An electro-pneumatic controller includes a base portion having at least one lateral surface and a plurality of passageways disposed through the base portion. A bore extends through the lateral surface, and the bore has a counterbore portion and a threaded engagement portion. A standard NPT plug may be coupled to the base portion, and the plug has a head portion and an engagement portion that threadedly engages the engagement portion of the bore. A top surface of the head portion of the plug is coplanar with the lateral surface of the base portion or is disposed within the counterbore portion of the bore.

FIELD OF THE DISCLOSURE

This disclosure relates generally to controllers for a process control valve or regulator, and more specifically to electro-pneumatic controllers.

BACKGROUND

Electro-pneumatic controllers (also called electro-pneumatic regulators) are typically used to precisely control the pressure of control fluid used to position a pneumatically-controlled device. For example, an electro-pneumatic controller can be used to control the pressure of control fluid into a pneumatic actuator of a process control valve or regulator to precisely position the process control valve or regulator. The electro-pneumatic controllers may include one or more passageways to receive the control fluid, and one or more solenoid valves may control the flow of the control fluid through the passageway of the electro-pneumatic controllers. The one or more solenoid valves may be in communication with a microprocessor and associated circuitry, and the microprocessor may be in communication with one or more sensors disposed outside of the electro-pneumatic controller (e.g., within an interior portion of the pneumatic actuator of the process control valve or regulator) to provide closed-loop control of the electro-pneumatic controller and/or the process control valve or regulator. The one or more passageways, one or more solenoid valves, and the microprocessor and associated circuitry may all be disposed within a housing that allows the electro-pneumatic controller to act as a modular device. Because inert gas is typically used as a control fluid, there is no danger of the microprocessor or associated circuitry igniting the control fluid.

BRIEF SUMMARY OF THE DISCLOSURE

An electro-pneumatic controller may include a base portion having at least one lateral surface, and a plurality of passageways may be disposed through the base portion. At least one of the plurality of passageway may be adapted to be coupled to a source of control fluid. At least one bore extends through the at least one lateral surface, and the at least one bore having a counterbore portion and an engagement portion having an outer surface and all or a portion of the outer surface may be threaded. The electro-pneumatic controller may also include a cap portion having an interior, and the cap portion may be removably secured to the base portion. At least one solenoid valve may be coupled to the base portion and may be disposed at least partially within the interior of the cap portion. The electro-pneumatic controller may additionally include a standard NPT plug86having a head portion and an engagement portion having an outer surface, and all or a portion of the outer surface may be threaded and may be in threaded engagement with all or a portion of the outer surface of the engagement portion of the bore to secure the standard NPT plug86to the base portion. A top surface of the head portion of the standard NPT plug may be coplanar with the at least one lateral surface of the base portion or may be disposed within the counterbore portion of the bore.

A method of providing a bore on a base portion of an electro-pneumatic controller is provided, the base portion comprising at least one lateral surface, and a plurality of passageways are disposed through the base portion. A first one of the plurality of passageways is adapted to be coupled to a source of a control fluid, and the electro-pneumatic controller includes a cap portion having an interior and that is removably secured to the base portion and at least one solenoid valve coupled to the base portion and disposed at least partially within the interior of the cap portion. The electro-pneumatic controller further includes a standard NPT plug having a head portion and an engagement portion having an outer surface, wherein all or a portion of the outer surface may be threaded, the head portion having a top surface. The method includes providing a counterbore portion of the bore and an engagement portion of the bore, the engagement portion having an outer surface and all or a portion of the outer surface is threaded, wherein when the standard NPT plug is disposed within the bore. All or a portion of the outer surface of the engagement portion of the standard NPT plug is in threaded engagement with all or a portion of the outer surface of the engagement portion of the bore, and a top surface of the head portion of the standard NPT plug is coplanar with the at least one lateral surface of the base portion or is disposed within the counterbore portion of the bore when the standard NPT plug is disposed within the bore.

