Cornerstones of Compression: The evolution of air compressors

From its human origins to the late 18th century, air compression was used mostly for the smelting of metals. But another early need for blowing machines was the ventilation of underground mines, which were important sources of the metal ores and coal required for smelting.

Underground mining has a very long history, dating back thousands of years. One of the earliest examples of underground mining was in ancient China, where coal was dug from shaft mines to be used for metalworking. European miners were known to have dug tunnels in search of flint since 4000 BC and throughout the Neolithic period.

As early as the first century, unskilled peasants and laborers would mine by torchlight in conditions that today would be considered hazardous and barbaric. They lit brushwood fires inside the mines, which promoted airflow from the surface down into the mine shafts. This technique was rediscovered by medieval Greeks and Romans in Britain and elsewhere in pursuit of metals such as copper, nickel, tin and iron. It was heavily used in Britain during the industrial revolution alongside increasingly sophisticated ventilation shafts.

The air in deep coal mines was stagnant, resulting in horribly polluted, and sometimes toxic, air. In the late 19th century, canaries in cages were used to detect the build-up of hazardous gases such as methane and carbon dioxide in mines. When the birds stopped singing and began to show signs of drooping or shortness of breath, it was a sign for miners to evacuate.

Early methods of ventilation relied upon natural ventilation through adits and shafts, which were the sole source of entrance and access to and removal of ore. Short lateral tunnels known as crosscuts connected major working tunnels and were also used for ventilation purposes. Heating the mine air with fire would cause it to rise in the channels, while simultaneously drawing fresh air through other channels farther away. The ventilation capacity was limited and it required enormous amounts of fuel.

Forced mine ventilation

There are records of devices referred to as bellows, oscillating fans, linen cloths and shaft-head wind sails being utilized in various manners to improve mine ventilation by the 16th century. With the advent of steam engines in the 18th century, bellows and crude blowing tubs began to be used for mine ventilation. By the 19th century, larger reciprocating walking beam type steam engine compressors were used.

By the 1870s, large versions of Roots Blower Company blowers were applied for mine ventilation, including several in mines of the Comstock Lode by 1870. Two of the largest blowers ever made were installed in a mine in England in 1877, moving 200,000 ft3/min (5663 m3/min) of air. Each impeller was 13 ft. (4 m) wide with a diameter of 25 ft. (7.6 m).

Toward the end of the 19th century, primitive fans, such as the one shown in Fig. 1, began to appear for mine ventilation. Early 20th century ventilation techniques included the use of blowers or low-pressure centrifugal or propeller fans situated at the tunnel portal connected to a system of pipes.

Technological advancement unleashes the potential of pressurized air

The first instance of an air compressor used for something other than smelting and blast furnaces occurred in 1762, when a “blowing cylinder” powered by a water wheel produced a whopping 14 psi (1 bar). The earliest industrial air compressors were steam powered. These devices were used in some of the first major underwater missions, in which air was pumped to the diver.

By the dawn of the 19th century, engineers were employing air compressors for the purpose of energy transmission. The 1820s saw the construction of a Welsh plant that utilized compressed air. It became apparent that compressed air was better than steam as a power source for heavy-duty machinery.

The real potential of pressurized air as an energy or motive power source emerged in the second half of the 19th century. For example, one of the most spectacular uses of Roots blowers was in the underground subway constructed in New York City in 1867. The big blower had an iron shell 21.5 ft. (6.6 m) high with impellers that were 16 ft. (4.9 m) long, requiring five railroad cars for shipment. At 60 rpm, it produced 100,000 ft3/min (2832 m3/min) of air that literally blew a 22-seat passenger car on tracks in one direction through the subway tunnel, and then sucked it back again.

The first major construction project powered by compressed air technology was the Fréjus Rail Tunnel. In 1857, workers began drilling this eight-mile tunnel joining Italy and France through Mt. Cenis in the European Alps...by hand. Progress was slow, averaging about 9 in. (229 mm) a day, and expected to take about 30 years for completion. Four years after the project began, compressed air was introduced to the drilling process. Construction and mining teams from both countries used pneumatic drills, along with wet compressors used to cool the air inside the tunnels as the miners made their way deeper into the rock. With the use of compressed air powered tools, the tunnel was completed in 1870, a total of 14 years.

As steam-powered rock drills gave way to more efficient air-powered drills, reciprocating air compressors quickly evolved. In the U.S., the Rand & Waring Drill and Compressor Company introduced the first Rand air compressor for powering rock drills in 1872. John Waring had invented a way to circulate water around the side and ends of air compressor cylinders. This was an important advance over simply spraying water into the cylinder for cooling.

At about the same time, Simon Ingersoll started the Ingersoll Rock Drill Company to manufacture his patented steam-powered rock drill. Henry Sargeant, a local skilled craftsman, improved Ingersoll’s design and convinced his boss to purchase Ingersoll’s company and patents. Sargeant became the first president of the Ingersoll Rock Drill Company, and he continued the research and development of reciprocating air compressors and rock drills, credited with 61 patents during his lifetime.

Almost all of the air compressors in this period were driven by steam engines. Although there were vertical, horizontal and angle machines, horizontal engine-compressors were the most common arrangement, such as the Ingersoll-Sargeant straight-line engine-compressor shown in Fig. 2. This Ingersoll-Sargeant series was introduced in 1878 and spanned more than two decades into the early 1900s.

The next issue will continue the rapid evolution of horizontal air compressors that supported the industrial revolution.