Pressure Vessels

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<p>PRESSURE VESSELS</p> <p>1</p> <p>What are Pressure vessels?Pressure vessels are containers used in holding or processing fluids under pressure (usually pressures above or below atmospheric).</p> <p>Applications</p> <p>Examples industrial compressed air receivers domestic hot water storage tanks. diving cylinder, recompression chamber, distillation towers, autoclaves vessels in mining or oil refineries and petrochemical plants,</p> <p>Examples nuclear reactor vessel, habitat of a space ship, habitat of a submarine, pneumatic reservoir, hydraulic reservoir under pressure, rail vehicle airbrake reservoir, road vehicle airbrake reservoir and storage vessels for liquified gases such as ammonia, chlorine, propane, butane and LPG.</p> <p>Shape Vertical Drum Horizontal Drum Vertical Towers Spheres</p> <p>ShapeHorizontal Drum On Saddles</p> <p>ShapeVertical Drum On Legs</p> <p>Shape</p> <p>Vertical Tower on Skirt</p> <p>ShapeSphere with legs reinforced with cross bracing For storing gaseous fluids</p> <p>Construction materialsGenerally, almost any material with good tensile properties that is chemically stable in the chosen application can be employede.g.</p> <p> Steel carbon steels, stainless steels composite materials, such as wound carbon fibre held in place with a polymer polymers such as PET in carbonated beverage containers and copper in plumbing. They may be lined with various metals, ceramics, or polymers to prevent leaking and protect the structure of the vessel from the contained fluid.</p> <p>DesignDesign Codes &amp; StandardsMinimum standards used as guides for design e.g. EN 13445: The current European standard, harmonized with the Pressure Equipment Directive. ASME Code Section VIII Division 1: US standard, widely used. ASME Code Section VIII Division 2 Alternative Rule ASME Code Section VIII Division 3 Alternative Rule for Construction of High Pressure Vessel ASME PVHO (Safety Standard for Pressure Vessels for Human Occupancy) BS 5500: Former British Standard, replaced in the UK by EN 13445 but retained under the name PD 5500 for the design and construction of export equipment.</p> <p>DesignDesign Codes &amp; Standards AD Merkbltter: German standard, harmonized with the Pressure Equipment Directive. API 510 "Pressure Vessel Inspection Code: In-Service Inspection, Rating, Repair, and Alteration". ISO 11439 "Gas cylinders - High pressure cylinders for the onboard storage of natural gas as a fuel for automotive vehicles EN 286 (Parts 1 to 4): European standard for simple pressure vessels, harmonized with Council Directive 87/404/EEC. AIAA S-080-1998: AIAA Standard for Space Systems Metallic Pressure Vessels, Pressurized Structures, and Pressure Components AIAA S-081A-2006: AIAA Standard for Space Systems Composite Overwrapped Pressure Vessels (COPVs)</p> <p>Failure modes Stress corrosion cracking Cracking Explosion Rupture Leakage Corrosion</p> <p>Failure modesHydrogen embrittlement Creep and stress rupture Fatigue Caustic embrittlement. Brittle fractures Erosion</p> <p>Factors Responsible for failure Operation above the maximum allowable working and test pressures. Improper sizing or pressure setting of relief devices. Improper operation of relief devices due to faulty maintenance and failure to test regularly. Failure of the vessel due to fatigue from repeated pressurization, general thinning from corrosion or erosion, localized corrosion, stress corrosion cracking, embrittlement, holes and leaks.</p> <p>Factors Responsible for failure Failure to inspect frequently enough. Improper repair of a leak or other defect involving welding and annealing that embrittles and further weakens the vessel Overpressuring and failure of the vessel due to exothermic reaction or polymerization. Vessel exposure to fire.</p> <p>Design Considerations Material Selection Thickness Determination Weights and Volume Calculations</p> <p>Design Considerations Material SelectionDepends on</p> <p> Strength: material must be able to withstand highstresses.</p> <p>Corrosion Resistance Resistance to Hydrogen Attack Fracture Toughness Fabricability: must be weldable and easy to form andfabricate.</p> <p>Design Considerations Thickness Determination (shells)Vessel must be thick enough to withstand stresses. Longitudinal design-</p> <p>PRo t! 2 SE 1.4 PPRo t! SE 0.4 Pt- thickness; P-Pressure; Ro-Outside radius; S-Design Stress; E-Longitudinal joint factor (for welded joints)</p> <p>Circumferential-</p> <p>Maximum of the two is chosen.</p> <p>Design Considerations Thickness Determination (heads)PRo t! 2 S 1.8 PNote: Corrosion Allowance must be added to the thicknesses obtained.</p> <p>Design ConsiderationsWeightsFabricated weight: Total weight as fabricated in the shop. weight added for shipping purposes, such as shipping saddles.</p> <p>Shipping weight: Fabrication weight plus any</p> <p>Erection weight: Fabrication weight plus any weight installed for the erection of the equipment, such as any insulation, fireproofing, piping, ladders, platforms.</p> <p>Design ConsiderationsWeightsEmpty weight: The overall weight of the vessel sitting on the foundation, fully dressed, waiting for operating liquid. Operating weight: Empty weight plus any operating liquid weight. Test weight: This weight can be either shop or field test weight, that is, the vessel full of water.</p> <p>Design Considerations Weights Shell Weight:</p> <p>W ! TDmtLV</p> <p> Weight of one 2:1 Semi Elliptical head</p> <p>W ! 1.084 D tV</p> <p>2 m</p> <p>Dm =mean vessel diameter (mm) L = vessel length T = vessel thickness = density of material</p> <p>Design ConsiderationsVolumes &amp;Surface Area formulasPart Shell: (Cylinder) Volume Surface Area2</p> <p>TDi l V ! 43</p> <p>A ! TDlA ! 1.084 D 2</p> <p>2:1 Semi Elliptical head</p> <p>TDi V! 24</p>