API 650 storage tank designed for seismic forces
Preheat TreatmentMany laboratory tests have shown preheat treatment of carbon steel to 300°F-400°F to be the equivalent of the post-heat treatment at no less than 1100°F insofar as the physical properties of the weldment are concerned.40,41 Some tests have indicated a slight advantage of the post-heat treatment. Most of the tests have been made on plates 3/4 in. - 1 in. thick; results must be viewed with caution if preheating is applied appreciably beyond this thickness range. However, for all practical purposes, improvement resulting from preheating is sufficiently well established so that preheat should be considered for field fabrication of API 620 crude oil tank plates over 3/4-in. thick whenever toughness of the tank API 650 storage tank is highly desired and the thermal post-heat treatment is impractical.
API 650 is constructed from carbon steel, austenitic duplex stainless steel, and API 650 storage tank aluminium A Welding Certification is stipulated by American Society of Mechanical Engineers (ASME), Section 10. There is a required inspection, no third party. The inspection cost is the cost of the NDE.
Due to irregular operation of API 650 storage tank welding, there are many weld deformations during the construction process. Before specific operations, most construction units have formulated relatively complete construction plans and set up special welding process instructions, but the operators have not fully performed welding in accordance with various process guidance requirements and construction specifications, resulting in some quality problems of oil storage tanks. How can we reduce or even avoid this kind of situation?
