This paper presents the effect of carburizing phenomena on the microstructure and weldability of tube coils in the ethylene heating furnace. A tube coil material was used the Ni-base alloy grade 35Cr-45Ni-Nb. The specimens obtained from three different height levels of carburized tube were tested. The results from the SEM-EDS and microstructure analyses show that the carbon was concentrated in carburized tube and deposited in the solid solution and chromium carbide compound. The prediction of new weldability in the carburized tube with Nieq/Creq ratio can be used for welding repair in petrochemical industry.

The aim of this research is to study the effects of welding repair parameters on weld joint of tube 35Cr-45Ni-Nb alloy by using the Gas Tungsten Arc Welding (GTAW) process of two different base metals. One was a new tube material and other was a used tube treated with carburized condition. The 35Cr-45Ni filler metal was sellected for welding repair experiments. The SEM-EDS analysis was used to observe a segregation of atom in the used tube specimen. The non-destructive examination (NDE) tests were done to check the imperfected area of weldment and heat affect zone (HAZ). Data from this research can be used as the guideline suggestion for the welding procedure specificcation (WPS) and the procedure qualification record (PQR) for the welding repair in the peroid of maintenace.

The research purposes to design, analyze and build a report (MDR) integrity. To use as the MDR prototype in accordance with international standards for industrial factories. The MDR is important to the operator of equipment, the factories, and petrochemical industry because of it is an index for the quality assurance, quality control of fabrication and planning of maintenance management (material upgrade/ equipment change) for safety during equipment operation. When the equipment has a problem we can check for cause from the fabrication history data on MDR. A survey was developed for people concerned with the MDR, totaling 141 people from 58 factories in Thailand industrial sector for find out the demands and problems on using the MDR. The result shows that preparation of the MDR can cost more than a week of time, with no clear pattern of standard format and require manpower more than 3 peoples. In summary, the development of the MDR prototype by comparative data between, the manufacturer, the Ministry of Industry of Thailand and the American Society of Mechanical Engineers (ASME). The specialists who have the experience in the MDR to determine the completeness and validate all content in the MDR 15 chapters.

This paper presents the effect of an Ammonium sulphate (NH4)2 SO4) leak mixed in the boiler feed water system on the microstructure, chemistry, metallurgy and mechanical properties of the water tube boiler. Tube specimens were water tube and super-heated tube materials made from ferritic-pearlitic steel alloy grade SA-210-Gr.A1 and ferritic steel grade SA213-Gr.T22, respectively. Specimens were obtained from different height levels of the boiler and tested. The results from the emission spectrometer revealed that the carbon (C) and sulfur (S) did not concentrate inside the tube during five days of operation. Whereas the operating temperature causes the change in the microstructure and mechanical properties due to a segregation of phase and change of mechanical properties (hardness and tensile) in the used tube.