Patent Application
20190003871
The present invention is related to tanks, pipes, conduits and system used for containing and transporting gases, liquids and multiphase hazardous materials properties, especially those having corrosive and reactive properties.
More particularly, the present invention is related to in situ measurement of the physical properties of the gasses, liquids and multiphase materials, especially those being designated as hazardous.
Recently, the Environmental Protection Agency and the Department of Transportation, as well as many state and local jurisdictions, have promulgated new rules regarding the proper handling, storage and transportation of many classes of hazardous materials (Hazardous Materials Regulations (HMR) USC 49 Parts 100-185), as well as designated new material as being hazardous. These new rules include new and upgraded designs for railcar tanks, trailer-tanks and mariner containers, heightened standards for terrestrial storage and processing tanks, as well as augmented rules for safe operation. While the bulk of the rule-making focuses on improved structural and mobility designs, others require new “safe-handling” and transportation procedures for the material as well as augmented monitoring, handling and transportation procedures especially for legacy structures that do not, or cannot conform to the new design regulations.
For the purposes of this discussion, hazardous materials include the following non-exhaustive list of hazardous categories: explosives; gases (flammable, nonflammable, nonpoisonous (nontoxic) compressed gas, poisonous (toxic) by inhalation; flammable liquids); flammable solids and reactive solids/liquids (flammable solid, spontaneously combustible material, dangerous when wet material); oxidizers and organic peroxides; poisonous (toxic) materials and infectious substances; radioactive materials; corrosive materials; and miscellaneous hazardous materials.
As mentioned above, the U.S. (as well as many state governments) have implemented new regulated designs essentially to provide further enhancements for containing hazardous materials, mitigating the spread of materials and limiting the exposure of the public in case of an accidental release, limiting the exposure of the public and monitoring the physical state of these materials.
As a practical matter, the benefits provided by many of these new regulations are offset, at least partially, by the reduction in risk and mitigation of exposure that the accidental release of these material may cause. The unchecked release of toxic, corrosive, radioactive, reactive or flammable materials into the environment can have a permanent effect on the environment, ecosystem and human habitation in the vicinity of the release.
With specific regard to liquids, gases and multi-phase (state) materials, many of these new regulations apply specifically to enhancing the structural design of containers, either static or transportation. New guidelines for construction practices, containment strength, materials section and reinforcing potential crumple zones enhance integral safety, while new operating procedures relate, at least partially, to safe storage and operating procedures, including enhanced material state monitoring procedures. This includes incorporating standards on materials in physical states that, heretofore, were considered safe and exempt from extensive monitoring, for example, extremely low pressure applications that scarcely differ from hydrostatic level.
Pressure sensors are well known in the prior art, such as deflection-type (see
Deflection-type pressure sensors have one interesting feature, as the area, a1, of the piston exposed to the external pressure, p1, is increased for the deflection piston/diaphragm, the force (p1×a1) on the biased diaphragm increases and therefore, assuming the biasing is constant, deflection, d1, increases, thereby increasing the dynamic measurement range of the device. Hence, although deflection-type pressure sensors are generally regarded for application in mid- to high pressure applications, it is possible to configure these sensors for measuring fairly low pressures. Deflection-type pressure sensors are highly accurate and produced in quantity, fairly inexpensive, however, as they utilize multiple moving parts, are prone to wear and ultimately, failure. With the advent of piezoelectric, piezo-resistive and piezo-capacitive devices, piezoelectric elements have been employed in piezoelectric-type pressure sensors that accurately measure pressures without any (or very slight) movements.
Piezoelectric-type pressure sensors, such as exemplary piezoelectric-type pressure sensor 200 depicted in
While both deflection-type and piezoelectric-type pressure devices have been extremely successful, their acceptance has largely been limited to general use applications. Conversely, special-use pressure sensors are sometimes extraordinarily expensive. For example, proposed environmental rule changes will re-classify low- and no-pressure chemical tanks (see the chemical tank depicted in
What is needed is an inexpensive pressure sensor, accurate in low and ultra-low pressure environments that is accurate and capable of prolonged, uninterrupted in situ service with hazardous chemicals.
The present invention is directed to in situ monitoring of low pressure, hazardous chemicals. A pressure sensor system is presented for accurately measuring low and ultra-low pressures. A sealed pressure bladder is formed from a pliable, yet chemically resistant material fluoropolymer, such as FEP (fluorinated ethylene propylene) or PFA (perfluoroalkoxy polymer sometimes referred to improperly as MFA). FEP has a working temperature of between −100° F. and 400° F., is chemically inert, a good transmitter of ultraviolet rays and, importantly, chemical and corrosion resistance. The texture of FEP fluoropolymer ranges between somewhat pliable to very soft and, therefore, may need additional structural support in certain applications. The pressure bladder is filled with an inert, non-reactive, stable fluid and is hydraulically coupled to a pressure sensor for measuring pressure. The fluid fills the pressure bladder and a measurement chamber of the pressure sensor. The pressure bladder is immersed in a fluid medium contained in a reservoir for monitoring the pressure of the fluid medium. Optimally, the pressure sensor's electronics are hydraulically isolated from the fluid medium and the hydraulic pressure of the reservoir. The pressure sensor is electrically connected to external electrical conductors that provide an electrical connection to electrical monitoring/processing equipment for powering the sensor and receiving its output signals. This bladder configuration insulates the internal components of the pressure sensor from the fluid medium contained in the reservoir, in so doing is particularly useful for monitoring the pressure of hazardous mediums.
