Temperature compensated differential pressure system

A temperature compensated differential pressure system is provided. The system includes a pair of flanges affixed together each having a flange diaphragm therein, wherein a plurality of capillary tubes extends between the pair of flanges and a pair of opposed remote diaphragm housings. The remote diaphragm housings include a remote diaphragm therein, wherein the remote diaphragm displaces a fill fluid in pressure capillaries to displace each flange diaphragm to detect a differential pressure between each location of the remote diaphragm housings. A compensating capillary extends from the remote diaphragm housings to an opposing flange diaphragm, wherein the compensating capillary is not in operable communication with the remote diaphragms. As such, any fluctuation in fill fluid volume of the compensating capillaries due to temperature fluctuations is applied to an opposing flange diaphragm to cancel temperature effects from the differential pressure determination.

BACKGROUND OF THE INVENTION

The present invention relates to remote differential pressure systems. More particularly, the present invention pertains to a remote differential pressure system having temperature compensation to eliminate temperature effects on the differential pressure detected by the system.

Many commercial and industrial processes require differential pressure monitoring to determine the pressure at two distinct points in a process. This is often measured utilizing diaphragm seals in communication with a closed fluid system, such the diaphragm is displaced upon the application of pressure, which then displaces the fluid to actuate a pressure gauge or other pressure sensor. Particularly, in differential pressure monitoring systems, two remote diaphragm seals are placed at distinct points in the process to measure pressures at those points, which are then compared at a joint pressure measurement device. However, as the different points in the process may significantly vary in location and exposure to the elements, the temperature at each remote diaphragm seal may differ significantly. As the fill fluid in the closed pressure system is similarly exposed to such differences in pressure, the fill fluid will expand or contract, thereby affecting the measured pressure the pressure sensor.

For example, a diaphragm seal at a high-pressure side of a process may be submerged within a vessel, whereas the opposing diaphragm seal at the how-pressure side of the process may be located outdoors exterior to the tank. On a hot day, the fill fluid on the low-pressure side may expand significantly, while the fill fluid on the high-pressure side may be comparably unaffected by the ambient temperature change. As a result, the reported differential pressure includes internal system pressure changes due to temperature fluctuation and is therefore inaccurate. As the expansion of the fill fluid on a single side of the differential pressure monitoring system affects the transmission of pressure from the remote diaphragm seal to the pressure sensor, the low-pressure side will report a combination of the desired local pressure measurement and the temperature effects on the internal pressure of the fill fluid. Therefore, a device that can compensate for temperature fluctuations on opposing sides of the pressure sensor in an efficient manner, such that accurate differential pressure readings are provided is desired.

In light of the devices disclosed in the known art, it is submitted that the present invention substantially diverges in design elements from the known art and consequently it is clear that there is a need in the art for an improvement to existing remote differential pressure systems. In this regard, the instant invention substantially fulfills these needs.

SUMMARY OF THE INVENTION

In view of the foregoing disadvantages inherent in the known types of remote differential pressure systems now present in the known art, the present invention provides a temperature compensated differential pressure system wherein the same can be utilized for providing convenience for the user when determining an accurate differential pressure between two points irrespective of fluctuations in pressure due to temperature changes.

The present system comprises a first flange affixed to a second flange, wherein the first flange comprises a first flange diaphragm therein and the second flange comprises a second flange diaphragm therein. A plurality of capillary tubes comprises a first pressure capillary tube, a second pressure capillary tube, a first compensating capillary tube, and a second compensating capillary tube. The first pressure capillary tube extends through a first flange inlet and is in operable communication with the first flange diaphragm. The first compensating capillary tube extends through the first flange inlet and is in operable communication with the second flange diaphragm. The second pressure capillary tube extends through a second flange inlet and is in operable communication with the second flange diaphragm. The second compensating capillary tube extends through the second flange inlet and is in operable communication with the first flange diaphragm. Each of the plurality of capillary tubes comprises a fill fluid therein. A first remote diaphragm housing includes a first remote diaphragm therein, wherein an opposing end of the first pressure capillary tube is in operable communication with the first remote diaphragm. A second remote diaphragm housing includes a second remote diaphragm therein, wherein an opposing end of the second pressure capillary tube is in operable communication with the second remote diaphragm. As each of the first and second remote diaphragms is displaced via pressure in a media, the pressure is transmitted to the first and second flange diaphragms via the first and second pressure capillary tubes, respectively.

