1. ;See that there is ample acetylene and oxygen for the job in hand before commencing work. It is injurious to the weld to stop in the middle of a job.

2. ;The operator should be provided with proper welding goggles or spectacles fitted with correctly coloured glasses. Suitable gauntlets to protect the hands and clothes from sparks, etc., are also desirable.

3. ;See that the pieces of metal to be welded are clean and properly prepared. (See page 91.) Use the correct size and type of filling wire or rod. (See page 430.) Adjust the flame to conditions. Fig. 221.

4. ;Welding on steel should be done at the apex or outer extremity of the small white cone. On cast iron, copper, aluminium and bronzes the cone should be slightly removed from the metal.

5. ;For welding steel the flame must be perfectly neutral. For welding cast iron, aluminium and bronze the very slightest excess of acetylene may be used.

6. ;A fierce discharge of sparks from the molten metal whilst the blowpipe is in operation indicates an excess of oxygen both in quantity and pressure, and when this takes place care should be taken to stop any such oxidising effect by reducing the oxygen supply.

7. ;An excess of acetylene is also detrimental to the weld, tending to Carbonise the metal, and is indicated by a black deposit around the welded area. When this is seen the acetylene supply should be reduced.

8. ;When work is carried on for a long time at a stretch and the blowpipe end becomes hot, it will be found necessary to slightly open the acetylene supply tap from time to time.

9. ;It is essential that the correct flame conditions be maintained throughout all operations to ensure good results.

10. ;Backfiring may be caused by the blowpipe not being properly regulated or the nozzle may have become momentarily obstructed by a spark. When a backfire does occur the acetylene tap C and the oxygen valve B should be shut off at once and a few seconds allowed to elapse before re-opening them and re-lighting the blowpipe. At the same time the position of the blowpipe should be altered so that oxygen cannot play on the heated surface of the metal, the action of the oxygen being injurious and liable to cause oxidation.

If, through a backfire, water is discharged from the hydraulic valve, always refill the chamber until the water overflows at the level tap E, the inlet tap A being closed.

Constant backfiring, together with excessive heating of the shank or handle, indicates internal leakage of the blowpipe. This is very unlikely to occur, but if it does, return the blowpipe to the makers for repair.

11. ;If the hole in the nozzle of the blowpipe gets obstructed at any time through beads of iron being splashed over it, or from any other cause, it may be cleared with a soft copper wire or piece of wood and cleaned with a copper wire brush. Never use a steel reamer or other sharp or hard instrument.

12. ;When welding a small section to a large section direct the flame towards the larger section.

13. ;Do not weld cold castings, otherwise fractures due to unequal expansion are almost inevitable ; on the other hand it is not always necessary to heat the whole of a large casting if only a small piece is to be welded. It is best to heat a casting in such a way that the heat may be maintained during the welding. A good method is to build a brick or rough welded sheet iron casing to suit the size and shape of the article, fill the space so formed with charcoal, light the charcoal, and after heating the casting weld it when in position in the fire.

14. ;Avoid cooling a job rapidly when welding is finished. In the case of a casting which has been welded in a fire it is best to leave the job in the fire until cool ; or, if the casting was heated in a furnace, return the job to the furnace, reheat, and then allow to cool.

15. ;Protect machined surfaces, when pre-heating, by means of graphite and oil-this prevents scaling.

16. ;Do not spread the flux on the metal ; heat the filling rod and dip it in the flux.

17. ;Aluminium flux is hygroscopic, that is, it absorbs moisture rapidly ; it is advisable, therefore, to remove from the tin only the quantity of flux required for the immediate needs, replacing the lid at once.

Welding In Boilers Or Confined Spaces

Boiler welding is highly responsible work, and should only be undertaken by thoroughlytrained workmen who have practised horizontal, vertical and overhead welding in confined and difficult positions.

18. ;Where welds are being carried out in a boiler or confined space where it is difficult to instantly change the position, never use blowpipes which are not fitted with a valve or valves controlling both the acetylene and oxygen supplies.

19. ;Before welding is commenced all manhole covers and mud doors should be removed, in order to ensure adequate ventilation and free egress for the products of combustion.

20- Two competent welders should be employed on all such jobs, and they should relieve each other at intervals of about half an hour. This is particularly desirable on overhead work or in positions where the workman is exposed to great heat.

21. ;Only workmen physically sound should be allowed to undertake such work. They should have a mate in attendance upon them within the boiler and another in charge of the cylinders of oxygen and acetylene generators, or cylinders, outside, ready to turn off the supply of gases at a moment's notice.

22. ;A bucket of water should always be available in a convenient position by the side of the welder for cooling the blowpipe or for any emergency use.