Verification of Vapor Pressure Using Measured Values of Fluid Density

Abstract

Meter electronics for verifying vapor pressure using density measurements of a fluid are provided. The meter electronics includes a processing system communicatively coupled to a meter assembly having a fluid, the processing system configured to measure the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly, measure the density of the fluid based on a resonant frequency of the meter assembly, derive a vapor pressure from the measured density, and compare the measured vapor pressure to the derived vapor pressure.

Description

Technical Field

[0001] The embodiments described below relate to the measurement of vapor pressure, and more specifically, to the verification of vapor pressure using measured values of fluid density.

Background Art

[0002] For example, vibration sensors such as vibrating densitometers and Coriolis flow meters are generally known and are used to measure the mass flow rate and other information of the material flowing through the conduit in the flow meter. Exemplary Coriolis flow meters are disclosed in U.S. Patent No. 4,109,524, U.S. Patent No. 4,491,025, and Reissue Patent No. 31,450 (all assigned to J.E. Smith et al.). These flow meters have one or more conduits in a linear or curved shape. Each conduit shape of the Coriolis mass flow meter has a set of natural vibration modes that can be, for example, a simple bend type, a twist type, or a combined type. Each conduit can be driven to vibrate in a preferred mode.

[0003] Material flows into the flow meter from a pipeline connected to the inlet side of the flow meter, is guided through the conduit, and exits the flow meter through the outlet side of the flow meter. The natural vibration mode of the vibration system is partially defined by the combined mass of the conduit and the material flowing through the conduit.

[0004] When there is no flow through the flow meter, the driving force applied to the conduit vibrates all points along the conduit in the same phase or with a small "zero offset", which is the time delay measured at zero flow. When the material begins to flow through the flow meter, the Coriolis force gives different phases to each point along the conduit. For example, the phase at the inlet end of the flow meter lags behind the phase at the central driver position, while the phase at the outlet advances from the phase at the central driver position. A sine wave signal representing the movement of the conduit is generated by the pickoff of the conduit. The signal output from the pickoff is processed to determine the time delay between the pickoffs. The time delay between two or more pickoffs is proportional to the mass flow rate of the material flowing through the conduit.

[0005] The meter electronic device connected to the driver generates a drive signal to operate the driver and determines the mass flow rate and other properties of the material from the signal received from the pickoff. The driver can comprise one of many well-known configurations, but magnets and opposing drive coils have been highly successful in the flowmeter industry. Alternating current flows through the drive coils to vibrate the conduit at the desired amplitude and frequency of the flow tube. Also in the art, it is known to provide the pickoff as a magnet configuration and coil configuration very similar to the driver configuration. However, the driver receives a current that induces movement, while the pickoff can induce a voltage using the movement provided by the driver.

[0006] Vapor pressure is an important property in applications dealing with the flow and storage of volatile fluids such as gasoline, natural gas liquids, and liquefied petroleum gas. Vapor pressure serves as an indicator of how the volatile fluid behaves during handling and further indicates conditions where bubbles are likely to form and pressure may increase. Thus, measuring the vapor pressure of volatile fluids enhances safety and prevents damage to transport containers and infrastructure. For example, if the vapor pressure of a fluid is too high, cavitation may occur during pump transfer operations. Additionally, the vapor pressure of a container or process line can potentially rise above a safe level due to temperature changes. Therefore, it is often necessary to know the vapor pressure before storage and transport.

[0007] Typically, vapor pressure is measured by taking samples, removing them to a laboratory for testing, and determining values from the samples. This poses difficult problems for implementing regulatory fuel quality standards due to delays in obtaining final results, costs for maintaining a laboratory, and the vulnerability of safety and legal evidence associated with sample handling. Therefore, there is a need for an in-line device or in-line system that can measure the vapor pressure of a fluid within a meter assembly continuously and on a real-time basis under process conditions. This is provided by the present embodiment, achieving progress in the art. On-site measurements are more reliable as they eliminate the need for periodic sampling and completely eliminate the risk of fluid property changes between sample collection and laboratory assay. Furthermore, safety is improved by performing real-time measurements as an unsafe condition can be immediately improved. Additionally, regulatory enforcement can be carried out via simple on-site checks, and decisions for inspection and enforcement can be made with little delay or process interruption, saving funds. These advantages can be enhanced by verifying the vapor pressure measurement values.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0009] A meter electronic device is provided for verifying vapor pressure using a measured value of the density of a fluid. According to one embodiment, the meter electronic device comprises a processing system communicably coupled to a meter assembly having the fluid. The processing system is configured to measure the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly, measure the density of the fluid based on the resonant frequency of the meter assembly, derive the vapor pressure from the measured density, and compare the measured vapor pressure with the derived vapor pressure.

[0010] A method is provided for verifying vapor pressure using a measured value of the density of a fluid. According to one embodiment, the method includes measuring the vapor pressure of the fluid by detecting a phase change of the fluid within a meter assembly, measuring the density of the fluid based on the resonant frequency of the meter assembly, deriving the vapor pressure from the measured density, and comparing the measured vapor pressure with the derived vapor pressure.

Means for Solving the Problem

[0011] According to one aspect, a meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid comprises a processing system (200) communicably coupled to a meter assembly (10) having the fluid. The processing system (200) is configured to measure the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measure the density of the fluid based on the resonant frequency of the meter assembly (10), derive the vapor pressure from the measured density, and compare the measured vapor pressure with the derived vapor pressure.

[0012] Preferably, the fluid is a multi-component fluid containing a hydrocarbon component.

[0013] Preferably, the hydrocarbon component includes at least two of propane, butane, and hexane.

