Welding Skills Chapter 4

How are oxygen and acetylene cylinders moved safely?

The best way to move a cylinder of compressed gas is to use a cylinder cart, with the cylinder secured to it and with the protector cap screwed onto the cylinder

Who is responsible for repairing a damaged regulator?

The manufacturer, welding supply company or a qualified, trained technician

What is a tip cleaner? When and why should it be used?

A tip cleaner is like a very small drill bit and made for use in cleaning the tips of welding and cutting torches. It is pushed into the hole of the tip and slid in and out to remove any carbon build-up of foreign materials from within the tip

Name three ways of distinguishing oxygen hoses from acetylene hoses. Name three ways of distinguishing oxygen fittings from acetylene fittings

Color (oxygen= green, acetylene = red); fitting threads (o= right-hand thread, A= left-hand thread) and fitting appearance (nut on O= plain, nut on A = groove around it)

What precautions should be observed in handling a pressure regulator?

Handle with care; don't drop or jolt, never use oil or grease on the adjusting screw, check frequently to ensure it does not "creep" and slowly go up to a higher output pressure, keep the inside of the valve seat and the regulator inlet-nipple seat clean and smooth

What are the advantages and disadvantages of using MAPP gas?

MAPP gas is quite similar to acetylene and unlike acetylene it is safer because it is not sensitive to shock. Also, because not sensitive to shock it can be stored and shipped in lighter cylinders. Although it produces lightly less heat for welding the amount produced is usually sufficient

What is a two-stage pressure regular?

With a two-stage regulator the reduction of the cylinder pressure to that required at the torch is accomplished in two stages. First it enters a chamber where a spring and diaphragm keep it at a preset pressure- about 200 psi for oxygen and 50 psi for acetylene. The gas then goes into a second chamber from which it is released to the torch at a pressure regulated by an adjusting screw.

Why is it dangerous to light a torch with a match or a lighter?

Using a match or a lighter requires your hand to be dangerously close to the torch tip; also, in order to use matches or a lighter you have to carry them in your clothing, which is not safe because a spark might ignite them and start your clothing on fire

Why is it dangerous to allow grease or oil to come in contact with the oxygen cylinder valve?

Although oxygen is non-flammable, it strongly supports combustion if exposed to flammable materials such as grease or oil

What type of protective clothing is commonly worn when oxyacetylene welding?

Non-flammable clothing including an apron, shop coat or coveralls; a long-sleeved shirt; a cap; work boots and light-weight gloves

How much should the cylinder valve be opened on an acetylene cylinder? on the oxygen cylinder?

One quarter turn on the acetylene cylinder; oxygen is opened all the way

What safety devices are used to prevent cylinders from exploding with subjected to intense pressure?

Oxygen cylinders have a special safety nut that permits the oxygen to drain slowly if the internal pressure exceeds a safe level; acetylene cylinders have a fusible plug that will melt if in a fire or be pushed out if subjected to too high an internal pressure

What is the purpose of the protector cap on a cylinder?

Protects the valve from being damaged.

What welding goggle shade numbers are commonly used for most oxyacetylene welding?

Shade numbers 4,5, and 6

Why are the oxygen and acetylene hose fittings made with different screw threads?

So they can not be misconnected

How is the size of a welding tip indicated?

The size of the tip is governed by the diameter of its opening, which is marked on the tip

What is the function of the needle valves on a welding torch?

They regulate the flow rate of the oxygen and fuel gases to the torch

Hydrogen is often used instead of acetylene for what operation?

Welding thin sections of metal, especially aluminum, and for underwater welding because it can be used at higher pressures than acetylene

What could happen if pliers are used when removing welding tips

Welding tips are designed to be installed and removed by hand- using pliers could result in the overtightening or bending or "squashing" of the tip