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Dear All I totally agree with the facts and that's what I have been saying all along but nevertheless they decided not to inspect despite the RBI interval and scope! Many thanks.

Many thanks Ed The Duplex is 22 Cr. The HX has been on service for 8 years and not inspected. It recently passed hydrotest (twice the operating Pressure ) hence the need to get some corrosion rate for remaining life calculation.

Dear All I am keen get your advice or perhaps case studies for potential pitting rate of Duplex X changer tubes with nominal of 1.7 mm. Most of the literature I have seen are based on seawater, which would not fit my conditions Operating Conditions : 1. Multiphase fluid (mainly oil)with 1.8...

Dear All Whilst there's strong evidence that pipeline deposits lower the inhibitor concentration and coverage, I am curious to see evidence of field experience supported (not laboratory )corrosion rates for under deposit corrosion under the following : 1. Export Condensate with no threat of MIC...

Thanks Steve.

On the same topic, the export pipeline received two stream of condensate, each with its own last stage separator. For the gas composition, i will be using the flow average of the streams. Just curios to know what about the Pressure? Would taking the highest Pressure of the two last stage...

Hi Andy & Steve Many thanks. That's why I love this website. Such an immense knowledge sharing! This is an eye opener for me to see these countless reports from "consultancies " with this issue not being highlighted by the end users! Many thanks all.

Hi Steve, The manual categorically states to use the last stage separator data for liquids.What confused me is to see so many reports using the pipeline Pressure when using Cassandra! Wouldn't the partial Pressure remain same as it's linked to Henry Constant? Wouldnt any dissolved gases in...

Dear All I am planning of modelling CO2 general corrosion on an export Condensate Pipeline(Cassandra) My understanding is that both CO2 content and Pressure input data should be from the last stage separator (where the gas is in equilibrium). I have seen a number of reports (from...

Thanks Ed. That's exactly what I thought. As always many thanks for sharing your immense knowledge. If we go other options, the pipework is also mixture of 316 and CS. This would surely cause as much damage? Thanks

Dear all I have been asked to evaluate if it's possible to utilise an existing 316 SS tank for a polymeric hydrate inhibitor containing either seawater or 4% sodium chloride solution. I highly discourage this given the enormous risk of pitting and crevice corrosion. The piping downstream of the...

Many thanks for the response. I calculated the theoretical weld throat using paragraph 328.5 in B31.3 using 1.09×Tnom×0.707. I assumed that it will be seeing shear stress and used the design pressure to calculate it. I then compared this to B31.3 0.8×allowable stress. My question is, are there...

Just a quick question regarding fillet welds. We are observing low fillet weld throat (2.0 mm) on a 0.75" offtake pipe with 5.56 mm nominal wall thickness. Design Pressure is 28 barg and 3 mm CA. I calculated the theoretical weld throat using B31.3 The calculated theoretical weld throat is 4.29...

Just a quick question regarding fillet welds. We are observing low fillet weld throat (2.0 mm) on a 0.75" offtake pipe with 5.56 mm nominal wall thickness. Design Pressure is 28 barg and 3 mm CA. I calculated the theoretical weld throat using B31.3 The calculated theoretical weld throat is...

Hi Steve, 1. Yes, I agree that the scales are presumably from the upstream CS. 2. The perforation was observed near the tubesheet inlet. The pitting were widespread both on inlet and outlet ends. The gas is essentially wet at this stage. I really don't understand on the alloy choice as I...

Thanks EdStainless for the fantastic contributions. Any idea on the rate of pitting degradation under thsee conditions? Given how thin the tubes are and the observed defects already observed, my fear is that the degradation rate will be rapid leading to another failure before the next shutdown...

Many thanks to EdStainless and metengr for your valuable inputs. The materials were selected prior to my arrival and I have to deal with the consequences. What intrigues me is whether the corrosion products have originated from the upstream CS pipework leading to subsequent under deposit...

Dear All, We recently had tube pitting failure on Incolloy 800 tubes with incoloy 800 clad tubesheet. The pitting occurred inside out and upon ECI inspection widespread pitting was found with upto 60% wall thickness loss. Black adherent solid was also found in the tubes. We were lucky to get...