When did welding replace rivets?
1945. Welding replaced riveting as the main method of assembly for ships with 5,171 vessels constructed through 1945.
Are ships welded or riveted?
The large groups of ships, how- ever, were made up almost entirely of Liberty Ships, T2 tankers, Victory ships and other new ships which were practically all welded. The only mass production program of riveted ships occurred during World War I.
What do we call the localized growing together of the grain structure during a weld?
An arc welding process that uses an arc between a tungsten electrode and the weld pool. An arc welding process with an arc between a covered electrode and the weld pool. weld. localized fusion or growing together of the grain structure of materials being welded.
Which gases are most commonly used for the OFW process?
Oxygen and acetylene are the principal gases used in OFW. Oxygen supports combustion of the fuel gases. Acetylene supplies both the heat intensity and the atmosphere needed to weld steel.
What are the two basic torch mixer types?
Cutting torches for use in cutting machines usually are fitted with two oxygen inlet connections, with oxygen supplied through separate regulators. As in the case of welding torches, cutting torches are offered with two types of mixers: the injector type, and the medium-pressure type.
What is the ratio of oxygen to acetylene?
1,2 to 1
What should oxygen and acetylene be set at?
In case the recommended working pressure settings are not indicated, safe numbers are 40 psi for oxygen and 10 psi for acetylene, regardless of cutting tip size. Simply adjust them until you get a neutral flame, but pay close attention to the acetylene pressure to prevent it from exceeding the limit.
Does acetylene burn without oxygen?
Decomposition is a chemical reaction whereby acetylene breaks down into its constituent elements, carbon and hydrogen. This reaction gives out a great deal of heat, which can cause the gas to effectively ignite without the presence of air or oxygen.
Can we store oxygen and acetylene together?
For safety purposes, oxygen and acetylene cylinders have to be stored a minimum of 10 feet from each other. That means they must be returned to storage at the end of a workday, even if they will be used together the next day. In the storage facility, both types of cylinders must be kept separate.
At what temperature will acetylene not ignite?
The adiabatic flame temperature (AFT) in air at atmospheric pressure is 2534 deg C. The auto ignition temperature of acetylene gas is 305 deg C. Its lower and upper explosive limits in air under STP conditions (0 deg C and 1.02 kg/sq cm) are 2.4 volume % to 83 volume %. The upper limit can reach 100 %.
Do you use more oxygen or acetylene?
For maximum flame temperature in oxygen, the ratio volume of oxygen to fuel gas are 1.2 to 1 for acetylene and 4.3 to 1 for propane. So, there is far more oxygen being consumed when using propane than acetylene.
Why must an oxygen cylinder valve be fully opened?
Oxygen cylinders must have the valve opened up all the way because of the high pressure in the cylinder. This prevents the high-pressure gas from leaking out through the threaded stem.
Is propylene hotter than acetylene?
The heat release in the primary flame cone is slightly less than that of acetylene. The BTU capacity of the outer flame is superior to that of acetylene. Propylene combines the qualities of an acetylene flame with the secondary heating capacity of propane. This fuel gas burns hotter than propane.
What is the difference between an oxygen and acetylene regulator?
The acetylene regulator design is generally the same as that of the oxygen regulator, but will not withstand such high pressures. The high pressure gauge, on the inlet side of the regulator, is graduated from 0 to 500 psi (3447.5 kPa).
What happens to acetylene above 15 psi?
Acetylene will not explode under low pressure at normal temperatures. However, it becomes unstable and spontaneously combustible when compressed to a pressure over 15 psi. Beyond 29.4 psi, it becomes self explosive, and a slight shock may cause it to explode even in the absence of air or oxygen.
Why should you never expose pure oxygen to petroleum products?
Oxygen under pressure and hydrocarbons (oil and grease) can react violently, resulting in explosions, fire, and injury to personnel and damage to property. Never allow oil or grease to come into contact with oxygen under pressure.
What causes acetylene to explode?
Acetylene is highly unstable. High pressure or temperatures can result in decomposition that can result in fire or explosion.
Is it safe to lay an acetylene bottle on its side?
Since acetylene is shock-sensitive and explodes above 30 psi, cylinders of acetylene contain acetylene dissolved in acetone. Acetylene cylinders must not be placed on their sides, since the acetone and binders will have dislodged.
Can you smell acetylene?
Acetylene is a colorless and odorless gas. Commercial grade Acetylene may have an Ether-like or garlic-like odor.
Can you transport acetylene in a car?
Use a well-ventilated vehicle to transport acetylene. Many acetylene cylinders are collected and transported in unventilated vehicles. If acetylene cylinders have been transported or stored horizontally, allow them to stand vertically for at least 30 minutes before use.
What is the best way to move oxygen and acetylene cylinders?
Cylinders shall be moved by tilting and rolling them on their bottom edges. They shall not be intentionally dropped, struck, or permitted to strike each other violently. When cylinders are transported by powered vehicles, they shall be secured in a vertical position.
Can oxygen tanks be laid down?
Liquid oxygen tanks should never be laid on their sides. Portable cylinders can be laid on their sides, but valves must be protected from collision. Tanks should never be placed in a tightly closed space like a trunk.
Why acetylene cylinders are kept upright?
Acetylene cylinders are not hollow. They are packed with porous rock that is saturated with acetone. Cylinders should be used or stored only in an upright position to avoid the possibility of the acetone leaking from the cylinder. This is to prevent liquid acetone from running through your regulator.
How dangerous is acetylene?
There are a number of incidents each year where a flashback into an acetylene cylinder triggers decomposition, leaving the cylinder in a dangerous, unstable condition, which can lead to an explosion. A flashback occurs if there is a flammable mixture of fuel gas and oxygen in the hoses when the torch is lit.
Can we keep gas cylinder horizontal?
Compressed gas cylinders shall be secured in an upright position at all times except, if necessary, for short periods of time while cylinders are actually being hoisted or carried. Accordingly, laying empty compressed gas cylinders horizontally on the ground is a violation of Section 1926.350(a)(9).
How much acetylene is in a cylinder?
The most common acetylene cylinder (#4) usually contains around 130 cubic feet of acetylene. So, if we divide to achieve the 1/10 rule: 130 / 10 = 13. As you can see, that isn’t even close to enough acetylene in most situations to safely run a heating tip.
What are the three types of flames?
There are three types of flames natural flame, carburizing flame and oxidizing flame.
How long does a 10 CF acetylene tank last?
10 cf tank / 7 = 1.42 cubic feet safe withdrawl per hour. 3 CFH / 60 minutes in an hour = 0.05 cubic feet per minute.
How much PSI is in a full acetylene cylinder?
A full acetylene cylinder which has a pressure of 250 psi at 700F (1725 kPa at 20 C) will have a pressure of 315 psi at 900F (2175 kPa at 310C) and a pressure of 190 psi at 500 F (1300 kPa at 90C). You must always take temperature into account when estimating how much acetylene the cylinder contains.