{"id":357,"date":"2025-10-08T21:15:41","date_gmt":"2025-10-08T21:15:41","guid":{"rendered":"https:\/\/pwhtsolutions.net\/?p=357"},"modified":"2025-10-08T21:15:41","modified_gmt":"2025-10-08T21:15:41","slug":"vyjimky-z-tepelneho-zpracovani-po-svarovani-podle-normy-asme","status":"publish","type":"post","link":"http:\/\/pwhtsolutions.net\/cs\/post-weld-heat-treatment-exemptions-in-the-asme-code\/","title":{"rendered":"V\u00fdjimky pro tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed v p\u0159edpisu ASME"},"content":{"rendered":"

Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) sni\u017euje riziko k\u0159ehk\u00e9ho lomu t\u00edm, \u017ee odstra\u0148uje zbytkov\u00e1 nap\u011bt\u00ed a zm\u011bk\u010duje tvrd\u00e9, potenci\u00e1ln\u011b k\u0159ehk\u00e9 mikrostruktur\u00e1ln\u00ed oblasti. Sou\u010dasn\u00e9 normy stanovuj\u00ed r\u016fzn\u00e9 po\u017eadavky na v\u00fdjimky z PWHT v z\u00e1vislosti na chemick\u00e9m slo\u017een\u00ed, po\u017eadavc\u00edch na vlastnosti podle Charpyho zkou\u0161ky nebo na z\u00e1klad\u011b kontroln\u00edch p\u0159edpis\u016f, kter\u00e9 umo\u017e\u0148uj\u00ed omezen\u00ed p\u0159\u00edpustn\u00e9 velikosti defekt\u016f (tabulka 1).<\/p>\n

Omezuj\u00edc\u00ed tlou\u0161\u0165ka<\/h2>\n

Sou\u010dasn\u00e9 normy vy\u017eaduj\u00ed proveden\u00ed tepeln\u00e9ho zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) u sva\u0159enc\u016f z trubkov\u00fdch materi\u00e1l\u016f o tlou\u0161\u0165ce men\u0161\u00ed ne\u017e 0,625 palce; limit stanoven\u00fd t\u011bmito normami je v\u0161ak \u010dasto v rozporu s metalurgick\u00fdmi hledisky a po\u017eadavky na konstruk\u010dn\u00ed n\u00e1vrh. V\u00fdzkum proveden\u00fd institutem EPRI p\u0159inesl d\u016fkazy podporuj\u00edc\u00ed zv\u00fd\u0161en\u00ed tohoto limitu, ani\u017e by t\u00edm byla ohro\u017eena bezpe\u010dnost \u010di spolehlivost.<\/p>\n

Byl proveden v\u00fdzkum s c\u00edlem posoudit st\u00e1vaj\u00edc\u00ed po\u017eadavky norem a v\u00fdjimky t\u00fdkaj\u00edc\u00ed se sva\u0159ov\u00e1n\u00ed chrom-molybdenov\u00fdch ocel\u00ed P-4 a P-5A pou\u017e\u00edvan\u00fdch v jadern\u00fdch aplikac\u00edch, p\u0159i\u010dem\u017e zvl\u00e1\u0161tn\u00ed pozornost byla v\u011bnov\u00e1na jejich p\u016fvodu a technick\u00e9mu z\u00e1kladu, a to prost\u0159ednictv\u00edm rozhovor\u016f s vedouc\u00edmi p\u0159edstaviteli normaliza\u010dn\u00edch org\u00e1n\u016f i prostudov\u00e1n\u00edm dokumentace, kter\u00e1 n\u00e1m byla k dispozici.<\/p>\n

