(19)
(11)EP 2 132 532 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
27.11.2019 Bulletin 2019/48

(21)Application number: 08725653.3

(22)Date of filing:  15.02.2008
(51)Int. Cl.: 
G01F 1/42  (2006.01)
G01L 19/00  (2006.01)
(86)International application number:
PCT/US2008/002043
(87)International publication number:
WO 2008/123906 (16.10.2008 Gazette  2008/42)

(54)

FLANGELESS DIFFERENTIAL PRESSURE SENSOR MODULE FOR INDUSTRIAL PROCESS CONTROL SYSTEMS

FLANSCHLOSES DIFFERENZDRUCKSENSORMODUL FÜR INDUSTRIELLE PROZESSSTEUERSYSTEME

MODULE DE CAPTEUR DE PRESSION DIFFERENTIELLE SANS BRIDES POUR SYSTEMES DE COMMANDE DE PROCEDE INDUSTRIEL


(84)Designated Contracting States:
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MT NL NO PL PT RO SE SI SK TR

(30)Priority: 04.04.2007 US 732570

(43)Date of publication of application:
16.12.2009 Bulletin 2009/51

(73)Proprietor: Rosemount Inc.
Eden Prairie, Minnesota 55344-3695 (US)

(72)Inventor:
  • HEDTKE, Robert C.
    Eden Prairie, MN 55344-3695 (US)

(74)Representative: Parker, Andrew James et al
Meissner Bolte Patentanwälte Rechtsanwälte Partnerschaft mbB Widenmayerstraße 47
80538 München
80538 München (DE)


(56)References cited: : 
JP-U- H04 138 228
US-A- 5 469 749
US-A1- 2005 172 738
US-B2- 6 920 795
US-A- 4 745 810
US-A1- 2005 072 242
US-B2- 6 640 650
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND OF THE INVENTION



    [0001] This invention relates generally to process instruments used in industrial process control systems. More particularly, the present invention relates to a flangeless differential pressure transmitter having an integrated primary element.

    [0002] Industrial process transmitters are used to monitor process variables of industrial process fluids. For example, pressure transmitters are commonly used in the process control industry for sensing pressures or flow rates of chemicals or petroleum products. A pressure transmitter includes a sensor or transducer that produces an electrical output in response to changes in a process pressure. For example, a capacitive pressure transducer produces a varying electrical signal based on the pressure of a process fluid changing the capacitance of the transducer. The electrical signal of the sensor is processed by transmitter circuitry to produce an electrical output that can be monitored as an indication of the pressure of the process fluid. Pressure transmitters also include electronics and circuitry that allow them to communicate with a process control system for either remotely monitoring the electrical output through a control loop or network, or locally such as with an LCD screen.

    [0003] A typical capacitive-based pressure transmitter is connected to the process fluid through a simple hydraulic system. The hydraulic system comprises one or more hydraulic passageways that are filled with precise amounts of fill fluid, which communicate the process fluid pressure to the capacitive transducer. At a first end of a hydraulic passageway is a sensor diaphragm that serves as a variable capacitor plate for the pressure sensor. At a second end of the hydraulic passageway is a transmitter isolation diaphragm that separates the fill fluid from the process fluid. In pressure transmitters, the transmitter isolation diaphragms can be positioned such that they are co-planar along a mating face on the base of the transmitter. Thus, the transmitter base allows transmitter isolation diaphragms to be extended to an outer surface of the transmitter suitable for mating with a process fluid source. However, since the transmitter isolation diaphragms are typically flush with the mating face of the transmitter base, a flange adapter union or process flange is typically required to join the process fluid source with the transmitter isolation diaphragms in a sealed arrangement. A process flange is a coupling device that provides a means for mechanically securing the transmitter base with a process fluid source. For example, COPLANAR™ process flanges are commercially available from the assignee of the present invention. A typical process flange comprises through-bores for bolted attachment to through-bores of the transmitter base, and threaded through-bores that align with the transmitter isolation diaphragms for joining with process fluid piping. Thus, the process fluid is brought into contact with the transmitter isolation diaphragms through a bolted connection. As the process fluid pressure fluctuates, the process fluid exerts a corresponding force on the isolation diaphragm at the first end of the hydraulic system, which through the fill fluid adjusts the position of a sensor diaphragm of the capacitive pressure sensor at a second end of the hydraulic system. Furthermore, in order to obtain flow measurements from the transmitter it is also necessary to include a primary flow element, such as a venturi tube, orifice plate, pitot tube or flow nozzle, in the process pipe. Thus, connecting a process fluid source to a pressure transmitter often requires multiple additional components, which provide potential leak points and add costs to installing process control systems. Therefore, there is a need for a simplified and less expensive pressure transmitter with a reduced number of potential leak paths. US 2005/072242 discloses a pressure module which includes a sensor assembly with tubes extending from a pressure sensor to fluid isolator members. The pressure sensor is contained in a cavity in a module housing. The module housing includes support members joined by joints to the fluid isolator members to provide barriers to leakage of process fluids into the cavity. Threaded process inlets on a bottom outside surface of the module housing couple the process fluids to the fluid isolator members through process passageways in the module housing. US 5,469,749 discloses a sensor module comprising a differential pressure sensor for sensing a pressure differential in a process fluid with a base having a process fluid flow duct with a primary element positioned therein for causing the pressure differential, two isolation diaphragms being positioned within the base.

