Integrally Reinforced Nozzles
Integrally reinforced nozzles are recommended for shell components that are 2-inches thick and greater, or that have maximum design temperatures of 650°F and higher. These nozzles can be nondestructively examined to the higher quality standards desired for service at high pressures and high temperatures, and they can also be more readily nondestructively examined for flaws that might develop during service (see Section 700).
The fabricator must procure these forgings from a forging vendor according to the materials specification and grade shown on the vessel drawing, which again is designated by a “SA Specification” in ASME Code, Section II.
The fabricator orders the forgings from forging vendors using a materials purchase specification that is a part of the fabricator’s Quality Control System, similar to his procurement of plate materials. The forgings must comply with all of the requirements of ASME Code, Section II, and the fabricator should incorporate all of the additional requirements in the pressure vessel specification into the materials purchase specification. Figure 600-4 shows integrally reinforced nozzle forgings.
The ASME Code does not require the forging vendor to provide a test report verifying that the forgings meet all of the test requirements of the SA Specification in ASME Code, Section II. Marking the forgings with the SA Specification and Grade is accepted as sufficient verification that all of the requirements are met. This procedure differs significantly from the requirement that the supplier of plate materials must submit a materials test report. It is up to the Company inspector to assure that the fabricator has correctly ordered the forgings; to obtain any additional materials property requirements; and to verify that either the forging vendor or the fabricator has performed the additional tests that are required. In most cases, the fabricator will require the forging vendor to provide materials test reports for review by the
The strength and CV-impact toughness properties of forgings can be highly directional, depending on the direction of metal flow. All forgings should be forged as close as practicable to finished size and shape to develop metal flow in a direction most favorably oriented for resisting the stresses encountered in service. This requirement is in the traditional concept of a forging, but some vendors and fabricators overlook this. The metal flow in forgings that are forged close to the finished shape follows the surface contour, as shown in Figure 600-4a, which is usually the most favorable orientation for the stresses encountered in service.
Some forging vendors produce a forged billet and then machine the billet to the finished shape. With this type of forging process, the metal flow does not follow the surface contours, as shown in Figure 600-4b. Consequently, the metal flow in a machined billet will not be favorably oriented for the bending stresses that can develop in the flange of a nozzle forging.
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