Non-metallic isolator system for industrial process pressure transmitter

Abstract

A pressure transmitter 105 comprises: a process connector 102 configured to be mounted to a process vessel carrying a process fluid; a process pressure sensor 111; and an isolator plug 114 coupled to the process connector 102 and configured to receive the process pressure sensor 111. The isolator plug 114 includes at least one internal fluid-filled cavity 106 in fluid contact with the process pressure sensor 111. At least one transfer mount 110 made of a metal material is coupled to the isolator plug 114. The transfer mount 110 includes an internal fluid-filled cavity 156 in fluid communication with the internal fluid-filled cavity 106 of the isolator plug 114. At least one isolation diaphragm 108 exposed to process fluid in the process connector 102 is coupled to the transfer mount 110 and configured to transfer process pressure to the transfer mount 110 and the internal fluid-filled cavity 106 / 156 of the isolator plug 114 and the process pressure sensor 111.

Description

Background Art

[0001] The present invention relates to a process variable transmitter of the type for sensing process pressure. Most particularly, the present invention relates to a non-metallic or semi-metallic isolation diaphragm for coupling such a pressure transmitter to the pressure of an industrial process.

[0002] Typically, metal isolation diaphragms are used to couple a pressure sensor to a process pressure. Such diaphragms can accurately couple the process pressure to an isolated fill fluid that conveys the pressure to the pressure sensor. The metal diaphragm can withstand shock and other disturbances without rupturing. However, in some industrial processes, the process fluid may corrode the metal diaphragm or otherwise cause eventual failure of the diaphragm.

[0003] Ceramic diaphragms have been used with process fluids that may corrode metal diaphragms. However, it is difficult to couple a ceramic diaphragm to a transmitter housing. Summary of the Invention

[0004] A pressure transmitter includes: a process connector configured to be mounted to a process vessel carrying a process fluid; a process pressure sensor; and an isolator plug coupled to the process connector and configured to receive the process pressure sensor. The isolator plug includes an internal fluid-filled cavity in fluid contact with the process pressure sensor. A transfer mount made of a metallic material is coupled to the isolator plug. The transfer mount includes an internal fluid-filled cavity in fluid communication with the internal fluid-filled cavity of the isolator plug. An isolation diaphragm exposed to the process fluid in the process connector is coupled to the transfer mount and configured to transfer the process pressure to the internal fluid-filled cavities of the transfer mount and the isolator plug and to the process pressure sensor. The isolation diaphragm includes a non-metallic material or a semi-metallic material.

[0005] A pressure transmitter includes: a process connector configured to be mounted to a process vessel carrying a process fluid; a process pressure sensor; and an isolator plug coupled to the process connector and configured to receive the process pressure sensor. The isolator plug includes an internal fluid-filled cavity in fluid contact with the process pressure sensor. A transfer mount made of a metallic material is coupled to the isolator plug. The transfer mount includes an internal fluid-filled cavity in fluid communication with the internal fluid-filled cavity of the isolator plug. A non-metallic assembly is coupled to the transfer mount and includes a base made of a non-metallic material and an isolation diaphragm made of a non-metallic material, the isolation diaphragm being exposed to the process fluid in the process connector and coupled to the base. The base includes an internal fluid-filled cavity in fluid communication with the internal fluid-filled cavities of the transfer mount and the isolator plug.

[0006] A pressure transmitter includes: a process connector configured to be mounted to a process vessel carrying a process fluid; a process pressure sensor; and an isolator plug coupled to the process connector and configured to house the process pressure sensor. The isolator plug includes an internal fluid-filled cavity in fluid contact with the process pressure sensor. A spacer is coupled to the isolator plug and includes an internal fluid-filled cavity that is in fluid communication with the internal fluid-filled cavity of the isolator plug. A transfer mounting member made of a metallic material is coupled to the spacer. The transfer mounting member includes an internal fluid-filled cavity that is in fluid communication with the internal fluid-filled cavities of the spacer and the isolator plug. A non-metallic assembly is coupled to the transfer mounting member and includes a base made of a non-metallic material and an isolation diaphragm made of a non-metallic material that is exposed to the process fluid in the process connector and is coupled to the base. The base includes an internal fluid-filled cavity that is in fluid communication with the internal fluid-filled cavities of the transfer mounting member, the spacer, and the isolator plug.

[0007] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to help determine the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the Background. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1a A simplified cross-sectional view of a sensor capsule using a direct-insert gauge pressure sensor for a direct-insert application is shown.

[0009] Figure 1b A simplified cross-sectional view of a sensor capsule using a differential pressure sensor for a coplanar application is shown.

[0010] Figure 2 A perspective view of a direct-insert pressure transmitter including a non-metallic isolator system according to an embodiment is shown.

