pipe suuports fabrication

[pdprao]

WE NEED TO FABRICATE BOX TYPE STEEL SUPPORTS FOR STEEM LINES, FEED WATER LINES WITH THE HELP OF CARBON STEEL CHANNELS TO FORM AS CLOSED BOX SECTIONS BY WELDING THE EDGES. IS IT NESSARY TO GASCUT /GRIND THE CHANNEL EDGES TO FACLITATE FULL PENETRATION WELDING BETWEEN TWO CHANNELS. WHAT IS THE PRATICE IN INDUSRY. DESIGN DRAWINGS ARE SILENT ABOUT IT. INDIAN STANDARDS SUGGEST GRINDIG, AND WELDING WITH BACKING STRIP TO OBTAIN FULL PENETRATION FOR SIMILAR APPLICATIONS.

 

[DSB123]

pdpro,
I would suggest you reconsider the use of closed box sections for pipe supports. We have these on our plant which has been operating for in excess of 20 years and we have corrosion problems with the closed sections which were used in those days. Our policy now is not to use closed sections since you cannot see the internal corrosion which will inevitably occur.

 

[mb44]

Good advice from DSB123 , dont use box section as you cannot see whats in side, it will corrode......experience tells you this dispite what anyone may try and tell you otherwise. If you have to cut it ouit and replace it every few years due to corrosion its not any cheaper

Regards

MB44

 

[quark]

DSB123's advice is good. I saw some installations where these channel boxes are filled with puf and the vertical columns with concrete.

All the installations I saw, used stitch welds and not full welds. Actually I am unaware of such an Indian standard. Which standard you are referring to?

Regards,

 

[pdprao]

WITH REGARD TO OBSERVATIONS OF DSB123, CORROSION PROBLEMS OF BOX SECTIONS, IT IS TO BE NOTED THAT THE BOX NEED TO BE CLOSED WITH WELDED PLATE AT OPEN END(FREE END) AND TOP END IS WELDED TO EMBEDDED PLATE INSTALLED IN BUILDING STRUCTURE. THIS WILL FORM AIR TIGHT ENCLOSURE AND AS SUCH NO SUCH CORROSIN PROBLEMSARE EXPECTED ON INSIDE SURFCE DUE TO LACK OF OXYGEN. EXERNAL SURFACE ALWAYS CAN BE TAKEN CARE BY MAINTENANCE PROCEDURES AND PAINTING. THEREFORE FULL LEGTH WELDING IS NECSSSARY FOR CORRISION RESISTENCE POINT.

-MOST IMPORANT COSIDARATION IN USE OF BOX SECTIONS IS THEIR FAR GREATER TORSIONAL RESISTANCE COMPARED TO OPEN SECTIONS.
IT IS FOR THIS REASON BOX SECTIONS ARE USED WHERE SEISMIC CONSIDARATION IS A FACTORTO IMPROVE THE TORSIONAL RIGIDTY.TO IMPROVE M.I. THE CLOSED BOXES ARE FILLED WITH CONCRETE. THIS MAY GIVE CORRISION PROTECTION TOO. BUT IT MAY NOT BE POSSIBLE PRACTICALLY FILL IN ALL MEMERS TO WITH COCRETE. USE PUFF IS NOT A BAD IDEA .INSTED WE CAN PAINT INSIDE AS WELL BY SUTABLE METHOD. ALL THESE ARE NOT ESSENTIAL ONCE THE BOX IS WEDED AND LEAK TIGHT. REGARDIG RELAVANT INDIAN STANDATRD I WILL COME BACK.

 

[pdprao]

Quark ,
This is with reference to your comments regarding Indian standard ref. in my thread. The relevant I.S. is I.S.Sructural engineering hand book S.P(6)2, and S.P(6)3 which gives typ. welding details of box sections made from I.S channels