Rapid Design and Construction of a 30K CRA Pressure Vessel Proof Tested to 50,000 psi

Abstract

This paper is a retrospective of a recent project to design, manufacture and qualify a NACE MR0175 / ISO15156 compliant custom HPHT pressure vessel for the purpose of conducting accelerated corrosion testing for a major oilfield operating company. A conventional mechanical design processes begins with the sizing of the vessel via design calculations, and proceeds to creation of a series of design iterations before building the first prototype unit. This is followed by prototype testing required to validate design assumptions and safety margins. This commonly results in redesign and re-manufacturing of the components or the entire prototype unit in order to achieve the desired function and satisfy the safety criteria, leading to a long and expensive development cycle. Virtual prototyping migrates the early "design validation" phases from the physical realm to the computer thus making the ability to test design margins safer and easier, and providing a more comprehensive understanding of the assets capabilities. Computer aided design methods allowed for multiple virtual prototypes to be assessed, with the entire process from product launch to commercial delivery taking less than 8 months. Multiple design challenges were resolved by development of internal design practices following virtual prototyping approach. The approach was validated using laboratory tests and FEA modeling. Numerous procedures addressing design and product delivery challenges were developed: a methodology to follow ASME BPVC design rules for CRA based metallurgies not specified in the Code; a revision of an existing 10,000 psi metal-to-metal seal design to sustain test pressures and a technique for prevention of seal moment in a many-material system with different thermal expansion rates. In the end, using this virtual design approach, following a robust design code such as ASME BPVC Section VIII Division 2 enabled us to produce a first of its kind 30,000 psi / 650°F corrosion test vessel on a short delivery schedule that passed the 50,000 psi proof test required by our operator on its first try. Post-delivery operator requirement changes required a re-assessment of the vessel to a higher working pressure. This resulted in a new FEA analysis following the same logic as the original analysis, but benchmarked against the "as-build" material properties instead of the original material specifications. Post analysis; the vessel was physically validated by a hydro-test to 50,000 psi.