[0011] Figure 3 Shown is Figure 2 an enlarged perspective view of the sensor module and the process connector of the pressure transmitter.

[0012] Figure 4 Shown is a cross-sectional view taken along the section line shown in Figure 3 therein.

[0013] Figure 5 Shown is Figure 4 an exploded perspective view of

[0014] Figure 6It is a graph of the coefficient of thermal expansion of various metal materials with respect to temperature.

[0015] Figure 7 Shows a cross-sectional view of a sensor capsule and a process connector of a process transmitter including a non-metallic isolator system according to an embodiment.

[0016] Figure 8 Shows Figure 7 exploded view of.

[0017] Figure 9 Shows a simplified diagram of a cross-sectional view of a part of a direct insertion pressure transmitter including a non-metallic isolator system according to an embodiment.

[0018] Figure 10 Is a table showing the electromotive series in seawater.

[0019] Figure 11 Is a simplified diagram of a cross-sectional view of a part of a direct insertion pressure transmitter including a non-metallic isolator system according to an embodiment.

[0020] Figure 12 Is a part of a non-metallic isolator system including a gasket according to an embodiment Figure 11 simplified diagram of a cross-sectional view of.

[0021] Figure 13 Is a simplified diagram of a cross-sectional view of a part of a direct insertion pressure transmitter including a non-metallic isolator system according to an embodiment.

[0022] Figure 14 Is a simplified diagram of a cross-sectional view of a part of a direct insertion pressure transmitter including an isolator system according to an embodiment.

[0023] Figure 15 Shows as Figure 14 perspective view of a silicon isolation diaphragm used in an isolator system of.

[0024] Figure 16 Is Figure 14 simplified diagram of a strain gauge sensor of a direct insertion pressure transmitter of.

[0025] Figure 17 Is a simplified diagram of a cross-sectional view of a part of a differential pressure transmitter including a non-metallic isolator system according to an embodiment.

[0026] Figure 18 Is a simplified diagram of a cross-sectional view of a part of a differential pressure transmitter including a non-metallic isolator system according to an embodiment. Detailed Description

[0027] Embodiments of a non-metallic isolator system and associated installation system are described below and allow the use of existing sensor technology and configurations but provide a fluid-filled system with a non-metallic process-wetting diaphragm for demanding applications, such as oil-filled systems. Advantages of the non-metallic isolation diaphragm include abrasion resistance, corrosion resistance, and hydrogen permeation resistance, where advantages of existing sensor technology include accuracy, repeatability, drift performance, overpressure protection, and adjustable range. Additionally, some embodiments alleviate the need for wetting O-rings typically used with ceramic diaphragms. The embodiments relate to a direct insertion pressure transmitter; however, embodiments can also be used for differential pressure transmitters.

[0028] Process conditions that a non-metallic diaphragm can better serve are highly corrosive processes, highly abrasive processes, and processes with a risk of hydrogen permeation. Hydrogen permeation is the diffusion of hydrogen ions through the isolation diaphragm used in a pressure transmitter by either an interstitial or substitutional (vacancy) mechanism. Over time, the fill fluid becomes saturated and hydrogen gas bubbles form. If enough hydrogen gas bubbles form, zero shift and span shift cause the transmitter to drift. In extreme cases, the hydrogen gas bubbles can accumulate enough volume to force the isolation diaphragm to expand outward, resulting in diaphragm cracking, which causes the fill fluid to leak into the process fluid and the pressure transmitter to fail.

[0029] A typical metal diaphragm can be 0.001 - 0.002 inches thick, and a single metal defect can cause pitting (corrosion). A single impact on the defect can pierce the metal (rupture), and single atomic hydrogen can eventually pass through the metal lattice structure (permeate). Typical solutions such as coatings or plating will improve resistance to hydrogen permeation but are costly and sacrifice device accuracy and temperature performance.

[0030] Embodiments of the present disclosure include a non-metallic isolator system that can operate with existing sensor technology, such as an existing sensor and sensor capsule within a sensor module housing. For example, Figure 1a A simplified cross-sectional view of a conventional sensor capsule 30 and process connector 32 using a gauge pressure sensor 31 for a direct insertion application is shown. In another example, Figure 1b A simplified cross-sectional view of a conventional sensor capsule 40 using a differential pressure sensor 41 for a coplanar application is shown. In a typical direct insertion application as Figure 1a shown, the sensor capsule 30 includes an isolation diaphragm 38 that is exposed to the process fluid pressure 34 and isolates the process fluid pressure from the fill fluid 36 and the gauge pressure sensor 31. For example, the fill fluid 36 can be oil or other fluid. The sensor capsule 30 also includes a gauge pressure vent 39 such that high pressure exists between the isolation diaphragm 38 and the sensor 31 and low pressure exists between the sensor 31 and the vent 39. In a Figure 1bIn the exemplary coplanar application shown, the sensor capsule 40 includes a pair of isolation diaphragms 47 and 48 that are exposed to the process fluid pressure 44 and isolate the process fluid pressure from the fill fluid 46 in the fluid-filled cavity and the differential pressure sensor 41.

