In our refinery many leg supports and were provided with weep hole in case of any internal corrosion happened be noted through the weep hole at the pipe support. Later in the deethanizer feed line at elbow and we noticed some snow at the weep hole .After that we predict the corrosion is internal but actually it was external due to the moist air that enters to the support through the weep hole and condensed on the elbow external surface. This leak cause hole unit shutdown. Please check your refineries and do inspection to all support that had weep hole. I stat this in order to share the information with you and to take care .Corrosion engineers need to contact in order to defeat the industrial enemy. Please any one had a technical alert or something to share regarding the corrosion at the refinery don’t hesitate to write in our fourm. Refinery corrosion Engineer

I am not aware whether weep hole is used for inspection purpose ( as per Mark) but to mention what I understand weep holes which remains at support bottom are provided to release any welding fumes during piping support construction and also to release ant internal aquous media in service and it's hole dimension is not too large to use it as "peep door inspection window". Secondly, for cryo service all the piping including the piping supports are to be cold insulated . regards

Debasis / MJ Cronin Adding to MJC's observation - which weep holes by and large serve the purpose of weep hole for reinforcement pad welds or for structural pipe support welds for vessels which are not supporting by skirting arrangements- weep hole is also used for pneumatic test of welds of pads after construction welding and during pressure test of a vessel before commissoning. This helps to check the integrity of reinforcement pad welds before threded screws on the pads are plugged. Usually weep holes are threaded and screwed after initial pressure test. Once leaks are identified in nozzle joints in pressure vessels , it also serves to monitor externally during operation to monitor teh rate of crack propagation. UT thickness of pad plates serves as a guideline of internal corrosion rate monitoring also. Point 3 of MJC observation / opinion : It is not any stretch of "logic". It really serves for identification of leaks in nozzle welds during cracks or in support pipe weld cracks. It also indirectly serves the purpose of corrosion rate monitoring of process by monitoring the pad thickness -on stream - to evaluate the internal corrosion conditions. Trust this is of help C.V.Srinivasan Nishi Engneers Pvt Ltd Chennai India June 23 E-mail: nishi@vsnl.com >Deb, > >My understanding of the purposes of a "weep hole" in a >pressure vessel or piping pad reinforcement are the >following: > >1) The hole serves as a vent during fabrication for >entrapped gasses, as stated above > >2) The hole serves as a vent when the welded component >comes to operating temperature, preventing buildup of any >pressure beneath the pad ( I suspect that this was the >original use) > >3) The hole serves as an early indicator of any cracking of >the weld beneath the pad after the component has been in >service ( I think that this is a bit of a "stretch" in >logic...) > >I do not believe that a weep hole serve can ever serve as >any type of corrosion indication > >See page #10 of this link...... > >http://www.tradesecrets.org/ilm/bb/012/3rd_period_012_comments.pdf > >My opinion only..... > >MJC