In accordance with one exemplary embodiment of the present invention, the pressure bladder forms substantially cylindrically shaped interior chamber having a closed distal end and an open proximate end. The open end of the cylindrically shaped interior chamber is hydraulically coupled to a substantially cylindrically shaped support mandrel with a second substantially cylindrically shaped interior chamber. The second substantially cylindrically shaped interior chamber has a smaller diameter than the bladder and the walls of the mandrel are much thicker, thereby forming a more rigid cylinder. The capillary tube provides a hydraulic path for the fluid that transmits pressures between the pressure bladder and sensor.
The support mandrel serves three purposes: it provides the rigidity necessary for securing a hydraulic fitting for isolating the sensor from the reservoir; it provides a path between the pressure bladder and sensor for communicating pressures; and it provides a structure for mechanically coupling the sensor. Fluoropolymer materials lend themselves to various economical fabrication techniques. Fluoropolymer rods can be easily drilled and shaped. They form good hydraulic coupling with other types of plastic, metals and ceramics. Fluoropolymer materials can be permanently jointed together. Most fluoropolymers, including PTFE, FEP, PFA or ETFE, can be welded and FEP welds form secure, strong and waterproof joints.
Although many off-the-shelf (OTS) pressure sensors are fitted with a barbed port for connecting to a flexible tube, a more secure connection with the mandrel is achieved by trimming the barbed fitting with the threaded die, thereby fashioning a male thread on the sensor, and then using that threaded port for attaching the sensor to the capillary tube of the mandrel.
The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings wherein:
FIG. 4B1 is a series of diagrams depicting FEP tubing coupling using a support mandrel having a smaller outer diameter than the pressure bladder in accordance with one exemplary embodiment of the present invention;
FIG. 4B2 is a series of diagrams depicting FEP tubing coupling using a support mandrel and a pressure bladder with identical outer diameters in accordance with one exemplary embodiment of the present invention;
FIG. 4G1 is a cross-sectional diagram of pressure sensors with barbed fitting connection to the mandrel and a spiral wire nut tubing clamp in accordance with one exemplary embodiment of the present invention;
FIG. 4G2 is a cross-sectional diagram of pressure sensors with threaded fitting connection to the mandrel in accordance with one exemplary embodiment of the present invention;
FIG. 4G3 is a cross-sectional diagram of pressure sensors with spiral barbed fitting connection to the mandrel and a crimp tubing clamp in accordance with one exemplary embodiment of the present invention;
Other features of the present invention will be apparent from the accompanying drawings and from the following detailed description.
indicates data missing or illegible when filed
In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized. It is also to be understood that structural, procedural and system changes may be made without departing from the spirit and scope of the present invention. The following description is, therefore, not to be taken in a limiting sense. For clarity of exposition, like features shown in the accompanying drawings are indicated with like reference numerals and similar features as shown in alternate embodiments in the drawings are indicated with similar reference numerals.
The need for accurate low pressure monitoring abound in industry, especially chemical, petroleum, transportation and facilities management. Storage tanks, i.e., gas, petroleum, chemical, water, etc. (see storage tank in
Another application where monitoring accurate pressure values is critical is in gas, liquid and multi-phase towers, tanks and separators (see separator tank in
Still another, and possibly most controversial application for monitoring pressure values is in small, usually independently operating, chemical injection tanks (see chemical tank in
Structurally, these types of chemical tanks cannot support an internal pressure or vacuum. By design, they rely exclusively on open venting for equalizing the tank's internal pressure. Furthermore, chemical injection tanks of the types discussed here are typically manufactured with a delivery port near the bottom of the tank, in order to accommodate gravity feed rather than internal pumps to reduce the chance of a tank implosion from a vacuum condition created by suction fed pumps. Chemical injection tanks are usually manufactured with integrated poly legs and strap guides for easy mounting on an elevated steel or poly frame. They are usually equipped with an oversized fill port at the top for refilling chemicals. Until recently, the only environmental requirement was the placement of spill containment basin directly under the tank (usually 110% volume of the tank's capacity).
Cracks and splitting have occurred in poly chemical injection, but on extremely rare occasions and are usually as a result of another factor, such as UV degradation, freezing, improper heating or vacuum implosion. However, recent clean air rules that no longer permit the unchecked venting of pipeline injection chemicals into the atmosphere, will require significant upgrades to most of these types of tanks. Firstly, with the exception of filling and maintenance, the injection tanks must be sealed completely and air tight. This greatly increases the likelihood of internal pressure spikes. Also, chemical vapors must be recaptured, usually by recirculating them into the injection system, which increases the likelihood of internal vacuum spikes. Therefore, chemical injection tanks that previously relied on passive monitoring and containment techniques now require active monitoring, especially of internal tank pressure. Fortunately, most chemical injection tanks operate in close proximity of some type of monitoring system, such as the Advantis Monitoring System (AMS) (available from Advantis, L.L.C. in Marshall, Tex.). However, low pressure sensors, of the type suitable for operation with hazardous chemicals, are extremely expensive; a single sensor can cost the equivalent of the 125 gallon poly tank it is intended to monitor.
Finally, maybe the most critical need for the in situ monitoring of internal pressure values is in the transportation industry. At any moment, tens of thousands of chemical tanks are being moved by truck, rail or ship. Accidental discharge of the chemical contents of these tanks usually occur in one of three ways: transportation related accident (collision, derailment, or grounding), uncontrolled reaction (a rapid or unexpected change in the properties of the chemical contents of the tank), or mechanical failure (a leak developing in one of the tank's systems). Of the three, transportation related accidents are usually considered the most dangerous, and, although marine accidents have the potential for releasing much greater amounts of chemicals, rail accidents are considered more dangerous because of the potential spill amount, the proximity to human habitation, as well as shifting weather patterns that may subject entirely different populations to the effects of airborne contaminants. Typically, the response from regulators is almost universal to require more stringent structural and crash guidelines (the “build it stronger” response).