DETAILED DESCRIPTION

As illustrated inFIG. 1, an electro-pneumatic controller10(that may use a non-inert fluid as a control fluid) may include a base portion92having at least one lateral surface100, and a plurality of passageways97is disposed through the base portion92. At least one of the plurality of passageway97may be adapted to be coupled to a source50of control fluid. Referring toFIG. 3B, at least one bore148extends through the at least one lateral surface100, and the at least one bore148having a counterbore portion149and an engagement portion151having an outer surface156and all or a portion of the outer surface156may be threaded. As illustrated inFIGS. 2A and 2B, the electro-pneumatic controller10may also include a cap portion94having an interior93, and the cap portion94is removably secured to the base portion92. At least one solenoid valve18is coupled to the base portion92and is disposed at least partially within the interior93of the cap portion94.

Referring toFIG. 3A, the electro-pneumatic controller10additionally includes a standard NPT plug86having a head portion87and an engagement portion88having an outer surface153, and all or a portion of the outer surface153may be threaded and may be in threaded engagement with all or a portion of the outer surface156of the engagement portion151of the bore148to secure the standard NPT plug86to the base portion92. A top surface90of the head portion87of the standard NPT plug86is coplanar with the at least one lateral surface100of the base portion92or is disposed within the counterbore portion149of the bore148. So configured, the top surface90of the head portion87of the standard NPT plug86does not extend upwardly from the lateral surface100of the base portion92, thereby creating a smooth cosmetic appearance. In addition, such a configuration allows a label or other attachment to be affixed to the lateral surface100of the base portion92.

Turning to the electro-pneumatic controller10in more detail, and with reference toFIGS. 2A and 2B, the housing assembly12may include a base portion92and a cap portion94secured to the base portion92. As illustrated inFIG. 2B, the cap portion94may have one or more interior walls that cooperate to define an interior93that may contain at least a portion of the first solenoid valve18, the second solenoid valve30, and/or the processor42. All or a portion of the interior93may correspond to the first interior portion14. In some embodiments, the cap portion94may have a cylindrical shape or a substantially cylindrical shape that extends along a longitudinal axis96from a closed first end61to an open second end63. The cap portion94may be made or fabricated from any suitable material, such as plastic, steel (e.g., stainless steel), or aluminum, for example. The cap portion94may be removably secured to the base portion92in any known manner. For example, the open second end63of the cap portion94may be sized to receive an annular flange95, and the open second end63may be coupled to the annular flange95(e.g., by a threaded connection) and/or to one or more portions of the base portion92(e.g., by mechanical fasteners).

As illustrated inFIG. 2B, the base portion92may also extend along the longitudinal axis96from a first end98to a second end99, and the open second end63of the cap portion94may be adjacent to the first end98when the cap portion94is secured to the base portion92. The base portion92may include one or more lateral surfaces100that may extend along or substantially along the longitudinal axis96, and the one or more lateral surfaces100may include one or more planar portions85.

The base portion92may be made or fabricated from any suitable material, such as plastic, steel (e.g., stainless steel), or aluminum, for example. The base portion92may include a plurality of passageways97, such as the input passageway44, the intermediate passageway52, the outlet passageway58, and/or the exhaust passageway66. All or a portion of the plurality of passageways97may be disposed through or within the base portion92, and all or a portion of the plurality of passageways97may extend within the second interior portion16of the housing assembly12. The plurality of passageways97(or each of the plurality of passageways97) may have any suitable cross-sectional shapes and/or dimensions or combinations of shapes and/or dimensions. For example, each of the plurality of passageways97may have a circular cross-sectional shape.

Referring toFIG. 1, the plurality of passageways97may include the input passageway44, and all or a portion of the input passageway44may extend within the second interior portion16of the housing assembly12. The input passageway44may include the first end46that may be coupled to the source50of the fluid (e.g., a non-inert gas, such as natural gas), and the first end46may be disposed at or adjacent to a first portion101of the lateral surface(s)100of the base portion92. The input passageway44may include a first segment102that may be linear and may extend through the base portion92normal (or substantially normal) to the longitudinal axis96from the first end46to a corner portion103. The input passageway44may also include a second segment104that may be linear and may extend through the base portion92along (or substantially along) the longitudinal axis96from the corner portion103to the second end48. The second end48may be coupled to the inlet20of the first solenoid valve18.

