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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsGeneral Corrosi...General Corrosi...LPD / HPV Valve Corrosion ManagementLPD / HPV Valve Corrosion Management
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2/26/2008 9:00 AM
 
Dear All I Need some opinion , suggestions regarding Low Point Discharge (LPD) Valve , High Point Valves (HPV) corrosion . In some parts of our plant (a naphtha cracker ) there is tremendous corrosion and rusting on some LPDs . It has become very risky to remove the thick rust scales and do ultrasonic thickness gauging. Is there any NDT method that may be suitable used to assess the valve condition (mostly 3/4 inch connections) . What painting/coating option is there which require minimal surface preparation , so the the valves may be protected. The valve metallurgy is Carbon Steel (pressure varies from 7 kg/cm2 to 20 kg/cm2). We already have plans to change some valves during Shutdown , but what measures can be taken in the running plant? Please suggest. Thanks & Regards
 
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2/26/2008 9:00 AM
 
I would like to know whether the corrosion takes place from atmosphere or due to ice formation on the valve external surface. In any case you can protect the valve by selecting epoxy coating.Painting on old rusted valves will be difficult however for the new valve you can try the following system: primer: Epoxy zinc Phosphate (2 coats) Intermediate: MIO(Optional) Finish: Epoxy polyurethane/aliphatic The above system can work up to 85 Deg.C if your system temperature is more than 85 Deg,C then you can select Zince silicate primer-2 coats High temp phenolic epoxy -1 coat :- Can withstand temperature up to 150 Deg.C Regards,
 
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3/7/2008 9:00 AM
 
May pl. readdress vicinity environment (external) and operating performance indictors like T cycling, fluid ( QOil or naptha or Steam etc. ) attributes. Pl. ensure by light tapping by a ball point wooden hammer in 3 shift or within a defined operating frequency whether the surface thick rust is loose or tightly adherent. You may put some mark or sticker on the valve surface and inspect for its spalling to assess aeration cycle and volume growth of rust. Also ensure for vibration - if so rust can be loosened. If the rust scale is firm and tight you can keep it as it is under a condition monitoring RBI focus with clear inspection frequency and record. Normally for SBP valves Hammer & Pressure testing is sufficient and No need to do further NDT. But depending upon the consequence of failure You may do on line profile radiography to ascertain valve conditions and inside fouling/debrises. If it is hot u can do Hot RT also by proper masking . you can have a idea about valve WT and internals condition. Try to do with slow speed film . May U get any opportunity just do distant shock -sand blast with care and apply 1 coat of IZS only. regds
 
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