A Practical Guide for Recognizing Elastic Follow-Up in Existing Power Piping Systems and Minimizing its Effects

2013 ◽  
Author(s):  
Lange Kimball
Keyword(s):  
High Pressure ◽  
High Energy ◽  
Point Of View ◽  
Repair Costs ◽  
Pressure Steam ◽  
Piping Systems ◽  
Safety And Reliability ◽  
Main Steam ◽  
High Temperature High Pressure

High temperature, high pressure steam piping can fail for many reasons. This can include some combination of metallurgical, operational, fabrication, erection and design short comings. This has proven that high-energy piping systems are not maintenance free and have a finite service life. From a safety and reliability point of view it is increasingly important to determine when this life is expended before failure occurs. This requires that conditions that can reduce life are recognized. Once recognized, it is equally important that these conditions be addressed in a manner that will help prevent personnel injury, forced outages and high repair costs. The ASME B31.1 Code states that piping is “subjected to strain concentrations due to elastic follow-up of the stiffer or lower stressed portions.” However, the phenomena of “elastic follow-up” is often overlooked in the design of creep prone piping such as main steam and hot reheat. It is also difficult to identify in the field. This paper addresses a methodology to recognize elastic follow-up in existing piping systems, possible consequences and the means to minimize its effect.

Ranking of Creep Damage in Main Steam Piping System Girth Welds Considering Multiaxial Stress Ranges

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Marvin J. Cohn ◽  
Fatma G. Faham ◽  
Dipak Patel
Keyword(s):  
Creep Damage ◽  
High Energy ◽  
Sustained Load ◽  
Piping System ◽  
Multiaxial Stress ◽  
Analysis Model ◽  
Principal Stresses ◽  
Piping Systems ◽  
Girth Welds ◽  
Main Steam

A high-energy piping (HEP) asset integrity management program is important for the safety of plant personnel and reliability of the fossil plant generating unit. HEP weldment failures have resulted in serious injuries, fatalities, extensive damage of components, and significant lost generation. The main steam (MS) piping system is one of the most critical HEP systems. Creep damage assessment in MS piping systems should include the evaluation of multiaxial stresses associated with field conditions and significant anomalies, such as malfunctioning supports and significant displacement interferences. This paper presents empirical data illustrating that the most critical girth welds of MS piping systems have creep failures which can be successfully ranked by a multiaxial stress parameter, such as maximum principal stress. Inelastic (redistributed) stresses at the piping outside diameter (OD) surface were evaluated for the base metal of three MS piping systems at the piping analysis model nodes. The range of piping system stresses at the piping nodes for each piping system was determined for the redistributed creep stress condition. The range of piping stresses was subsequently included on a Larson–Miller parameter (LMP) plot for the grade P22 material, revealing the few critical (lead-the-fleet) girth welds selected for nondestructive examination (NDE). In the three MS piping systems, the stress ranges varied from 55% to 80%, with only a few locations at stresses beyond the 65 percentile of the range. By including evaluations of significant field anomalies and the redistributed multiaxial stresses on the outside surface, it was shown that there is a good correlation of the ranked redistributed multiaxial stresses to the observed creep damage. This process also revealed that a large number of MS piping girth welds have insufficient applied stresses to develop substantial creep damage within the expected unit lifetime (assuming no major fabrication defects). This study also provided a comparison of the results of a conventional American Society of Mechanical Engineers (ASME) B31.1 Code as-designed sustained stress analysis versus the redistributed maximum principal stresses in the as-found (current) condition for a complete set of MS piping system nodes. The evaluations of redistributed maximum principal stresses in the as-found condition were useful in selecting high priority ranked girth weldment creep damage locations. The evaluations of B31.1 Code as-designed sustained load stresses were not useful in selecting high priority creep damage locations.