The plurality of passageways97may also include the intermediate passageway52that may be disposed at least partially within the base portion92, and all or a portion of the intermediate passageway52may extend within the second interior portion16of the housing assembly12. The intermediate passageway52may extend from the first end54coupled to the outlet22of the first solenoid valve18and the second end56coupled to the inlet32of the second solenoid valve30. More specifically, as illustrated inFIG. 1, the intermediate passageway52may include a first segment106that extends from the first end54to a first corner portion108, and the first segment106may be linear (or substantially linear) and may extend along (or substantially along) the longitudinal axis96from the first end54to the first corner portion108to the second end48. The intermediate passageway52may also include a second segment110that extends from the second end56to a second corner portion112, and the second segment110may be linear (or substantially linear) and may extend along (or substantially along) the longitudinal axis96from the second end56to the second corner portion112. The intermediate passageway52may further include a third segment114that extends between the first segment106and the second segment110between the first corner portion108and the second corner portion112, and the third segment114may be normal (or substantially normal) to the longitudinal axis96.

The plurality of passageways97may also include the outlet passageway58that may be disposed at least partially within the base portion92, and all or a portion of the outlet passageway58may extend within the second interior portion16of the housing assembly12. The outlet passageway58may be coupled to the intermediate passageway52and a volume122of the pneumatic actuator64of, for example, a control valve (not shown). More specifically, the outlet passageway58may include the first end60that is coupled to the third segment of the intermediate passageway52between (e.g., midway between) the first corner portion108and the second corner portion112. The second end62of the outlet passageway58adapted to be coupled to the volume122of the pneumatic actuator64, and the outlet passageway58may be linear and parallel to (or coaxially-aligned with) the longitudinal axis96.

The plurality of passageways97may also include the exhaust passageway66, and all or a portion of the exhaust passageway66may extend within the second interior portion16of the housing assembly12. The exhaust passageway66may include the first end68that may be coupled to the outlet34of the second solenoid valve30. The exhaust passageway66may include a first segment116that may be linear and may extend through the base portion92along (or substantially along) the longitudinal axis96from the first end68to a corner portion118. The exhaust passageway66may also include a second segment120that may be linear and may extend through the base portion92normal (or substantially normal) to the longitudinal axis96from the corner portion118to the second end70. The second end70may be coupled to the atmosphere72, and the second end70may be disposed at or adjacent to a second portion121of the lateral surface(s)100of the base portion92.

The electro-pneumatic controller10may also include the processor42in communication with the first solenoid valve18and/or the second solenoid valve30. The processor42may be in communication (e.g., hardwire communication or wireless communication) with one or more devices (not shown) located remote from the electro-pneumatic controller10. The processor42may be mounted to a circuit board84disposed within the interior93of the cap portion94. The circuit board84may be disposed adjacent to or offset from a top portion of each of the first solenoid valve18and/or the second solenoid valve30, and the circuit board84may be normal to the longitudinal axis96.

The first solenoid valve18may be secured or coupled to the base portion92, and the first solenoid valve18may be disposed within the interior93of the cap portion94. So secured, the first solenoid valve18may be disposed within the first interior portion14of the housing assembly12. The first solenoid valve18may have an inlet20that is in communication with the second end48of the input passageway44and an outlet22that is in communication with the first end54of the intermediate passageway52. The first solenoid valve18also has a valve member24movable between a closed position26(seeFIG. 4B) to an open position28(seeFIG. 4A), and the first solenoid valve18may be a normally closed valve. The first solenoid valve18may also have an interior portion134that may be a volume in the interior of the first solenoid valve18in fluid communication with the inlet20and the outlet22. In the closed position26, flow from the inlet20to the outlet22is prevented. In the open position28, flow from the inlet20to the outlet22(e.g., flow through the inlet20, into the interior portion134, and out of the outlet22) is allowed.