[0031] Figure 2 A perspective view of a through-hole pressure transmitter 105 including a non-metallic isolator system according to an embodiment is shown. The pressure transmitter 105 includes a process connector 102, a sensor module 103 having a sensor capsule ( Figure 2 not shown in the figure), and electronics 107. Figure 3 An enlarged perspective view of the sensor module 103 and the process connector 102 of the pressure transmitter 105 is shown. Figure 4 Shown by Figure 3 a cross-sectional view taken along the cross-sectional line shown in the figure, and Figure 5 shown Figure 4 a disassembled perspective view of the pressure transmitter 105. The process connector 102 is configured to be mounted to a process vessel carrying a process fluid. The sensor module 103 includes a process pressure sensor 111 and an isolator plug 114 that is coupled to the process connector 102 and is configured to house the process pressure sensor 111. In Figure 3 the figure, the sensor 111 can be a gauge pressure sensor. The isolator plug 114 includes an internal fluid-filled cavity 106 that is in fluid contact with the process pressure sensor 111. For example, the fluid in the fluid-filled cavity 106 can be oil.

[0032] In one embodiment, the pressure transmitter 105 includes an isolation diaphragm 108 made of a non-metallic material and coupled to a transfer mounting member 110 made of a metallic material, which in turn is coupled to the isolator plug 114. The isolation diaphragm 108 is a thin member that is exposed to the process fluid in the process connector 102 and is configured to transfer the process pressure to the internal fluid or the fluid-filled cavity 106 of the isolator plug 114, and needs to be flexible enough to accommodate the expansion and contraction of the fill fluid under temperature changes and also under high pressure. For example, the isolation diaphragm 108 can be made of ceramics, such as transparent ceramics, such as single crystal alumina or sapphire, alumina, zirconia, or zirconia toughened alumina (ZTA), and can be diffusion bonded to a base 109 also made of a non-metallic material. For example, the base 109 can be made of ceramics (such as alumina) and together with the isolation diaphragm 108 forms a non-metallic assembly 113. The base 109 couples the isolation diaphragm 108 to the transfer mounting member 110.

[0033] A conventional isolator plug 114 (such as a stainless steel isolator plug) can be used to interface with the process pressure sensor 111 and the housing 116 of the sensor module 103. As Figure 4 and 5As shown, the isolator plug 114 can have an extended length to allow external threading to the housing 116 of the sensor module 104 and attachment to the process connector 102. For example, the process connector 102 can be attached to the isolator plug 114 by a welded connection, a threaded connection, or a bolted connection.

[0034] The transfer mount 110 includes an internal fluid or fluid-filled cavity 156 that is in fluid communication with the internally fluid-filled cavity 106 of the isolator plug 114. The base 109 includes an internal fluid or fluid-filled cavity 159 that is in fluid communication with the internally fluid-filled cavity 156 of the transfer mount 110 and the internally fluid-filled cavity 106 of the isolator plug 114. Thus, the isolation diaphragm 108 is configured to transfer process pressure to the internal fluid-filled cavity 156 of the transfer mount 110 and the internally fluid-filled cavity 106 of the isolator plug 114 and ultimately to the process pressure sensor 111.

[0035] Figure 6 is a graph of the coefficient of thermal expansion (CTE) values of various metal materials relative to temperature. The transfer mount 110 can be made of a metal material (such as tantalum, niobium, Kovar, or Invar) that has a CTE close to that of the non-metallic material of which the base 109 and the isolation diaphragm 108 are made. For example and as Figure 6 shown, each metal material includes a CTE at different temperatures. Each of these CTE values intersects the non-metallic material of alumina at least once. Thus, any one of tantalum, niobium, Kovar, Inver, alloy 42, alloy 46, or alloy 52 is close to the CTE of the non-metallic material of alumina and is a possible material choice for the transfer mount 110. In other words, the metal material of the transfer mount 110 includes a CTE that has a CTE value range (y-axis) that overlaps the CTE value range (y-axis) of the non-metallic material of the base 109 and / or the isolation diaphragm 109. For example, the metal mount 110 can be made of tantalum or niobium whose CTE substantially matches or is close to the CTE of the alumina of the non-metallic body 109.

[0036] The non-metallic component 113 or more specifically the base 109 of the non-metallic component 113 can be joined to the transfer mount 110 by, for example, soldering, brazing, or glass. The joint joining the non-metallic component 113 to the metal mount 110 should have high corrosion resistance and withstand high temperatures. One example includes soldering 123, such as 80Au / 20Sn soldering. Opposite the joint of the non-metallic component 113 is a prominent feature 117 of the metal mount 110, which will be discussed in more detail below.