With further reference to the rail industry, new regulations for chemical tanks rail cars, such as that depicted in
In addition to the in situ monitoring systems and communications link described above, each tank would require an electrical power supply and, perhaps, a backup source. For rail cars, this probably requires modifying each car with a system of rechargeable batteries and a generator, probably mechanically coupled to its wheels. An alternative proposed by the Department of Transportation is to place electronic interrogators at fixed locations along the rail- or road-way. These electronic interrogators would optically identify the tank for identifying numbers or patterns (or by RFID) and then simultaneously interrogate passing tanks using an onboard transceiver coupled to the monitoring system by issuing a specific ‘wake-up’ call to the tank based on the tank's unique identification. These transceiver interrogation systems are well known and in extensive use in the utilities industry, water and gas especially, wherein a transceiver, powered by a lithium battery, is connected to the water (or gas) meter and is “read”, or interrogated by a reader vehicle as it passes the property location. With regard to the transportation industry, the reading received at the integration location would be immediately passed to the owner/operators of the tank, who then verify that the monitored values are within tolerances for the chemical being transported. If not, the driver/operator is notified and given precise instructions. Interestingly, the DOT further proposes designated safe areas where a tank can be parked for servicing. With regard to rail, DOT has proposed creating and improving emergency spurs for the fast decoupling of single cars for safe servicing. The Department of Homeland Security, although not directly involved, has endorsed these improvements in its counterterrorism efforts.
Here again, with regard to the transportation of chemical tanks, the relative expense of low pressure sensors capable of accurate operation in hazardous conditions is a paramount concern for regulators and operator. What is needed is an accurate low pressure sensor, extremely reliable, relatively inexpensive pressure sensor, but that can be exposed to and operate in hazardous materials.
Before continuing, it should be mentioned that some sources make a distinction between sensors and transducers and provide varying support for the distinctions between the types of pressure measuring devices. For the purposes of the descriptions of the present invention, the term pressure sensor and the term pressure transducer may be considered as synonymous, as both will sense a pressure as a physical quantity and then transform that pressure quantity into a signal (electrical). Inexpensive pressure sensors exist. Highly accurate pressure sensors exist that are relatively inexpensive. However, none of the aforementioned sensors will operate in hazardous environments.
Typically, sensors that are designed to operate in hazardous environments have the pressure sensing element shielded by a material that will not degrade with exposure to a wide range of reactants, oxidizers, corrosives and other classes of hazardous materials and one that will communicate external pressure internally, to the pressure sensing material. This is often a rather difficult engineering feat, and expensive. One exemplary means for accomplishing these objectives is to, essentially, transform a stress gauge into a pressure sensor (not shown in the drawings). A material is selected to form a semi-elastic membrane that is both strong (pressure resistant) and resistant to hazardous materials. The membrane provides a hydraulic seal for the device. On the external side of the membrane, strain-sensitive material is deposited, often in a pattern of multiple strips. When the device is exposed to pressure, the membrane stretches and the strain-sensitive material measures the stress in the membrane. Onboard electronics transforms the strain measurement to a pressure measurement. As might be appreciated, because of the relative complexity of the device, higher precision and quality materials are used in the fabrication, which, again, adds to expense.
In accordance with exemplary embodiments of the present invention, a cost-effective, precision, low pressure sensor system is disclosed for in situ pressure monitoring of a variety of fluid medium types, including hazardous materials. The term “fluid” should be understood as meaning any fluid, liquid or gas. One objective of the present invention is to utilize proven components that are available in bulk, in order to reduce cost and assure reliability, especially the pressure sensor itself. As mentioned elsewhere above, low-cost, accurate pressure sensors for monitoring low pressure fluids are plentiful, but not for hazardous environments. The aim is to protect the pressure sensor from the hazardous mediums it monitors. Therefore, in accordance with one exemplary embodiment of the present invention, generic low pressure sensor system 300 (depicted in
OTS low pressure sensor 302 measures the pressure of measurement fluid 308 which is encapsulated in interior pressure chamber 306 of pressure bladder 307. Pressure bladder 307 is comprised of an extremely pliable material and is exposed to an external pressure, p1, to be measured, such as in a closed system, for example pressurized fluid mediums in pipes, tubes, conduits, vascular/arterial structures, containers, chambers, tanks, etc. In so doing, the external pressure, that is the medium pressure, p1, (such as the exemplary tank's internal pressure) is transferred from the exterior of pressure bladder 307 into mandrel measurement fluid 308 contained in the bladder's interior pressure chamber 306, depicted as interior pressure, p1′. Although it is physically possible to hydraulically couple pressure bladder 307 directly to OTS low pressure sensor 302, this type of connection is rather complicated and, for some applications, a pressure interface should be created to isolate OTS low pressure sensor 302 from the exterior pressure (for example the tank pressure), or at least from contact with the fluid being measured (the contents of the exemplary tank). For most applications, OTS low pressure sensor 302 should be coupled to a more rigid structure than pressure bladder 307. Hence, support mandrel 305 is interposed between OTS low pressure sensor 302 and pressure bladder 307. Support mandrel 305 serves three purposes: it provides a structure for capillary channel 304 for measurement fluid 308 to communicate interior pressure, p1′, between interior pressure chamber 306 of pressure bladder 307 and the measurement chamber of OTS low pressure sensor 302; support mandrel 305 also provides the additional structural integrity necessary for hydraulically coupling to OTS low pressure sensor 302; and finally, support mandrel 305 provides the additional lateral integrity necessary for supporting a pressure interface to seal in exterior pressure p1, (within (pressurized) fluid medium 103) e.g., using compression fitting 315.
