Temporary Repair of Water Tubes by Welding

TASK 20-23-38-300-802-A
Temporary Repair of Water Tubes by Welding

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

1. Reason for the Job
This procedure gives the method for the temporary repair of water tubes.
This method uses a manual TIG welding process.

NOTE: This procedure is applicable to:

Corrosion-resistant steel (21-6-9) tubes, ref. DAN41-2 and ABS5434, sizes -06 to -16.

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	BRUSH - WIRE, STAINLESS STEEL
No specific	AR	CLOTH-EMERY (GRADE 400)
No specific	AR	CUTTER - MILLING, 2 CUT
No specific	AR	PAPER - ABRASIVE (GRADE 200)

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.08BAA9)	Non Aqueous Cleaner-General - -

C. Referenced Information

REFERENCE	DESIGNATION
TASK 20-23-38-400-003-A	Installation of the Tube Assembly of the Potable Water and the associated Air Supply System
Preparation of the Damage Area

3. Job Set-up
Subtask 20-23-38-860-060-A

A. Procedure Requirements
(1) You must not do this repair on the aircraft. You must remove the pipe from the aircraft.
(2) Life limit of the weld repair
(a) A temporary repair with this manual TIG welding method has a maximum limit of 20 Flight Cycles or one month (that which occurs first).

NOTE: It is necessary to replace the repaired tube with a new one before a maximum of 20 Flight Cycles or one month (that which occurs first).

(3) Certification of the operators
(a) The operators must have an approved licence/certificate (refer to the local Airworthiness Authorities) for:

The manual TIG welding process
The dye penetrant test.

(4) Repair criteria
(a) You can do this repair procedure only if:

The damage is a through crack with a maximum length of 10 mm (0.3937 in.).
The distance between two cracks is not less than 15 mm (0.5906 in.).
The weld does not change the geometry of the pipe.
There is not already a repair in the repair area.
Two longitudinal cracks are not on the same generatrix (line).
The tube does not have more than 5% ovalization for stainless steel pipes.

(b) Only one weld is permitted on the circumference.
(5) Adjustment of the welding parameters
(a) Before the repair, do a welding test on a tube specimen of the same material and with the same diameter/thickness, to get the applicable welding parameters (electrode diameter, amperage, power, etc).

NOTE: It is mandatory to do the steps given in this procedure during the welding test.

(b) Identify the test specimens and keep them until the replacement of the repaired pipe.
(6) Weldable materials
(a) This repair method is applicable only for the tube materials that follow:

Corrosion-resistant Steel (21-6-9) Tubes

Size Tube	Tube DIA. in.	Tube DIA. mm	Thickness in.	Thickness mm	Operating Pressure psi	Operating Pressure bar
-06	3/8	9.53	0.016	0.406	290	20
-08	1/2	12.70	0.016	0.406	290	20
-10	5/8	15.88	0.016	0.406	290	20
-12	3/4	19.05	0.016	0.406	290	20
-16	1	25.40	0.02	0.508	290	20

4. Procedure
Subtask 20-23-38-917-050-A

A. Welding Procedure

Preparation of the Damage Area

NOTE: You must remove the pipe from the aircraft to do this procedure.

(1) Clean the pipe
(a) If the tube is painted (for stainless steel tubes):
1 Remove the paint with CLOTH-EMERY (GRADE 400) from the full circumference of the tube along a sufficient length around the damage area.
(b) Clean the outside of the tube with Non Aqueous Cleaner-General - - (Material No.08BAA9) .
(c) Flush the inside of the tube with Non Aqueous Cleaner-General - - (Material No.08BAA9) . Do the operation three or four times to remove all grease from the tube.
(d) Flush the tube with water.
(e) Let the tube dry at ambient air.
(2) Identify the location of the damage
(a) Blow dry compressed air, at a pressure of approximately 10 bar (145.0377 psi), through the tube.
(b) Soak the outer surface of the tube in water or apply a leak detection product to see the leak.
(c) Grind the surface of the tube along the full length of the crack to identify the damage area.
(d) Accurately identify each end of the crack. The identification mark must not be more than 2 mm (0.0787 in.) on each side of the length of the crack.
(3) Prepare the damage area for the repair.
(a) With a CUTTER - MILLING, 2 CUT, make a groove along the length of the defect plus 5 mm (0.1969 in.) on each side of the crack.