As illustrated inFIG. 6A, a bottom surface136of the first solenoid valve18may be disposed on or adjacent to a first portion of a top surface137of the base portion92, and a seal138(e.g., an O-ring) may be disposed between the bottom surface136of the first solenoid valve18and the top surface137of the base portion92. The seal138may be (at least partially) disposed in a groove139,140formed in each of the bottom surface136of the first solenoid valve18and the top surface137of the base portion92, respectively. The grooves139,140and the seal138may have a circular shape (when viewed normal to the top surface137of the base portion92) and the grooves139,140and the seal138may surround the outlet20and inlet22of the first solenoid valve18to prevent leakage of fluid (flowing from the inlet20to the outlet22of the first solenoid valve18) between the gap formed between the bottom surface136of the first solenoid valve18and the top surface137of the base portion92. The first solenoid valve18may include components made of carbon steel (e.g., chrome plated carbon steel) and/or brass (chrome plated brass).

The first solenoid valve18may be in communication with the processor42(e.g., by a communication line123), which may provide one or more signals to move the valve member24from the open position28to the closed position26and/or from the closed position26to the open position28. For example, the processor42may provide a first signal to move the valve member24from the closed position26to the open position28and/or a second signal to move the valve member24from the open position28to the closed position26.

The second solenoid valve30may have an inlet32that is in communication with the second end56of the intermediate passageway52and an outlet34that is in communication with the first end68of the exhaust passageway66. The second solenoid valve30also has a valve member36movable between a closed position38(Illustrated inFIG. 5B) to an open position40(illustrated inFIG. 5A), and the second solenoid valve30may be a normally closed valve. The second solenoid valve30may also have an interior portion135that may be a volume in the interior of the second solenoid valve30in fluid communication with the inlet32and the outlet34. In the closed position38, flow from the inlet32to the outlet34is prevented. In the open position40, flow from the inlet32to the outlet34(e.g., flow through the inlet32, into the interior portion135, and out of the outlet34) is allowed.

As illustrated inFIG. 6B, a bottom surface141of the second solenoid valve30may be disposed on or adjacent to a second portion of a top surface137of the base portion92, and a seal142(e.g., an O-ring) may be disposed between the bottom surface141of the second solenoid valve30and the top surface137of the base portion92. The seal142may be (at least partially) disposed in a groove143,144formed in each of the bottom surface141of the second solenoid valve30and the top surface137of the base portion92, respectively. The grooves143,144and the seal142may have a circular shape (when viewed normal to the top surface137of the base portion92) and the grooves143,144and the seal142may surround the outlet34and inlet32of the second solenoid valve30to prevent leakage of fluid (flowing from the inlet32to the outlet34of the second solenoid valve30) between the gap formed between the bottom surface141of the second solenoid valve30and the top surface137of the base portion92.

The second solenoid valve30may be in communication with the processor42(e.g., by a communication line124), which may provide one or more signals to move the valve member36from the open position40to the closed position38and/or from the closed position38to the open position40. For example, the processor42may provide a first signal to move the valve member36from the closed position38to the open position40and/or a second signal to move the valve member36from the open position40to the closed position38. The second solenoid valve30may include components made of carbon steel (e.g., chrome plated carbon steel) and/or brass (chrome plated brass).

One or more pressure transducers126may be coupled to or in communication with the processor42, and the one or more pressure transducers126(or pressure sensors) may be adapted to measure pressure in a desired portion(s) of one or all of the plurality of passageways97. For example, a pressure transducer126may be positioned or disposed to measure pressure in the intermediate passageway52and/or outlet passageway58. For example, as illustrated inFIG. 1, a cylindrical tube128may be secured to the base portion92adjacent to an aperture of a passageway129of the base portion92that is in communication with the intermediate passageway52and/or outlet passageway58, and the cylindrical tube128and passageway129may (at least partially) define a transducer passageway130that be in communication with the intermediate passageway52and/or outlet passageway58and that may extend vertically upward and parallel to or along the longitudinal axis96. The pressure transducer126may be disposed at or adjacent to an end portion132of the transducer passageway130, and a top portion145of the transducer126may be disposed adjacent to a bottom portion146of the circuit board84. The one or more pressure transducers126may be any type of transducer or sensor known in the art, such as a digital, analog, and/or mechanical sensor.