In some embodiments, a first capillary housing is disposed about the first pressure capillary tube and the first compensating capillary tube, and a second capillary housing is disposed about the second pressure capillary tube and the second compensating capillary tube. In another embodiment, each of the first capillary housing and the second capillary housing comprises an articulated metal enclosure. In other embodiments, a vacuum is maintained within each of the first capillary housing and the second capillary housing. In yet another embodiment, the first pressure capillary tube is maintained parallel to the first compensating capillary tube between the first remote diaphragm housing and the first flange, and the second pressure capillary tube is maintained parallel to the second compensating capillary tube between the second remote diaphragm housing and the second flange. In some embodiments, each of the first flange inlet and the second flange inlet comprises a pair of openings, wherein each opening of the pair of openings receives one of the plurality of capillary tubes therethrough. In another embodiment, the first compensating capillary tube is equal in volume to the second compensating capillary tube. In other embodiments, a remote end of each of the first compensating capillary tube and the second compensating capillary tube is closed. In yet another embodiment, a forward portion of each of the first compensating capillary tube and the second compensating capillary tube is angled to bypass the first flange diaphragm and the second flange diaphragm, respectively. In some embodiments, the first compensating capillary tube and the second compensating capillary tube extend through a gap defined between each of the first flange and the second flange to enter an opposing flange. In another embodiment, the forward portion of each compensating capillary tube traverses through a channel defined through each of the first flange and the second flange. In other embodiments, a gap is defined between the first flange and the second flange, the gap dimensioned to removably receive a differential pressure measurement device therebetween. In yet another embodiment, the first flange is secured to the second flange via a plurality of fasteners, wherein the plurality of fasteners is disposed on opposing lateral sides of each of the first flange and the second flange. In some embodiments, the first compensating capillary tube and the second compensating capillary tube extending between the first flange and the second flange are disposed parallel and adjacent to at least one of the plurality of fasteners. In another embodiment, at least one fill port is disposed within each of the first flange and the second flange, wherein the fill port is in fluid communication with an interior volume of one of the plurality of capillary tubes. In other embodiments, each of the first remote diaphragm housing and the second remote diaphragm housing comprises a media inlet in operable communication with the first remote diaphragm and the second remote diaphragm, respectively. In yet another embodiment, the media inlet extends from a front side of each of the first remote diaphragm housing and the second remote diaphragm housing to the first remote diaphragm and the second remote diaphragm, respectively. In some embodiments, each of the plurality of capillary tubes is welded in place within the first flange inlet and the second flange inlet. In another embodiment, the first flange inlet and the second flange inlet each include a flange shroud extending over a portion of the first capillary housing and the second capillary housing, respectively. In other embodiments, the first remote diaphragm housing and the second remote diaphragm housing comprise a remote shroud extending over a portion of the first capillary housing and the second capillary housing, respectively.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made herein to the attached drawings. Like reference numerals are used throughout the drawings to depict like or similar elements of the temperature compensated differential pressure system. The figures are intended for representative purposes only and should not be considered to be limiting in any respect.

Referring now toFIG.1, there is shown a perspective view of an embodiment of the temperature compensated differential pressure system. The temperature compensated differential pressure system11comprises a first flange12affixed to a second flange13via a plurality of fasteners36. In the shown embodiment, the plurality of fasteners36comprise a series of bolts, however, other means of securing the first flange12to the second flange13are contemplated. The first and second flanges12,13are secured together defining a gap therebetween, such that a differential pressure measurement device35can be secured between the first and second flanges12,13within the gap. The differential pressure measurement device35can comprise a differential pressure transmitter, gauge, or other measurement device. In the shown embodiment, the differential pressure measurement device35includes a display screen for displaying a detected difference in the pressures detected at each of the first and second flanges12,13as further described elsewhere herein.

