Download Hardbanding Procedures

Office 940-627-7473 Fax 940-626-4273
P.O. Box 900 Decatur, TX 76234
Hardbanding Procedures
Section 1 WELDING EQIPMENT REQIREMENTS
1.1 The welding equipment power supply must have a Direct Current (DC). Constant Voltage output
capable of 24-30 Volts and of 240 to 320 Amps with the wire Positive (DCEP). Reverse polarity (DCEP) is
to be utilized. Constant Current output power supplies are not suitable when applying “MIG” type
wires. Some DC power supplies have the capability to deliver either a Constant Voltage (CV) or Constant
Current (CC) output. If the power supply is if this type, the selector switch must be in the “CV” position.
1.2 The welding equipment should have a clean grounding system that will not resist the flow of electric
current. The resistance can be seen as heat build-up in the welding lead or in its connection after a
short weld time.
1.3 The equipment should have the ability to grip and rotate the tool joint under the welding torch
concentric to within .030” (0,76mm) and at a constant uniform speed of between 60 and 200 seconds
per revolution. The tool join O.D. is the factor that determines the speed at which to rotate the tool
joint.
1.4 The equipment must have the ability to move the welding torch from vertical center so that welding
takes place on the uphill side if the tool joint as it is being rotated. Further, the offset adjustment must
be positioned correctly so that the electrode wire, during welding, is NOT to far forward to top-deadcenter and allows the welding arc to burn “within the molten puddle”. Welding within the molten
puddle can cause porosity and lack of fusion with the parent metal.
1.5 The equipment must have the ability to oscillate the welding torch at a standoff or “stick –out”
distance of 1” to 1-1/8” (25, 4mm to 28, 6mm), from the welding surface and at the approximately 50 to
90 oscillations per minute. This distance is measured from the torch tip and not the nozzle cover. A
stick-out distance less than 1” (<25, 4mm) can sometimes cause turbulence of the gas flow, at the nozzle
cover, which can cause porosity in the weld bead.
1.6 The equipment must be able to move the torch, parallel to the joint axis, for a minimum distance of
12”.
1.7 Welding equipment should include a wire feed system capable of feeding the wire through the torch
at a variable, uniform speed without damaging the surface or the shape of the wire. Special wire-feed
rollers designed for feeding soft-skinned, flux-cored wire should be utilized. The wire feeder should also
have a wire straightener to remove, as best as possible, the normal “cast” of the wire.
1.8 A shielding gas of 98% Argon and 2 % Carbon Dioxide must be supplied to the arc when welding. The
regulated flow of gas must be controlled to deliver 30 to 35 CFH to the arc area. During windy
conditions, when operating portable hardband units in pipe yards or at rig locations, every precaution
shall be taken to protect gas flow at the nozzle, inside the torch cabinet from being blown away from
the arc when welding.
Section 2 MATERIAL PREPARATION
NOTE: Preparation of the hardband area must be performed to minimize, if not eliminate, foreign
matter become an impurity in the molten weld puddle and to ensure a good fusion bond with the
parent metal. Preparation must be performed when applying hardbanding onto either new or used
material.
2.1 Visually inspect the weld surface of all the tool joints or hardband areas to ensure they are clean and
free of all foreign matter such as rust, dirt, grease, oil, paint or pipe coating.
2.2. The threaded connections should be cleaned of all thread lubricants or storage compounds. This
will ensure a much cleaner welding process and eliminate the probability of the lubricant or
compounding igniting during pre-heat.
2.3 Preheat the hardband area to the appropriate temperature rang.
It is strongly recommended that preheat temperature be measured with digital, electric pyrometer. The
minimum acceptable requirement is the use of two tempstiks; one for each of the minimum and
maximum temperatures of the range. The unit operator must ensure that the desired preheat
temperature range is controlled.
NOTE: If tempstiks are used on the prepared hardband surface, the residue left by the tempstik must
not be excessive. If the residue is excessive, it must be removed prior to welding. If not, the residue can
become an impurity that may affect the fusion bond of the hardbanding to the prepared surface.
2.4 The preheat area needs to be buffed with a grinder equipped with a wire cup brush.
Section 3 HARDBAND APPLICATION
3.1 Placement and number of bands on new joints are to be specified by the customer.
Reapplications of hardbands are to be applied over the existing hardband area unless a change is
specified by the customer.
3.2 The unit operator should adjust the hardband equipment to attain a flat or slightly convex weld
profile. Each weld bead should overlap the previous weld bead ~1/8” and consistently “tie-in” with the
edge of the preceding weld bead.
3.3 The tungsten particles are to be dropped from the feed tube so as to penetrate the weld pool.
Section 4 COOLING
4.1 The applicator must “slow-cool” the hardbanded tool joint. To ensure the required slow cooling, the
tool joints need to be wrapped immediately in thermally insulated blankets or insulation. The blankets
or insulation shall remain on the tool joint ends unit the tool joint has cooled down to less the 150F.
Section 5 INSPECTIONS
5.1 Cracks that are oriented perpendicular to the weld bead and normally as close as ½” or as far as 3’
apart are considered acceptable.
5.2 Oblique cracks occur and are acceptable as they may intersect perpendicular or circumferential
cracks. Sometimes, they are a continuation of a perpendicular crack.
5.3 Any crack found that is wider the 1/16” shall be rejected as this may be an indication of rapid cooling
of the hardbanding after application.
NOTE: After cool down and inspection the hardband area shall be painted as a rust inhibitor for
transport and storage.
Section 6 Water Cooling
CAUTION: When capping pipe - with water inside - extreme pressure WILL build up during preheating and welding. Serious injury can result when removing the plugs due to steam pressure inside
the pipe. ONLY use a vented plug on the opposite end of the pipe that is being welded.
6.1 When customers specifications call for reducing the normal temperature the core pipe will reach
during pre-heating and welding, 2 to 3 gallons of water is pumped into the pipe and the ends are
capped to keep the water inside the pipe during the hardbanding process.
6.2 Metal plugs/caps must be used on the welded end of the pipe and securely tightened to prevent
water from dripping into the hardband unit. Use caution and wear protective gloves to remove them to
prevent burns.
6.2 When the water is drained after hardbanding it must be recovered to prevent any contamination
that may exist inside the pipe (including pipe thread lubrication) from contaminating the ground on the
jobsite.
6.3 Water that is drained can be reused however any used (contaminated) water that is remaining after
the job is finished must be disposed of in an environmental safe manner, or properly stored for the next
job.
Note: 35 ft of 4.5 inch drill pipe can hold 15 gallons of water. The volume of steam is 1,603 times the
volume of an equal mass of liquid water. One Gallon of water produces 223 cubic feet of steam.
Experience has proven that the best method – when using water – is to elevate the racks opposite the
hardband unit, about 4 inches. This will prevent water from running out the opposite end -- and an end
cap will not be needed on that end – thus eliminating any risk of high pressure build up inside the pipe.