    BRIEF SUMMARY OF THE INVENTION



    [0004] The present invention relates to a sensor module as disclosed in claim 1; the dependent claims present preferred embodiments of the invention.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0005] 

    FIG. 1 shows a process control system including a flangeless pressure transmitter of the present invention.

    FIG. 2 shows an exploded view of the flangeless pressure transmitter of FIG. 1 including a sensor module and a transmitter housing.

    FIG. 3 is a cross-sectional side view of the pressure transmitter of FIG. 2 showing the sensor module having a capacitance-based differential pressure sensor.

    FIG. 4 shows a cross-sectional top view of the base portion of the sensor module of FIG. 2.

    FIG. 5A shows the flangeless pressure transmitter of FIG. 3 with external valves and piping in an open configuration.

    FIG. 5B shows the flangeless pressure transmitter of FIG. 5A with the external valves and piping in a closed configuration.


    DETAILED DESCRIPTION



    [0006] FIG. 1 shows industrial process control system 10 in which industrial pressure transmitter 12 of the present invention is used. Process control system 10 includes flangeless pressure transmitter 12, pipe 14, control room 16 and control loop 18. Control room 16 includes communication system 20 and power supply 22. In one embodiment, pressure transmitter 12 is a two-wire transmitter for operating on a 4-20 mA loop. In such an embodiment, control loop 18 includes a pair of wires for supplying power to process transmitter 12 from power supply 22. Control loop 18 also enables control room 16 to transmit data to and receive data from pressure transmitter 12 utilizing communication system 20. Typically, a 4 mA DC current provides sufficient energy for operating the sensor and transmitter circuitry of process transmitter 12 and any local display. In other embodiments, process transmitter 12 communicates with control room 16 over a digital bus, over a wireless network or through a handheld device.

    [0007] Pressure transmitter 12 includes a pressure sensor and transmitter circuitry for generating an electrical signal based on a sensed pressure of an industrial process fluid. Pressure transmitter 12 also includes other electrical and electronic components for transmitting the electrical signal over control loop 18 to control room 16 or a local display such as an LCD screen, or both, and for processing the sensor output. Pressure transmitter 12 also comprises transmitter housing 24 and sensor module 25 such that it is directly coupled with pipe 14, in which a process fluid flows, to obtain differential pressure measurements.

    [0008] Sensor module 25 includes integrated process connector 26 to which pipe 14 is directly connected through an integral process fluid flow duct. Process connector 26 includes a primary element, such as an orifice plate, positioned in the process fluid flow duct such that flow measurements of the process fluid in pipe 14 are readily obtained. Integrated process connector 26 also includes coupling features such that pressure transmitter 12 is directly connectable to both a process fluid source, such as pipe 14, and mounting components, such as bracket 28. Thus, pressure transmitter 12 is flangeless such that the use of additional process flanges, manifolds, pipe extensions or primary elements is not required.

    [0009] FIG. 2 shows an exploded view of one embodiment of pressure transmitter 12 of FIG. 1. Pressure transmitter 12, including housing 24 and sensor module 25, is configured for measuring flow of the process fluid of pipe 14. Pressure transmitter 12 also includes circuitry 30, terminal 32, cover 34A and cover 34B. Connector 26 includes sensor pocket 36 and base 38, to which pipe 14 is connected at process fluid flow duct 39. Fluid flow duct 39 can be manufactured in various diameters to interface with various sizes of process pipes. Pocket 36 includes the differential pressure sensor and electronic circuitry for producing a pressure signal from the sensor for transmission to transmitter circuitry 30 through cable 43 and plug 44. Circuitry 30 and terminal 32 are secured within housing 24 at hub 46, which provides an anchor point for securing components of transmitter 12 inside housing 24. Circuitry 30 generates an output based on the sensed process variable of the sensor within pocket 36, and transmits the output to control room 16 over control loop 18, a local display situated in transmitter circuitry 30, or both. Terminal 32 and circuitry 30 are sealed within access openings of housing 24 with covers 34A and 34B. Covers 34A and 34B provide a repeatable and resealable entry into transmitter housing 24 for accessing circuitry 30 and terminal 32. Covers 34A and 34B are typically threaded onto housing 24 by at least seven threaded engagements to prevent water or other contaminants from entering transmitter 12 and to provide a flame-quenching function. Additionally, control loop 18 is brought into housing 24 through conduit connections 48A and 48B. Conduit connections 48A and 48B are sealed around control loop 18 with, for example, a plug in order to isolate circuitry 30 and terminal 32 within housing 24 at covers 34A and 34B. Base 38 includes mounting bores 50A and 50B for securing pressure transmitter 12 to mounting bracket 28, or some other such fixture. In other embodiments, transmitter 12 is supported within process control system 10 solely by the weight of pipe 14. Pressure transmitter 12 is spliced directly into pipe 14 such that threads 14A and 14B of pipe 14 are threaded directly into duct 39 of connector 26. Thus, additional mounting hardware or flanges are not needed to connect transmitter 12 with the process fluid pipe 14.

