蓝色中国心 发表于 2013-1-9 14:25 
Spec break：应该是指 与规格书相背离部分；
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Specification breaks are required in piping systems for transition from high to low pressure, between high and low temperature service (sometimes), and between corrosive and non-corrosive environments. Temperature is also a consideration because it has an effect on material strength and corrosion resistance. When setting specification breaks it is important to look at the complete piping system from source to destination. The specification break must be positioned so that there is no possibility for the lower pressure, lower/higher temperature or less corrosive resistant piping to be exposed to the harsher condition under any circumstance. Situations to consider include; operator or instrument failure, startup/shut down conditions, line plugging due to hydrate formation or water deposition and freezing, Joule-Thompson expansion (sub-cooling) and plugging with corrosion products or dirt. Also, the destination system must be properly protected with appropriately sized relief valves, vents, etc. Methods that are used to protect a lower pressure piping system downstream from the specification break can include: a. No valves downstream b. CSO valves downstream, plus a stringent management policy for such valves. c. Where appropriate, instrument and control valve failure modes that ensure piping system integrity. d. Tracing and insulation where appropriate to prevent hydrate formation and ice plugs. e. Frequent inspection where line plugging or corrosion is suspected to be a problem. f. Thermal expansion reliefs for trapped fluids. Where appropriate, the procedural solutions discussed above can be covered in a note on the P&ID, and ultimately can be addressed in the plant operating procedures.
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发表于 2013-1-9 14:18
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