Pressure regulating valves are used in myriad industrial and residential applications for controlling the downstream pressure of a fluid. By controlling downstream pressure, pressure regulating valves compensate for variations in downstream demand. For example, as downstream demand increases, pressure regulating valves open to allow more fluid to flow through the pressure regulating valve, thus maintaining a relatively constant downstream pressure. On the other hand, as downstream demand decreases, pressure regulating valves close to reduce the amount of fluid flowing through the pressure regulating valve, again maintaining a relatively constant downstream pressure.
Pressure regulating valves can be categorized as either balanced or unbalanced, and different valves are used in different global marketplaces due to variations in emission standards and methods of monitoring the amount of gas supplied.
For example, a conventional balanced pressure regulator valve that is commonly used in Europe is illustrated in FIG. 1. The conventional gas regulator 10 comprises an actuator 12 and a balanced pressure regulator valve 14. The regulator valve 14 defines an inlet 16, an outlet 18, and a valve port 22 disposed between the inlet 16 and the outlet 18. Gas must pass through the valve port 22 to travel between the inlet 16 and the outlet 18 of the regulator valve 14. The actuator 12 is coupled to the regulator valve 14 to ensure that the pressure at the outlet 18 of the regulator valve 14, i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator 12 includes a control assembly 22 for regulating the outlet pressure of the regulator valve 14 based on sensed outlet pressure. Specifically, the control assembly 22 includes a diaphragm 24, a connecting post 32, and a control arm 26 having a valve plug 28. The diaphragm 24 divides a housing 23 of the actuator 12 into an atmospheric cavity 25 and a control pressure cavity 27. The control pressure cavity 27 is in fluid communication with the outlet 18 of the regulator valve 14 such that a bottom side of the diaphragm 24 senses the outlet pressure and responds to move the valve plug 28 between open and closed positions. The control assembly 22 further includes a control spring 30 disposed in the atmospheric cavity 25 and in engagement with a top-side of the diaphragm 24 to offset the outlet pressure sensed by the diaphragm 24 in the control pressure cavity 27. Accordingly, the desired outlet pressure, which may also be referred to as the control pressure, is set by the selection of the control spring 30.
One problem with the conventional regulator 10 having the outlet pressure controlled and set by the control spring 30, however, is that as the valve plug 28 opens or moves away from the valve port 22 to open the valve 14, the control spring 30 expands or elongates and loses force. As the force is reduced, outlet pressure decreases, resulting in a rated capacity reduction. In other words, the control spring 30 inherently generates less force as it expands towards an uncompressed length when displacing the control arm 26 to open the valve 14. Additionally, as the control spring 30 expands, the diaphragm 24 deforms, increasing the area of the diaphragm 24. The decreased force supplied by the control spring 30 and the increased area of the diaphragm 24 combine such that the force provided by the control spring 30 cannot adequately balance the force generated by the diaphragm 24. As a result, the diaphragm 24 rises and the outlet control pressure falls below the desired control pressure. This phenomenon is known as “droop.” When “droop” occurs, the outlet pressure decreases below its set control pressure, and the amount of fluid transferred while maintaining the outlet pressure range, also known as the rated flow value, also decreases.
In the United States, attempts to address the effects of “droop” include using a pilot regulator valve to control and adjust the delivery of loading pressure above the diaphragm. Such pilot regulators are typically limited to use with unbalanced regulator valves however, and in general, supply and control the amount of loading pressure applied to the actuator diaphragm during operation of the regulator. For example, FIG. 2 depicts a conventional regulator 110 for the United States' market having an unbalanced regulator valve 114, an actuator 112 and a pilot regulator 160 operatively connected to both the regulator valve 114 and the actuator 112. More specifically, the valve 112 defines an inlet 116, an outlet 118, and a valve port 122 disposed between the inlet 116 and the outlet 118. Gas must pass through the valve port 122 to travel between the inlet 116 and the outlet 118 of the regulator valve 114. The actuator 112 is coupled to the regulator valve 114 to ensure that the pressure at the outlet 118 of the regulator valve 114, i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator 112 includes a control assembly 122 having a diaphragm 124, a connecting stem 132, and a control arm 126 having a valve plug 128. The diaphragm 124 senses the outlet pressure of the regulator valve 114 and provides a response to move the valve plug 128 to open and close the regulator valve 114. The diaphragm 124 divides the actuator housing into a loading pressure cavity 125 and a control pressure cavity 127.