In accordance with yet another exemplary aspect of the present invention, pressure bladder 307, as well as support mandrel 305, are fabricated from a chemical resistant material that is impervious to most types of corrosives, reactants, oxidizers and other hazardous materials. In addition, the present invention is equally functional in non-hazardous environments, such as municipal water reservoir tanks and other potable water containers, as well as food grade shipping tanks and the like. One such chemically resistant material is a class of fluoropolymers. Exemplary fluoropolymers include fluorinated ethylene propylene (FEP), perfluoroalkoxy polymer (PFA) (sometimes referred to improperly as MFA), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE) and others. In general, these fluoropolymer materials have high corrosion resistance, strength over a wide temperature range, most are easily welded and have high electrical resistivity. Fluoropolymers, of the type polymers described immediately above, have several distinct advantages over the materials typically used in the prior art to isolate pressure sensors from the hazardous fluid mediums. First, fluoropolymer materials lend themselves to various economical fabrication techniques, they are infinitely configurable and available in many forms (sheet, round stock, square stock, tubular, etc.). Fluoropolymer materials can be cut, bent and shaped into precise geometries using relatively inexpensive manufacturing equipment. For example, fluoropolymer rods can be easily drilled and shaped; fluoropolymer sheets and tubing can be welded together or to one another; and standard polymer welding techniques yield excellent hydraulically coupling without the use of adhesives. Many types of fluoropolymers are available in a wide range of durometers (Shore hardness). Most of these fluoropolymers are available in quantity and extremely cost effective (as an example, the materials cost for fluoropolymer bladder and mandrel for generic low pressure sensor system 300 is less than five percent (5.0%) of the cost of a suitable pressure sensor for the device (excluding the costs associated with fabrication). Most importantly, many fluoropolymers are resistant to a wide range of corrosive and reactant chemicals, they will not oxidize, are chemically inert and UV stable.
Returning to generic low pressure sensor system 300 depicted in
Here it should be mentioned that many off-the-shelf pressure sensor exhibit temperature induced measurement shifts of their pressure readings. Operating in exposed areas, sometimes with wide temperature variations, such as in direct sunlight and cold nights, or adjacent to or immersed in hot or alternative hot and cool fluids, may induce a shift in the sensor's readings. These measurement shifts may be linear and predictable, but more often they are non-linear and/or not readily predictable. Therefore, for accurate pressure readings, a temperature correction should be formulated for the particular OTS low pressure sensor being employed. Ideally, this is accomplished by creating a comprehensive table of temperature-corrected pressure readings. Typically, a pressure sensor is exposed to a range of environmental temperatures (e.g., −10 degrees Fahrenheit to 140 degrees) for each rated pressure increment of the sensor (e.g., 0 psi-30 psi). Hence, temperature thermistor 303 is optimally provided for monitoring the temperature of OTS low pressure sensor 302 in order to determine the temperature induced pressure correction. For example, an OTS pressure sensor may read 10.0 psig (per square inch gauge) which is the correct fluid medium pressure and requires no pressure correction at 77 degrees Fahrenheit. However, a 10.0 psi fluid pressure reading taken at 37 degrees Fahrenheit (40 degrees lower than the original 77 degrees) will result in a pressure reading of 9.6 psig, thus requiring a temperature correction of 0.4 psi (0.4 psi @ 37 degrees Fahrenheit). But measuring 10.0 psi fluid pressure at 117 degrees Fahrenheit (40 degrees higher than the original 77 degrees) the sensor will read 11.1 psig, necessitating a temperature correction of −1.1 psi (−1.1 psi @ 117 degrees Fahrenheit). The following drawing figures may or may not depict the optional thermistor, however, each of the following embodiments may be provided with a thermistor as necessary for the particular application of the OTS low pressure sensor. In practice, certain OTS low pressure sensors are provided with a thermistor integrated within its electronic circuitry.
The OTS pressure sensor, while extremely accurate in sensing pressures over its pressure range at its rated operating temperatures, is extremely susceptible to many types of corrosives, reactants, oxidizers and other hazardous materials. Therefore, the OTS pressure sensor must not be exposed to any of these types of materials. The OTS pressure sensor must, therefore, not be used in a hazardous environment, or, in accordance with various embodiments of the present invention, be isolated from any hazardous materials. This is accomplished by providing an isolation interface between the pressurized hazardous medium and the OTS pressure sensor. This isolation interface must be both resistant to hazardous materials and yet be transparent to pressures.
In accordance with one exemplary embodiment of the present invention, the OTS pressure sensor is isolated from the pressurized fluid medium being monitored by using a chemically inert and resistant material as an interface, but that is transparent to the pressure to be monitored in highly hazardous fluids, such as a fluoropolymer. Returning to the description associated with
Fabricating the FEP structure for isolating the pressure sensor is relatively uncomplicated, extremely cost-effective and highly adaptable for different applications and design criteria. One exemplary technique involves fashioning pressure bladder 307 and support mandrel 305 from a single length of round-stock FEP. The diameter and length of FEP round stock is selected, and then capillary channel 304 is bored through the round-stock bar. Next, interior pressure chamber 306 is formed by boring a larger diameter hole across the capillary channel a predetermined depth and then pinch-welding the open end of pressure chamber 306 (alternative, the open end can be plug-welded, see
Alternatively, pressure bladder 307 and support mandrel 305 can be cut directly from separate stocks of PEF tubing and assembled as shown in the exemplary fabrication process depicted in
Here, it should be mentioned that using the FEP material enables the manufacturer some flexibility in the diameter of the pressure bladder 307 as depicted in the series of figure drawings depicted in FIGS. 4B1 and 4B2. Series FIG. 4B1 depicts a build using support mandrel 305 having an outer diameter a, and pressure bladder 307 having an outer diameter b and an inner diameter a. In so doing, pressure bladder 307 easily slides over support mandrel 305 and can be welded in place as depicted in the last two drawing frames of the series. Series FIG. 4B2 depicts a build using support mandrel 305 having an outer diameter a, and pressure bladder 307 having an identical outer diameter, diameter a, hence the inner diameter of pressure bladder 307 is less than diameter a. (the outer diameter of support mandrel 305). In so doing, pressure bladder 307 must be stretched over the outer diameter of support mandrel 305. Only then can pressure bladder 307 be welded in place, as also depicted in the last two drawing frames of the series. Using pressure bladder 307 with a larger outer diameter b has the advantage of easily coupling pressure bladder 307 to support mandrel 305 for welding, however stock FEP tubing is generally not available in a particularly wide range of inner diameters. Using pressure bladder 307 with an outer diameter a, identical to the outer diameter of support mandrel 305 has the advantage of being readily available without the need for special ordering, and therefore less expensive. Additionally, notice that the diameter of internal pressure chamber 306 depicted in the series of FIG. 4B1 is larger than that in series FIG. 4B2, thereby increasing the volume of internal pressure chamber 306, which may be important for a particular application.
