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Thermal power plant components operated at high temperatures (>500°C) and pressures, such as superheater headers, steamline sections and Y-junctions, deserve great attention for both operation safety and plant availability concerns. In particular, during plant operation transients -startups, shutdowns or load transients - the above components may undergo high rates of temperature / pressure variations and, consequently, non-negligible time-dependent stresses which, in turn, may locally destabilize existing cracks and cause the release of acoustic emission. 

After preliminary shop tests on different mockups (e.g. superheater and reheater headers and steamline pipe sections), since 1996 AEBIL systems have been installed and are at work on several power plant components. In particular, three different components have been monitored throughout 1997 (monitoring still under way at the time being) ... 

Outlet Superheater (SH) header of Unit 3 (600 MW. supercritical multi-fuel l of an ENEL power station it consists of 2 twin and independent bodies (22 m length, 488.5 mjn internal diameter, 76.2 mm thickness material SA 430 TP 321H stairdess steel). This header has suffered from relevant cracking problems in assembly welds after 108.000 hours of service and... 

Outlet Superheater (SHI header of Unit 4 (600 MW. supercritical multi-fliel l of an ENEL power station it also consists of 2 twin and independent bodies (23 m length, 215 mm internal diameter, 103 mm thickness material ASTM A335 P22 - 2.25CrlMo - low alloy). Structural integrity problems and monitoring requirements and objectives same as above. 

Results of Long-term On-line Structural Integrity Surveillance of H.T./H.P. Steam Headers by an Innovative Acoustic Emission Approach. 

The results of over 1 year of continuous, on-line acoustic emission (AE) structural surveillance of high temperature / high pressure steam headers, gained on 2 M-scale 600MW supercritical multifuel ENEL power units in normal operation, are presented in the paper. The influence of background noise, the correlation between plant operating conditions (steady load, load variations, startup / shutdown transients) and AE activity and the diagnostic evaluation of recorded AE events are also discussed. 

Assessing the effectiveness and reliability of Acoustic Emission (AE) in continuous, on-line monitoring of the structural integrity of critical thermal power plant components, such as steam headers and steamline sections, is the main objective of the work reported in this paper. This is part of the work carried within the BRITE - EURAM 6056 "SIMON" Project from 10.1993 to 9.1997 with the support of the EU Commission. The "SIMON" Project Consortium included CISE [I, coordinator], MITSUI BABCOCK ENERGY [UK] HERIOT WATT University [UK], PROET / EDP[P]andENEL[I],... 

Steam headers and steamline sections may undergo high rates of temperature / pressure variations during plant operation transients - startups, shutdowns or load transients - and are... 

The paper focuses on the presentation and discussion of the results of the application of long term, continuous, AE structural monitoring to 2 large superheated (SH) steam outlet headers, belonging to 2 different full-size (600 MW, supercritical multifuel) ENEL power units. Continuous AE surveillance of the 2 SH headers started in October 1996 and is still ongoing. 

Outlet Superheater (SH) header / 600 MW ENEL power unit (Unit 3)... 

This header consists of 2 twin and independent bodies (upper and lower), with the following characteristics (fig.J) ... 

This header has undergone repair after through-thickness cracking of an assembly weld after 108.000 hours of service, it is presently in operation and periodically submitted to ultrasonic inspection during planned maintenance shutdown. Continuous on-line AE monitoring of the integrity of critical welds is expected to contribute supporting continued and safe operation of the header until its replacement, platmed to take place in 1999. 

Waveguides 4 waveguides (points 5L-8L,. I), made of AISI 304 stainless steel, L = variable, (j>=6 mm, have been installed on the lower body of the SH header of unit 3 and 8 waveguides (points 2A-5A and points 2P-5P,y5. 2), made of AISI 304 stainless steel, L = 3240 mm, if>=6 mm, have been installed on the front (4 waveguides) and rear (4 waveguides) bodies of the SH header of unit 4. 