Studie proveden\u00e9 na r\u016fzn\u00fdch norm\u00e1ch odhalily, \u017ee krit\u00e9ria tlou\u0161\u0165ky jsou \u010dasto ur\u010dov\u00e1na sp\u00ed\u0161e tradi\u010dn\u00edmi postupy v konkr\u00e9tn\u00edch odv\u011btv\u00edch ne\u017e v\u011bdeck\u00fdmi anal\u00fdzami kov\u016f \u010di mechanick\u00fdmi \u00favahami, co\u017e vedlo k obrovsk\u00fdm rozd\u00edl\u016fm mezi nimi; v sou\u010dasn\u00e9 dob\u011b se mezn\u00ed hodnoty v jednotliv\u00fdch norm\u00e1ch zna\u010dn\u011b li\u0161\u00ed, p\u0159i\u010dem\u017e odv\u011btv\u00ed v\u00fdroby elekt\u0159iny m\u00e1 mnohem vy\u0161\u0161\u00ed limity ve srovn\u00e1n\u00ed s petrochemick\u00fdm pr\u016fmyslem; co\u017e je v rozporu s v\u00fdzkumem, kter\u00fd ukazuje, \u017ee zbytkov\u00e9 nap\u011bt\u00ed ve svaru kles\u00e1 s rostouc\u00edm pr\u016fm\u011brem trubky a lomov\u00e1 hou\u017eevnatost v z\u00f3n\u011b ovlivn\u011bn\u00e9 teplem (HAZ) odpov\u00eddaj\u00edc\u00edm zp\u016fsobem kles\u00e1.<\/p>\n

Charpyho zkou\u0161ka<\/h2>\n

Charpyho zkou\u0161ka je standardn\u00ed r\u00e1zov\u00e1 zkou\u0161ka ur\u010den\u00e1 k m\u011b\u0159en\u00ed mno\u017estv\u00ed energie absorbovan\u00e9 p\u0159i lomu vzork\u016f materi\u00e1lu; obvykle se skl\u00e1d\u00e1 z kyvadla s r\u00e1zov\u00fdm kladivem, kter\u00e9 se rozhoup\u00e1 a dopadne na obroben\u00e9 vzorky, kter\u00e9 mohou, ale nemus\u00ed obsahovat z\u00e1\u0159ezy sm\u011b\u0159uj\u00edc\u00ed od kyvadla; \u00farovn\u011b absorpce energie se m\u011b\u0159\u00ed a p\u0159ev\u00e1d\u011bj\u00ed na hodnoty z\u00e1\u0159ezov\u00e9 hou\u017eevnatosti.<\/p>\n

Tato zkou\u0161ka umo\u017e\u0148uje ur\u010dit teplotu p\u0159echodu z tv\u00e1rn\u00e9ho do k\u0159ehk\u00e9ho stavu (DBTT) kov\u016f, co\u017e je z\u00e1sadn\u00ed vlastnost v kritick\u00fdch aplikac\u00edch, jako je sva\u0159ov\u00e1n\u00ed a v\u00fdroba tlakov\u00fdch n\u00e1dob. Krom\u011b toho slou\u017e\u00ed tato zkou\u0161ka tak\u00e9 k ur\u010den\u00ed celkov\u00e9 hou\u017eevnatosti materi\u00e1lu a k detekci p\u0159\u00edpadn\u00fdch lok\u00e1ln\u00edch k\u0159ehk\u00fdch z\u00f3n, kter\u00e9 by mohly b\u00fdt citliv\u00e9 na tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT). Automatizace zkou\u0161ky pomoc\u00ed zku\u0161ebn\u00edho syst\u00e9mu roboTest zaji\u0161\u0165uje p\u0159esn\u00e9 v\u00fdsledky s omezen\u00fdm vlivem obsluhy, jako jsou kol\u00eds\u00e1n\u00ed teploty a vlhkosti rukou nebo excentrick\u00e9 \u010di \u0161ikm\u00e9 vlo\u017een\u00ed vzorku; poskytuje spolehliv\u00e1 data s vy\u0161\u0161\u00ed propustnost\u00ed vzork\u016f a ni\u017e\u0161\u00ed chybovost\u00ed, ne\u017e jak\u00fdch lze dos\u00e1hnout pouze ru\u010dn\u00edmi zku\u0161ebn\u00edmi metodami \u2013 co\u017e vede k vy\u0161\u0161\u00ed celkov\u00e9 propustnosti a ni\u017e\u0161\u00edmu po\u010dtu chyb.<\/p>\n