[0037] The spacer 118 connects the non-metallic component 113 and the transfer mount 110 to the isolator plug 114 and can be configured to relieve stress on the base 109. The feature 117 of the metal mount 110 allows the spacer 118 to be projection welded or soldered to the metal mount 110. Additionally, the spacer 118 can be laser welded to the isolator plug 114 and can be made of a material resistant to pitting and crevice corrosion and have a CTE close to that of the metal mount 110. For example, the spacer 118 can be made of a nickel alloy (such as C-276), which is a nickel-chromium-molybdenum alloy. The spacer 118 includes an internal fluid-filled cavity 158 that is in fluid communication with the internal fluid-filled cavity 159 of the base 109, the internal fluid-filled cavity 156 of the transfer mount 110, and the internal fluid-filled cavity 106 of the isolator plug 114.

[0038] In other embodiments, gaskets are used to mitigate corrosion between joints. For example, Figure 7 A cross-sectional view of a sensor capsule 200 and a process connector 202 of a process transmitter 205 including a non-metallic isolator system according to an embodiment is shown. Figure 8 Shown is Figure 7 an exploded view. In one embodiment, the sensor capsule 200 includes a non-metallic isolation diaphragm 208 and a non-metallic base 209 that is bonded to a metal transfer mount 210, which is attached to a sensor (not shown). The non-metallic isolation diaphragm 208 is a thin member that transfers process pressure to an internal fluid (such as oil) or a fluid-filled cavity 206 and needs to be flexible enough to accommodate the expansion and contraction of the fill fluid under temperature changes and also under high pressure. For example, the non-metallic isolation diaphragm 208 can be made of a ceramic, such as a transparent ceramic, such as single crystal alumina or sapphire, alumina, zirconia, or zirconia toughened alumina (ZTA), and can be diffusion bonded to the non-metallic base 209 to form a non-metallic component 213, and the non-metallic base can be made of a ceramic (such as alumina).

[0039] A conventional isolator plug or sensor housing adapter 214 (such as a stainless steel isolator plug) can be used to interface with the sensor and housing (not shown) of the sensor capsule 200. As Figure 7 and 8 shown, the isolator plug 214 can have an extended length to allow an external threaded connection to the housing of the sensor capsule 200 and attachment to the process connector 202. For example, the process connector 202 can be attached to the isolator plug 214 by a welded connection, a threaded connection, or a bolted connection.

[0040] The metal transfer mount 210 is connected to the non-metallic component 213 by, for example, soldering, brazing, or vitrification. The metal transfer mount 210 should be made of a material with a coefficient of thermal expansion (CTE) that overlaps with the materials of the non-metallic base 209 and the isolation diaphragm 208. For example, the metal transfer mount 110 can be made of tantalum or niobium with a CTE that overlaps with alumina, such as the non-metallic base 209. The joint connecting the non-metallic component 213 to the metal transfer mount 210 should have high corrosion resistance and withstand high temperatures. An example includes soldering, such as 80Au / 20Sn soldering.

[0041] According to this embodiment, the spacer 218 connects the non-metallic component 213 and the metal transfer mount 210 to the isolator plug 214 and can be arranged to relieve stress on the non-metallic body 209. The metal mount 210 can include a protruding feature 217. The protruding feature 217 allows the spacer 218 to be projection welded or soldered to the metal transfer mount 210. Additionally, the spacer 218 can be laser welded to the isolator plug 214 and can be made of a material resistant to pitting and crevice corrosion and have a CTE that overlaps with the CTE of the metal transfer mount 210. For example, the spacer 218 can be made of a nickel alloy (such as C-276), which is a nickel-chromium-molybdenum alloy.

[0042] In this embodiment, the non-metallic base 209 includes a groove 215 facing the metal transfer mount 210. The groove 215 is configured to receive and accommodate a gasket 221. Figure 8 and 9 In, the gasket 221 is a C-ring gasket. The C-ring gasket 221 prevents wetting between the non-metallic component 213 and the metal transfer mount 210 and protects the bonding or joint area between the non-metallic component 213 and the metal transfer mount 210. The C-ring gasket 221 is useful if soldering, brazing, or vitrification is used to connect the non-metallic component 213 to the metal mount 210. However, other gasket types are possible, including O-ring gaskets made of polymer materials.

