Abstract:
Methods and apparatus are disclosed for a substantially non-porous, non-ferrous actuator casing for housing a diaphragm and diaphragm plate for use with a valve. The actuator casing includes first and second portions of forged aluminum and first and second flanges around the perimeters of the first and second portions, respectively. The flanges each further have at least one aperture. Also, there is at least one fastening device that connectively couples the first and second flanges via their respective apertures.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/590,741, which was filed on Jul. 23, 2004, the entire disclosure of which is incorporated by reference herein. 
     
    
     FIELD OF THE DISCLOSURE  
       [0002]     The present disclosure relates generally to fluid control devices and, more specifically, to a forged aluminum actuator casing for use with a fluid regulator disposed within a valve body.  
       BACKGROUND  
       [0003]     Process control plants or systems often employ fluid control devices (e.g., control valves, pressure regulators, etc.) to control the flow and pressure of process fluids such as, for example, liquids, gases, etc. One particularly important fluid valve application involves the distribution and delivery of natural gas. Typically, many portions of a natural gas distribution system are configured to convey or distribute relatively large volumes of gas at relatively high pressure. The relatively high pressure at which the gas is conveyed reduces the flow rates needed to deliver a desired volume of gas and, thus, minimizes the distribution efficiency losses (e.g., pressure drops) due to piping restrictions, valve restrictions, etc.  
         [0004]     In addition to being configured to control relatively high-pressure gas, the fluid valves used within a natural gas distribution system must also be configured to minimize or eliminate the escape of natural gas into the surrounding ambient or atmosphere. The escape of natural gas from a fluid valve can result in dangerous conditions such as, for example, explosions, fire, asphyxiation of persons, etc.  
         [0005]     Thus, the actuators used to control the flow of natural gas through a fluid valve body must be designed to withstand the high gauge pressures associated with natural gas distribution. In addition, the actuators must be designed to bleed or vent little, if any, gas to the surrounding atmosphere or ambient. As a result, the casings used for the actuators are typically designed to provide high strength and to minimize or eliminate venting or bleeding of gas to atmosphere.  
         [0006]     Some actuator casings designed for use with natural gas control devices (e.g., pressure reducing regulators) use stamped or forged steel casing halves. A steel actuator casing provides a relatively high degree of strength and can withstand extremely high gauge pressures over a relatively long service life. Further, steel actuator casings are substantially non-porous and, as a result, are not prone to bleeding or venting of the gas being controlled to atmosphere. While steel actuator casings provide excellent safe, reliable performance for a wide range of control pressures, such steel casings are cost prohibitive and too heavy for many lower pressure gas distribution applications. For instance, the control of natural gas within a natural gas distribution system typically involves lower pressures nearer to the points of delivery or usage.  
         [0007]     Cast aluminum actuator casings are typically used to implement the fluid valves that control lower pressure gas within a gas distribution system. Cast aluminum casings are relatively inexpensive but are typically porous and may have voids within the walls of the casings. The porosity and voids require a higher safety factor (i.e., the ratio of maximum or burst pressure to rated operating pressure) to be used and, thus, greater wall thickness. Some cast aluminum actuator casing designs require a safety factor as high as four to one. The greater wall thickness needed results in the use of more material, which increases both the weight and the cost of the cast aluminum casings.  
         [0008]     Additionally, the porosity of the cast aluminum casings requires the casing halves to be sealed via a secondary process. One known process involves chemically impregnating the cast aluminum casing halves with, for example, an adhesive or sealant. However, such secondary processing steps are costly and prone to some degree of yield loss (i.e., some parts may not be adequately sealed to be used in a shippable valve). 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  depicts an example forged aluminum actuator casing for use with fluid valves.  
         [0010]      FIG. 2  is a cross-sectional view of an example gas valve that uses the example actuator casing of  FIG. 1 .  
         [0011]      FIG. 3  depicts the upper actuator casing half of the example forged aluminum actuator casing of  FIG. 1 .  
         [0012]      FIG. 4  is a detailed plan view of the upper actuator casing half of  FIG. 3 .  
         [0013]      FIG. 5  is a detailed cross-sectional view of the upper actuator casing half of  FIG. 3 .  
         [0014]      FIG. 6  depicts the lower actuator casing half of the example forged aluminum actuator casing of  FIG. 1   
         [0015]      FIG. 7  is a detailed plan view of the lower actuator casing half of  FIG. 6 .  
         [0016]      FIG. 8  is a detailed cross-sectional view of the lower actuator casing half of  FIG. 6 . 
     
    
     DETAILED DESCRIPTION  
       [0017]     The example forged aluminum actuator casing described herein provides a significantly lower weight part in comparison to conventional cast aluminum actuator casings. In particular, the material and processing techniques used to fabricate the example forged aluminum actuator casing described herein results in a casing that is substantially non-porous and non-ferrous and which is substantially more ductile that cast aluminum actuator casings. The substantial ductility of the example forged aluminum actuator casing described herein (as well and the non-porous nature of the example casing) significantly reduces the design safety factor (i.e., the ratio of the maximum safe pressure to rated operating pressure of the actuator casing). For example, a safety factor of about four to one is typically used when designing cast aluminum actuator casings, whereas with the example forged aluminum actuator casing described herein, a safety factor of about one and a half to one may be used.  
