Improved coplanar process fluid pressure sensor module

background Process transmitters generally include transducers or sensors that respond to process variables. Generally, the chemical or physical state of a substance, or the conversion of energy, is called a process variable. Examples of process variables include pressure, temperature, flow rate, conductivity, pH and other properties. Pressure is considered a basic process variable in that it can be used to measure flow rate, liquid level, and even temperature.

Pressure transmitters are used in industrial processes for measuring and monitoring the pressure of various industrial process fluids, such as slurries, liquids, vapors and gases in chemical, pulp, petroleum, gas, chemicals, food and other fluid processing plants. Widely used. Differential pressure transmitters generally include a pair of process pressure fluid inputs that are operably coupled to a differential pressure sensor (inside the transmitter) that responds to the pressure difference between the two inputs. Differential pressure transmitters typically include a differential pressure sensor operably coupled to a pair of isolator diaphragms. The isolator diaphragm is placed at the process fluid inlet to isolate the differential pressure sensor from the harsh process fluid being detected. Pressure is transmitted from the process fluid to the differential pressure sensor through a substantially incompressible filling fluid carried in a passage extending from the isolator diaphragm to the differential pressure sensor.

Process fluid pressure transmitters are typically coupled to the process via instrument manifolds or flanges. One type of arrangement provides an instrument manifold that presents a process fluid pressure inlet within a pair of substantially coplanar ports. One example of such a manifold is sold under the Model 305 Coplanar part number available from Rosemount Inc., Chanhassen, Minnesota. The coplanar design allows flangeless valve integration and generally provides a compact and lightweight assembly. Moreover, the coplanar design facilitates in-process calibration and provides substantially fewer potential leak points than traditional non-coplanar manifold-transmitter assemblies.

Process fluid pressure transmitters are generally considered field equipment and can be installed in the field. A "field" is generally an external area of a process facility that can be exposed to harsh climates, vibrations, humidity changes, electromagnetic or radio frequency interference, or other environmental difficulties. Therefore, the robust physical packaging of the process fluid pressure transmitter provides the transmitter with the ability to operate in the "field" for extended periods of time (eg, years) at a time.

Overview A coplanar process fluid pressure sensor module is provided. The module includes a coplanar base and a housing body. The coplanar base has a pair of process fluid pressure inlets, each with an isolator diaphragm. The housing body is coupled to the coplanar base at the junction between the coplanar base and the housing body. The differential pressure sensor is operably coupled to a pair of process fluid pressure inlets and is located in the housing body in close proximity to a coplanar base.

<figref num="1">A front view of an exemplary prior art pressure transmitter is illustrated.</figref><figref num="2">The inclined sectional view of the module housing is illustrated.</figref><figref num="3">It is a perspective view of the coplanar pressure sensor module of the prior art and the flange according to the prior art.</figref><figref num="4">An exploded perspective view of an improved coplanar pressure sensor module according to an embodiment of the present invention is shown.</figref><figref num="5">It is a cross-sectional view of the coplanar pressure sensor module according to another embodiment of the present invention.</figref>

Detailed description of the illustrated embodiment FIG. 1 illustrates a front view of an exemplary prior art pressure transmitter 100. The pressure transmitter 100 includes an electronic device housing 101 that encloses an electronic circuit and a pressure sensor module housing 102 that houses an isolator diaphragm, a pressure sensor, and associated sensor circuits. The pressure sensor module housing 102 is bolted to the pressure flange 104 by bolts 105. The bolt 105 also passes through the flange adapter joint 118. The flange adapter fitting 118 has a threading inlet that can be connected to a threading process pipe (not shown). The pressure flange 104 provides one or more process fluid pressures to the transmitter 100 for pressure measurement. The pressure transmitter 100 energizes the pressure transmitter 100 and is connected to a process loop 103 that provides bidirectional communication used in the process control system.

The pressure sensor module housing 102 includes an isolator diaphragm 110 (shown in FIG. 2) that is welded directly to the pressure sensor module housing 102. Housing 102 also includes bolt holes 112 threaded in a standard pattern around the isolator diaphragm 110.

FIG. 2 illustrates an inclined sectional view of the pressure sensor module housing 102. The differential pressure sensor 140 is located inside the pressure sensor module housing 102 and is connected to the isolator diaphragm 110 by pipes 142 and 144. The isolator diaphragm 110 is welded directly to the pressure sensor module housing 102. The circuit board 146 provides circuits related to the processing of electrical signals from the differential pressure sensor 140. The flat cable reel 148 houses a flat cable that provides electrical connectivity from the circuit board 146 to the circuitry within the electronics housing (eg, housing 101 shown in FIG. 1).

The coplanar pressure sensor module is a major factor in the total cost of the final process fluid pressure transmitter. One of the reasons for such high cost is that coplanar pressure sensor modules are made from complex stainless steel investment cast and machined parts to provide such robust parts.