[0043] Figure 9A simplified cross-sectional view of a portion of a sensor capsule 300 and a process connector 302 of a direct-acting pressure transmitter 305 including a non-metallic isolator system according to another embodiment is shown. The sensor capsule 300 includes an isolator plug 314 made of, for example, stainless steel, a metal transfer mount 310 made of, for example, niobium, and a non-metallic isolation diaphragm 308 made of, for example, ceramic. The non-metallic isolation diaphragm 308 is a thin member that transfers process pressure to the internal fluid (such as oil) or fluid-filled cavity 306 of the sensor capsule 300 and can be made of ceramic, such as alumina, single crystal sapphire, zirconia, or zirconia toughened alumina (ZTA). The diaphragm 308 needs to be flexible enough to deflect primarily when the temperature changes, but also under high pressures, such as up to and exceeding 20,000 PSI, and this travel is necessary to accommodate the expansion and contraction of the fluid-filled system over a certain temperature range. The non-metallic isolation diaphragm 308 is attached to the metal transfer mount 310. In the case where the metal mount 310 is made of niobium, niobium is a heat-resistant metal that provides an excellent CTE match or overlap with alumina ceramics, as Figure 6 shown. Thus, stress from CTE mismatch is substantially eliminated.

[0044] Another metal transfer mount 310 made of niobium can be directly bonded to the ceramic via pressure bonding or diffusion bonding. The heat and pressure applied to the niobium-alumina assembly result in solid-state diffusion bonding, where alumina (Al2O3) and niobium (Nb) share an oxide layer. This results in an extremely strong bond between the ceramic and niobium, which eliminates the risk of brazed joints and the need for gaskets. The niobium-ceramic joint shares oxides and can be directly wetted during the process. Niobium itself has excellent corrosion resistance. Niobium can experience hydrogen permeation, but in Figure 9 this case, the metal transfer mount 310 is a thick member under a minimum compressive load and there is no risk of material failure. The ASM Special Metals Corrosion Handbook (13B) discusses niobium and current coupling effects: "If niobium is cathodically polarized by current coupling, then niobium is susceptible to hydrogen embrittlement... However, if niobium is anodically polarized, then niobium forms a very stable passive film that protects the metal from corrosion". As Figure 10 shown in the table of, the niobium falls between 304 SST and 316 SST in the electromotive series. Thus, the metal transfer mount 310 made of niobium and attached to a 316L stainless steel isolator plug will be anodically polarized and thus protected from hydrogen embrittlement and corrosion. Thus, no gaskets will be required and all components can be wetted. The metal transfer mount 310 is connected to the isolator plug 314 by, for example, welding or brazing 326. However, other types of connections are possible.

[0045] Figure 11A simplified cross-sectional view of a portion of a sensor capsule 400 and a process connector 402 of a direct-acting pressure transmitter 405 including a non-metallic isolator system according to an embodiment. The sensor capsule 400 includes four main components: 1) a ceramic isolation diaphragm 408; 2) a ceramic base 409; 3) a metal transfer mount 410 made of, for example, Kovar; and 4) an isolator plug 414 made of, for example, 316L stainless steel. The concept of this design is similar to Figure 9 the niobium ceramic design, but this design includes copper weld joints and may include O-rings or gaskets to protect the copper weld joints from corrosion.

[0046] In Figure 11 , the process connector 402 is welded to the isolator plug at 432. The ceramic isolation diaphragm 408 is also a thin component that must deflect under temperature and pressure. Finite element analysis (FEA) has shown that the ceramic diaphragm 408 is not damaged by deflection and applied stress. The ceramic isolation diaphragm 408 is brazed or vitrified to the ceramic base 409. Both the isolation diaphragm 408 and the base 409 will be metallized on one side to allow copper weld joints.

[0047] The base 409 is a relatively thin ceramic disk that is metallized on both sides. The metallization allows brazing to attach the base 409 to the isolation diaphragm 408 on one side and to the metal transfer mount 410 on the other side. The purpose of the base 409 is to isolate stress from CTE mismatch. The CTE differences of different materials in the assembly will stress the components and joints and may cause failure. The matching materials of the base 409 and the isolation diaphragm 408 avoid these stress concentrations in the isolator 408 or in the diaphragm base joint. This improves performance by allowing a thinner isolation diaphragm 408 and limiting the aging time required for relaxation and stable joints. The isolation diaphragm 408 and the base 408 can be obtained as an assembly 413 or can be provided as components and brazed (or vitrified) together. This diaphragm base assembly 413 is then attached to the metal mount 410 via brazing.

[0048] The metal transfer mount 410 is a machined disk whose purpose is to connect the non-metallic diaphragm 408 and the base 409 to the isolator plug 414 that holds the sensor 411. Kovar and ceramic are a close CTE match, which makes Kovar a good choice for connection to the ceramic. The close CTE match minimizes stress in the assembly. Niobium can also be selected for the metal transfer mount 410. The metal transfer mount 410 such as Kovar or niobium is then welded to the stainless steel isolator plug 414 at 430. The metal transfer mount 410 can also be brazed to the plug 414 at 430.