In any case, returning to
Here it should be mentioned that the present low pressure sensor system can be adapted for two separate operating modes, a distal sensor configuration where the pressure sensor is positioned away from the hazardous medium, see for example
In any case, once the mandrel is trimmed, measurement fluid 308 is injected through capillary channel 304 (using injection tube 415) and into interior chamber 306 until the chamber and capillary channel are both full and bubble-free, see
Here, it should be noted that most off-the-shelf basic board mounted pressure sensors, of the type discussed herein, utilize a barbed port fitting for making a connection to a flexible tubing, see basic sensor 302 shown in FIG. 4G1 having barbed port 414. For many applications, using basic sensor 302 with barbed port 414 will provide sufficient mechanical coupling strength without leakage. However, often it is advantageous to use FEP materials with higher Shore Hardness values, especially support mandrel 305 in order to ensure a good coupling (via compression fitting 315) for pressure isolation of the fluid medium. Hence, coupling support mandrel 305 to basic sensor 302 may be difficult using a standard barbed fitting (barbed port 414). Furthermore, good sensor/mandrel mechanical coupling strength is critical for operating safety. One solution is to reconfigure basic sensor 302 with male threads. Male threads on the port simplifies the coupling operation because rather than forcing a barbed fitting into a stiff tube, the sensor can merely be screwed into the tubing. Additionally, for many types of tubing materials, a threaded connection provides greater sensor/mandrel coupling strength. As the exterior cases (and barbed ports) on these sensors comprise a workable plastic composition, male threads can easily be manually cut into barbed port 414 by using a threaded die to form male threaded port 312 as depicted in FIG. 4G2. Alternatively, sensor manufacturers may also provide pressure sensors with spiral barbed port 416 as depicted in FIG. 4G3. Spiral barbed port 416 are not only easier for the fabricator to couple to the mandrel, but also provide greater coupling strength than a standard barbed fitting, such as barbed port 414.
Notice from
As may be appreciated from the following discussions, a coupling failure will result in loss of measurement fluid 308 and failure of the sensor. Additionally, certain types of measurement fluid 308 have a penetrating effect on the coupling joint, causing the measurement fluid to weep out at the sensor-mandrel coupling. In extreme cases, a coupling failure may result in the escape of hazardous material into the environment, for example in an exposed sensor system, such as low pressure sensor system assembly 900. Therefore, preventing the escape of measurement fluid, even slight weeping, and securing the mechanical coupling between the pressure sensor and mandrel are crucial. One mechanism to prevent leaks and weeping is to employ an additional seal, such as O-ring or Q-ring 422 as depicted in FIG. 4G2. O-ring or Q-ring 422 may be used in addition to any other coupling or clamping mechanism employed. Better coupling mechanics is achieved by using a tubing clamp, such as a common spring clamp (not shown), spiral wire nut tubing clamp 426, as depicted in FIG. 4G1 or crimp tubing clamp 428, as depicted in FIG. 4G3.
Generic low pressure sensor system 300 depicted in
Other modifications are possible to generic low pressure sensor system 300 without departing from the scope and intent of the present invention. For example and with regard to the previous examples, support mandrel 305 is secured to any of pressure bladders 307-707 by slipping support mandrel 305 into the pressure bladder a short distance and then FEP welding the adjacent surfaces of the pieces, as discussed above with regard to FIGS. 4B1 and 4B2. While this fabrication technique is quite economical, it creates sensor system bodies with two distinct external diameters, and furthermore, the larger diameter on the pressure bladder, makes it much more difficult to insert the low pressure sensor system into a compression fitting for mounting. An alternative is to use a longer pressure bladder (referred to hereinafter as a full-length pressure bladder), as seen on any of pressure mandrels 307-707. The entire length of support mandrel 305 is inserted into the full-length pressure bladder, thereby forming coaxial support mandrel 805. For example, coaxial support mandrel 805 comprising support mandrel 305 and the upper portion of hemispheric-end pressure bladder 807 (depicted as a full-length pressure bladder) is shown in low pressure sensor system 800, and also coaxial support mandrel 805 comprising support mandrel 905 and the upper portion of full-length pressure bladder 907 is shown in low pressure sensor system assembly 900 in
Generic low pressure sensor system 300 is almost infinitely configurable for measuring pressures in a variety of hazardous applications. For example, generic low pressure sensor system 300 may be configured for static pressure measurements, see any of sensor system assemblies 800, 1000, 1001, 1800 and 1900, for example, either externally, see sensor system assemblies 800, 900, 1800 and 1900, with only the pressure bladder exposed to the fluid medium, or fully submerged, see submersible pressure sensor system assemblies 1000 and 1001 in which the entire sensor system is immersed in the fluid medium. Submerged sensor systems can also be deployed for making dynamic measurements, such as by moving generic low pressure sensor system 300 through a tubing structure, see, for example, the discussion of the submerged low pressure sensor system assemblies associated with
With further regard to static pressure measurements, a common configuration for making static pressure measurements for generic low pressure sensor system 300 utilizes a compression fitting (or other pressure isolating device) for mounting the low pressure sensor system across a pressure barrier. Typically, the pressure bladder is immersed in the fluid medium and a compression fitting is secured about the support mandrel to pressure-isolate the pressure sensor from the fluid medium.
