Some manufacturers offer an asme 8010 head where the dish radius is 80 of the head diameter and the knuckle radius is 10 of the head diameter. The advantage of an asme 8010 head is that it is thinner (66 of the thickness of an asme torispherical head which results in a smaller blank size and reduced labor cost. A third option for a torispherical head is an asme high-crown head, where the dish radius is 80 of the head diameter and the knuckle radius is a minimum of 6 of the head diameter. A 2:1 elliptical flanged and dished head provides a dish radius that is approximately 90 of the inside head diameter and a knuckle that is approximately.3 of the inside head diameter. The geometry of the ellipsoidal head is provided in Section ug-32(d) of the asme code. The decision of whether to specify and use a torispherical head versus an ellipsoidal head is mainly an issue of head clearance. Users should decide which head better suits their needs.
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Can be essay provided upon request. For some head manufacturers, a 3-in. Straight flange can be provided for head diameters ranging from 36 to. As long as there is a minimum wallpaper plate thickness of 3/16. For heads. And larger, a 3-in. Straight flange can be provided with a minimum plate thickness.25. The geometry of an asme 80-10 torispherical head is such that the dish radius is 80 of the head diameter and the knuckle radius is 10 of the head diameter, while an ellipsoidal head has a dish radius that is 90 of the inside head. Standard flanged and dished heads are manufactured, but do not meet the code requirement of a minimum 6 inside-crown radius for the knuckle region. As a result, the standard flanged and dished heads provide a higher stress concentration factor and discontinuity in the knuckle region.
Nominal thicknesses up to and including.5-in. 9/16-in nominal thickness up to and including.0-in. Plate 15 Torispherical heads. Torispherical heads have dish radii equal to the diameter of the head or vessel shell, report and the knuckle is 6 of the head inside-crown radius as required by section ug-32(e) of the asme code (Figure 2). The straight flange (skirt) is a standard.5. For heads formed from 3/16-in. Straight flanges up to.
Photographs for comparison of certain standard finishes (Nos. 1, 2B, 2D, 2ba, 3, 4, 6, 7 and 8) for sheets or various nominal thicknesses can also be found at the website. Vessel heads Some of the most common heads in service are as follows: asme flanged and dished (torispherical 2:1 elliptical flanged and dished (ellipsoidal conical, toriconical, hemispherical and flat. Heads are formed based upon outside vessel diameter, with the exception of elliptical and hemispherical heads, which are formed to the inside diameter. When ordering the head, the vessel manufacturer will provide the head manufacturer with the minimum permitted teresa thickness that is required based upon the calculations. Thinning of the vessel head takes place primarily at the knuckle regions and the center of the dish (Table 2). Guideline for head thinning during you forming head thickness range Allowable thinning during forming 12-gauge, up to and including.25-in.
Nevertheless, simply specifying the grit size cannot be equated to a specific surface finish. Buffing is not intended to remove metal from the surface. It is intended to brighten and smooth the existing surface with cotton- or felt-based media and with the application of lubricants to the buffing wheel. For precise and consistent results, it is recommended that the surface finish be specified in a range of minimum and maximum level of roughness average (Ra). This can be expressed in microinches or micrometers (Table 1). Grit finish, ra (microinch rMS (µm) 36 142.25 Mirror /-.13 The Specialty Steel Industry of North America (ssina) publishes a designer handbook of specialty finishes for stainless steel, which provides detailed descriptions and sample photographs. The handbook can be downloaded free of charge.
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Items such as lifting lugs, support lugs, skirts and support legs can often be specified with a different grade material the than that of pressure retaining items. The user may have a vessel where all of the pressure-retaining items and wetted surfaces are 316L stainless steel, but the lifting lugs and support ring may be fabricated from 304 stainless steel. Depending on the user and the service, a stainless-steel vessel with carbon-steel legs might be acceptable, provided there is a poison pad between the two materials such that the pressure-retaining items are not at risk of carbon contamination. Often manufacturers will specify an alternate material grade for appurtenances in order to minimize fabrication cost. If alternate material grades are unacceptable for appurtenances, that should be stated in the specification, particularly when manufacturers are competitively bidding for the contract.
Stainless-steel surface finish, for users in the food-and-beverage and pharmaceutical industries, there are often requirements for special internal- and external-surface finishes. Ambiguity and different interpretations about user expectations and manufacturer capabilities can arise when the mechanical finish is specified as one of the following: satin, polished, bright, dull or mirror. Parameters such as contact time, material feedrate, abrasive pressure and application of lubrication will have an impact on the finished product. Special finishes supplied by the manufacturer are not published by astm international. Polishing and grinding involve the removal of metal from a surface with an abrasive, resulting in surface directional marks. There is no definition of an abrasive grit size that differentiates grinding from polishing. As a guide, however, grit sizes of 80 and coarser can be associated with grinding, whereas grit sizes of 120 and finer can be associated with polishing.
The user should provide the specific gravity of the process fluid, since the manufacturer must account for the additional static pressure due to the static head of the liquid, per section ug-22(b). Materials of construction, while the material of construction is commonly included in equipment specifications, clarification is often required as to the impact the material specification has on the fabrication and the". Information in the specification should allow the manufacturer to determine whether or not its qualified weld procedures and qualified welders are sufficient for the alloy specified. In cases where the manufacturer has to qualify a procedure for an alloy not commonly welded in the shop, the cost impact should be evaluated. The material specification and the grade designation should also be provided to the manufacturer. For example, if the vessel is fabricated from austenitic stainless plate, then indicate the astm international (astm)specification and grade, such as: A240-316L.