    [0010] FIG. 3 is schematic side view of pressure transmitter 12 as taken through section 3 - 3 of FIG. 2. Pressure transmitter 12 includes transmitter housing 24 and sensor module 25. Transmitter housing includes circuitry 30, terminal 32, cover 34A, cover 34B, cable 43, plug 44, conduit connection 48A and connectors 54. Sensor module 25 includes integrated process connector 26, which comprises sensor pocket 36 and base 38. It is appreciated that transmitter housing 24 and sensor module 25 may alternatively be formed together as an integral unit. Sensor pocket 36 houses sensor 56 and sensor electronics 57 while sensor base 38 includes process fluid duct 39 (including threaded couplings 39A and 39B), fill fluid passageways 58A and 58B, impulse piping lines 60A and 60B, isolation diaphragms 62A and 62B, primary element 64, and diaphragm bases 68A and 68B.

    [0011] In this embodiment, circuitry 30 and terminal 32 are joined to housing 24 at hub 46. Terminal 32 receives process control loop 18 from control room 16 such that communication system 20 and power supply 22 are connected with transmitter 12. Terminal 32 is connected to circuitry 30 through connector 54, which is connected to sensor electronics 57 through cable 43. Sensor 56 produces an electrical output based on a sensed pressure differential in process fluid duct 39. The electrical output is relayed to sensor electronics 57 then to transmitter circuitry 30 through cable 43. Circuitry 30 processes the output signal of sensor 56, whereby the pressure of the pressurized fluid can be relayed to a local display, such as LCD screen 69 associated with circuitry 30, or to control room 16 over control loop 18. In one embodiment circuitry 30 produces a 4 to 20 mA signal. In another embodiment, circuitry 30 includes software, circuitry and other electronic components for interacting and communicating on a digital network using a digital protocol such as HART® or FOUNDATION™ Fieldbus. Alternatively, a wireless communication network could be used.

    [0012] Threaded couplings 14A and 14B of process fluid pipe 14 are connected to base 38 at threaded couplings 39A and 39B. Base 38 can be custom manufactured with a variety of thread types for different industrial process connections. In various embodiments, threaded couplings 39A and 39B comprise 1/4" national pipe thread (NPT) or 1/8" NPT male pipe thread (MPT). However, in other examples not part of the invention, couplings 39A and 39B can comprise other fluid couplings, such as quick disconnects, or poppet valve type connectors. The process fluid flows through duct 39, for example, from coupling 39A toward coupling 39B. Primary element 64 is positioned between couplings 39A and 39B in duct 39 such that a pressure differential is produced in the process fluid.

    [0013] Primary element 64 comprises a flow restriction means for producing a pressure differential in the process fluid, while also permitting the process fluid to flow through duct 39. In the embodiment shown, primary element 64 comprises an orifice plate, however in other embodiments of the present invention, primary element 64 comprises a venturi tube, a pitot tube or a flow nozzle. As such, a pressure differential is produced across the primary element as the process fluid traverses primary element 64, with first pressure P1 on a first, high-pressure side of primary element 64 and second pressure P2 on a second, low-pressure side of primary element 64. The pressure differential is sensed by sensor 56.

    [0014] Sensor 56 is, for example, a capacitance-based pressure cell, in which the capacitance of pressure sensor 56 changes as a function of position of diaphragm 70. The position of diaphragm 70 changes as pressures P1 and P2 of the process fluid changes, as presented through the fill fluid and passageways 58A and 58B. Sensor diaphragm 70 provides a flexible barrier between passageways 58A and 58B that deflects in response to a change in the pressure difference between channels 60A and 60B (e.g. the pressure difference across primary element 64, or P1 - P2). Thus, the change in capacitance of sensor 56 can be used to determine various parameters of the process fluid, such as volumetric or mass flow rates, in duct 39 based on the pressure differential between P1 and P2. In other embodiments, sensor 56 operates on other known sensing principles, such as with piezoresistive strain gauge technology.

    [0015] Pursuant to one embodiment, integrated process connector 26 is typically cast and machined such that base 38 and pocket 36 are a unitary piece. In various embodiments of the invention, base 38 and pocket 36 are comprised of alloys such as stainless steel, HASTELLLOY™ or MONEL™. Pocket 36 primarily comprises a hollowed-out cavity for receiving sensor 56 and fill fluid passageways 58A and 58B above base 38. In other embodiments, pocket 36 can be welded to base 38 and then provided with a cover. Pocket 36 and base 38 of integrated process connector 26 together provide a framework that permits sensor 56 to communicate with process fluid duct 39 and control room 16. Differential pressure sensor 56 is connected to control room 16 through circuitry 30 and 57, and control loop 18. Sensor 56 is presented with two different pressures from duct 39 from which to sense a differential pressure through a hydraulic system. The hydraulic system comprises fill fluid passageways 58A and 58B, impulse piping lines 60A and 60B, and isolation diaphragms 62A and 62B.