The temperature compensated differential pressure system11further comprises a first remote diaphragm housing24operably connected to the first flange12, and a second remote diaphragm housing26operably connected to the second flange13. In operation, the first and second remote diaphragm housings24,26are placed in remote locations that the user wishes to determine a differential pressure between. For example, the first remote diaphragm housing24can be placed within a vessel and the second remote diaphragm housing26can be placed exterior to the vessel, such that the detected differential pressure can be utilized to determine the volume of fluid presently within the vessel. The operation of the temperature compensated differential pressure system11will be further discussed elsewhere herein.

The first and second flanges12,13are operably connected to the first and second remote diaphragm housings24,26via a plurality of capillary tubes as further described in relation toFIG.2of the present disclosure. In the shown embodiment, the plurality of capillary tubes is encased within a first capillary housing28between the first remote diaphragm housing24and the first flange12, and a second capillary housing29between the second remote diaphragm housing26and the second flange13, respectively. In this manner, the plurality of capillary tubes is shielded to minimize damage thereto, as well as reducing wear and tear during use. In sonic embodiments, an interior volume of the first and second capillary housings28,29are maintained at a vacuum so as to reduce heat transfer between the surrounding area and the plurality of capillary tubes. The temperature compensated differential pressure system11comprises a closed system, wherein the ambient pressure of the surrounding area is sampled at the first and second remote diaphragm housings24,26and transmitted to the first and second flanges12,13via the plurality of capillaries. In the shown embodiment, the connection between the first and second capillary housings28,29and each of the first and second remote diaphragm housings24,26are protected by a rigid remote shroud41extending over a portion of each of the first and second capillary housings28,29. The remote shroud41provides structural integrity to the connection between the first and second capillary housings28,29and the first and second remote diaphragm housings24,26. Similarly, in the shown embodiment, a rigid flange shroud42extends from the first and second flanges12,13over a portion of the first and second capillary housings28,29to increase the structural integrity of a connection therebetween. In this manner, the remote shrouds41and the flange shrouds42protect the first and second capillary housings28,29at each end thereof, such that the connections are maintained.

Referring now toFIG.2, there is shown a lower cross-sectional view of an embodiment of the temperature compensated differential pressure system. The first flange12further comprises a first flange diaphragm14therein, wherein the first flange diaphragm14is in operable communication with a first remote diaphragm25disposed within the first remote diaphragm housing24via a first pressure capillary tube17. The first pressure capillary tube17extends into the first flange12via a first flange inlet21, wherein the first flange inlet21retains file first pressure capillary tube17therein. The first pressure capillary tube17comprises a fill fluid therein, such that as the first remote diaphragm25is displaced by local pressure in the first remote location, the fill fluid is displaced, thereby transferring the pressure detected from the first remote diaphragm25to the first flange diaphragm14, Similarly, the second remote diaphragm housing26includes a second remote diaphragm27therein, wherein the second remote diaphragm27is in operable communication with a second flange diaphragm15disposed within the second flange13via a second pressure capillary tube18. The second pressure capillary tube18extends into the second flange13via a second flange inlet22, wherein the second flange inlet22retains the second pressure capillary tube18therein. As the second remote diaphragm27is displaced via pressure at the second remote location, the second pressure capillary tube18transfers the pressure to the second flange diaphragm15, such that the first and second flange diaphragms14,15transmit the two detected pressures to the differential pressure measurement device therebetween.

