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我这里有本压力管道方面的书籍,里面谈及到标准和规范间的差别,请大家看一看,希望有助于理解标准和规范的不同,不过是英文的。
Differentiation between Codes and Standards
Codes and standards both provide criteria through which pressure integrity can be
ensured and simplified design rules to ensure adherence to the criteria. Many
designers and engineers think the terms code and standard are synonymous, or at
least somewhat interchangeable, but this understanding is incorrect.
Codes.
Piping codes provide specific design criteria such as permissible materials
of construction, allowable working stresses, and load sets that must be considered
in design. In addition, rules are provided to determine the minimum wall thickness
and structural behavior due to the effects of internal pressure, deadweight, seismic
loads, live loads, thermal expansion, and other imposed internal or external loads.
Piping codes provide design rules for nonstandard components and for the reinforce-
ment of openings in the pipe wall. They do not provide design rules for standard
in-line components such as valves, flanges, and standard fittings; rather, they define
the design requirements for these classes of components by reference to industry
standards.
The use of specific codes for the design and construction of piping systems is
frequently mandated by statute or regulations imposed by regulatory and enforce-
ment agencies.
Typically codes are structured around technology or industry user lines. For
example,ASME B31.1, Power Piping, covers piping systems in power plants, district
heating plants, district distribution piping systems, and general industrial piping
systems while ASME B31.3, Process Piping, is structured around the chemical,
petroleum, and petrochemical industries. Any one of the above-named industrial
facilities might have a pipeline with similar service requirements such as a
high-pressure steam main, a boiler feedwater line, or a cooling water line. How-
ever, the requirements of the specific code, as influenced by the needs and
experience of the user industry, will dictate the pipeline’s design and construc-
tion requirements.
Many piping design and construction codes are listed in the section ‘‘Reference
Codes and Standards.’’ The systems and subsystems covered by these codes are
defined in their scope sections. The scope sections of all potentially applicable codes
should be reviewed early in the design phase of a piping project to determine which
code, or codes, should be applied to the piping design and construction.
In some cases, multiple codes may be required for the design and construction
of the same piping system, depending upon its location. For example, a steam main
serving a petrochemical plant from a major utility’s district heating system would
be designed and constructed toASME B31.1, up to the petrochemical plant property
line. The balance of the piping on the petrochemical plant’s property would be
designed to ASME B31.3. In the case of a natural gas main serving a utility power-
house, the outdoor piping is designed and constructed to ASME B31.8 up to and
including the meter set, and the in-plant piping is designed and constructed to
ASME B31.1. For more details, refer to Chap. A4.
Sometimes, different piping systems within the same building or facility will be
designed and constructed to different codes. For example,most of the piping systems
in a utility power plant are designed and constructed to ASME B31.l. However, the
building heating and air conditioning piping systems are designed and constructed to
ASME B31.9, Building Services Piping.
Standards.
Standards provide specific design criteria and rules for individual com-
ponents or classes of components such as valves, flanges, and fittings. There are
two general types of standards: dimensional and pressure integrity.
Dimensional standards provide configuration control parameters for compo-
nents. The main purpose of dimensional standards is to ensure that similar compo-
nents manufactured by different suppliers will be physically interchangeable. Con-
formity to a particular dimensional standard during the manufacture of a product
does not imply that all such similarly configured products will provide equal perfor-
mance. For example, two different styles of NPS 10 (DN 250) Class 150 flanged-
end gate valves could be manufactured, in part, to ASME B16.10, Face-to-Face and
End-to-End Dimensions of Valves. The valves would be physically interchangeable
between mating flanges in a particular piping system. However, because of com-
pletely different seat and disk design, one valve might be capable of meeting far
more stringent seat leakage criteria than the other.
Pressure-integrity standards provide uniform minimum-performance criteria.
Components designed and manufactured to the same standards will function in an
equivalent manner. For example, all NPS 10 (DN 250) Class 150 ASTM A105
flanges, which are constructed in accordance with ASME B16.5, Pipe Flanges and
Flanged Fittings, have a pressure-temperature rating of 230 psig (1590 kPa gage)
at 300F (149C).
Statute or regulation does not normally mandate standards; rather they are
usually invoked by a construction code or purchaser’s specification. |
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