As depicted, compression fitting 930 cooperates with threaded collar 921 to secure continuous diameter low pressure sensor system into low pressure sensor system assembly 900. Threaded collar 921 may be fastened directly into a female fitting on a tank or pipe with full-length pressure bladder 907 extending into an interior cavity of a pipe, tank or other vessel, however, as the pressure bladder is highly susceptible to tears from moving fluid, suspended particles, and other forces. Therefore, optimally, full-length pressure bladder 907 does not extend into any interior cavities, but instead is offset away from the interior by, for example, using a threaded sub or collar 921 as an offset to protect the bladder from hydraulic forces or containment particles that might compromise it. Exemplary collar 921 is coupled between threaded couplers 930 and 923, and male pipe thread coupler 923 is further coupled to exemplary tee fitting 918, the piping system that conveys fluid medium 309. A similar configuration is possible for any container, tank, or tube having an open fitting for receiving threaded coupler 923.
Low pressure sensor system assembly 900, generally comprising only the components shown above compression fitting 930 and is assembled as a unitary assembly that can be threaded into any threaded sub, pin or other port as needed. Assembly starts at the cable end, with upper lock nut 934, protective pipe 940 and upper compression fitting 932 being slid over conductor tubing 916 thereby leaving conductors 917 exposed. Inner shrink tube 920, intermediate shrink tube 922 and outer shrink tube 924 are also slid over conductor tubing 916 and conductors 917. The connection pins on OTS low pressure sensor 302 are then electrically coupled to conductors 917 (as is optional thermistor 303, if present). Inner shrink tube 920, which may be an electrically insulating shrink tube or FEP, is moved across the connection pins and over conductor tubing 916 and heat-shrunk in place. Next, intermediate shrink tube 922 is moved over the body of OTS low pressure sensor 302, completely over inner shrink tube 920 and over conductor tubing 916. Intermediate shrink tube 922, which also may be either an electrically insulating shrink tube or FEP, is then heat-shrunk in place. Finally, outer shrink tube 924, which is an FEP-type of shrink tube, is moved over intermediate shrink tube 922 and OTS low pressure sensor 302 and positioned from conductor tubing 916 to coaxial support mandrel 805 (recall that pressure bladder 907 is mechanically coupled to support mandrel 905 by coupling weld 410). Outer shrink tube 924 is then heat-shrunk in place. After shrinking, outer shrink tube 924 fits tightly around both conductor tubing 916 and mandrel 905. Finally, the top end of outer shrink tube 924 is secured to conductor tubing 916 by coupling weld 410 and the lower end of outer shrink tube 924 is secured to coaxial support mandrel 805 by second coupling weld 410.
With OTS low pressure sensor 302 and coaxial support mandrel 805 both secured to conductor tubing 916, compression fitting 930 is lowered positioned on coaxial support mandrel 805 and secured. Protective pipe 940 (with upper compression fitting 932) is then moved across the sensor to a position with the lower end protective pipe 940 just above the outer tightening nut on lower compression fitting 930. The position of upper compression fitting 932 is then marked on conductor tubing 916. Protective pipe 940 is then moved up on conductor tubing 916 and away from upper compression fitting 932, which remains aligned with the mark. Upper compression fitting 932 is then secured to conductor tubing 916 at that position. Protective pipe 940 can then be moved back down over upper compression fitting 932 and secured in place using upper locking nut 934.
With protective pipe 940 locked in place and covering everything between the lower part of upper compression fitting 932 and the outer tightening nut on lower compression fitting 930, a closed cell, rigid cure spray foam 942, can be injected between protective pipe 940 and allowed to cure. Low pressure sensor system assembly 900 is then complete, but care should be taken as full-length pressure bladder 907 extends beyond lower compression fitting 930 and is unprotected.
Alternative to using protective pipe 940, one off-the-shelf solution for increasing structural rigidity is by using a cable protector (not shown) that couples to compression fittings 932 and 930 or other rigid structure, and encases OTS low pressure sensor 302 with conductors 917. This cable protector can also be filled with rigid cure spray foam 942 as desired.
Continuous diameter low pressure sensor system assembly 900 may be used anywhere an external port or fitting provides access to an interior chamber or cavity holding fluid medium such as pipes, tubing, casing, various locations on storage tanks as shown in
In accordance with another exemplary embodiment of the present invention, utilizing a continuous diameter pressure bladder has other advantages not discussed above. These continuous diameter pressure bladders, such as continuous diameter variant of a hemispheric-nosed, generic low pressure sensor assembly 800 and low pressure sensor system assembly 900 depicted in
As depicted in the drawing figures, submersible low pressure sensor system assemblies 1000 and 1001 utilize low pressure sensor system 300, but may be fitted with any of the low pressure sensor system embodiments as discussed above. The primary difference between low pressure sensor system assembly 1000 and low pressure sensor system assembly 1001 is that assembly 1000 utilized an FEP shrink tube to protect the assembly, while assembly 1001 utilized a rigid tube.