Due to operating conditions, the differential pressure between the first and second remote diaphragm housings24,26may be misreported as additional external effects are applied to the first and second pressure capillary tubes17,18, respectively. Particularly, as the temperature between the two remote locations can significantly differ, the first and second pressure capillary tubes17,18report a combination of the detected pressure and any fluctuations of fill fluid pressure caused by temperature differences. As such, the system further comprises an additional compensating capillary tube on each of the high-pressure side and the low-pressure side of the system. A first compensating capillary tube19is in operable communication with the second flange diaphragm15, whereas a second compensating capillary tube20is in operable communication with the first flange diaphragm14. The first and second compensating capillary tubes19,20extend towards the first and second remote diaphragm housings24,26, respectively, however each of the first and second compensating capillary tubes19,20are separate from the first and second remote diaphragms25,27. As such, the only pressure effects on the fill fluid within the first and second compensating capillary tubes19,20are temperature related. Therefore, as the first and second compensating capillary tubes19,20bypass the first and second flange diaphragms14,15to apply pressure against the opposing flange diaphragm, the first and second compensating capillary tubes19,20offset the pressure effects of temperature fluctuations on each of the high-pressure and low-pressure sides of the temperature compensated differential pressure system.

Referring now toFIG.3, there is shown a cross-sectional view of a remote diaphragm housing of an embodiment of the temperature compensated differential pressure system. In the shown embodiment, a single remote diaphragm housing, particularly the first remote diaphragm housing24, and its associated elements for brevity, however, it should be understood that the second remote diaphragm housing comprises an identical and mirrored configuration. In the shown embodiment, the first remote diaphragm housing24includes a first remote diaphragm25therein, wherein the first remote diaphragm25is configured to be displaced upon an application of pressure from an outlying media exterior to the first remote diaphragm housing24. The first pressure capillary tube17is in operable communication with the first remote diaphragm25, such that displacement of the first remote diaphragm25affects the fill fluid within the first pressure capillary tube17, thereby allowing the first pressure capillary tube17to transmit the displacement pressure of the first remote diaphragm25. In the illustrated embodiment, the external pressure is applied via a media inlet39disposed on a front side40of the first remote diaphragm housing24. The media inlet39is configured to allow the external media, such as a fluid within a vessel or surrounding atmosphere, to displace the first remote diaphragm25. Upon displacement of the first remote diaphragm25, the pressure of the fill fluid within the first pressure capillary tube17transmits the detected pressure to the first flange diaphragm. In this way, the user can sample the pressure at a remote location via placement of the first remote diaphragm housing24in the remote location.

The first capillary housing28extends from the first remote diaphragm housing24about each of the first pressure capillary tube17and the first compensating capillary tube19. In the illustrated embodiment, the remote shroud42extends over a portion of the first capillary housing28providing an additional layer of protection to the plurality of capillaries in addition to that provided by the first capillary housing28. As the remote shroud42extends over the portion of the first capillary housing28directly connected to the first remote diaphragm housing24, the remote shroud42adds further protection to the weakest point of the first capillary housing28. In the shown embodiment, the first capillary housing28comprises an articulated material having a plurality of recesses therein, allowing the first capillary housing28to flex about the recesses. In this manner, the user can position the plurality of capillaries in a plurality of configurations to ensure the temperature compensated differential pressure system is capable of use in a variety of process configurations, such as angled or curved positions as required by geometries present at the desired location. In some embodiments, the first capillary housing28comprises a durable metallic material to increase the protection provided to the capillaries disposed within the first capillary housing28. In the shown embodiment, the first compensating capillary tube19comprises a closed remote end31adjacent to the first remote diaphragm housing24, such that the first compensating capillary tube19is unassociated with the first remote diaphragm25. In this manner, the first compensating capillary tube19does not transmit any displacement pressure from the first remote diaphragm25, ensuring that the first compensating capillary tube19only transmits changes due to temperature fluctuations resulting in expansion or contraction of the fill fluid within the first compensating capillary tube19.

In the shown embodiment, the first pressure capillary tube17and the first compensating capillary tube19are maintained in a parallel relationship relative to each other within the first capillary housing28. This parallel relationship results in each capillary following a similar path, thereby minimizing minor differences in pressure caused by resistance due to curves or angles defined within each capillary tube17,19. In this manner, the system negates fluctuations in pressure caused by capillary geometry to ensure that the first compensating capillary tube19corrects solely for pressure fluctuations due to temperature differences between each side of the system.

