The concept of a control valve goes at least as far back as the bronze plug cocks used by the Romans in their aqueducts [Ref. 1]. The concept of a moving-stem (automatic) valve was introduced by James Watt in the late eighteenth century as a part of his fly-ball governor, which was developed to regulate the speed of his steam engine. Predecessors of the control valve developed concurrently with the age of steam throughout the nineteenth century. Late in the century, self-contained pressure and level regulators were applied to the ever-larger steam boilers in central power stations. The valve stem of a pressure regulator was moved by pressure from the process through a diaphragm; the stem of the level regulator was moved by a mechanical linkage to a ball float.

In 1880, William Fisher, an engineer at the city waterworks in Marshalltown, Iowa, worked continuously for over twenty-four hours to manually maintain constant discharge pressure on a steam-driven water pump. Constant manual regulation was required because of the extreme demand made on the system to supply water to fight a fire [Ref. 2]. From this experience, Mr. Fisher invented the constant-pressure pump governor and founded the Fisher Controls Company to manufacture his regulator. By 1907, these governors were installed in power plants in the United States, Canada, and England.

In 1882, William B. Mason founded the Mason Regulator Co. The factory building was built in the Dorchester section of Boston, Massachusetts, in 1888. Mr. Mason had served as chief engineer on a steam-powered ship and also in a small stationary plant. He patented a pump speed governor in 1883, a steam pressure-reducing valve in 1885, and a pump pressure regulator in 1886. The pressure-reducing valve made possible the steam heating of railroad cars and was used in that service for many years. In 1890, the regulator was introduced on U.S. Navy ships to secure the efficiencies of higher steam operating pressures [Ref. 3]. By the turn of the century, regulators were also being manufactured by Leslie, Kieley-Mueller, Atlas, and O.C. Keckley.

The turn of the century also saw the beginning of the oil and gas industry. In the beginning, the crude oil was pumped into a tank, where the natural gas was taken off and the components were separated by a batch distillation. Existing regulators easily handled this operation. However, demand increased rapidly, necessitating higher production rates. Concurrently, powerhouses became larger, requiring larger valve mechanisms. Larger valves called for more power in order to move a plug of greater area even though the pressure drop remained quite moderate.

The pilot-operated regulator was developed in response to the need for more power in the larger regulators. The pilot was essential a small direct-acting spring and diaphragm valve that acted on the larger main throttling valve. The process fluid was still used as the pilot-operating medium. The pilot permitted the narrowing of the control band and made possible the operation of larger valves.

In the early part of the twentieth century the individual oil well with its individual collection tank and batch still was replaced by collection tanks for a number of wells and continuous distillation. Pressures, temperatures, and capacities increased, with concomitant demand for larger valves, more powerful positioning mechanisms, and improved materials of construction. Up to this time, small regulators were of bronze and the larger regulators were of cast iron with integral seats and quick-opening disks for maximum flow at minimum lift. The quick-opening disks and oversizing led to periodic instability and the need for some sort of a slow-opening characteristic that would compensate for the oversizing. These developments were pioneered by the Hanlon-Waters Company of Tulsa, Oklahoma, who were later acquired by Black, Sivalls, and Bryson, also of Tulsa. This company made many innovative contributions to valve technology in the refineries in the 1920s and 1930s and then in later years became a commodity valve manufacturer.

Supplying adequate power to position the valve plug continued to be a challenge. Figure 2-1 shows a double-seated valve from a 1906 catalog of the Mason Regulator Co. The double-seated design was introduced to balance the dynamic forces on the plug and to stabilize the assembly by guiding the plug. The balanced seats accommodated valve sizes between 2 and 12 inches. Actuation was from a ball float in a self-contained level regulator.

The Fisher Governor catalog of 1915 comments on the bad experiences that resulted from the oversizing of control valves [Ref. 4]. The catalog contains a nomograph for accurately selecting the valve size for the service conditions. The user is advised that "it is possible to use a much smaller size Fisher valve and get better results." Nomographs, which were based on experimental results for each valve style, continued in use until 1930, when Ralph Rockwell and Dr. C. E. Mason of the Foxboro Company published valve sizing formulas. The formulas, shown in Figure 2-2, are from a 1940 publication [Ref. 5], where C_v is notably absent.

The process for cracking crude oil at very high temperatures and pressures was developed in the 1920s. During this period, Thomas Neilan founded the Neilan Company on the West Coast to serve the needs of the petroleum industry. The company developed a line of regulators as well as models of remarkably sophisticated pressure and temperature controllers. By this time, automatic control was booming, and the concept of using 15 psi air pressure for actuation came into being. The live zero lower end of the scale remained unsettled for some years.

The Neilan Company specialized in very rugged equipment and produced control valves for the refineries with cast steel bodies and heavy flanging. They also produced a very rugged valve actuator with multiple springs and ball bearing guides. By 1930, the valve had developed into the control valve as it is known today, as shown in Figure 2-3. Innovations on the valve included the machine-turned parabolic plug and seat ring guiding.