December 5, 2014
The design cycle of a pressurized system begins with the blueprints or computer design phase, the act of laying pen to paper or mouse pointer to computer terminal. The engineer produces a schematic that is approved and moved on to the fabrication stage. Each stage gets progressively more intricate. There's the implementation and distribution of safety valves to plan, the type of welding to institute, electronic processing instrumentation to install, and copious miscellaneous components to test. Every part has a role to play, a purpose, but let's strip some of this complexity away and reduce the issue to a simpler form. Suffice to say, a pressurized vessel, the pipes and all of the other associated components mentioned above, are subject to a logical design process. This process begins with the aforementioned design phase, moves on to a physical fabrication and welding stage, and ends with certification.
The legislature that rules the certification phase comes from in-process inspections that are designed to match the rated properties of the fabricated vessel with recorded properties. Hopefully, and this is a crucial aspect of a production facility, the two sets of measurements match, with the inspected data exceeding the rated values by a certain factor to account for peak transient spikes. 1.5 times the rated design specification is a common figure here. National and international standards regulate acceptable limits during the inspection process. ASME regulations are a core part of the stipulations, but the relevant AS (Australian codes) should also be referenced when conducting the tests for industrial markets in Australia and New Zealand.
The body of the testing procedures encompass visual inspections, stress analysis tests, and pressure testing sequences designed to stretch the design limitations of the pressure vessel. Additionally, the inspection team requires detailed technical documentation on the projected operation of the vessel, where it will be situated, what pressure it will hold, and a comprehensive list of design characteristics. In short, the entirety of the vessels fabrication is placed under a virtual microscope. The examination takes account of weld seams and wall thickness, safety valve placement and overall vessel functionality. A trained eye checks every inch of steel, but technology also has role, a critical one. Ultrasonic testing reveals invisible flaws and potential stress fractures. There's even further options depending on the vessel, the choice to use computer simulation software to replicate hazardous pressures.
The rigorous inspection procedure is mandatory. It concludes with certification and installation, but the precisely calculated design calculations created by the engineers are continually put to the test. As such, time can take its toll, which is why onsite servicing and inspections are necessary. These tests aren't as comprehensive as the initial inspection and resultant certification regime, but they're more than adequate for monitoring metallurgical changes over the years.
Fusion - Weld Engineering Pty Ltd
ABN 98 068 987619
1865 Frankston Flinders Road,
Hastings, VIC 3915
Ph: (03) 5909 8218
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