For the nozzles the specification and grade will be A312-316L. If the process safety review determines that seamless pipe is required for the nozzles, then this should be clarified, since it will impact the vessels cost. For flanges, the specification and grade will be A182F-316L. Depending on the process, some users may prefer using a carbon-steel backing flange in conjunction with a stainless-steel stub-end. If that is the case, clearly indicate it in the specification. A material specification for appurtenances is commonly not given.
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The manufacturer will determine if impact testing is required and if the shop has a qualified weld procedure to meet the requirements of the code. The pickling process removes the heat tint produced during welding (left before; right after vessel contents. With regard to vessel contents, the key phrase for the fabricator is lethal service. Vessels are considered lethal service if the contents, whether mixed with air or alone, are dangerous to life when inhaled. Lethal service imposes mandatory code-compliance requirements on the manufacturer, such as 100 radiography of all welds. These requirements can substantially increase the vessels fabrication cost. If the process involves hydrogen sulfide, where there is a risk of sulfide stress cracking, then the manufacturer needs to be advised of the requirements of the national Association of Corrosion Engineers (nace) standard RP0472 and nace publication 8X194. Hydrogen sulfide service will have restrictions for material-grade, post-weld heat treatment, and allowable hardness of the weld and heat-affected zone; all of which will impact the manufacturers cost for fabrication. The user literature should identify dangerous compounds in its process and address the dangers in a process safety review meeting.
Section ug-21 of the code recommends a suitable design pressure above the operating pressure of the vessel at which the vessel will normally operate. The operating pressure should represent the most severe exposure of pressure and temperature the vessel is expected to experience under normal operating conditions, whereas the design pressure should allow for potential pressure surges up to the setting of the pressure-relief thomas device. The design temperature should account for the lowest and highest operating temperature, in addition to operational upsets, atmospheric temperature and other sources of cooling. The design and operating conditions should be established in a process safety review meeting within the users organization. Based upon the material of construction, the nominal plate thickness and the minimum design temperature, the manufacturer will have to determine the requirements for welding. For carbon steel and low-alloy vessels, the requirement for Charpy impact testing can be determined in Section ucs-66 of the code. For high-alloy vessels, such as those fabricated of austenitic stainless steel, the manufacturer will refer to section uha-51 of the code.
from users in areas such. The incomplete specification information makes a proper and complete vessel design difficult and can lead to inaccurate price"s. Providing complete information will help avoid cost overruns and change-orders. The intent of this article is to clarify those areas of pressure vessel specification where information is commonly omitted and areas where further clarification is required. Further, this article is intended to improve understanding of which responsibilities are shouldered by vessel users and which by manufacturers. By providing a more comprehensive basis of design for a vessel, users and manufacturers can save money and formulate specifications with public safety in mind. States, all Canadian provinces and many local jurisdictions and territories have formally adopted the asme code as a safety standard for boilers and pressure vessels. Each jurisdiction employs a chief inspector who is a member of the national board of boiler and Pressure vessel Inspectors. Meanwhile, the code is frequently a prevailing basis in other countries throughout the world. Design versus operating, t and, p In engineering specifications, often no distinction is made between the design pressure and operating pressure.
At the same time, the center works with wpi faculty and staff to continue to advance this proven pedagogy on our own campus. Wpis Corporate and Professional Education (CPE) specializes in helping working professionals achieve their educational goals. Tracing its origins to 1915, the American Society of Mechanical Engineers (asme) boiler and Pressure vessel Code (the code) 1 has become the established safety standard governing the design, fabrication and inspection of boilers and pressure vessels, as proposal well as nuclear power plant components during. Section viii, division i of the code addresses pressure vessels operating at either internal or external pressures exceeding 15 psig. Despite the prevalence of pressure vessels in the chemical process industries (cpi a clear understanding of the basis-of-design responsibilities involved in designing, fabricating and repairing such a device remains elusive. Vessel users are responsible for providing all necessary data to ensure the manufacturer can design and fabricate a pressure vessel in full compliance with the code. The lack of clear understanding can result in a disconnect between users and manufacturers during pressure vessel specification. The disconnect is often magnified because, although Section U-2(a) of the asme code clearly defines the responsibilities for establishing the basis of design, users often lack access to the code language and its associated interpretations. Basis of design refers to well-defined information that could form the foundation for inspection and test acceptance criteria.
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Academics wpi, skip to main content, while our foundation has held firm, we pride ourselves on continuing to modernize the curriculum and our teaching practices. The prestigious 2016 Bernard. Gordon Prize for Innovation in Engineering and Technology Education is a nod both to our history and to our future, recognizing wpis project-based curriculum developing leadership, innovative problem-solving, interdisciplinary collaboration, and global competencies. Arguably every student who attends wpi learns to think like an engineer; these days there is just as much attention to assuring our students think like entrepreneurs. Our Signature Approach to Undergraduate Education. Through wpi's distinctive plan, you'll learn how to learn by applying your classroom experiences in research and projects that challenge you from a proficiency, social, and global perspective. Learn more about how wpi can prepare you to pursue your passions outsiders in solving critical problems and develop skills employers value. The center for Project-based learning at wpi provides support to faculty and administrators across higher education who are aiming to advance project-based learning on their campus. .