Analýza příčin poškozování trubek přehřívače

ROOT-CAUSE ANALYSIS OF SUPERHEATER-TUBE FAILURE

článek v časopise ve Web of Science, Jimp

en

Superheater-tube failure is listed among the major causes of a fossil-fuel-fired boiler outage. Therefore, it is necessary not only to identify and repair it in the case of failure but also to eliminate the root cause of this problem. As there may be multiple reasons of failure in exposed equipment such as a superheater, a thorough investigation of more than one probable cause is usually required. This article focuses on a failure analysis of a boiler located in a chemical plant. After a leak was discovered, several cracks on the superheater tubes were identified as its main cause. It was necessary to assess the extent of the damage, detect the root cause and propose corrective actions. Two problematic locations with cracks were identified during the visual inspection: the first was on the superheater-tube bends and the other was the weld joint between the superheater and the transition pipe. As the first step, the material-microstructure and composition analyses of the tubes in these critical locations were carried out. Even though small weaknesses were found in the microstructure, the main cause of the tube failure was not identified. As the next probable cause, thermal-dilatation stresses were investigated using the finite-element analysis (angl. FEA). The support system, consisting of fixed and spring supports, as well as the compensator were included in the analysis that confirmed the thermal-dilatation stresses as the major cause of the failure. Based on the results, a new technical solution for the supports was suggested and verified with the FEA.

Článok je zameraný na analýzu poškodenia kotla umiestneného v chemickej prevádzke. V kotle došlo k úniku média, ktorého príčinou boli trhliny na prehrievači. Viedlo to k nutnosti identifikácie rozsahu poškodenia, odhalenia príčin poškodenia a určeniu nápravných opatrení. Počas detailnejšej analýzy boli vykonané vizuálne a materiálové rozbory trubiek vstupnej komory výstupného prehrievača kotla, čomu sa venuje druhá časť článku. Následne pomocou MKP analýzy bol vykonaný kontrolný dilatačný výpočet spalinovej cesty za účelom overenia správneho spôsobu návrhu pevných a klzných miest, a taktiež overenie tuhosti uloženia katalyzátora a overenie správneho návrhu kompenzátorov, taktiež MKP analýzou. V závere bol vykonaný návrh nápravných opatrení pri zachovaní dilatácií jednotlivých častí, vrátane návrhu technického riešenia s minimálnym zásahom do zariadenia. Výsledný návrh bol overený MKP analýzou.

Superheater-tube failure is listed among the major causes of a fossil-fuel-fired boiler outage. Therefore, it is necessary not only to identify and repair it in the case of failure but also to eliminate the root cause of this problem. As there may be multiple reasons of failure in exposed equipment such as a superheater, a thorough investigation of more than one probable cause is usually required. This article focuses on a failure analysis of a boiler located in a chemical plant. After a leak was discovered, several cracks on the superheater tubes were identified as its main cause. It was necessary to assess the extent of the damage, detect the root cause and propose corrective actions. Two problematic locations with cracks were identified during the visual inspection: the first was on the superheater-tube bends and the other was the weld joint between the superheater and the transition pipe. As the first step, the material-microstructure and composition analyses of the tubes in these critical locations were carried out. Even though small weaknesses were found in the microstructure, the main cause of the tube failure was not identified. As the next probable cause, thermal-dilatation stresses were investigated using the finite-element analysis (angl. FEA). The support system, consisting of fixed and spring supports, as well as the compensator were included in the analysis that confirmed the thermal-dilatation stresses as the major cause of the failure. Based on the results, a new technical solution for the supports was suggested and verified with the FEA.

koroze, trhliny ve svaru, podpěry přehříváku, teplotní dilaace

corrosion, weldment cracks, superheater supports, thermal dilatation

01.06.2017

1580-2949

3

51

503–507

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