CON 03-03-06 PROCEDURE 01 September 2014 CONSTRUCTION

Welding Procedures Thermite Welding (Cadwelding) Replaces: CON 03-03-06 from 29 July 2008

Overview This standard provides the procedures for using thermite welding to attach wire to pipe.

Audience This standard is intended for installation and operations personnel, corrosion technicians and designers.

References DES 08-05 Protective Coatings for Buried Steel Piping Systems CON 13-02 Wrapping Wire-to-Pipe Connections Review of Thermite Welding on Pipelines, Dr. G.T. Beynon, March

15, 2002 Drawing 99000-E-030-101 Typical Thermite Weld Connection

Equipment 5 mm 57 mm copper sleeves bonding wire or test leads thermite weld mold (sized for the pipe being welded to) #15 (15 gram) cartridges and steel disc flint gun crimping pliers scraper lino knife wire brush file pipe recoating material

Safety Concerns Thermite weld process produces very high temperatures and molten

metal. Wear gloves, safety goggles, and a long sleeve shirt or coveralls when igniting the charge.

Do not inhale the fumes from thermite welding. Do not thermite weld in combustible atmospheres and ensure the

ground below the thermite weld is free of all hydrocarbons. It is important that thermite welding not be performed on a wet

surface as this can cause the water to vaporize and flash molten metal back out of the crucible.

Only employees having taken the available training course may thermite weld.

Other Joining Methods There are other methods of joining wire to pipe however thermite welding is the only company approved welding process for field connection of test lead wires, bond wires, galvanic anode leads, rectifier negative cables, and plastic distribution system tracer wires to live steel piping systems.

Mechanical connections are also acceptable, but only for non-current carrying lead wires.

Torch brazing, arc welding, or pin-brazing of field connections is not permitted.

Procedure 1. Prepare the pipe.

The weld area must be at least 150 mm from other thermite welds and circumferential or longitudinal pipe welds.

Remove wrapping or other coating from the pipe in accordance with DES 08-05 Protective Coatings for Buried Steel Piping Systems.

Clean the pipes surface thoroughly with a wire brush and a file attaining a bright, clean, dry surface free of mill scale and grease.

Refer to Drawing 99000-E-030-101 Typical Thermite Weld Connection.

2. Inspect the pipe.

Visually inspect the weld area to confirm the absence of surface defects.

Ultrasonically inspect IP pipelines with an outer diameter greater than 60.3 mm and all TP pipelines (of any diameter) to confirm adequate wall thickness (See Table 1) and the absence of laminations.

Select and prepare a new weld location if there are surface defects, inadequate wall thickness or laminations.

3. Determine the maximum line pressure for safe thermite welding.

Ensure that during thermite welding process the maximum line pressure will not exceed the value given in Table 1 for the wall thickness of the line.

Table 1: Maximum Safe Line Pressures During Thermite Welding

Nominal Pipe Wall Thickness Maximum Allowable Gas Pressure less than 2.8 mm (0.109") thermite welding not permitted

2.8 mm (0.109") 700 kPa (100 psi)

3.2 mm (0.125") 2890 kPa (419 psi)

3.6 mm (0.141") 3450 kPa (500 psi

4.0 mm (0.156") or thicker design pressure

NOTE: The maximum safe line pressures during thermite welding are lower than the pressure rating of the gas lines and the manufacturer ratings for thermite product because of FortisBC (Natural Gas) (FBC (Gas)) concerns regarding the quality of older piping in the ground.

If unable to reduce the pressure to less than the maximum allowable pressure in Table 1, test leads can be attached to the pipe with a stainless steel clamp. However an alternative means of attaching current carrying leads such as rectifier negative leads will have to be determined because below ground mechanical connections will not be permitted.

4. Prepare and position the wire on the pipe.

Remove 65 mm of insulation from the wire. Make sure the bare wire is bright, clean, and dry.

For #10, 12, or 14 AWG wire:

slide a copper sleeve over the bare wire and crimp it into place.

For #6 or #8 AWG wire:

a copper sleeve is not required

place the stripped end over the prepared pipe surface

Loop the wire around the pipe tieing it off with sufficient slack to ensure that the finished weld will not be strained and place the copper sleeve over the prepared pipe surface.

Where a conductor larger than #6 AWG is required, a multi-strand conductor must be used and the strands arranged into groups no larger than #6 AWG. Each group will be attached to the pipe with a separate charge.

Figure 1: Thermite Weld Connection (top view)

Figure 2: Picture showing the wire positioned on the pipe with crucible on top. Note the absence of voids between the crucible and the pipe.

5. Position the thermite weld mold.

Choose the correct crucible for the job. Crucibles come in different configurations depending on the

size of the wire and the size of the pipe being welded.

Ensure that the crucible is thoroughly clean and dry. Wet or damp crucibles produce porous welds.

Position the thermite weld mold over the copper sleeve or bared

wire on top of the prepared surface.

Make sure the copper sleeve or wire extends fully into the thermite weld mold cavity. There should be no wire insulation in contact with the

thermite weld mold.

Make sure the thermite weld mold sits flat, flush with the pipe so that there are no voids between the crucible and the pipe caused by the curvature of the pipe.

Insert the metal disc in the bottom of the crucible with the concave side up.

Figure 3

6. Prepare the charge.

Dump the entire contents of a #15 cartridge into the crucible. DANGER: Use only #15 (15 gram) cartridges and only one cartridge per connection.

Do not upset the metal disc. Make sure the ignition powder, stored in the lower part of the

cartridge, is placed in its entirety on top of the copper oxide and aluminum powder mixture, allowing a little ignition powder to sit on the outside edge of the crucible. Do not mix the ignition powder with the copper oxide and aluminum powder mixture otherwise it may be difficult to ignite the charge with a spark gun.

Close the cover of the crucible.

7. Ignite the charge. DANGER: The thermite weld process produces very high temperatures and molten metal. Wear gloves, safety goggles, and long sleeves for this operation.

Using the handle, hold the thermite weld mold firmly in position on the pipe.

Make sure all persons are away from or protected from the flash. Be prepared for the flash that will result so as to avoid sudden movements (i.e., flinching). Prior to ignition turn your face away to avoid any flash danger.

Ignite the charge with the spark igniter. Do not use matches.

If the charge fails to ignite, dump the entire thermite weld charge

and try again. Under no circumstances add another charge to the first one!

Hold the thermite weld mold in position for 30 seconds before lifting it from the pipe. Clean the mold.

Tap the slag away from the weld and file down any irregularities.

8. Ensure that the weld has achieved a good bond between the wire and the pipe. Examine the copper wire for any burn throughs. Test the strength of the bond by gently tugging on the wire lead

noting any give or failure in the wire. Tap the thermite weld button gently with a slag hammer.

Again noting any give or failure of the weld to the surface of the pipe.

If there are burn throughs in the wire, or if there is evidence of give or connection failure when the wire is gently tugged, or if there is evidence of the weld giving or failing when the weld button is tapped with the slag hammer, abandon the weld site and go back to Step 1 of this procedure, selecting another site at least 150 mm removed from the abandoned site.

9. Properly coat the thermite weld connection.

Refer to CON 13-02 Wrapping Wire-to-Pipe Connections.

10. Properly recoat the pipe. Refer to DES 08-05 Protective Coatings for Buried Steel Piping

Systems.

OverviewAudienceReferencesEquipmentSafety ConcernsOther Joining MethodsProcedure