: Failure in HP. Reactor R-101, Urea – 1 Plant |
| 01-17 20:09:11 来源： 作者： |
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: Failure in HP. Reactor R-101, Urea – 1 Plant Inquiry (采购产品): : Failure in HP. Reactor R-101, Urea – 1 Plant Subject: Failure in HP. Reactor R-101, Urea – 1 Plant Dear Specialists: We have a Urea Production Plant at Brea Libya. In the Urea plant, we are having one urea reactor. In this reactor, mixing of liquid ammonia and gaseous CO2 takes place to convert carbamate which further dissociates to form urea having 33% concentration. This reactor is having carbon steel shell with internal lining of SS 316-L (urea grade). Lining is provided so as to protect the shell against highly corrosive urea & carbamate solution. Please refer to the technical informations below. You are kindly asked to evaluate and recommend your repair procedures of the failure. Below you will find the details. And answer the following: General Information: Vessel Manufacture: VEW Kapfenberg, Austria. Year of fabrication: 1977 Vessel construction: Single Wall Liner material: 1.4435 Liner thickness: 7 mm Shell Material: 1.6368 Shell thickness: 82 mm Shell thickness on top dome: 60 mm in the drawing (recorded 70 mm on site by UT.) Design & Operating Temperature: 183 c Design Pressure: 162 kg / cm2 Operating Pressure: 140 to 142 kg / cm2 Inside Diameter: 2400 mm Length: 30000 mm No of trays: 8 Tray Material: 1.4435 Introduction: During planned turnaround of Urea-1 Plant which started on June 8th, 2008, HP Reactor was offered for internal visual inspection, heavy corrosion of the liner was noted at one of the vertical welds of the top dome (see pictures 1, 2, & 3). Investigation Actions: The investigation actions were as follows: 1 – The affected liner area was cleaned form Urea carbamate deposits. 2- The linear was found completely corroded at that area. 3- Bigger area of the liner was cut around the affected zone until clean surface achieved on the liner (see pictures 4, 5, &6). 4 –Accumulation of urea carbamate deposits and further corrosion was noted on the carbon steel section. (see pictures 4, 5, &6). 5- Further grinding and cleaning of the carbon steel section was done in order to perform UT. and MT. 6- UT. Was done and the thickness recorded was 61 mm (the nominal is 70mm) meaning that 9 mm were gone. 7- MT .was done, several cracks were noted spread mostly on the affected area. (See pictures 7, 8, 9 & 10). 8- In order to assess the depth of the cracks they were ground about 9 mm and the crack appearance still appear. 9- The thickness of the carbon steel section left after grinding the cracks is 60 mm Min. at the top area upto 40cm under the top manway; and 49mm Min. at the area underneath. (See pictures 11 & 12). 10- After removal of the cracks final Fluorescent MT was carried-out after 48hrs and revealed minute cracks (See pictures 13 & 14). We seek your valued opinion in the above case and suggest: 1. What is the exact reason for damage and cracking in the Stainless Steel liner, and the Carbon Steel? 2. Is this cracking a Hydrogen Damage Crack or a S.C.C.? 3. After removal of the cracks final Fluorescent MT was carried-out after 48hrs and revealed minute cracks. (See pictures 13 & 14). Can those minute cracks be accepted for safe operation of the plant for one year until we purchase a new reactor? 4. Is the remaining thickness acceptable for safe operation in the plant until we purchase a new reactor? 5. Finally, can we run the plant safely for one year? Attachments: Photos of the failure. Your urgent reply is highly appreciated. Regards. El-Mabruk Omar Al-Irwi NDT Inspector Brea/ Libya **** Hidden Message ***** El-Mabruk Omar Khalifa Brega/ Libya Tripoli/ Libya Trioli LBY Company: Sirte Oil Co. Title: NDT Inspector E-mail: mabrookndt@yahoo.com **** Hidden Message ***** mabrookndt@yahoo.com |
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