The electro-pneumatic controller10may be a proportional-integral-derivative (“PID”) controller that calculates an error value as the difference between a measured process variable and a desired setpoint, and the RID controller attempts to minimize the error by adjusting the process through use of a manipulated variable. To this end, when it is desired to increase pressure in the volume122of the actuator64, the processor42sends an appropriate signal open the first solenoid valve18and to close the second solenoid valve30. Consequently, the valve member24of the first solenoid valve18is moved to the open position28, allowing fluid from the source50to travel through the input passageway44, through the intermediate passageway52, through the outlet passageway58, and into the volume122of the pneumatic actuator64, thereby increasing pressure inside the volume122. When the valve member36of the second solenoid valve30is moved to the closed position38, fluid from the volume122of the actuator64is prevented from flowing through the second solenoid valve30and venting through the atmosphere72.

When it is desired to decrease pressure in the volume122of the actuator64, the processor42sends an appropriate signal close the first solenoid valve18and to open the second solenoid valve30. Consequently, the valve member24of the first solenoid valve18is moved from the open position28to the closed position26, preventing fluid from the source50from traveling through the input opening44, the intermediate passageway52, the outlet passageway58, and into the volume122of the pneumatic actuator64. When the valve member36of the second solenoid valve30is moved to the closed position38to the open position40, fluid from the volume122of the actuator64is allowed to flow from the outlet passageway58, the intermediate passageway52, and the outlet passageway66to vent to the atmosphere72. By adjusting the pressure in the volume122of the pneumatic actuator64as described, a position of a valve member (not shown) of a control valve (not shown) can be precisely controlled.

In some applications, the source50may include a non-inert control fluid (for example, natural gas). Because the non-inert control fluid may be flammable, precautions must be taken to prevent the ignition of the non-inert control fluid. For example, the processor42and associated electronics disposed within the first interior portion14of the housing assembly (e.g., within the interior93of the cap portion94) may be intrinsically-safe, which means that the associated voltages and/or currents are regulated to a maximum value that is below a value that would ignite the non-inert control fluid. However, such intrinsically-safe electronics may require a significant redesign of the existing non-intrinsically-safe electronics that are provided with a conventional controller, and therefore providing intrinsically-safe electronics significantly increases the cost of the controller. Instead of providing intrinsically-safe electronics, a flameproof barrier may be disposed between the first interior portion14of the housing assembly12(which contains the processor42, communication lines123,124, and associated electronics) and the plurality of passageways97disposed within the second interior portion16of the housing assembly12. The flameproof barrier prevents the combustion of an explosion from escaping outside of a barrier in the event that the non-inert control fluid is ignited by the processor42or associated electronics.