The aim here is to insulate OTS low pressure sensor 302 and electrical conductors 1017 from fluid medium, which may be hazardous, even while being fully immersed in fluid medium 309. A further aim is to protect the system's pressure bladder from being damaged, even while being fully submerged at or near the bottom of a tank or other vessel. Low pressure sensor system assembly 1000 is similar in many regards to low pressure sensor system assembly 900, discussed immediately above, however, low pressure sensor system assembly 1000 uses FEP tubing to insulate the submerged sensor that is proximate to the fluid medium, rather than using a compression fitting as pressure interface to isolate the distal pressure sensor from the fluid medium, as can be appreciated as low pressure sensor system assembly 900 in
In practice, a low pressure sensor system used in this assembly could be any of sensor systems discussed above, but as depicted in the figure, the low pressure sensor system utilizes coaxial support mandrel 805 with full-length pressure bladder 1007 that is terminated with a pinched end closure weld 412 similarly to that described in
Next, intermediate shrink tube 1022 is moved over the body of OTS low pressure sensor 302, ballast weights 1055, and completely over inner shrink tube 1020 from mandrel 1005 to conductor tubing 1016. Intermediate shrink tube 1022, which also may be insulating type of shrink tube, or alternatively FEP, is then heat-shrunk in place (which also secures ballast weights 1055 in place). Next, isolating tube 1024, which is an FEP-type of tube and might also be an FEP-type of shrink tube as discussed above, is moved over intermediate shrink tube 1022 and OTS low pressure sensor 302, from conductor tubing 1016 to axial support mandrel 805 and then heat-shrunk in place. After which, the heat-shrunk intermediate shrink tube 1022 is mechanically coupled to both mandrel 1005 and conductor tubing 1016, optionally, but not necessarily, by FEP-welding a pair of coupling welds 410. Here it should be mentioned that most protective tubing that is not exposed to the fluid medium, including hazardous mediums, are mechanically secured in-place, usually by shrinking the tubing in-place. Typically, this inner tubing not welded in-place, but may be. On the other hand, the exterior tubing that does come in contact with the fluid medium, must be mechanically fasten in-place securely, typically by welding the end or ends in-place. One of ordinary skill in the art would readily understand that the mechanical fastening technique employed is dependent on the type of isolation desired. If the fastening requires a leak-free connection, then welding, clamping or some other water-proofing connection is necessary. However, if what is needed is merely a protective isolation layer, for electrical isolation for instance, than shrinking tubing in-place may be a more economical solution.
At this point, the assembly is functional and may be immersed in fluid medium 309, however, full-length pressure bladder 1007 is exposed and would likely be damaged by fluid flow and/or contaminants in the fluid medium. In order to protect pressure bladder 1007, protective FEP shrink tube 1026 is positioned from conductor tubing 1016 and extending beyond the end of full-length pressure bladder 1007, thereby covering the entire sensor assembly including the pressure bladder. Protective FEP shrink tube 1026 is then mechanically coupled to conductor tubing 1016 by heat shrinking it in place and with coupling weld 410.
One benefit of using a shrinkable tubing is that the tubing shrinks and usually adheres circumferentially to an inner tube. The two tubes can then be fully joined together with an FEP weld. Often, however, a gap exists between an inner and outer tubing because the outer tubing does not fit tightly about the inner. There the solution is to draw the outer tube tight around the inner tube by forming a pair of ear flaps on either side of the tube that takes up the extra outer tube.
Upper annular stand-off 1010A and lower annular stand-off 1010B may be die-cut from fluoropolymer (FEP) sheet stock, or alternatively, fabricated from a continuous strip of sheet fluoropolymer (typically FEP). The latter fabrication method of annular stand-offs 1010A and 10108 is depicted in
One interesting feature of an exemplary embodiment of the presently described sensor system assemblies, is that the measurement range of the pressure reading can be altered merely by adjusting the length of the pressure bladder that is exposed to the fluid medium. The measurement range refers to the resolution of the measurement readings, for example, some pressure sensors may be accurate to the tenth psi (0.1 psi), others to the hundredths psi (0.01 psi). Sensors with the capability of reading greater resolution are, as may be expected, far more expensive than those capable of reading lower resolutions.
The principle of altering the measurement range of the pressure reading works by using a deflection-type pressure sensor, such as deflection-type pressure sensor 100 discussed above with regard to
Deflection-type pressure sensors, such as deflection-type sensor 100 discussed above with regard to
Deflection-type pressure sensors operate on a mechanical deflection mode, in that the force with the pressurized fluid medium increases, then the force against the measurement membrane increases (that is the pressure of the fluid medium increases), resulting in the measurement membrane deflecting a distance that is related to the increased force. That deflection distance is a function of primarily two factors, the biasing force of the membrane and the size (area) of the measurement membrane. The biasing force is the internal resistance within the measurement membrane, for example diaphragm 104 resists the force within the measurement fluid. The greater the biasing force, the less measurement membrane will deflect. Also, larger measurement membranes will deflect more than smaller ones with the same force being applied.
It is not possible to alter the measurement range of a deflection-type pressure sensor directly, as may be better appreciated from a discussion of the following.
