At the moment I am in the commissioning team of a Hydro cracking construction. We are still in the engineering phase of the project but sooner we will start with on site field erection. As I am not familiar with Hydro crackers what is forum advice on inspection matters of this kind of units? What we should look closer in the disciplines of rotating, static and piping equipment. I know the main corrosion mechanisms in hydro crackers is ABS (ammonium bisulphide corrosion) and high temperature corrosion related with hydrogen but I would like to know from forum experience inspection point of view at what matters the commissioning inspectors must take more attention. Thanks in advance luis

Added to Mr.Sivasankaran points,please ensure adequate wash water flow during commissiong at OVHD coolers to avoid severe corrosion in later stage. Please check the adequacy of water injection line size and flow as per the design requirements.Excess water injection will not create more problem however inadequate water injection will cause the ovhd tube plugging and subsequent premature failure. The OVDH piping material is chosen based on feed H2S,N2 present and there is no standard/mandatory rule to go for DSS material.Even CS material with balance header design(kp value) can work if the above design parameters are taken into consideration.

There is long time I haven’t been here, for that reasons I want to thank the answers of SivasanKaran and Krish123. Feed effluent exchanger tubes of first stage are in SSTP 347 Feed effluent exchanger tubes of second stage are in SSTP 321 Piping & aircooler upstream high pressure separator are in Duplex SS 2205 Now we are facing some problems with ferrite content of first and second reactor heaters. The ferrite content of deposit weld was measured after stabilising PWHT. The ferrite content in some welds is above 10%. In some welds to lower ferrite content, they performed in my opinion wrongly, more than one stabilizing PWHT. Again in my opinion wrongly the PWHT was only applied with electrical resistances in the weld and HAZ and not as it should be in all piece of pipe in a furnace. It is LICENSOR of heater understanding that the elevated temperature heat treatment would need to be performed in the temperature range of 1065ºC to 1121ºC; and will convert the sigma phase. The higher temperature is required to ensure the carbides can be restabilized after the heat treatments. After the elevated heat treatment the tubes will then require the stabilizing heat treatment at 899ºC. During the stabilizing heat treatment there is the potential to form sigma phase again. Then during operation there is the potential to form sigma, if the tubes are exposed to temperatures above 537ºC. The basic issues are the chemistry of the welds is not correct and this has resulted in the formation of higher levels of delta ferrite, which has the potential to convert to sigma during heat treatments and operation. The only solution for the LICENSOR to address this issue is to remove the welds. My opinion is that there was a mistake to specify a stabilising PWHT for TP347H in the operating conditions of this particular furnace tubes. Regards