NOTE: For this task, a 2-cut milling cutter with the characteristics that follow will be necessary:

40 teeth
Cut angle: 110 deg (110.0000 deg)
DIA.: 15 mm (0.5906 in.)
Width: 1.8 mm (0.0709 in.) or 2 mm (0.0787 in.) or 2.2 mm (0.0866 in.).

1 The shape of the tool gives the width of the groove.
2 The cutter must almost go through the tube wall (95% of the thickness).

NOTE: If the cutter goes through the wall, the opening (at the inner surface) must not be more than 0.2 mm (0.0079 in.) on a length of a small number of millimeters.

(4) Clean the prepared area
(a) For stainless steel tubes:
1 Clean the area with a BRUSH - WIRE, STAINLESS STEEL.

NOTE: A clean, stainless-steel wire brush is necessary.

2 Make sure that you do not cause damage to the pipe around the prepared area.
3 Remove dust with Non Aqueous Cleaner-General - - (Material No.08BAA9) .
4 Do not use a compressed air gun to remove dust.
(5) Weld the tube (TIG welding process).
(a) Do the gaseous protection.

NOTE: The welding torch gives protection to the outer side of the tube.

1 Blow a neutral gas inner side of the tube with a flow rate of 4 to 10 l/min. for a sufficiently long time (about 10 min. for a long pipe). Decrease the flow rate to 4 l/min. during the welding operation.
(b) Weld the tube
1 Make sure that the welding equipment parameters are the same as those used on the test specimen.
2 For stainless steel 21-6-9 tubes:

Use Z2 CND 20-10-3 filler metal.

Continue the argon flow for a minimum of one minute after welding.

2 Inside the tube:

Continue to blow the inert gas through the tube for one minute after welding.

(6) Inspection of the repaired area
(a) Do a visual inspection of the weld bead.
1 Make sure that the width of the weld bead is:

3 mm (0.1181 in.) for a tube thickness of less than 0.48 mm (0.0189 in.).

2 Make sure that the maximum height of the weld bead is not more than 0.1 mm (0.0039 in.).
If the maximum weld bead height is more than 0.1 mm (0.0039 in.):

Grind and finish with the PAPER - ABRASIVE (GRADE 200) or finer. Make sure that the remaining thickness is more than the thickness measured on the base metal.

3 Make sure that the crater at the start and the end of the weld bead has no subsiding, cracking and staining.

NOTE: Light staining is permitted. On a small diameter tube, staining on the opposite side of the weld must be in the limits of the zone with thermal effects.

(b) Pressure test
1 Do a pressure test for 3 minutes minimum at ambient temperature with water at:

13 bar (188.5490 psi) for tubes in stainless-steel 21-6-9 - water pipes.

NOTE: No leak is permitted.

(c) Dye penetrant test
1 Do a dye penetrant test in the welded area.
2 Make sure that there is no sign of a defect.
3 If you are not sure of the quality of the weld, rub with the PAPER - ABRASIVE (GRADE 200) or finer and do the dye penetrant test again.
4 If the dye penetrant test shows that there is a defect:

Discard the repaired pipe and install a new one on the aircraft (Ref. AMM TASK 20-23-38-400-003).
Or remove the repaired part of the pipe. Cut the pipe at a minimum of 1.5 in. (38.0999 mm) from each end of the weld bead and do an approved repair given in this topic.

5 If the dye penetrant test shows that there is no defect:

Install the water tube (Ref. AMM TASK 20-23-38-400-003).

[Rev.10 from 2021] 2026.03.31 22:59:48 UTC