    [0016] Base 38 is fabricated such that impulse piping lines 60A and 60B and duct 39 are integrally included to provide a leak proof connection with impulse piping lines 60A and 60B. Impulse piping lines 60A and 60B typically comprise narrow channels machined into base 38 between duct 39 and diaphragm bases 68A and 68B. In one embodiment, electrical discharge machining (EDM) is used to produce impulse piping lines 60A and 60B. Likewise, duct 39 is machined directly out of base 38. Impulse piping line 60A extends from duct 39 on the first side of primary element 64 such line 60A fills with the process fluid of pipe 14. As such, pressure P1 is transmitted to isolation diaphragm 62A by the process fluid. Similarly, impulse piping line 60B extends from duct 39 on the second side of primary element 64 and is filled with the process fluid such that pressure P2 is transmitted to isolation diaphragm 62B by the process fluid. Diaphragms 62A and 62B seal impulse piping lines 60A and 60B to prevent process fluid from entering passageways 58A and 58B.

    [0017] Fill fluid passageways 58A and 58B typically comprise segments of stainless steel tubing connected to impulse piping 60A and 60B through welded connections with diaphragm bases 68A and 68B. Diaphragm bases 68A and 68B comprise stainless steel disks welded to apertures within pocket 36 of base 38. Diaphragm bases 68A and 68B include drilled or machined holes to accept fill fluid passageways 58A and 58B, respectively, from the top side of bases 68A and 68B. Diaphragms 62A and 62B typically comprise flexible foil membranes that are welded, or otherwise secured, to the bottom sides of diaphragm bases 68A and 68B, respectively. Passageways 58A and 58B and the cavities formed between diaphragm bases 68A and 68B and diaphragms 62A and 62B, respectively, are filled with hydraulic fill fluid and are sealed at their first ends by flexible diaphragms 62A and 62B, and at their second ends by sensor 56. The hydraulic fill fluid is comprised of a pressure transmitting hydraulic fluid, which can be of any suitable hydraulic fluid that is known in the art. Such hydraulic fill fluids are typically inert, stable and substantially incompressible. Additionally, the hydraulic fluids have dielectric properties that make them suitable for serving within capacitance-based pressure sensors. In various embodiments, the first and second hydraulic fluids are comprised of DC 200 ®, DC 704 ® or Syltherm XLT ® silicone oil as is commercially available from Dow Corning Corporation, Midland, MI, USA. In other embodiments, similar fluids can be used such as Halocarbon ® from Halocarbon Products Corporation, River Edge, NJ, USA. The fill fluid communicates the pressure of the process fluid from impulse piping lines 60A and 60B to sensor 56 within pocket 36. Diaphragm bases 68A and 68B provide durable weld points for securing diaphragms 62A and 62B to base 38.

    [0018] In prior art transmitters such as is described in the background, the diaphragms are typically joined to a planar mating face on the bottom of a transmitter such that they can be readily joined with a process flange or the like. However, the weld points of the diaphragms can become stressed as they are mechanically strained when bolted to the process flange. With the present invention, diaphragms 62A and 62B are moved into the interior of base 38, away from any mechanical couplings. The recesses into which diaphragm bases 68A and 68B are seated extend into base 38 to a depth to reduce stress points around diaphragms 62A and 62B. The recesses also extend into base 38 such that diaphragm bases 68A and 68B are substantially co-planar with each other, although they need not be to be functional. The disks of bases 68A and 68B are shaped to match the shape of the recesses into which they are inserted such that diaphragms 62A and 62B are fully encapsulated between base 38 and the bottoms of bases 68A and 68B, and that the tops of bases 68A and 68B are flush with the top of base 38. In one embodiment, diaphragm bases 68A and 68B are about 0.125 inches (∼0.3175 cm) to about 0.25 inches (∼0.635 cm) thick. In one embodiment, the bottoms of diaphragm bases 68A and 68B are located half way between the top surface of base 38 and the top surface of duct 39. Diaphragm bases 68A and 68B are recessed within base 38 to provide a reduced-stress pocket for diaphragms 62A and 62B. Stress on diaphragms 62A and 62B is further reduced by the unitary construction of base 38. Thus, due to the configuration of sensor module 26, transmitter 12, including primary element 64 and pressure sensor 56, is directly connectable to process fluid pipe 14 through a reduced-stress connection, without the need for additional process flanges or manifolds.

    [0019] FIG. 4 shows a cross sectional view of one embodiment of base 38 of sensor module 26 as taken through section 4 - 4 of FIG. 2. Base 38 includes process fluid duct 39, mounting bore 50A, mounting bore 50B, primary element 64, and impulse piping lines 60A and 60B. Process pipe 14 is connected to duct 39 with threaded coupling 39A and 39B. Primary element 64 is generally positioned in the center of duct 39, between impulse piping lines 60A and 60B. In the embodiment shown, primary element 64 comprises an orifice plate, which is integrally cast and machined as a portion of base 38. Thus, primary element 64 is formed directly into and from duct 39. As described above, primary element 64 produces a pressure differential within the process fluid that is transmitted to sensor 56 through impulse piping lines 60A and 60B. Thus, process fluid continuously flows through base 38 and primary element 64 such that sensor 56 can derive a differential pressure signal.