[0049] Figure 12 is according to an embodiment and also includes a gasket 421 Figure 11Simplified cross-sectional view of a portion of a non-metallic isolator system. For example, gasket 421 can be an O-ring as shown in Figure 13 . One reason for including an O-ring is that the Kovar metal mount 410 and the stainless steel isolator plug 414 are mated. Kovar is towards the active end of the potential sequence and stainless steel is on the passive end. Directly connecting these two materials creates current coupling. If this joint is wetted, a galvanic cell will be activated and may cause Kovar deterioration (the least expensive). To protect this joint from a corrosive environment, coating or plating the cover can provide protection and eliminate the need to keep the joint dry from the process. Another reason for the O-ring is to protect the brazed joint. Brazing can be vulnerable to corrosion. Good brazing material selection can mitigate the problem and eliminate the need for an O-ring.

[0050] O-ring 421 has been designed to have some unique characteristics to ensure successful assembly. First, in Figure 12 , the consequences of O-ring failure are much less severe. This is because the process fluid will still be contained between the isolator plug 414 and the process connector 402. Over time, the process fluid in the thin gap 434 may appear between the process connector 402 and the metal transfer mount 410 and the ceramic base 409, and may cause corrosion of the brazed joint or galvanic corrosion between different materials. However, O-ring 421 will prevent the destruction of the fluid-filled cavity 406 and fluid loss. Another characteristic of O-ring 421 is that it is designed to minimize or eliminate the possibility of gasket creep by including a flow barrier and centering features. The centering feature 436 maintains the thin gap 434. However, one wall of the gland of O-ring 421 acts as a flow barrier with gap 434. These features prevent the O-ring from extruding under high pressure. The flow barrier is used to force the O-ring into the corners and energize it in such a way that the seal becomes stronger as the pressure increases.

[0051] Figure 13 Simplified cross-sectional view of a portion of the sensor capsule 500 and the process connector 502 of a direct-insert pressure transmitter 505 including a non-metallic isolator system according to an embodiment. In Figure 13 , a simplified Kovar-ceramic-ceramic system is shown where the ceramic base is eliminated. In this configuration, the isolation diaphragm 508 is directly attached to the metal mount 510, which can be made of Kovar. The Kovar and ceramic CTEs match well over a limited temperature range. Due to the higher CTE difference, the brazing process or brazed joint attaching the isolation diaphragm 508 to Kovar will result in welding pre-tension. This will help reduce the isolator effect and non-linearity that may occur when the isolation diaphragm crosses the zero plane.

[0052] The diaphragm system can also use crystalline silicon instead of ceramic as the diaphragm material. Crystalline silicon is a metalloid (neither a metal nor a non-metal) and is inert. Most acids do not affect metalloids, which would make it a good choice for a process-wetting material. Silicon has high tensile strength and compressive strength. Additionally, single-crystalline silicon has a Young's modulus (stiffness) that is 2.5 times lower than that of ceramic (such as alumina). This is advantageous because for the same pressure level, the silicon diaphragm will have a greater deflection compared to ceramic, thus reducing the impact of the isolator on sensor performance. Additionally, for the same deflection level, the silicon diaphragm will have a lower stress level compared to ceramic, thus increasing the safety margin for robustness.

[0053] Figure 14 - 16 An example design of such a configuration is shown. Figure 14 is a simplified cross-sectional view of a portion of the sensor capsule 600 and the process connector 602 of a direct-insert pressure transmitter 605 including a silicon isolator system according to an embodiment. Figure 15 shows Figure 14 a perspective view of the silicon isolation diaphragm 608 included in the sensor capsule 600 of. The silicon isolation diaphragm 608 can be metallized on one side and brazed to a metal transfer mount 610 made of, for example, Kovar (or niobium). The silicon isolation diaphragm 608 is thicker at the braze joint 638 and is etched in the fluid-filled cavity 606 to obtain better flexibility.

[0054] Figure 14 and 15 The embodiment shown in will cause the hinge point to project outward into the thin diaphragm 608, which has better flexural strength and which moves the stress away from the braze joint 638 between the Kovar and the silicon. Figure 16 shows a simplified non-scaled drawing of a strain gauge sensor 611 housed in the sensor capsule 600. The strain gauge sensor 611 can be made of silicon and is etched with an overpressure stop 640 using isotropic and anisotropic etching to prevent the isolation diaphragm 608 from rupturing under overpressure conditions. Figure 16 shows a gap 642 located between the boss 644 and the protrusion 646. The frit 648 is located on either side of the gap 642. This will also help reduce the fluid volume and improve performance.