Posouzen\u00ed z hlediska mechaniky lomu<\/h2>\n

Mechanika lomu zahrnuje dv\u011b vlastnosti materi\u00e1l\u016f: pevnost a hou\u017eevnatost. Pevnost ud\u00e1v\u00e1, jak dob\u0159e materi\u00e1l sn\u00e1\u0161\u00ed zat\u00ed\u017een\u00ed, zat\u00edmco hou\u017eevnatost ud\u00e1v\u00e1, jak \u00fa\u010dinn\u011b br\u00e1n\u00ed \u0161\u00ed\u0159en\u00ed trhlin.<\/p>\n

Mechanika lomu se stala pr\u016fmyslov\u00fdm standardem a je zohledn\u011bna v norm\u00e1ch pro tlakov\u00e9 n\u00e1doby, kotle a potrub\u00ed. V sou\u010dasn\u00e9 dob\u011b tato norma umo\u017e\u0148uje provozovatel\u016fm upustit od tepeln\u00e9ho zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT), pokud jejich lomov\u00e1 hou\u017eevnatost ve sva\u0159ovan\u00e9m stavu spl\u0148uje nebo p\u0159ekra\u010duje maxim\u00e1ln\u00ed hodnotu stanovenou pro tlou\u0161\u0165ku svaru.<\/p>\n

Kritick\u00e9 in\u017een\u00fdrsk\u00e9 posouzen\u00ed (ECA), kter\u00e9 vyu\u017e\u00edv\u00e1 teorii lomov\u00e9 mechaniky, umo\u017e\u0148uje in\u017een\u00fdr\u016fm prov\u00e9st toto hodnocen\u00ed. Vysok\u00e1 hodnota lomov\u00e9 hou\u017eevnatosti sv\u011bd\u010d\u00ed o zv\u00fd\u0161en\u00e9 odolnosti proti \u0161\u00ed\u0159en\u00ed trhlin, dobr\u00e9 toleranci po\u0161kozen\u00ed a \u00fanavov\u00e9 odolnosti \u2013 to v\u0161e jsou z\u00e1sadn\u00ed vlastnosti pro efektivn\u00ed a ekonomicky v\u00fdhodn\u00e9 navrhov\u00e1n\u00ed, v\u00fdrobu a provoz konstrukc\u00ed \u010di sou\u010d\u00e1st\u00ed. Vy\u0161\u0161\u00ed hodnota m\u016f\u017ee p\u0159in\u00e9st \u00fasporu n\u00e1klad\u016f d\u00edky prodlou\u017een\u00ed interval\u016f kontrol nebo sn\u00ed\u017een\u00ed po\u010dtu neo\u010dek\u00e1van\u00fdch poruch v d\u016fsledku zv\u00fd\u0161en\u00e9 \u017eivotnosti.<\/p>\n

V\u00fdjimky<\/h2>\n

Osvobozen\u00ed je v\u00fdsada, kter\u00e1 umo\u017e\u0148uje jednotlivci, skupin\u011b nebo organizaci vyhnout se ur\u010dit\u00fdm povinnostem a z\u00e1vazk\u016fm. Osvobozen\u00ed m\u016f\u017ee spo\u010d\u00edvat v da\u0148ov\u00e9 \u00falev\u011b (osvobozen\u00ed od dan\u00ed) nebo v tom, \u017ee ur\u010dit\u00e9 \u010d\u00e1stky nejsou v\u016fbec p\u0159edm\u011btem zdan\u011bn\u00ed (status bez da\u0148ov\u00e9ho osvobozen\u00ed). Osvobozen\u00ed se obvykle vztahuje na osoby, skupiny, organizace i majetek a \u010dasto se vyskytuje v pr\u00e1vn\u00ed praxi i v jin\u00fdch oblastech, jako je nap\u0159\u00edklad podnik\u00e1n\u00ed.<\/p>\n