    [0020] Duct 39 is typically cast into base 38 such that sensor module comprises a compact, uni-body construction. Base 38 can be roughcast and then machined to the desired dimensions. For example, the sizes of duct 39 and threaded couplings 39A and 39B can be machined to the final dimensions after casting based on the industrial process control system it is to be used with. Also, primary element 64 can be cast into duct 39 with oversized dimensions and then machined down to produce an orifice plate or some other element having the desired flow restriction. In other embodiments, base 38 can be cast and machined such that primary element 64 does not include an opening and, as such, divides duct 39 into two separate halves or chambers closed off from each other. Thus, transmitter 12 can be used as a standard differential pressure transmitter or in conjunction with remote seal systems. The differential pressure connections can be connected to couplings 39A and 39B. In this configuration, duct 39 provides a leakproof connection to base 38. Base 38 is therefore constructed without the need for brazed or welded joints.

    [0021] The unitary construction of base 38 thus eliminates the need for joining transmitter 12 with external process control devices such as manifolds or process flanges. This reduces the cost of transmitter 12 as the need for a multitude of bolts and fasteners is eliminated. This enhances the stability, and hence reliability, of transmitter 12 as errors and leakage associated with typical threaded couplings are eliminated. For example, process transmitters are typically bolted to process flanges at their bottom surface where the isolation diaphragms are located. However, the bolted connections can contribute to transmitter instability in certain applications. For example, over large temperature changes and high range down conditions, the bolted connections may relax, which may alter the interface between the process flange and the isolations diaphragms of the transmitter, thus causing a change in the pressure measurement and producing error. The uni-body construction of integrated process connector 26 eliminates threaded connections between the process fluid source and the isolation diaphragms, thus eliminating potential sources of error due to bolted connections.

    [0022] Base 38 of integrated process connector 26 permits transmitter 12 to be connected to a plurality of industrial process fluid pipes with only a single process fluid junction. For example, mounting bores 50A and 50B extend into base 38 such that pressure transmitter 12 can be mounted to bracket 28, or some other such fixture, with, for example, threaded fasteners. Process fluid duct 39 and process fluid couplings 39A and 39B permit transmitter 12 to be directly connected to a process fluid source, such as pipeline 14. Primary element 64 is placed inside duct 39 such that transmitter 12 is directly connected with a fluid flow metering device. Thus, a complete pressure sensing system can be quickly and simply integrated into an industrial process having to make only a single wet connection, i.e. a connection through which the process fluid flows. It is oftentimes, however, desirable to cease fluid flow through primary element 64 such that transmitter 12 can execute various functions, or maintenance can be performed on transmitter 12. Accordingly, base 38 can be connected with external bypass piping.

    [0023] FIGS. 5A and 5B show an embodiment of the invention in which base 38 of sensor module 25 is configured to include bypass manifold or bypass piping 72, first bypass valve 74, second bypass valve 76 and vent valve 78. Pipe 14 is connected to base 38 through couplings 39A and 39B. As explained above, couplings 39A and 39B can comprise any type of repeatable connector such as threaded couplings, quick disconnects, poppet valve type connectors or any other suitable connector. Bypass piping 72 is spliced into pipe 14 upstream of where the process fluid enters base 38. Piping 72 is spliced into pipe 14 at a valved juncture such that the flow or process fluid can be routed through or around duct 39.

    [0024] FIG. 5A shows sensor module 25 under normal operating conditions in which valves 74, 76 and 78 are closed to direct process fluid through duct 39 to measure flow with primary element 64. Thus, pressure sensor 56 is able to obtain pressure readings from the interaction of diaphragms 62A and 62B with the process fluid. It is sometimes desirable to perform diagnostic tests or other maintenance on transmitter 12 or sensor 56 such that it is required to cease flow of the process fluid through duct 39. Accordingly, valves 74, 76 and 78 can be adjusted to direct process fluid flow through bypass piping 72 without interrupting the flow of the process fluid through pipe 14.

    [0025] FIG. 5B shows valves 74, 76 and 78 configured to direct process fluid from pipe 14 to bypass piping 72. In this configuration, the process fluid ceases to exert a pressure on diaphragms 62A and 62B so that pressure sensor 56 does not produce a pressure signal responsive to the process fluid pressure. Vent valve 78 can be opened to allow venting of duct 39 to atmospheric conditions. As such, various testing, maintenance and diagnostics can be performed on transmitter 12, including transmitter circuitry 30 and sensor 56. Valves 74, 76 and 78 can comprise any type of valves suitable for controlling flow of a process fluid in a process control system. Particularly, valves 74 and 76 comprise valves that alternatively direct fluid between duct 39 and piping 72. In various embodiments of the invention, valves 74, 76 and 78 comprise threaded valve pins, directional valves, poppet type valves, T- or L-type ball valves, or standard vent/drain valves as are known in the industry. In yet other embodiments, transmitter 12 is used in conjunction with control valves and a proportional-integral-derivative (PID) controller for automating process fluid flow through pipe 14 to transmitter 12. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention.


