Sheet31)Introduction:Hot tapping is the technique of attaching a mechanical or welded branch fitting to piping or equipment in service and creating an opening in that piping or equipment by drilling or cutting a portion of the piping or equipment within the attached fitting.Hot tapping is potentially hazardous and therefore should be avoided up to maximum extent.2)Standards applicableAPI 2201:Pocedures for welding or Hot tapping on equipment in serviceAPI RP 1107:Pipeline MaintenanceWelding practicesB31.3:Chemical Plant and petroleum refinery pipingB31.4:Liquid transportation system for hydrocarbons,LPG etcB31.8:Gas transmission pipelines3)Materials:Hot tapping can be done on ferritic and austenitic steel.The base metal must be free of laminations and othet defects.A minimum base metal thickness of 4.8 mm is recommended for most applications of welding and hot tapping.4)Operating parametersHot Tapping machine (make M/S TDW) is able to do hot tapping in following condition :Maximum operating pressure : 100 kg/square cm at 37 degree CMaximum operating temperature(intermittent service): 370 degree C at 48 kg/square cmMaximum operating temperature(continuous service): 177 degree C at 70 kg/square cm5)Velocity of process fluida) Minium velocity :Welding on no -flow conditions(i.e. 0 m/s) or intermittent -flow e.g flare line shall not be attempted,unless it has been confirmed that no inflammable mixture will occur during welding.If this can not be met,purging shall be used with minimum purge velocity of 0.4 m/secb)Maximum velocity: Maximum liquid flow velocity allowed is 1.75 m/secThere is no restricition on maximum velocity for gas lines subject to attainment of acceptable interpass temperature during welding.6)Hot tap connection typesa)Reduced branch fittings:sockolets,weldolets etc shall be used for ratio of branch pipe diameter to run pipe diameter less than or equal to 0.5 for on plot piping.For off plot piping the branch pipe NPS shall be 2" maximum and ratio of branch pipe diameter to run pipe diameter is less than or equal to 0.5.Reduced branch fitting shall not be used where vibrations are expected.b)Reinforced set on branches:Reinforced pad or Full encircle sleeve type may be used for branch pipe sizes larger than those defined in (a).Note:Use only full encircle sleeve for ratio of branch pipe diameter to run pipe diameter greater than 0.5c)Pre-formed split tees:Used for full bore stopple operation7)Hot tap Branch location &weld test pressureOn horizontal surface branch location is preferred in vertical up position. The hydro test pressure should be at least equal to operating pressure of line or equipment to be tapped.But it should not exceed present internal pressure by more than approximately 10%.The temperature of metal should be considered to prevent brittle fracture.8)Dimensions /weight of machineType of machine available with CESHot tap sizeHeadroom clearance reqd. from face of isolation valve flangeHot tap machine approx.weight(KG)Type 11.5" to 2"3 meter100Type 23" to 8"4.5meter100010" to 14"5 meter1200Machine with outside agency16 to 24"7 meter1500For sizes greater than 16" detail information will be provided by CES in consultation with finalized outside agency .9)Cutter dimensionsNominal tap sizeDrill/cutter OD in mm1.5"33.342"47.633"73.034"98.436"138.98"185.810"241.312"292.114"323.9For sizes greater than 16" detail information will be provided by CES in consultation with finalized outsideagency .10)Hot tapping loads:During hot tapping the weight of isolation valve,drilling machine may tend to bend the run pipe , if unsupported and possibly buckle the pipe wall at base of branch.Some time branch is not in vertical plane causing cantilever loads.These all to be stress checked for suitability of hot tapping.11)Cautions:Welding or Hot tapping should not be performed in following conditionsa)Welding or hot tapping should not be performed on piping or equipment under vacuum.b)Piping or equipment containing Vapor /air or vapor/oxygen mixture near or within their flammable or explosive range.c)In hydrogen serviced)Line/equipment containing hazardous substances or substances like chlorine,acids,ethylene,propene,ethylene oxide,HP steam,Hydrogen etc.XXXXXXXXXXXXXXX

&C&"Arial Black,Bold"&12HOT TAPPING-TIPS&C&P