         [0018]     The reduced safety factor associated with the example forged aluminum actuator casing described herein enables the production of an aluminum casing having significantly reduced wall thicknesses in comparison to cast aluminum casings. The reduced wall thicknesses, in turn, result in an actuator casing composed of significantly less material (and which weighs significantly less) than a comparable performance cast aluminum actuator casing. In addition to being lighter weight in comparison to cast aluminum actuator casings, the forged aluminum actuator casing described herein is substantially non-porous and, thus, a secondary sealing process (such as those conventionally used with known cast aluminum actuator casings) is not needed.  
         [0019]     Further, the example forged aluminum actuator casing described herein may be fabricated using a material complying with The American Society of Mechanical Engineers (ASME) standard SB247 CL.T4, which may be formed from Unified Numbering System for Metal and Alloys (UNS) standard A92014 aluminum. The use of such an ASME compliant material can greatly simplify the approval process for applications using the example forged aluminum actuator in many world markets. For example, the aforementioned material (i.e., ASME SB247 CL.T4) is compliant with the ASME boiler code, which greatly simplifies the approval process for the example forged aluminum actuator casing described herein.  
         [0020]     Now turning to  FIG. 1 , an example forged aluminum actuator casing  100  for use with fluid valves is shown. The example forged aluminum actuator casing  100  includes an upper casing half  102  and a lower casing half  104 . The terms “upper” and “lower” are merely used to distinguish the first and second halves of the actuator casing  100  and are not intended to be restrictive of the manner in which the example actuator casing  100  is used. For example, the actuator casing  100  may be field mounted in any desired orientation to satisfy the needs of a particular application and the casing halves  102  and  104  may still be referred to as “upper” and “lower,” respectively.  
         [0021]     The casing halves  102  and  104  are sealingly coupled at respective flange portions  106  and  108  via fasteners  110 . The fasteners  110  may be any suitable fastening mechanism such as, for example, nuts, bolts, washers, etc.  
         [0022]     The lower casing  104  includes a mounting flange portion  112  that enables the actuator casing  100  to be fixed (e.g., bolted) to a valve body as depicted in  FIG. 2 . The mounting flange portion  112  may include a pattern of holes or other apertures  114  that enable the actuator casing  100  to be fixed to any one of a plurality of different valve bodies. The lower casing  104  also includes a hub portion  116  which, as shown in greater detail in  FIG. 2 , serves to align and couple the actuator casing  100  to a valve body, guide the operation of the valve trim, facilitate the tight sealing of the actuator casing  100  to a valve body, etc.  
         [0023]      FIG. 2  is a cross-sectional view of an example gas valve  200  that uses the example actuator casing  100  of  FIG. 1 .  FIG. 2  generally depicts an example relationship between the example actuator casing  100  and a valve body  202  and valve trim  204 . The valve body  202  and valve trim  204  may be any known or other suitable valve body and trim and, thus, are not described further herein. As depicted in  FIG. 2 , a diaphragm  206  and a diaphragm plate  208  may be disposed within the actuator casing  100 .  
         [0024]      FIG. 3  depicts the upper actuator casing half  102  of the example forged aluminum actuator  100  casing of  FIG. 1 . As shown in  FIG. 3 , the upper actuator casing half  102  includes a plurality of apertures  302  that are circumferentially spaced about the flange portion  106 . A first angled wall portion  304  extends between the flange portion  106  and a shoulder portion  306 . The shoulder portion  306  may be configured to function as a mechanical support or stop against which the diaphragm plate  208  and/or the diaphragm  206  may be supported and/or stopped. The depth and angle of the wall portion  304  may be selected to achieve a desired amount of diaphragm travel and/or to control the stresses applied to the diaphragm  206  during use of the actuator  100  ( FIG. 1 ). The upper casing half  102  also includes a hub  308 , which may be used to guide the operation the valve trim  204  and/or a bias spring (not shown).  
         [0025]      FIG. 4  is a detailed plan view of the upper actuator casing half  102  of  FIG. 3  and  FIG. 5  is a detailed cross-sectional view of the upper actuator casing half  102  of  FIG. 3 .  
         [0026]      FIG. 6  depicts the lower actuator casing half  104  of the example forged aluminum actuator casing  100  of  FIG. 1 . The lower actuator casing half  104  includes a plurality of apertures  602  configured to receive the fasteners  110  as shown in  FIG. 1 .  
         [0027]      FIG. 7  is a detailed plan view of the lower actuator casing half  104  of  FIG. 6  and  FIG. 8  is a detailed cross-sectional view of the lower actuator casing half  104  of  FIG. 6 .  
         [0028]     In some applications such as, for example, pit applications, the actuator casing halves  102  and  104  may be anodized to protect the casing halves  102  and  104  from corrosion and the like.  
         [0029]     Although certain example methods, apparatus and articles of manufacture have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.