Cad Welding12

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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 moltenmetal. 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 theground below the thermite weld is free of all hydrocarbons.

• It is important that thermite welding not be performed on a wetsurface 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 fieldconnection 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 pipe’s 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 WeldConnection.

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 confirmadequate 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 linepressure 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 arelower 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 thepipe 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 slackto 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 crucibleon 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 andaluminum 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 temperaturesand molten metal. Wear gloves, safety goggles, and long sleeves for this

operation.

• Using the handle, hold the thermite weld mold firmly in positionon 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 suddenmovements (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 chargeand 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 ofgive 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 andgo 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.

Documents

Cad Welding12