Section VIII – Division 2 Criteria and Commentary
|Publication Date:||27 May 2014|
Part 1, paragraph 1.2 defines the scope of coverage for VIII-2. The term scope refers to both the type of pressure equipment being considered in the development of these rules, as well as the geometric scope of the vessel that is stamped with the Certification Mark and U2 Designator as meeting VIII-2.
In accordance with Part 1, paragraph 18.104.22.168, pressure vessels are defined as containers for the containment of pressure, internal or external. This pressure may be obtained from any external source, or by the application of heat from a direct or indirect source, as a result of a process, or any combination thereof.
The manner in which the scope of the standard is described follows very closely to the introduction section of VIII-1. In the following paragraphs, a discussion of requirements is provided only where a significant difference exists between VIII-2 and the scope definition from VIII-1, or where a major change was made from Old VIII-2.
With regard to pressure vessels installed in non-stationary applications, Part 1, paragraph 22.214.171.124.b now permits stamping with the Certification Mark and U2 Designator of VIII-2 vessels installed on motor vehicles and railway cars. This particular application was prohibited in the Old VIII-2. Construction and stamping with the Certification Mark and U2 Designator of VIII-2 vessels in non-stationary applications requires a prior written agreement with the local jurisdictional authority covering operation and maintenance control for a specific service. This operation and maintenance control must be retained during the useful life of the pressure vessel by the user in conformance with the Users Design Specification.
Part 1, paragraph 126.96.36.199.e defines pressure vessels in which steam is generated but which are not classified as Unfired Steam Boilers that require construction in accordance with the rules of Section I or VIII-1. A third category for a vessel that generates steam that may be constructed to VIII-2 was added, paragraph 188.8.131.52.e.3: vessels in which steam is generated but not withdrawn for external use.
One significant difference between VIII-2 and the Old VIII-2 is special service vessels such as those in lethal service. In Old VIII-2, paragraph AG-301.1(c), the user and/or his designated agent had to define in the UDS if a vessel was intended for lethal service. If lethal service was specified, then additional technical requirements (e.g. enhanced NDE, restrictions on material, etc.) were imposed on this vessel. In VIII-2, additional requirements are not specified for lethal service or any other special service condition. The rationale behind this change is that the user and/or his designated agent are responsible to describe in the UDS (see Part 2, paragraph 2.2.2), the intended operation of the vessel, and if a vessel is intended for a service that is dangerous to life and property, then the user should specify any additional requirements to mitigate the risks. Just as it has been the rule in ASME that it's standards would not define when a vessel is in lethal service, what additional requirements would be appropriate for any given vessel are best defined by the user, and not by the Committee.