U n\u011bkter\u00fdch sva\u0159ovan\u00fdch ocelov\u00fdch sestav m\u016f\u017ee b\u00fdt nezbytn\u00e9 prov\u00e9st tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT), aby se sn\u00ed\u017eilo riziko k\u0159ehk\u00e9ho lomu prost\u0159ednictv\u00edm sn\u00ed\u017een\u00ed zbytkov\u00fdch nap\u011bt\u00ed a zm\u011bk\u010den\u00ed tvrd\u00fdch, potenci\u00e1ln\u011b k\u0159ehk\u00fdch mikrostruktur\u00e1ln\u00edch oblast\u00ed. Nutnost proveden\u00ed PWHT z\u00e1vis\u00ed na lomov\u00e9 hou\u017eevnatosti materi\u00e1lu p\u0159i teplot\u011b sva\u0159ov\u00e1n\u00ed.<\/p>\n

Po\u017eadavky na PWHT se v jednotliv\u00fdch norm\u00e1ch li\u0161\u00ed, proto\u017ee ka\u017edou z nich vypracovaly r\u016fzn\u00e9 odborn\u00e9 org\u00e1ny s p\u0159ihl\u00e9dnut\u00edm k rozs\u00e1hl\u00fdm zku\u0161enostem a in\u017een\u00fdrsk\u00fdm postup\u016fm. Za \u00fa\u010delem zaji\u0161t\u011bn\u00ed ur\u010dit\u00e9 jednotnosti teplot PWHT nap\u0159\u00ed\u010d normami navrhuje McEnerney7 zv\u00fd\u0161it tyto teploty u materi\u00e1l\u016f P \u010d. 4 o 30 \u00b0F, podobn\u011b jako v p\u0159\u00edstupech CEN, a t\u00edm usnadnit sjednocen\u00ed.<\/p>","protected":false},"excerpt":{"rendered":"

Tepeln\u00e9 zpracov\u00e1n\u00ed po sva\u0159ov\u00e1n\u00ed (PWHT) sni\u017euje riziko k\u0159ehk\u00e9ho lomu eliminac\u00ed zbytkov\u00fdch nap\u011bt\u00ed a popou\u0161t\u011bn\u00edm tvrd\u00fdch, potenci\u00e1ln\u011b k\u0159ehk\u00fdch mikrostrukturn\u00edch oblast\u00ed. Sou\u010dasn\u00e9 p\u0159edpisy maj\u00ed r\u016fzn\u00e9 po\u017eadavky na v\u00fdjimku z PWHT v z\u00e1vislosti na chemick\u00e9m slo\u017een\u00ed, vlastn\u00edch po\u017eadavc\u00edch na vlastnosti podle Charpyho zkou\u0161ky nebo prost\u0159ednictv\u00edm kontroln\u00edch p\u0159edpis\u016f umo\u017e\u0148uj\u00edc\u00edch omezen\u00ed p\u0159\u00edpustn\u00e9 velikosti vad (tabulka 1). Omezen\u00ed tlou\u0161\u0165ky Sou\u010dasn\u00e9 p\u0159edpisy vy\u017eaduj\u00ed PWHT pro ... <\/p>\n

P\u0159e\u010dt\u011bte si v\u00edce “Post-Weld Heat Treatment Exemptions in the ASME Code”<\/span><\/a><\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-357","post","type-post","status-publish","format-standard","hentry","category-pwht-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/357","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/comments?post=357"}],"version-history":[{"count":1,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/357\/revisions"}],"predecessor-version":[{"id":358,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/posts\/357\/revisions\/358"}],"wp:attachment":[{"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/media?parent=357"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/categories?post=357"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/pwhtsolutions.net\/cs\/wp-json\/wp\/v2\/tags?post=357"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}