    Claims

    1. A sensor module (25) for use in an industrial process transmitter (12), the sensor module (25) comprising:

    a differential pressure sensor (56) for sensing a pressure differential in a process fluid;

    a base (38) having a process fluid flow duct (39) for receiving the process fluid, the flow duct (39) extending from a first threaded coupling (39A) of the base (38) through to a second threaded coupling (39B) of the base (38);

    a primary element (64) positioned in the process fluid flow duct (39) between the first threaded coupling (39A) and the second threaded coupling (39B) and for causing the pressure differential in the process fluid;

    first (68A) and second (68B) isolation diaphragm bases positioned on a non-mating face of the base (38) facing away from the fluid flow duct (39);

    first (60A) and second (60B) impulse piping lines extending from the fluid flow duct (39) on either side of the primary element (64), through the base (38), and to the first (68A) and second (68B) isolation diaphragm bases, respectively;

    first (58A) and second (58B) fill fluid passageways extending from the first (68A) and second (68B) isolation diaphragm bases, respectively, to connect the impulse piping lines (60A, 60B) with the differential pressure sensor (56); and

    first (62A) and second (62B) isolation diaphragms positioned within the first (68A) and second (68B) isolation diaphragm bases, respectively, to seal the first (68A) and second (68B) isolation diaphragm bases from the first (60A) and second (60B) impulse piping lines, respectively, wherein the isolation diaphragms (62A, 62B) are positioned internally within the base (38) and mounted along the non-mating face of the base (38).


     
    2. The sensor module (25) of claim 1, wherein the process fluid flow duct (39), the primary element (64) and the impulse piping lines (60A, 60B) are shaped from the base (38) such that the sensor module (25) has a uni-body construction.
     
    3. The sensor module (25) of claim 1, wherein the process fluid flow duct (39) includes couplings (39A, 39B) for joining a process fluid source to the sensor module (25), and the sensor module (25) further includes couplings (50A, 50B) for securing the sensor module (25) to a mounting fixture.
     
    4. The sensor module (25) of claim 1, wherein the base (38) includes a bypass manifold (72) connecting portions of the process fluid flow duct (39) on either side of the primary element (64) such that fluid is permitted to flow around the primary element (64).
     
    5. The sensor module (25) of claim 4, wherein the bypass manifold (72) comprises:

    a bypass flow duct connecting a first end of the process fluid flow duct (39) with a second end of the process fluid flow duct (39) external to the base (38);

    a first bypass valve (74) positioned between the bypass flow duct (39) and the first end of the process fluid flow duct; and

    a second bypass valve (76) positioned between the bypass flow duct and the second end of the process fluid flow duct (39).


     
    6. The sensor module (25) of claim 1, wherein the isolation diaphragms (62A, 62B) are secured to a pair of process diaphragm base disks recessed within a surface of the base (38).
     
    7. The sensor module (25) of claim 1, wherein the primary element (64) is selected from the group consisting of: a venturi tube, an orifice plate, a pitot tube or a flow nozzle.
     
    8. A pressure transmitter (12) for use in industrial process control systems, the pressure transmitter (12) comprising:

    the sensor module (25) of claim 1;

    a transmitter housing (24) connected to the sensor module (25), the transmitter housing (24) containing transmitter circuitry (30) for processing output of the pressure sensor; and

    wherein the sensor module (25) includes a sensor pocket (36) for housing the differential pressure sensor.


     
    9. The sensor module (25) of claim 6, wherein the isolation diaphragms (62A, 62B) are welded to the process diaphragm base disks, respectively, and the process diaphragm base disks are welded to the base (38).
     
    10. The sensor module (25) of claim 6, wherein the pair of process diaphragm base disks are co-planar with each other.
     
    11. The pressure transmitter (12) of claim 8, wherein the sensor module (25) and the transmitter housing (24) comprise an integral unit.
     
    12. The sensor module (25) of claim 5, and further comprising a vent valve (78) positioned between the first bypass valve (74) and the first end of the process fluid flow duct (39).
     


    Ansprüche

    1. Sensormodul (25) zur Verwendung in einem Industrieprozesssender (12), wobei das Sensormodul (25) umfasst:

    einen Differenzdrucksensor (56) zum Abfühlen einer Druckdifferenz in einem Prozessfluid;

    eine Basis (38) mit einem Prozessfluidströmungskanal (39) zur Aufnahme des Prozessfluids, wobei sich der Strömungskanal (39) von einer ersten Gewindekupplung (39A) der Basis (38) durch eine zweite Gewindekupplung (39B) der Basis (38) erstreckt;

    ein Primärelement (64), das in dem Prozessfluidströmungskanal (39) zwischen der ersten Gewindekupplung (39A) und der zweiten Gewindekupplung (39B) angeordnet ist, um die Druckdifferenz im Prozessfluid zu bewirken;

    eine erste (68A) und zweite (68B) Isolationsmembranbasis, die sich auf einer nicht verbindenden Fläche der Basis (38) befinden, die vom Fluidströmungskanal (39) abgewandt ist;

