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API 620:2009 pdf download

API 620:2009 pdf download.Design and Construction of Large, Welded, Low-pressure Storage Tanks.
3.1 Stress and Pressure Terms
3.1.1 design pressure: The maximum positive gauge pressure permissible at the top of a tank when the tank is in operation. It is the basis for the pressure setting of the safety-relieving devices on the tank. The design pressure is synonymous with the nominal pressure rating for the tank as referred to in this standard (see 5.3.1).
3.1.2 maximum allowable stress value: The maximum unit stress permitted to be used in the design formulas given or provided for in this standard for the specific kind of material, character of loading, and purpose for a tank member or element (see 5.5 and 5.6).
3.2 Capacity Terms
3.2.1 nominal liquid capacity: The total volumetric liquid capacity of a tank (excluding deadwood) between the plane of the high liquid design level and elevation of the tank grade immediately adjacent to the wall of the tank or such other low liquid design level as the Manufacturer shall stipulate.
3.2.2 total liquid capacity: The total volumetric liquid capacity of a tank (excluding deadwood) below the high liquid design level.
3.3 Tank Wall
The tank wall is any or all parts of the plates located in the surface of revolution that bounds the tank and serves to separate the interior of the tank from the surrounding atmosphere. Flat bottoms of cylindrical tanks are covered by the rules of 5.9.4. As such, the tank walls include the sidewalls (or shell), roof, and bottom of the tank but not any of the following elements located on or projecting from the walls:
a) Nozzles and manways or their reinforcement pads or cover plates.
b) Internal or external diaphragms, webs, trusses, structural columns, or other framing.
c) Those portions of a compression-ring angle, bar, or girder that project from the walls of the tank.
d) Miscellaneous appurtenances.
3.4 Welding Terms
The terms defined in 3.4.1 through 3.4.21 are commonly used welding terms mentioned in this standard. See 5.22 for
descriptions of fusion-welded joints.
3.4.1 automatic welding: Welding with equipment which performs the welding operation without adjustment of the controls by a welding operator. The equipment may or may not perform the loading and unloading of the work.
3.4.2 backing: The material—metal, weld metal, carbon, granular flux, and so forth—that backs up the joint during welding to facilitate obtaining a sound weld at the root.
3.4.3 base metal: The metal to be welded or cut.
3.4.4 depth of fusion: The distance that fusion extends into the base metal from the surface melted during welding.
3.4.5 filler metal: Metal added in making a weld.
3.4.6 fusion: The melting together of filler metal and base metal, or the melting of base metal only, which results in coalescence.
3.4.7 heat-affected zone: The portion of the base metal that has not been melted but whose mechanical properties or microstructures have been altered by the heat of welding or cutting.
3.4.8 joint penetration: The minimum depth a groove weld extends from its face into a joint, exclusive of reinforcement.
3.4.9 lap joint: A joint between two overlapping members. An overlap is the protrusion of weld metal beyond the bond at the toe of the weld.
3.4.10 machine welding: Welding with equipment that performs the welding operation under the constant observation and control of a welding operator. The equipment may or may not perform the loading and unloading of the work.
3.4.11 manual welding: Welding wherein the entire welding operation is performed and controlled by hand.
3.4.12 oxygen cutting: A group of cutting processes wherein the severing of metals is effected by means of the chemical reaction of oxygen with the base metal at elevated temperatures. In the case of oxidation-resistant metals, the reaction is facilitated by use of a flux.
3.4.13 porosity: The existence of gas pockets or voids in metal.
3.4.14 reinforcement of weld: Weld metal on the face of a groove weld in excess of the metal necessary for the specified weld size.
3.4.15 semiautomatic arc welding: Arc welding with equipment that controls only the filler metal feed. The advance of the welding is manually controlled.
3.4.16 slag inclusion: Nonmetallic solid material entrapped in weld metal or between weld metal and base metal.
3.4.17 undercut: A groove melted into the base metal adjacent to the toe of a weld and left unfilled by weld metal.
3.4.18 weld metal: The portion of a weld that has been melted during welding.
3.4.19 welded joint: A union of two or more members produced by the application of a welding process.
3.4.20 welder: One who performs manual or semiautomatic welding.
3.4.21 welding operator: One who operates machine welding equipment.
3.5 Other Terms
3.5.1 Manufacturer: The party having the primary responsibility for constructing the tank.
3.5.2 Purchaser: The owner or the owner’s designated agent, such as an engineering contractor.


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