Accordingly, in some embodiments of the electro-pneumatic controller10using a non-inert gas as a control fluid, the flameproof barrier assembly74may include one or more flameproof joints75. Each of the flame proof joints75may be disposed within a desired one of the plurality of passageways97to prevent or to limit the spread of an open fire or explosion that might occur due to the ignition of the non-inert process fluid. Each flameproof joint75may be a flame arrestor76. The flame arrestor76functions by absorbing heat from a flame front traveling at sub-sonic velocities, thus dropping the burning gas/air mixture below its auto-ignition temperature and extinguishing the flame. Each flame arrestor76, as illustrated inFIGS. 7A and 7B, may be elongated and extend along an axis77from a first end82to an open second end83. Each flame arrestor76may be shaped and dimensioned along that axis to fit tightly within a desired portion of any of the plurality of passageways97(e.g., the passageway44,52,58,66). For example, each flame arrestor76may have an outer wall78that may be elongated and may extend along the axis77from the first end82to the second end83of the flame arrestor76, and the outer wall78may be sized and dimensioned to fit tightly in a desired portion of any of the plurality of passageways97, and a cross-sectional shape of an exterior surface79of the outer wall78may correspond to the interior shape of the one of the plurality of passageways97in which the flame arrestor76is disposed. For example, each of the cross-sectional shapes of the exterior surface79of the outer wall78and the interior shape of the one of the plurality of passageways97may be circular. An end wall80may be disposed at the first end82of the outer wall78, and the end wall80may be perforated. That is, a plurality of apertures81may be formed in the end wall80. Each of the plurality of apertures81may have any suitable maximum diameter (or maximum dimension, if not circular). For example, each of the plurality apertures81may have a maximum diameter that is less than 5% (or less than 3%, or less than 2%, or less than 1%) of the diameter of the exterior surface79of the outer wall78. More specifically, each of the plurality of apertures81may have a maximum diameter between 90 micrometers and 50 micrometers (e.g., 70 micrometers). The heat of the flame resulting from the ignited non-inert gas may be absorbed through the plurality of apertures81formed in the end wall80of the flame arrestor76. The flame arrestor76(e.g., the end wall80and the outer wall78) may be integrally formed or may be an assembly of two or more component parts. The flame arrestor76may be formed or may comprise any suitable material, such as a sintered metal (e.g., stainless steel). Each flame arrestor may be secured within a desired portion of any of the plurality of passageways97(e.g., the passageway44,52,58,66) in any manner known in the art. For example, a snap ring (not shown) may be disposed around an outer circumferential portion of the exterior surface79of the outer wall78, and the snap ring may engage a circumferential groove formed in a desired portion of any of the plurality of passageways97.

As illustrated inFIG. 1, a first flame proof joint75a(e.g., a first flame arrestor76a) may be disposed in the input passageway44. The first flame proof joint75amay be disposed within the first segment102of the input passageway44, and the first flame proof joint75amay be adjacent to the first end46of the input passageway44. A second flame proof joint75b(e.g., a second flame arrestor76b) may be disposed within the outlet passageway58, and the second flame proof joint75bmay be disposed between the first end60and the second end62. A third flame proof joint75c(e.g., a third flame arrestor76c) may be disposed in the exhaust passageway66. The third flame proof joint75cmay be disposed within the second segment120of the exhaust passageway66, and the third flame proof joint75cmay be adjacent to the second end70of the exhaust passageway66.

The flame proof joints75(e.g., the first, second, and third flame proof joints75a,75b,75c) are positioned at portions of the plurality of passageways97that are in communication with components that can be catastrophically harmed by the propagation of flames due to ignition. For example, the first flame proof joint75amay be disposed within the first segment102of the input passageway44to prevent flames from propagating towards the source50of the non-inert control fluid. The second flame proof joint75bmay be disposed within the outlet passageway58to prevent flames from propagating towards the actuator64and control valve (not shown). A third flame proof joint75c(e.g., a third flame arrestor76c) may be disposed in the exhaust passageway66to prevent flames from propagating towards the atmosphere72. Any further flame proof joints75may be included or positioned in any further one of the plurality passages97(including passages that are not expressly disclosed, such as passageways extending through the base portion92to accommodate pressure sensors or transducers) to prevent flames from propagating through that passageway.

In addition to (or as part of) the flameproof barrier assembly74previously discussed, other modification may be necessary for the electro-pneumatic controller10to be certified as flameproof. Specifically, standards such as ANSI/ASMI B1.20.1 and IEC 60079-1 apply, and, among other things, these standards regulate the types of bolts (or plugs) that are to be used to plug bores on the electro-pneumatic controller10. For example, the standards require the use of plugs having a National Pipe Thread Taper (NPT), which is a U.S. standard for tapered threads used on threaded pipes and fittings. In contrast to straight threads that are found on a bolt, a taper thread will pull tight (as the flanks of the threads compress against each other) and therefore make a fluid-tight seal. As the thread body is tapered (0.75 in/ft or 62.5 mm/m) a larger diameter keeps compressing into a smaller diameter and finally forms a seal (no clearance remains between the crests and roots of the threads because of the taper). The standards also allow for a straight thread, but a minimum of 0.315″ of thread contact is required and an O-ring is necessary to retain pressure.

