2 ENGINEERING ACHIEVEMENTS


CODES AND STANDARDS


What is the first concern of any engineer? At one time, perhaps, the answer to this question was: to solve a problem or to improve an existing machine, or even to make more money. Nowadays, however, the answer is simple. The first concern is safety. This concern has led to the introduction of worldwide codes and standards for the manufacture and maintenance of machines.


Machinery of all kinds has certainly made the world a more dangerous place. Hundreds of people are at risk from the crash of a jumbo jet, or the explosion of a power station. At one time, of course, engineers did not know how to make a machine safe. But as they began to understand the science behind the behaviour of metals and other materials, engineers started to construct codes of manufacturing and standards to which machines must be built.


The steam engine was one of the first machines which aroused interest in safety standards. The danger of steam under pressure was recognized very early in the history of the machine. Denis Papin, a French mathematician, designed the first safety valve for boilers in 1679. But safety valves sometimes failed and explosions were quite common.


The steam engine works on a very simple scientific principle. When you heat water in a vessel, the molecules expand, until, at a certain temperature, the liquid turns into a gas. This gas needs a greater space than the same volume of liquid. If the vessel is sealed, the gas cannot occupy a greater volume, so the pressure increases.


At first, engineers tried to avoid the problem by only working with low-pressure steam. The first practical low-pressure engine was built by Thomas Newcomen, an English inventor, in 1712. It was used to pump water out of a coal mine. The invention helped to spark the Industrial Revolution, the time of fast progress in mechanization of agriculture and the textile industry.


James Watt improved the efficiency of the engine. His first patent, in 1769, included oil lubrication, and insulation of the cylinder to maintain the high


temperature needed for efficient operation. Further improvements were made in the 1830s by a man called Jacob Perkins. His boiler could produce 1,400 pounds per square inch (psi). The normal pressure of the air around us, atmospheric pressure, is 14.7 psi.


However, as the boilers used higher temperatures and developed higher pressures, the dangers rose. In 1854, an explosion in England killed ten people. On 30th July, 1870, the boiler of the Staten Island ferry in New York City exploded, killing 62 people. It was time for mechanical engineers to act.


The Staten Island ferry accident of 1870


In 1882, a new law on boiler safety was passed in the UK. As a result, the number of deaths from boiler accidents fell from 35 in 1883 to 14 in 1905. However, there was no similar legislation in the United States and 383 people died in the same period. Finally, in 1914, the American Society of Mechanical Engineers (ASME) produced the Boiler Safety Code.


The boiler code was only the start. Over the next 80 years, the ASME produced codes in all areas of mechanical engineering, including safety standards for cranes, industrial ladders, elevators, machinery shafts, liquid fuels and incinerators for hazardous medical waste.


Codes and standards in engineering are often unknown to the general public. However, they are fundamental to the safety of manufactured products and they have led to a safer world.


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