The regulator 110 in FIG. 2 does not include a control spring in the loading cavity 125, as the regulator 10 in FIG. 1 does. Rather, the pilot regulator valve 160 is operatively connected to the actuator 112 to control and adjust the load or loading pressure delivered to the load pressure cavity 125. Moreover, the pilot regulator valve assembly 160 does this in response to changes in pressure in the control pressure cavity 127 of the actuator 112. More specifically, the pilot regulator valve assembly 160 includes a body 162 having an inlet 164, an outlet 166, and a valve port 168 disposed between the inlet 164 and the outlet 166. The inlet 164 is in fluid communication with the inlet 116 of the unbalanced regulator valve 114 and the outlet 166 is in fluid communication with the control pressure cavity 125 of the actuator 112. The pilot regulator valve assembly 160 further includes a bonnet 174 coupled to the body 162, a valve plug 170 disposed within the body 162, and a diaphragm 178 disposed within the bonnet 174. The diaphragm 178 divides the bonnet 174 into a first cavity 179 and a second cavity 181, wherein the second cavity 181 is operatively coupled to and in fluid communication with the control pressure cavity 127 of the actuator 112 and the first cavity 179 includes a pilot control spring 176. So configured, the pressure in the control pressure cavity 127 of the actuator 112 is equal to the pressure in the second cavity 181 of the pilot regulator valve assembly 160, while the pilot control spring 176 offsets or balances the position of the diaphragm 178. Changes to the control pressure sensed by the diaphragm 178 cause the valve plug 170 to move between a closed position and an open position, for example. Such a configuration allows the pilot regulator valve 160 to control and adjust the loading pressure delivered to the loading pressure chamber 125 of the actuator 112 by responding to minor changes in the control or outlet pressure within the control pressure cavity 127 of the actuator 112.
While the effects of “droop” are reduced for the unbalanced regulator valve 114 by using the pilot valve, the unbalanced valve 114 has several drawbacks. For example, unbalanced valves have difficulty withstanding high inlet pressures, and high fluid pressure acting on valve ports 122 with large valve orifices can crush the valve port. As a result, unbalanced valves are not ideal for high pressure, large orifice applications. In addition, unbalanced valves suffer from an undesirable effect known as inlet pressure sensitivity. Inlet pressure sensitivity is a phenomenon in which an unbalanced valve experiences an unintended increase in control pressure as inlet pressure increases.
In addition, different markets around the world have historically demanded different pressure regulating valves due to variations in emissions standards and methods of monitoring the amount of gas supplied to end users. For example, in the United States, meters typically only monitor the amount of pressure supplied, as such it is important to control the flow rate of pressure, and pilot-operated regulator valves are typically used to do the same. Not many balanced regulator valves, such as the valve depicted in FIG. 1, however, are used in the United States because balanced ports often clog the passageways through a throat in the valve, affecting and interfering with the operation of relief valves. Instead, unbalanced regulator valves, such as those operated by a pilot regulator valve and depicted in FIG. 2, are more commonly used in the United States.
In Europe, emissions standards have historically been higher than in the U.S., such that relief valves are not acceptable. As such, balanced ports are typically used because there is not a concern with any clogging of passageways affecting the operation of any relief valves exhausting excess gas into the atmosphere. However, the conventional balanced regulator valves used in Europe, such as the balanced pressure regulator valve depicted in FIG. 1, suffer from the problems of “droop,” for example, as explained above.
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