NPT plugs are commonly available, and such standard off-the-shelf standard plugs are typically used with the electro-pneumatic controller10. A standard NPT plug86, as illustrated inFIG. 3A, may have a head portion87and an engagement portion88, and the head portion87and engagement portion88may extend along a longitudinal axis89. The head portion87may have a first length D1along the longitudinal axis89and the engagement portion88may have a second length D2along the longitudinal axis89, and these lengths combine to form an overall (third) length D3. The head portion87may also have a diameter W1, and the diameter W1may be greater than a maximum diameter of the engagement portion88. As illustrated inFIG. 9, the diameter W1may be equal to or substantially equal to the maximum diameter of the engagement portion88. Referring toFIG. 3A, the head portion87may have a chamfered edge152that may be adjacent to a top portion of the engagement portion87. The head portion87may also include a top surface90, and the top surface may be normal or substantially normal to the longitudinal axis89of the standard NPT plug86. However, the top surface may be faceted (or partially faceted) or curved (or partially curved) or otherwise contoured (or partially contoured). One or more tool retention features158may be formed on or in or through the head portion87. In some embodiments, one or more tool retention features158may extend downwardly (e.g., along the longitudinal axis89from the top surface90towards the engagement portion88) from the top surface90of the head portion87. As illustrated inFIG. 9, the first length D1of the head portion87may be significantly shorter than the second length D2of the engagement portion88. In some embodiments, the head portion87may comprise only the top surface90(that is, the first length D1may be 0) and the engagement portion88may extend to a circumferential perimeter edge of the top surface90.

Referring toFIG. 3A, the engagement portion88may extend along the longitudinal axis89from a first end190to a longitudinally-opposite second end191. The first end190may be adjacent to the head portion87and the second end191may be at or adjacent to an end portion of the standard NPT plug86. The engagement portion88may have an outer surface153that may be cylindrical, and all or a portion of the outer surface153may be threaded (and may have an NPT standard taper). For example, the outer surface153may be threaded from the first end190to the second end191of the engagement portion88. In one embodiment of a standard NPT plug86, the head portion87may have a first length D1of 0.07″ (1.78 mm), the engagement portion88may have a second length D2of 0.18″ (4.57 mm), and the overall length D3is therefore 0.25″ (6.35 mm). As such, if such a standard NPT plug86is secured within a conventional bore160(illustrated inFIG. 8, where a maximum diameter MD of a top portion162of the conventional bore is less than the diameter W1of the head portion87) disposed in the lateral surface100of the base portion92, the top surface90of the head portion87may be longitudinally offset from the lateral surface100of the base portion92by (or approximately by) the first length D1(e.g., the first length D1of 0.07″ (1.78 mm)). This longitudinal offset (i.e., an offset along the longitudinal axis89of the standard NPT plug86) of the top surface90of the head portion87beyond the lateral surface100of the base portion92of the electro-pneumatic controller10is esthetically displeasing and prevents a label or plate from being applied over a desired portion of the electro-pneumatic controller10(e.g., the base portion92) having such a bore160.

In order to avoid this longitudinal offset between the top surface90of the head portion87and a portion of the lateral surface100of the base portion92(e.g., a planar portion85of the lateral surface100), a bore148may include a counterbore portion149and an engagement portion151that extend along a bore longitudinal axis150, as illustrated inFIG. 3B. The bore148may be a portion (e.g., an end portion) of one of the plurality of passageway97or may be any bore or aperture formed in the base portion92. The bore longitudinal axis150may be normal or substantially normal to the lateral surface100of the base portion92(e.g., the planar portion85of the lateral surface100). The counterbore portion149of the bore148may include a side surface164that may be cylindrical (or at least partially cylindrical) and may not be threaded. In alternative embodiments, all or portions of the side surface164may be threaded. The side surface164may extend from a first end166to a second end168along the bore longitudinal axis150. The counterbore portion149may also have a chamfered edge154(e.g., if the head portion87also has a chamfered edge152) that may extend form or adjacent to the second end168of the side surface. The counterbore portion149may also include a bottom surface180that may be normal to the side surface164and/or the bore longitudinal axis150, and the chamfered edge154may extend between the bottom surface170and the side surface164. In some embodiments, the counterbore portion149may only include the side surface164and the chain chamfered edge152without a bottom portion.

