Mark Leak at sight glass weld joint ( it should be fillet weld - i guess) may not be not related to any corrosion due to LPG or low HCl levels (HCl -1-3 ppm). It appears that it could be due to poor welding quality at the sight glass joints or poor weld joint (fillet weld joint) design and if a low hydrogen filler or electrode had been chosen that should take care of this temperature and LPG service with traces of HCl. Sight glass welding is usually not given the same importance in many construction welding practices. Also in some manufacturing practices all necessary NDT tests are not done or inspected carefully after or before welding. Your problem could get solved if during a shut down you are able to remove the leaky welding joint and re-prepare and provide good welding joint and good welding. Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India April 3, 2008 E-mail: nishi@vsnl.com >In our refinery a new unit which name is Advance Extraction >Technology unit developed a leak around the welding joint >of the sight glass line. With temp. about -15 c and the >service is LPG and about 1 to 3 ppm of hcl. IS Their any >possibility to corrosion to occur at the minus temp. IS >their any one had the same unit I am looking to know the >damage mechanism for this unit. > >Thanks

Mark /Luis Big and small story : Poor weld quality. Attend to this when opportunity arises soon. Corrosion related problem would be negligible and even if it occurs it would be surface fissures only (with this ppm of HCl traces and from LPG contaminants). Hope this helps C.V.Srinivasan Nishi Engineers Pvt Ltd India April 4, 2008 E-mail: nishi@vsnl.com >To help you, one needs to have a more detailed info about >the subject > >Tell us all the story and you will be given a more >conclusive answer > >regards > > >Luis marques