    eine erste (60A) und zweite (60B) Pulsrohrleitung, die sich vom Fluidströmungskanal (39) auf jeder Seite des Primärelements (64) durch die Basis (38) und zur ersten (68A) bzw. zweiten (68B) Isolationsmembranbasis erstrecken;

    einen ersten (58A) und zweiten (58B) Füllfluiddurchgang, die sich von der ersten (68A) bzw. zweiten (68B) Isolationsmembranbasis erstrecken, um die Pulsrohrleitungen (60A, 60B) mit dem Differenzdrucksensor (56) zu verbinden; und

    eine erste (62A) und zweite (62B) Isolationsmembran, die sich in der ersten (68A) bzw. zweiten (68B) Isolationsmembranbasis befinden, um die erste (68A) bzw. zweite (68B) Isolationsmembranbasis jeweils von der ersten (60A) bzw. zweiten (60B) Pulsrohrleitung abzuschotten, wobei sich die Isolationsmembranen (62A, 62B) innen in der Basis (38) befinden und entlang der nicht verbindenden Fläche der Basis (38) montiert sind.


     
    2. Sensormodul (25) nach Anspruch 1, wobei der Prozessfluidströmungskanal (39), das Primärelement (64) und die Pulsrohrleitungen (60A, 60B) ausgehend von der Basis (38) so geformt sind, dass das Sensormodul (25) einen Einkörper-Aufbau hat.
     
    3. Sensormodul (25) nach Anspruch 1, wobei der Prozessfluidströmungskanal (39) Kupplungen (39A, 39B) aufweist, um eine Prozessfluidquelle an das Sensormodul (25) anzuschließen, und das Sensormodul (25) darüber hinaus Kupplungen (50A, 50B) aufweist, um das Sensormodul (25) an einer Montagebefestigung zu befestigen.
     
    4. Sensormodul (25) nach Anspruch 1, wobei die Basis (38) einen Umgehungsverteiler (72) aufweist, der Abschnitte des Prozessfluidströmungskanals (39) auf jeder Seite des Primärelements (64) verbindet, so dass Fluid um das Primärelement (64) strömen darf.
     
    5. Sensormodul (25) nach Anspruch 4, wobei der Umgehungsverteiler (72) umfasst:

    einen Umgehungsströmungskanal, der ein erstes Ende des Prozessfluidströmungskanals (39) mit einem zweiten Ende des Prozessfluidströmungskanals (39) verbindet, das außerhalb der Basis (38) liegt;

    ein erstes Umgehungsventil (74), das sich zwischen dem Umgehungsströmungskanal (39) und dem ersten Ende des Prozessfluidströmungskanals befindet; und

    ein zweites Umgehungsventil (76), das sich zwischen dem Umgehungsströmungskanal und dem zweiten Ende des Prozessfluidströmungskanals (39) befindet.


     
    6. Sensormodul (25) nach Anspruch 1, wobei die Isolationsmembranen (62A, 62B) an einem Paar Prozessmembranbasisscheiben befestigt sind, die in eine Fläche der Basis (38) eingelassen sind.
     
    7. Sensormodul (25) nach Anspruch 1, wobei das Primärelement (64) aus der Gruppe ausgewählt ist, die besteht aus: einem Venturirohr, einer Messblende, einem Staurohr oder einer Strömungsdüse.
     
    8. Drucktransmitter (12) zur Verwendung in industriellen Prozesssteuerungssystemen, wobei der Drucktransmitter (12) umfasst:

    das Sensormodul (25) nach Anspruch 1;

    ein Transmittergehäuse (24), das an das Sensormodul (25) angeschlossen ist, wobei das Transmittergehäuse (24) eine Transmitterschaltung (30) zum Verarbeiten des Ausgangs des Drucksensors enthält; und

    wobei das Sensormodul (25) eine Sensortasche (36) zum Unterbringen des Differenzdrucksensors aufweist.


     
    9. Sensormodul (25) nach Anspruch 6, wobei die Isolationsmembranen (62A, 62B) jeweils an die Prozessmembranbasisscheiben angeschweißt sind, und die Prozessmembranbasisscheiben an die Basis (38) angeschweißt sind.
     
    10. Sensormodul (25) nach Anspruch 6, wobei das Paar der Prozessmembranbasisscheiben koplanar zueinander sind.
     
    11. Drucktransmitter (12) nach Anspruch 8, wobei das Sensormodul (25) und das Transmittergehäuse (24) eine integrale Einheit umfassen.
     
    12. Sensormodul (25) nach Anspruch 5, und darüber hinaus ein Entlüftungsventil (78) umfassend, das sich zwischen dem ersten Umgehungsventil (74) und dem ersten Ende des Prozessfluidströmungskanals (39) befindet.
     


