in Brisbane, Australia. He reviewed the process for evaluating the integrity of pressure vessels at the time of fabrication. He determined that when pressure vessel fabricators make a new pressure vessel they have a few options available to them. To take full advantage of the strength of the vessel, they need it to be inspected for an additional cost. Alternatively, they can go in for limited inspection, add some material and claim 85% weld efficiency. Or they can choose not to have any inspection at all, make the vessel even thicker and claim 70% weld efficiency. Frith tried to find out where these numbers came from and looked into ASME history. He couldn't find anything and decided that somewhere along the line history has lost it. The most he came up with was that sometime in the 1920s a number of pressure vessels were pumped up until they leaked and, based upon that data, the subsequent standards have been in effect ever since. But whatever the level of inspection, a pressure vessel is also subject to a hydrostatic test, which pumps it up beyond the pressure the vessel was intended to maintain. Frith asked the question: "Why don't we just push it to the limit? Why don't we go backwards and say: 'How much pressure do we have to apply before it's genuinely distressed?'"