According to an embodiment of the present invention, the design constraints of each part of the coplanar pressure sensor module are considered individually and adjusted according to specific requirements. The entire assembly of coplanar pressure sensor modules according to embodiments of the present invention can be more complex than prior art designs, such embodiments rely on flexibility for different applications and specific components. It gives the ability to reduce costs while potentially adding greater structural integrity to other components.

FIG. 3 is a perspective view of the prior art coplanar pressure sensor module and the pressure flange according to the prior art. As illustrated in FIG. 3, the pressure sensor module 102 is a single-body investment cast stainless steel machined part. In contrast, FIG. 4 illustrates an exploded perspective view of an improved coplanar pressure sensor module according to one embodiment of the present invention. In this embodiment, module 192 includes a plurality of components. Specifically, module 192 includes a coplanar base 194 and housing 196. The housing 196 is preferably threaded. The coplanar base 194 and threaded housing 196 were assembled together during module manufacturing, and the completed assembly is visually similar to the prior art coplanar pressure sensor module 102. The coplanar base 194 and the housing body 196 come into contact at the joint. As used herein, a junction is intended to mean a point, line, surface or position where two different components come into contact. The coplanar base 194 can be made from investment casting, but can also be forged and even cut from plate metal materials. The threaded housing body 196 can be cast, forged, compression molded, threaded and assembled from pipe metal material. According to one embodiment, the coplanar base 194 and the threaded housing body 196 can be made of different materials. This difference can be clearly demonstrated by different grades of stainless steel, for example, the coplanar base 194 can be made from 316 stainless steel, while the threaded housing 196 can be made from 304 stainless steel or carbon steel. Can be done. In embodiments where both components are made of the same basic material, eg stainless steel, the two components can be welded together using a method, eg TIG welding. However, embodiments of the present invention include different metals, eg, those used for coplanar bases. For example, it also includes making the threaded housing body 196 from aluminum. In such an embodiment, direct welding between the stainless steel coplanar base 194 and the aluminum threaded housing body 196 is not practical. Instead, the two components are preferably mechanically fixed together using shrink fit and aging. Aging is a well-known process used to change (decrease or increase) the diameter of pipes and / or pipes.

As illustrated in FIG. 2, the differential pressure sensor 140 can be of a generally cylindrical type. According to embodiments of the present invention, the coplanar base 194 can include a bowl or dish-shaped recess 198 that allows the pressure sensor 140 to be placed lower than the prior art module. This also reduces the overall height of the entire assembly and also reduces material costs. Smaller physical sizes generally provide the effect of lower material costs. To further reduce the size of the coplanar pressure sensor module assembly 192, the circuit board 146, which is usually provided inside the pressure sensor module, can be completely removed and installed in the upper electronics housing 101. This makes it possible to further reduce the height of the housing. Such reductions in height and width allow the use of thinner walls, further reducing material costs. In some embodiments, a temperature sensor can also be provided within the threaded housing body to assist in providing accurate temperature compensation for pressure.

FIG. 5 is a cross-sectional view of the coplanar pressure sensor module according to another embodiment of the present invention. Module 292 differs from Module 192 (shown in Figure 4) in that it is made up of three distinct components. Specifically, module 292 is made from coplanar base 294, tubular housing 296 and stiffener 300. In the embodiment illustrated in FIG. 5, the most complex part of the assembly is the coplanar base 294. Preferably, the component is relatively thinner when compared to the coplanar base 194 and uses metal injection molding, or some other suitable technique suitable for the manufacture of complex shapes and components. Is formed. Due to its thinner construction, the base 294 is generally not stiff enough on its own to form a strong seal against the process flange. Alternatively, a stiffening plate 300 is provided that presses the coplanar base 294 at the joint 302. The stiffening plate 300 preferably includes a plurality of bolt holes that allow the assembly 292 to be mounted in a coplanar manifold in exactly the same manner as the prior art design. However, if the specific product application requires extremely high pressure, such considerations can be included by simply providing a stronger or thicker stiffening plate 300.

The threaded housing body 296 preferably comprises a lip 304 having a diameter larger than the opening 306 through which the tubular housing 296 passes. Therefore, when the reinforcing plate 300 is fixed in place, the threaded housing body 296 is sandwiched between the reinforcing plate 300 and the base plate 294. The threaded housing body 296 preferably accommodates an elastomer O-ring that seals the threaded housing body 296 and the coplanar base 294 when the threaded housing body 296 is sandwiched between the reinforcing plate 300 and the base plate 294. Includes an O-ring recess 308 configured in.

Although the present invention has been described with reference to preferred embodiments, one of ordinary skill in the art will appreciate that changes in form and detail can be made without departing from the essence and scope of the invention.