[0055] The metal mount 610 made of niobium and Kovar can be interchangeable. The embodiment can be implemented using either material because both materials are good choices for matching the CTE of silicon. Additionally, due to the issues discussed previously in other embodiments, the sensor capsule can include a gasket or O-ring 621.

[0056] As Figures 2 - 5As in the case of the embodiments shown in FIGS. 6 - 8, tantalum can replace niobium in the above components because it also has a close CTE match with alumina. Although tantalum provides a far more difficult and intensive manufacturing process because tantalum cannot be directly bonded to ceramics by diffusion bonding and a brazed tantalum - ceramic joint will be required, brazing can be used to bond tantalum to the stainless - steel body of the isolator plug.

[0057] The concept of the plug - in system disclosed herein can be used in coplanar differential pressure measurement systems, such as Figure 1b the coplanar differential pressure system. The coplanar system presents additional challenges for the isolation diaphragm travel, but a larger isolation diaphragm can provide better flexure characteristics to address these issues. Figure 17 and 18 FIGS. 9A and 9B illustrate an embodiment of a coplanar non - metallic isolator system in a coplanar differential pressure measurement system 705. Ceramic isolation diaphragms 708 are each brazed to a metal transfer mount 710, such as made of Kovar, and act as sub - assemblies. The Kovar transfer mounts 710 are brazed or welded into a slightly modified module casting. This is the same module casting, but without the machined curl pattern and only includes cavities. The weld joints 750 can be laser, TIG, spin welding, or projection welding 752. Projection welding can help seal the fluid - filled cavity 706 near the entrance from the module housing. This would be desirable for minimizing the fluid volume. The coplanar differential pressure measurement system 705 includes O - rings 721 on the module that expose the brazed joints 754 and Kovar to the process fluid. In another design, the O - rings 721 are placed on the process flange and seal directly on the ceramic diaphragm.

[0058] This design can also be used with a "remote seal" configuration where the non - metallic isolation diaphragm is positioned away from the sensor and a fluid - filled impulse line is used to couple to the transmitter. In a "remote seal" application, the process connector can include an over - pressure stop to protect the diaphragm from rupturing in a vacuum or due to fluid expansion. The O - ring may not need to be a polymer or a sealing member, but can provide mechanical compression to the assembly. This potentially relieves higher line pressures or higher temperatures as it supports the assembly joints.

[0059] Embodiments of the present disclosure are described more fully hereinafter with reference to the accompanying drawings. Elements identified by the use of the same or similar reference numerals refer to the same or similar elements. For simplicity of illustration, certain elements may not be shown in every figure.

[0060] However, the various embodiments of the present disclosure may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. Indeed, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0061] Although the present invention has been described with reference to preferred embodiments, those skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. The non-metallic isolation diaphragm can be made of any suitable material, and the suitable materials include alumina, single crystal sapphire, zirconia or zirconia toughened alumina (ZTA), single crystal silicon, silicon nitride or silicon carbide.

Claims

1. A pressure transmitter, comprising: a process connector configured to be mounted to a process vessel carrying a process fluid; Process pressure sensors; an isolator plug coupled to the process connector and configured to receive the process pressure sensor, wherein the isolator plug includes at least one internal fluid-filled cavity in fluid contact with the process pressure sensor; at least one transfer mount, the at least one transfer mount being made of a metallic material and coupled to the isolator plug, wherein the at least one transfer mount includes an internal fluid-filled cavity in fluid communication with at least one internal fluid-filled cavity of the isolator plug; as well as and at least one isolation diaphragm exposed to the process fluid in the process connector and coupled to the at least one transfer mount, the at least one isolation diaphragm configured to transfer process pressure to the transfer mount and internal fluid-filled cavities of the isolator plug and the process pressure sensor, wherein the at least one isolation diaphragm comprises a non-metallic material or a metalloid material.

2. The pressure transmitter of claim 1, wherein the material of the at least one isolation diaphragm is the non-metallic material and comprises alumina, single crystal sapphire, zirconium oxide, or zirconium oxide toughened alumina (ZTA). 3 . The pressure transmitter according to claim 1 , wherein the material of the at least one isolation diaphragm is the metal-like material, and the metal-like material of the isolation diaphragm comprises single crystal silicon, silicon nitride or silicon carbide.

4. The pressure transmitter of claim 1, wherein the metallic material of the at least one transfer mount comprises a coefficient of thermal expansion that comprises a range of values ​​that overlaps with a range of values ​​of the coefficient of thermal expansion of the non-metallic material of the at least one isolation diaphragm. 5 . The pressure transmitter of claim 4 , wherein the metal material of the at least one transfer mount comprises tantalum, niobium, Kovar, Invar, Alloy 42, Alloy 46, or Alloy 52.

