CrazyEngineers Forum - Chemical & Metallurgy Engineering |
| Posted: 08 Sep 2010 09:43 AM PDT We are facing one serious concern regarding PWHT of weld joints of A335 Grade P11 & P22 piping in very high pressure superheated steam and syn gas service. Due to some unforeseen circumstances at our site, PWHT of some weld joints was not done effectively and resulted in higher hardness of weld joints although HAZ area hardness values are OK. The hardness number of weld joints is in the range of 260 - 320 HB which is unacceptable as per code requirements. I want to seek your expert opinion on the following: 1. Can we take these weld joints is operation and defer PWHT for planned Outage after one and a half year from now? 2. Is there any relaxation which can be taken in hardness readings, for example, welds with hardness up to 260 may be accepted and above this number must be PWHT again? 3. What effects can it cause after taking these weld joints in service? Weld failure can occur immediately or would take some time? 4. As HAZ area hardness number is standing in the range of 115 - 150, would repeating PWHT effect this number and further reduce the hardness of HAZ which may not be acceptable? Your inputs would definitely help me in making a correct decision. Regards, Ashfaq |
| Methylene diphenyl diisocyanate - What detriment/hazards to Production Plant Assets? Posted: 07 Sep 2010 09:36 PM PDT During the production processes of Methylene diphenyl diisocyanate (MDI - all three isomers) - what are the inherent hazards one might need to consider to the detriment of the production plant's assets (I am not concerned about personnel safety matters - I understand the non benign nature of MDI)? In other words what are the main corrosive / other effects due to the WHOLE production process on metallurgical / other assets (structure / tanks / piping etc)? Are special alloys required during new build plant construction? Are special Hazards involved - likelihood of explosion / corrosive leakages etc? What should a Techical Integrity Assurance Manager look out for in particular during the construction of a new MDI plant? Thank you for your consideration. |
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