ACETYLENE, PURE OXYGEN AND THE NECESSITY OF TRAINING
By Steve Ababan, G.M.
Atlas Safety
How dangerous is acetylene when mixed with pure oxygen? Obviously, the awnser to the question is relative to various conditions. However, the Compressed Gas Association says: "few other products with such inherently dangerous properties are as available to the general public as acetylene is. most people who use acetylene, either regulatly or only periodically, have recieved only rudimentary training which does not provide them with sufficient information to protect themselves and others from serious injury." Because of this, pure acetylene is considered most dangerous.
Under high pressure (pressures above 15 psig.) pure acetylene can decompose violently with the evolution of heat. Shock, high temperature or reactive substances can initiate decomposition, and oxygen is not required to either initiate or sustain this process. The higher the pressure the smaller the initial energy input required to cause decomposition. Itis vitally important for everyone who uses acetylene to remember that acetylene is unstable at pressures above 15 psig., and without a properly functioning acetylene regulator to accuratley control outlet pressure, there is a real danger of a serious accident occuring.
Because of particular flame and heating characteristics, acetylene is the most commonly used fuel gas in our industry. However, like any other fuel gas when combined with pure oxygen, acetylene becomes violenty explosive.
A ballon only two inches in diameter containing equal parts of acetylene and pure oxygen has the explosive force of one quarter of a stick of dynamite. This is enough force to cause serious injury. Inflating the two-inch ballon, with the same mixture, to a nine-inch diameter increases the explosive force 80 times equaling twenty sticks of dynamite. Now, consider the fact that it's not uncommon to see 100 foot sections of oxy-fuel gas hose being used anywhere in our industry. The point here is, a common inside diameter of oxy-fuel gas hose is 1/4 inch and, if you calculate the volume of 100 feet of hose with an inside diameter of 1/4 inch, you'll find the volume is equal to the 9-inch diameter baloon. this means, should oxygen be allowed to enter the fuel gas hose or shoule fuel gas be allowed to enter the oxygen hose, a mixed gas explosion with the force of 20 sticks of dynamite could occur, resulting in serious if not fatal injury to anyone close by.
Mixed gas explosions are potentialy the most devistating of all oxy-fuel gas related accidents. It is essential to the prevention of mixed gas explosionthat all operators be trained to recognize and properly react to the conditionsassociated with their occurence. However, other accidents that can lead to serious injury are: flashbacks; regulator explosions and violating the 1/7th rule when using acetylene which are just as important to prevent.
All oxy-fuel gas equipment operators and supervisors are responsible for their own safety as well as the safety of everyone around them. Gaining a clear understanding of the cause of serious injury accidents is an essential step in altering the behavior neccessary in decreasing the probability of their occurrence.