Risk-Based Inspection Applied to Main Steam and Hot Reheat Piping Systems

2007 ◽  
Author(s):  
Marvin J. Cohn
Keyword(s):  
Cost Effective ◽  
High Energy ◽  
Accurate Estimate ◽  
Terminal Point ◽  
Rational Approach ◽  
Piping System ◽  
Piping Systems ◽  
Risk Areas ◽  
Main Steam ◽  
Life Consumption

Many utilities select critical welds in their main steam (MS) and hot reheat (HRH) piping systems by considering some combination of design-based stresses, terminal point locations, and fitting weldments. The conventional methodology results in frequent inspections of many low risk areas and the neglect of some high risk areas. This paper discusses the use of a risk-based inspection (RBI) strategy to select the most critical inspection locations, determine appropriate reexamination intervals, and recommend the most important corrective actions for the piping systems. The high energy piping life consumption (HEPLC) strategy applies cost effective RBI principles to enhance inspection programs for MS and HRH piping systems. Using a top-down methodology, this strategy is customized to each piping system, considering applicable effects, such as expected damage mechanisms, previous inspection history, operating history, measured weldment wall thicknesses, observed support anomalies, and actual piping thermal displacements. This information can be used to provide more realistic estimates of actual time-dependent multiaxial stresses. Finally, the life consumption estimates are based on realistic weldment performance factors. Risk is defined as the product of probability and consequence. The HEPLC strategy considers a more quantitative probability assessment methodology as compared to most RBI approaches. Piping stress and life consumption evaluations, considering existing field conditions and inspection results, are enhanced to reduce the uncertainty in the quantitative probability of failure value for each particular location and to determine a more accurate estimate for future inspection intervals. Based on the results of many HEPLC projects, the author has determined that most of the risk (regarding failure of the pressure boundary) in MS and HRH piping systems is associated with a few high priority areas that should be examined at appropriate intervals. The author has performed many studies using RBI principles for MS and HRH piping systems over the past 15 years. This life management strategy for MS and HRH critical welds is a rational approach to determine critical weldment locations for examinations and to determine appropriate reexamination intervals as a risk-based evaluation technique. Both consequence of failure (COF) and likelihood of failure (LOF) are considered in this methodology. This paper also provides a few examples of the application of this methodology to MS and HRH piping systems.

The Research on New Utilization Technology of Waste Steam from Autoclave Kettle

2014 ◽  
Vol 953-954 ◽  
pp. 710-713
Author(s):  
Zhi Pan Gu ◽  
Yuan Hai Jiang ◽  
Xiang Jiang Zhou ◽  
Jing Liu ◽  
Xiao Yan Wu
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Building Materials ◽  
Economic Benefits ◽  
Environmental Benefits ◽  
Steam Curing ◽  
Concrete Production ◽  
Pressure Steam ◽  
Aerated Concrete ◽  
High Temperature High Pressure

This paper has studied using steam injector to recycle waste steam emission from autoclave kettle and it will produce great economic benefits and environmental benefits. Autoclave kettle which is a kind of resistance to high temperature high pressure steam curing equipment, and it’s mainly used for pipe pile, lime-sand brick and aerated concrete production. We will get more technical and economic benefits, if the research results can be popularized and applied in the national building materials products production.

scholarly journals III. On the agency of water in volcanic eruptions; with some observations on the thickness of the earth's crust from a geological point of view; and on the primary cause of volcanic action

1885 ◽  
Vol 38 (235-238) ◽  
pp. 253-260
Keyword(s):  
High Pressure ◽  
Volcanic Eruptions ◽  
Point Of View ◽  
Mineral Matter ◽  
High Pressure Steam ◽  
The Earth ◽  
Difference Of Opinion ◽  
Pressure Steam ◽  
Volcanic Vent ◽  
The One

That water plays an important part in volcanic eruptions is a wellestablished fact, but there is a difference of opinion as to whether it should be regarded as a primary or a secondary agent, and as to the time, place, and mode of its intervention. The author gives the opinions of Daubeny, Poulett-Scrope, and Mallet, and dismissing the first and last as not meeting the views of geologists, proceeds to examine the grounds of Scrope’s hypothesis — the one generally accepted in this country—which holds that the rise of lava in a volcanic vent is occasioned by the expansion of volumes of high pressure steam generated in the interior of a mass of liquefied and heated mineral matter within or beneath the eruptive orifice, or that volcanic eruptions are to be attributed to the escape of high pressure steam existing in the interior of the earth.

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