Fakhor Thank you for your feed back on your reactor liner and leak detection approach done. 25-22-2 is superior to S.S. 316 L (U) but still if u get minor leaks not detectable by ammonia / D.P. test you could think of the following: 1. Vacuum Leak Detection System This is a highly sensitive leak detection method when communication between the lead detection holes (provided in the shell in each compartiment of 25/22/02 liner) is not detectable by conventional D.P. or ammonia vapor detection test. For this the leak detection system is kept under vaccum (by a vacuum pump) with a header / cooler instlallation. Fluids leaking from a liner are continuoulsly sucked to a gas monitor by this vacuum pump. Temp in the system should be kept > 150 deg cent to avoid crystallization of leaking product (urea carbamate product) . Piping for each liner detection hole compartment should end with the header / cooler. In the header / cooler the gas, if any, is collected and cooled down ot ambient temp. The gas enters a gas monitor for ananlyzing for ammonia continuously. Gases leaving the gas monitor shuold be discharged via a flow indicator and a seal vessel. 2. Pressurzied Lead Detection System After ensuring that each liner compartmetn weep hole is having enough communication. a pressurized leak with air. Air ciruculates between the grooves and gaps of the compartment between liner and C.S shell by an air purmp kept at slight pressure of max. 0.5 to 1.0 KSC via a small piping. Keep one SRV (or pressure set valve ) to ensure that the pressure does not increase beyond the set pressure of 0.5 to 1.0 KSC. This will prevent any high pressure and ensure that the liner will not buckle. One can use instrument air also for a low pressure with a flow meter. Temp in the system should always be kept > 150 deg cent to avoid crystallaization of leaking product (urea carbmate leak through liner). Leak monitoring piping should be as short as possible with the piping for each compartment of liner ends in a header / cooler. This air is then fed into a gas monitor where ammonia is analyzed continuously. 3. Other Leak Detection Approaches During a shut down of Reactor, water fill and pressurize with air the annular gap . Observe from inside any leak or pin hole leak develops in internal liner. Soap solution test with air in the annular gap by spraying soap solution. You will notice bubbling of soap bubblesat defect spots. This is quite reliable for most Reactor liner leak detection from world wide experience in reactor leak detection. Eddy current test is used to check if uniformity of gap exists between annular gaps (Permascope to measure uniformity of annular gap). Helium Sensitive Leak test (Helium Mass Spectrometer Leak test) is quite sensitive with sniff probe and sensor mass analyzer. This can be done as pressurized air at the annular gaps using a protable helium gas leak detector. Ammonia vapor leak test can finally be used in the annular gap after attending to the leaky spots by pressurized air or helium leak detection tests. These tests will be far better than conventional UT Flaw or RT for multi coil C.S shell for leak detection. If you do not find any leak in one or a combination of any of these leak detection tests, your reactor leak is so minor as not to worry you. If in-built inspection capability is limited in this, you can think of external consultants and external agencies with facilities to carry out these tests. Trust this helps you for your tests C.V.Srinivasan Nishi Engineers Pvt Ltd India Sept 14, 2006 E-mail: nishi@vsnl.com >Dear Sir, >1. Our Urea reactor was originally lined with SS 316 L Mod . >2. Some Leakages were observed from this liner. >3. The Reactor was relined with 25-22-02 in 1992. >4. We are experiencing very small leaakage from the relined >section.The leakage cannot be visually seen but checked with >dragger tube and lab analysis. The internal inspections are >done every available oppurtunity if reactor is leaking >otherwise in annual TAs. >5. Multiple Ammonia Tests and Dye cheecks have been >performed to locate the leakage but have not been >successful. >5. The weep holes are monitored per 8 hr shift and are >flushed to ensure clear passage for any leaking fluid >6. The Vent holes provided for welding of multilayer shell >courses are also being closesly monitored but so far there >is no observation. >we have no evidence to support that the leakage has come in >contact or damaged the CS shell >7. In spite of all these tests we would like to verify the >thickness of multilayer coil while the reactor is running. >Brian Shanon of IESCO does mention such a technique in list >of paper but we have not been able to obtain a copy from >them. > >8. We would like to learn more about the the mutlilayer >technology and its pros and cons and inspection methodology > >Hope you can help