An interesting feature is that by adjusting the ratio of the areas of the primary piston to the secondary piston, the proportional distance moved by the second piston can be altered. Conceptually, this is can be visualized by comparing the responses of the closed hydraulic piston system in
A typical deflection-type pressure sensor does not completely correlate to the conceptual illustration depicted in
Turning to
This enhancement of measurement range can be achieved for the present invention merely by adjusting the surface area of the pressure bladder exposed to the fluid medium, while using a deflection-type pressure sensor system, such as deflection-type pressure sensor systems 1500 and 1501, respectively, shown in
In order to realize the benefit of the enhanced measurement range, it should be understood that the force at diaphragm 104 of deflection-type pressure sensor systems 1501 is greater than for deflection-type pressure sensor systems 1500. Therefore, deflection-type pressure sensor systems 1501 will read higher (psig) than the actual pressure of the fluid. Hence, for most applications, it is necessary to select deflection-type pressure sensor 100 with a higher (and wider) pressure range in order to accommodate the higher and wider pressure readings (psig). For example, if by modifying (increasing) the size of the pressure bladder the ratio is doubled, than it might be expected that the deflection of diaphragm 104 might increase a correspondingly amount (doubling the range and scale of the readings (psig)) and, therefore, might exceed the higher end operating range of the particular pressure sensor. Hence, a deflection-type pressure sensor with twice the operating range of the original sensor would be an appropriate selection. For example, a 0 psi-40 psi range pressure sensor might be substituted for a pressure sensor having a 0 psi-20 psi pressure range to accommodate the increase in pressure readings (psig). Importantly, when this replacement pressure sensor is disposed within the present invention, such as within deflection-type pressure sensor systems 1501, the readings received from that system must be reduced or scaled proportional in order to realize the true enhanced measurement range. For example, if as in the above example the measurement range is doubled, then the reading from the substitution sensor system should be decreased by the same proportion to be accurate, or by half. Hence, the resulting reading will be accurate, but twice as precise, that is it will have twice the pressure resolution.
In accordance with still another exemplary embodiment of the present invention, generic low pressure sensor system 300 can be deployed in a dynamic configuration, not just static. Pipes, tubing, vascular and arterial structures all have the potential for collapsing, bending, constricting, or accumulating deposits of scale, sludge, plaque, and other materials that affect the flow of the fluid medium. While many inspection techniques are available, sonar, ultrasound, video, radar, gauging pigs, etc., most of these options are expensive and/or have a fairly limited use in a narrow range of fluid types, or some other detriment to the conveyance system.
One economical solution for evaluating the interior condition of a vascular system is by using generic low pressure sensor system 300 to map the flow pressures throughout the line.
Tubing/vascular structure 1702 contains various defects to the interior walls, including various types of contaminant build-ups 1712 and wall thickening and kinks 1713, each that result in a reduction of flow of fluid medium 1720. Tubing/vascular structure 1702 may be organic or inorganic, if organic, the physical components represented in the accompany figures may be greatly miniaturized. Here, submergible low pressure sensor system assembly 1001 (see
As mentioned elsewhere above, the present invention provides as highly economical alternative to low pressure sensors designed to operate in hazardous fluid mediums. This economy is achieved by utilizing an economical, off-the-shelf, non-hazardous rated pressure sensors and then insulating the OTS sensor from the hazardous fluid mediums using the presently described low pressure sensor system. It should be mentioned that if the insulation system fails and hazardous fluid reaches the pressure sensor, it is likely that the hazardous fluid will leak through the sensor. With regard to prior art sensor 200 depicted in
Double bladder low pressure sensor system 1800 is depicted in
Double bladder low pressure sensor system 1800 provides additional protection between OTS low pressure sensor 302 and a pressurized fluid medium, however, it does not prevent hazardous materials from flooding past OTS low pressure sensor 302 in the event of a catastrophic failure.
Flow control low pressure sensor system 1900 is depicted in
Flow control low pressure sensor system 1900 utilizing flow control valve 1920 should be oriented above horizontal and ideally near vertical to avoid sealing balls 1922/1923 inadvertently sealing off capillary channel 1904, even in a no-flow condition. Ideally, sealing balls 1922/1923 in flow control valve 1920 rest away from conical-shaped sealing surface 1924 and near the lower surface of flow control valve 1920. Sealing balls 1922/1923 should have a density much greater than measurement fluid 308, but at least one and a half times (×1.5) the density of the fluid medium. Exemplary fluoropolymer, such as solid PTFE balls, have an exemplary density of between 2.03 gm/cm and 2.18 gm/cm depending on the source and grade of the PTFE balls. Hollow balls that are available have gross densities less than 2.03 gm/cm. Flow control valve 1920 may be configured with multiple sealing balls 1922, see
Although not discussed in great detail, any embodiment of generic low pressure sensor system 300 may be electrically coupled to a monitoring unit, such as a computer, smart device, tablet, or other computational device. Basically, the monitoring unit delivers power to generic low pressure sensor system 300 and receives voltage or other sensor signals and in response communicates that data to data/processing remote centers, clouds, or portable devices. Ideally, information gathered from t h e monitoring unit, whether remote, local, or mobile sources, makes its way to a web application in the cloud, such as the Advantis Web Application also available from Advantis, L.L.C., which can be viewed by computer and smart phone. These devices may then process the data locally and/or compare the data to alarm thresholds (or a predetermined pressure range) and the like. In accordance with exemplary embodiments of the present invention, the monitoring unit may support a variety of different priority cry-out alarms. The purpose of a cry-out alarm is to alert someone that a pressure alarm threshold has been crossed and a warning condition exists. Whenever a warning condition is detected (such as the internal pressure of the fluid medium is outside a predetermined pressure range for the fluid medium), the monitoring unit activates a cry-out alarm. Also, the monitoring unit may utilize electronic (digital) cry-out means in the event of a warning condition, such as sending an email message, text message, pager message, voice message, web app message, mobile app message or other type of electronic message to designated recipient(s) at a predetermined electronic address(es). In either case, the monitoring unit typically determines whether an alarm threshold(s) has(ve) been exceeded, rather than the threshold determination being made at a remote site.
The exemplary embodiments described above were selected and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated. The particular embodiments described below are in no way intended to limit the scope of the present invention as it may be practiced in a variety of variations and environments without departing from the scope and intent of the invention. Thus, the present invention as embodied in the claims below is not intended to be limited to the embodiment shown, but is to be accorded the widest scope consistent with the principles and features described herein.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