6. The pressure transmitter of claim 1 further comprising at least one base formed from a non-metallic material, the at least one base coupling the at least one isolation diaphragm to the at least one transfer mount, wherein the at least one base comprises an internal fluid-filled cavity fluidically connected to the at least one transfer mount and the internal fluid-filled cavity of the isolator plug.

7. The pressure transmitter of claim 6, wherein the non-metallic material of the base comprises alumina.

8. The pressure transmitter of claim 6, wherein the at least one isolation diaphragm is diffusion bonded to the at least one base to form a non-metallic assembly.

9. The pressure transmitter of claim 8, wherein at least one base of the non-metallic component is soldered, brazed or vitrified to the at least one transfer mount.

10. The pressure transmitter of claim 8, wherein the at least one base further comprises a groove facing the at least one transfer mount and configured to receive a gasket, wherein the gasket is configured to prevent wetting between the non-metallic component and the at least one transfer mount.

11. The pressure transmitter of claim 1 , further comprising at least one spacer configured to connect the at least one transfer mount to the isolator plug, wherein the at least one spacer comprises an internal fluid-filled cavity fluidically connected to the base, the at least one transfer mount, and the internal fluid-filled cavity of the isolator plug.

12. The pressure transmitter of claim 11, wherein the spacer is laser welded to the isolator plug, and wherein the at least one transfer mount includes a protruding feature for projection welding or soldering the at least one transfer mount to the at least one spacer.

13. The pressure transmitter of claim 1, wherein the process pressure sensor comprises a gauge pressure sensor and the pressure transmitter comprises an in-line pressure transmitter, or the process pressure sensor comprises a differential pressure sensor and the pressure transmitter comprises a differential pressure transmitter.

14. A pressure transmitter comprising: a process connector configured to be mounted to a process vessel carrying a process fluid; Process pressure sensors; an isolator plug coupled to the process connector and configured to receive the process pressure sensor, wherein the isolator plug includes an internal fluid-filled cavity in fluid contact with the process pressure sensor; a transfer mount made of a metallic material and coupled to the isolator plug, wherein the transfer mount includes an internal fluid-filled cavity that is in fluid communication with the internal fluid-filled cavity of the isolator plug; as well as a non-metallic assembly coupled to the transfer mount and including a base made of a non-metallic material and an isolation diaphragm made of a non-metallic material, the isolation diaphragm being exposed to the process fluid in the process connector and coupled to the base, wherein the base includes an internal fluid-filled cavity in fluid communication with the transfer mount and the internal fluid-filled cavity of the isolator plug.

15. The pressure transmitter of claim 14, wherein the metallic material of the transfer mount includes a coefficient of thermal expansion that includes a range of values ​​that overlaps with a range of values ​​of the coefficient of thermal expansion of the non-metallic component.

16. The pressure transmitter of claim 14, wherein the non-metallic material of the base comprises alumina and the non-metallic material of the isolation diaphragm comprises sapphire.

17. The pressure transmitter of claim 14, further comprising a spacer configured to connect the transfer mount to the isolator plug, wherein the spacer includes an internal fluid-filled cavity in fluid communication with the base, the transfer mount, and the internal fluid-filled cavities of the isolator plug.

18. The pressure transmitter of claim 14, wherein the base further comprises a groove facing the transfer mount and configured to receive a gasket, wherein the gasket is configured to prevent wetting between the non-metallic component and the transfer mount.

19. The pressure transmitter of claim 14, further comprising a gasket between the process connector and the non-metallic component, the gasket configured to prevent damage to the internal fluid-filled cavity of the isolator plug and configured to prevent gasket creep.

20. A pressure transmitter, comprising: a process connector configured to be mounted to a process vessel carrying a process fluid; Process pressure sensors; an isolator plug coupled to the process connector and configured to receive the process pressure sensor, wherein the isolator plug includes an internal fluid-filled cavity in fluid contact with the process pressure sensor; a spacer coupled to the isolator plug and including an internal fluid-filled cavity in fluid communication with the internal fluid-filled cavity of the isolator plug; a transfer mount made of a metallic material and coupled to the spacer, wherein the transfer mount includes an internal fluid-filled cavity in fluid communication with the spacer and the internal fluid-filled cavities of the isolator plug; as well as a non-metallic assembly coupled to the transfer mount and including a base made of a non-metallic material and an isolation diaphragm made of a non-metallic material, the isolation diaphragm being exposed to the process fluid in the process connector and coupled to the base, wherein the base includes an internal fluid-filled cavity in fluid communication with the internal fluid-filled cavities of the transfer mount, the spacer, and the isolator plug.

21. The pressure transmitter of claim 19, wherein the base further comprises a groove facing the transfer mount and configured to receive a gasket, wherein the gasket is configured to prevent wetting between the non-metallic component and the transfer mount.

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