No firm conclusion should be drawn from the above data, through the observed pattern deserves attention. The AE activity observed on the SH header can originate from the weld, but could be due to other causes, namely to the settlement of the hanger. Ultrasonic inspection of the weld at regular intervals checks whether any sizeable change in NDT response from the weld has taken place. 

Localized AE sources appear during load variations, startups or shutdowns, but their positions are uniformly spread over the length of the two bodies of the header this can be seen from the histogram of the localized AE events for the front body (fig.S) and for the rear body (fig.9). 

Examination of the cumulated histogram of localized AE sources for all monitoring intervals, in different operating conditions, suggests the conclusion that no structurally significant sources have been active in the monitored area of the SH header. 

Two large Superheated Steam outlet headers with potential stmctural integrity problems, belonging to 2 600 MW multifuel ENEL power Units, have been submitted to continuous AE... 

AE activity recorded on the SH header of Unit 3 is substantially lower than that recorded the SH header of Unit 4 this could be traced to the different materials of the 2 headers (stainless steel vs low alloy steel). 

At steady electrical load the background noise is normally low and fairly constant along the SH headers and with time no AE sources come up on the Unit 3 header, while the very few localized events recorded on Unit 4 are spread out over the whole length of the header. 

During electrical load variations the background noise is low and constant along the SH headers, it increases with load variations. AE sources appear during load variations, but their position are again uniformly scattered over the length of the headers. 

Fig. 1 Sketch of the outlet SH header of a 600 MW ENEL power plant, Unit 3.

Fig.6 600 MW ENEL power plant, unit 4. Monitoring period from 22-01-1997 to 03-03-1997. Histogram of the localized AE events on the front body of the SH header...

Each Molfile consists of two parts the so-called header block specific to Molfiles (lines 1-3) and a eonnection table - Ctab (lines 4-18), which is fundamental to all MDL s CTfile formats. 

The first line of the header block contains the molectrle name and does not require any particular format (a rare case). If no name is available the line is blank. For ethanal two names are specified its identifier within the NCI database (NSC 7594) and the regular name. 

The third line of the header block is usually empty or contains comments. 

Figure 2-27. Counts line of the Molfile s header block from the sample f...

The flic presented contains 11 data items. The header lines arc property names as used by CACTVS [64, 65], and arc sufficiently self-descriptive. For example, E NHDONORS is the number of hydrogen bond donor.s, E SM1LES" is the SMILES string representing the structure of sulfamidc, and E LOGP is the logP value (octanol/water partition coefficient) for this substance. 

Each record in this category can appear only once in a PDB file and it occupies exactly one line. Examples of such records arc HEADER - the starting record of each PDB file discussed in detail below, END - the last (terminating) record, and CRYSTl - describing the crystallographic cell. 

The fir.-fit line of the file (see Figure 2-110) - the HEADER record - hold.s the moleculc. s classification string (columns 11-50), the deposition date (the date when the data were received by the PDB) in columns 51-59, and the PDB (Dcode for the molecule, which is unique within the Protein Data Bank, in columns 63-66. The second line - the TITLE record - contains the title of the experiment or the analysis that is represented in the entry. The subsequent records contain a more detailed description of the macromolecular content of the entiy (COMPND), the biological and/or chemical source ofeach biological molecule in the entiy (SOURCE), a set ofkeywords relevant to the entiy (KEYWDS). information about the experiment (EXPDTA), a list of people responsible for the contents of this entiy (.AUTHOR), a history of modifications made to this entiy since its release (REVDAT), and finally the primaiy literature citation that describes the experiment which resulted in the deposited dataset ()RNL). 

The header delivers any relevant additional information helpful to define the nature of the task and its peculiarities. The body contains the variables, which are usually floats. Next, there are the integers defining the class to which the patterns belong (indispensable for classification tasks) and pattern names. 

The JCAMP-DX file format is split into the sections CORE and NOTES with the intention of keeping less important data separated from the essential content. The CORE itself contains CORE HEADER and CORE DATA. NOTES are just between HEADER and DATA (see Figure 4-4 for an example). 

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