The counterbore portion149of the bore148may have a fourth length D4along the bore longitudinal axis150and the engagement portion151may have a fifth length D5along the bore longitudinal axis150, and these lengths combine to form an overall (sixth) length D6. The engagement portion151may formed at an end portion on any of the plurality of passageways97, or the bore148may be a blind bore having a bottom surface (not shown). The fourth length D4of the counterbore portion149of the bore148may be greater than or equal to the first length D1of the head portion87of the standard NPT plug86, and the fifth length D5of the engagement portion151of the bore148may be greater than or equal to the second length D2of the engagement portion88of the standard NPT plug86. In some embodiments, the fifth length D5of the engagement portion151of the bore148may be less than the second length D2of the engagement portion88of the standard NPT plug86if the overall (third) length D3of the standard NPT plug86is less than or equal to the overall (sixth) length D6of the bore148.

In addition, the counterbore portion149of the bore148may have a diameter W2(e.g., a maximum diameter of the side surface164) that may be slightly greater than (e.g., 5% to 10% greater than) the diameter W1of the head portion87of the standard NPT plug86. The engagement portion151may have an outer surface156that may be cylindrical, and all or a portion of the outer surface156may be threaded (and may have an NPT standard taper) and may be adapted to threadedly engage the outer surface153of the engagement portion88of the standard NPT plug86when the standard NPT plug86is disposed within the bore148.

With the longitudinal axis89of the standard NPT plug86aligned with the bore of the standard NPT plug86, the engagement portion88of the standard NPT plug86may be inserted into the engagement portion151of the bore148and the standard NPT plug86may be rotated relative to the bore148. That is, a tool (not shown) may have a portion inserted into the tool retention feature158formed in the top surface90of the head portion87, and the tool may be rotated. By way of this rotation, the threaded portion of the outer surface153of the engagement portion88of the standard NPT plug86threadedly engages the threaded portion of the outer surface156of the engagement portion151of the bore148to secure the standard NPT plug86to the base portion92. When the threaded portion of the outer surface153of the engagement portion88of the standard NPT plug86fully threadedly engages the threaded portion of the outer surface156of the engagement portion151of the bore148, the chamfered edge152of the head portion87may be adjacent or in contact with the chamfered edge154of the counterbore portion149. Also in this position, the head portion87of the standard NPT plug86may be fully disposed or contained within the counterbore portion149of the bore. That is, as illustrated inFIG. 3C, the top surface90of the head portion87of the standard NPT plug86may be coplanar with the lateral surface100of the base portion92(e.g., a planar portion85of the lateral surface100). In other embodiments, such as that illustrated inFIG. 3D, the top surface90of the head portion87of the standard NPT plug86may be disposed within (e.g., partially or entirely within) the counterbore portion149(i.e., disposed such that the top surface90of the head portion87of the standard NPT plug86is disposed between the lateral surface100of the base portion92and the engagement portion151of the bore148.

With the standard NPT plug86disposed as described in the bore148of the base portion92, the top surface90of the head portion87of the standard NPT plug86does not extend upwardly from the lateral surface100of the base portion92(e.g., a planar portion85of the lateral surface100), thereby creating a smooth cosmetic appearance. Moreover, with the top surface90of the head portion87of the standard NPT plug86coplanar with (or below) the lateral surface100of the base portion92, a label or other attachment can be affixed to the lateral surface100of the base portion92. One having ordinary skill in the art would recognize that the counterbore portion149of the bore148achieves these objectives while realizing the cost benefits of using off-the-shelf plugs and while maintain the strict standards required for explosion or flameproof housings. The skilled person would recognize that the bore86may be disposed on any suitable surface of the base portion92and not only the lateral surface(s)100.

While various embodiments have been described above, this disclosure is not intended to be limited thereto. Variations can be made to the disclosed embodiments that are still within the scope of the appended claims.