    Revendications

    1. Module de capteur (25) destiné à être utilisé dans un transmetteur (12) de processus industriel, le module de capteur (25) comprenant :

    un capteur de pression différentielle (56) destiné à détecter un différentiel de pression dans un fluide de processus ;

    une base (38) comportant un conduit d'écoulement de fluide de processus (39) destiné à recevoir le fluide de processus, le conduit d'écoulement (39) s'étendant depuis un premier accouplement fileté (39A) de la base (38) via un deuxième accouplement fileté (39B) de la base (38) ;

    un élément primaire (64) positionné dans le conduit d'écoulement de fluide de processus (39) entre le premier accouplement fileté (39A) et le deuxième accouplement fileté (39B) et destiné à engendrer le différentiel de pression dans le fluide de processus ;

    une première (68A) et une deuxième (68B) base de diaphragme d'isolation positionnées sur une face non appariée de la base (38) du côté opposé au conduit d'écoulement de fluide (39) ;

    une première (60A) et une deuxième (60B) ligne de tuyauterie à impulsion s'étendant depuis le conduit d'écoulement de fluide (39) de l'un et l'autre côté de l'élément primaire (64), via la base (38), et jusqu'à la première (68A) et la deuxième (68B) base de diaphragme d'isolation, respectivement ;

    un premier (58A) et un deuxième (58B) passage de fluide de remplissage s'étendant depuis la première (68A) et la deuxième (68B) base de diaphragme d'isolation, respectivement, pour raccorder les lignes de tuyauterie à impulsion (60A, 60B) au capteur de pression différentielle (56) ; et

    un premier (62A) et un deuxième (62B) diaphragme d'isolation positionnés à l'intérieur de la première (68A) et de la deuxième (68B) base de diaphragme d'isolation, respectivement, pour étanchéifier la première (68A) et la deuxième (68B) base de diaphragme d'isolation par rapport à la première (60A) et la deuxième (60B) ligne de tuyauterie à impulsion, respectivement, sachant que les diaphragmes d'isolation (62A, 62B) sont positionnés en interne à l'intérieur de la base (38) et montés le long de la face non appariée de la base (38).


     
    2. Le module de capteur (25) de la revendication 1, sachant que le conduit d'écoulement de fluide de processus (39), l'élément primaire (64) et les lignes de tuyauterie à impulsion (60A, 60B) sont formés à partir de la base (38) de telle sorte que le module de capteur (25) ait une construction monocorps.
     
    3. Le module de capteur (25) de la revendication 1, sachant que le conduit d'écoulement de fluide de processus (39) inclut des accouplements (39A, 39B) destinés à relier une source de fluide de processus au module de capteur (25), et le module de capteur (25) inclut en outre des accouplements (50A, 50B) destinés à fixer le module de capteur (25) à une fixation de montage.
     
    4. Le module de capteur (25) de la revendication 1, sachant que la base (38) inclut un distributeur de dérivation (72) raccordant des parties du conduit d'écoulement de fluide de processus (39) de l'un et l'autre côté de l'élément primaire (64) de telle sorte que du fluide puisse circuler autour de l'élément primaire (64).
     
    5. Le module de capteur (25) de la revendication 4, sachant que le distributeur de dérivation (72) comprend :

    un conduit d'écoulement de dérivation raccordant une première extrémité du conduit d'écoulement de fluide de processus (39) à une deuxième extrémité du conduit d'écoulement de fluide de processus (39) externe à la base (38) ;

    une première soupape de dérivation (74) positionnée entre le conduit d'écoulement de dérivation (39) et la première extrémité du conduit d'écoulement de fluide de processus ; et

    une deuxième soupape de dérivation (76) positionnée entre le conduit d'écoulement de dérivation et la deuxième extrémité du conduit d'écoulement de fluide de processus (39).


     
    6. Le module de capteur (25) de la revendication 1, sachant que les diaphragmes d'isolation (62A, 62B) sont fixés à une paire de disques de base de diaphragme de processus logés dans une surface de la base (38).
     
    7. Le module de capteur (25) de la revendication 1, sachant que l'élément primaire (64) est sélectionné dans le groupe constitué par : un tube Venturi, une plaque à orifice, un tube de Pitot ou une tuyère d'écoulement.
     
    8. Transmetteur de pression (12) destiné à être utilisé dans des systèmes de commande de processus industriel, le transmetteur de pression (12) comprenant :

    le module de capteur (25) de la revendication 1 ;

    un boîtier de transmetteur (24) raccordé au module de capteur (25), le boîtier de transmetteur (24) contenant un circuit de transmetteur (30) destiné à traiter une sortie du capteur de pression ; et

    sachant que le module de capteur (25) inclut une poche de capteur (36) destinée à loger le capteur de pression différentielle.


     
    9. Le module de capteur (25) de la revendication 6, sachant que les diaphragmes d'isolation (62A, 62B) sont soudés aux disques de base de diaphragme de processus, respectivement, et les disques de base de diaphragme de processus sont soudés à la base (38).
     
    10. Le module de capteur (25) de la revendication 6, sachant que la paire de disques de base de diaphragme de processus sont coplanaires l'un par rapport à l'autre.
     
    11. Le transmetteur de pression (12) de la revendication 8, sachant que le module de capteur (25) et le boîtier de transmetteur (24) forment une seule unité.
     
    12. Le module de capteur (25) de la revendication 5, et comprenant en outre une soupape d'évent (78) positionnée entre la première soupape de dérivation (74) et la première extrémité du conduit d'écoulement de fluide de processus (39).
     




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    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description