Referring now toFIG.4, there is shown a cross-sectional view of the flanges of an embodiment of the temperature compensated differential pressure system. The first flange12is affixed to the second flange13via the plurality of fasteners36extending through opposing lateral sides of the first and second flanges12,13, such that a gap is formed therebetween. The gap is dimensioned to receive the differential pressure measurement device therein, such that the differential pressure measurement device is in operable communication with each of the first and second flange diaphragms14,15. The first flange inlet21is dimensioned to receive each of the first pressure capillary tube17and the first compensating capillary tube19therethrough. Similarly, the second flange inlet22is dimensioned to receive each of the second pressure capillary tube18and the second compensating, capillary tube20therethrough. In some embodiments, each of the first flange inlet21and the second flange inlet22comprise a plate having a pair of openings30therethrough, wherein each of the pair of openings30receives one of the plurality of capillaries therethrough. In this manner, the plurality of capillaries is maintained in a parallel configuration. In some such embodiments, the plurality of capillaries is welded in place within the pair of openings30, further securing the plurality of capillaries in position. In the shown embodiment, the flange shrouds41extend from a perimeter of the first and second flange inlets21,22to extend over a portion of the first and second capillary housings to further protect and secure the plurality of capillaries to the flange.

The first compensating capillary tube19bypasses the first flange diaphragm14and extends through the gap between the first and second flanges12,13to operably connect to the second flange diaphragm15. Similarly, the second compensating capillary tube20bypasses the second flange diaphragm and extends through the gap between the first and second flanges12,13to operably connect to the first flange diaphragm14. In the shown embodiment, a forward portion32of each compensating capillary tube is angled to bypass the first and second flange diaphragms14,15through a channel34defined through each of the first and second flanges12,13. The channel34anchors the forward portion32within the first and second flanges12,13to stabilize and protect the first and second compensating capillary tubes19,20. In the illustrated embodiment, the portion of each of the first and second compensating capillary tubes19,20extending through the gap between the first and second flanges12,13extends parallel and adjacent to one of the plurality of fasteners36. In this manner, the exposed portion of the compensating capillary tubes is provided additional protection from external sources of damage. In some such embodiments, the exposed portion of the compensating capillary tubes is disposed between two fasteners of the plurality of fasteners36for maximal protection. As the first and second compensating capillary tubes19,20are in operable communication with the opposing flange diaphragm and separate from the first and second remote diaphragms, the first and second compensating capillary tubes19,20serve to offset the temperature fluctuations present within the first and second pressure capillary tubes17,18. In the shown embodiment, a fill port38is disposed in each of the first and second flanges12,13, wherein the fill port38is in fluid communication with an interior of at least one of the plurality of capillaries. In this manner, the fill port38allows the user to add or remove fill fluid from the plurality of capillaries as necessary to maintain proper operation of the temperature compensated differential pressure system.

In one use, the first remote diaphragm housing is placed at a high-pressure side of a process and the second remote diaphragm housing is placed at a low-pressure side of the process, such that the local pressure at each location can be sampled by the first and second remote diaphragms, respectively. As the remote diaphragms are displaced by the ambient pressure of the surrounding media, the displacement pressure is transferred into the fill fluid within the first and second pressure capillary tubes17,18to similarly displace the first and second flange diaphragms14,15. The first and second compensating capillary tubes19,20are unassociated with either of the remote diaphragms, such that the only fluctuations in fill fluid pressure therein is due to changes in ambient temperature at each of the high-pressure and low-pressure sides of the process. The first and second compensating capillary tubes19,20are operably connected to opposing flange diaphragms14,15, such that the pressures applied to the first and second flange diaphragms14,15offset the pressures applied by the first and second pressure capillary tubes17,18. As each pair of capillary tubes on each side of the system is exposed to the same ambient temperature, the expansion or contraction of the fill fluid of each of the pair of capillaries is identical. Therefore, the compensating capillary tubes19,20negate the temperature fluctuations of the first and second pressure compensating tubes17,18to ensure an accurate differential pressure is measured between the high-pressure and low-pressure sides of the system.