[0014] Preferably, the processing system (200) configured to derive the vapor pressure from the measured density includes a processing system (200) configured to utilize a predetermined correlation between a plurality of vapor pressures and a plurality of densities.

[0015] Preferably, the processing system (200) configured to utilize a predetermined correlation between a plurality of vapor pressures and a plurality of densities includes a processing system (200) configured to interpolate between the predetermined correlations.

[0016] Preferably, the processing system (200) configured to compare the measured vapor pressure with the derived vapor pressure includes a processing system (200) configured to determine whether the measured vapor pressure is within a predetermined range of the derived vapor pressure.

[0017] Preferably, the processing system (200) is further configured to measure the vapor pressure using a drive gain.

[0018] According to one aspect, a method for verifying a vapor pressure using a fluid density measurement value includes measuring the vapor pressure of the fluid by detecting a phase change of the fluid within a meter assembly, measuring the density of the fluid based on a resonant frequency of the meter assembly, deriving the vapor pressure from the measured density, and comparing the measured vapor pressure with the derived vapor pressure.

[0019] Preferably, the fluid is a multi-component fluid containing a hydrocarbon component.

[0020] Preferably, the hydrocarbon component includes at least two of propane, butane, and hexane.

[0021] Preferably, the step of deriving the vapor pressure from the measured density includes utilizing a predetermined correlation between a plurality of vapor pressures and a plurality of densities.

[0022] Preferably, the step of utilizing a predetermined correlation between a plurality of vapor pressures and a plurality of densities includes interpolating between the predetermined correlations.

[0023] Preferably, the step of comparing the measured vapor pressure with the derived vapor pressure includes determining whether the measured vapor pressure is within a predetermined range of the derived vapor pressure.

[0024] Preferably, the method further includes measuring the vapor pressure using a drive gain.

Brief Description of the Drawings

[0025] It should be understood that the same reference numerals represent the same elements in all the figures. The figures are not necessarily to scale.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0026] Figures 1 through 7 and the following description set forth specific examples for teaching those skilled in the art a method for creating and using the best mode of an embodiment for verifying vapor pressure using fluid density measurement values. For the purpose of teaching the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand variations from these examples that fall within the scope of this specification. Those skilled in the art will understand that the features described below can be combined in various ways to form multiple variations for verifying vapor pressure using fluid density measurement values. As a result, the embodiments described below are not limited to the specific examples described below and are limited only by the claims and their equivalents.

[0027] FIG. 1 shows a vibrator 5. As shown in FIG. 1, the vibrator 5 includes a meter assembly 10 and meter electronics 20. The meter assembly 10 responds to the mass flow rate and density of the process material. The meter electronics 20 is connected to the meter assembly 10 via a lead wire 100 and provides density, mass flow rate, temperature information across path 26, and / or other information.

[0028] The meter assembly 10 includes a set of manifolds 150 and 150', flanges 103 and 103' having flange necks 110 and 110', a set of parallel conduits 130 and 130', a driver 180, a resistance temperature detector (RTD) 190, and a set of pickoff sensors 170l and 170r. The conduits 130 and 130' have two essentially straight inlet legs 131, 131' and outlet legs 134, 134', which converge toward each other at conduit mounts 120 and 120'. The conduits 130, 130' bend at two symmetric positions along their lengths and are essentially parallel throughout their lengths. Brace bars 140 and 140' serve to define axes W and W' about which each conduit 130, 130' vibrates. The legs 131, 131' and 134, 134' of the conduits 130, 130' are firmly attached to the conduit mounts 120 and 120', which in turn are firmly attached to the manifolds 150 and 150'. This provides a continuous closed material path through the meter assembly 10.

[0029] When flanges 103 and 103' having holes 102 and 102' are connected to a process line (not shown) carrying the process material being measured via inlet ends 104 and 104', the material enters the meter's inlet end 104 through the opening 101 of flange 103 and is directed through manifold 150 to conduit mount 120 having a surface 121. Within manifold 150, the material is split and sent through conduits 130, 130'. Upon exiting conduits 130, 130', the process material recombines into a single stream within mount 120' having a surface 121' and manifold 150', and is then sent to an outlet end 104' connected to the process line (not shown) by flange 103' having hole 102'.

[0030] The conduits 130, 130' are each selected to have substantially the same mass distribution, moment of inertia, and Young's modulus about the bending axes W-W and W'-W', and are suitably attached to the conduit mounts 120, 120'. These bending axes pass through the brace bars 140, 140'. Since the Young's modulus of the conduit varies with temperature, this variation affects the calculation of flow and density, and the RTD 190 is attached to the conduit 130' to continuously measure the temperature of the conduit 130'. The temperature of the conduit 130', and thus the voltage generated across the RTD 190 for a given current flowing therethrough, is determined by the temperature of the material flowing through the conduit 130'. The temperature-dependent voltage generated across the RTD 190 is used in a well-known manner by the meter electronics 20 to compensate for changes in the elastic modulus of the conduits 130, 130' due to any change in conduit temperature. The RTD 190 is connected to the meter electronics 20 by lead wires 195.

[0031] Both conduits 130, 130' are driven in opposite directions by the driver 180 about their respective bending axes W and W' and in the so-called first phase-displaced bending mode of the flowmeter. This driver 180 may include any one of many well-known configurations, such as a magnet attached to the conduit 130' and opposing coils to which an alternating current flows to vibrate both conduits 130, 130' attached to the conduit 130. A suitable drive signal is applied to the driver 180 by the meter electronics 20 via the lead wire 185.

[0032] The meter electronics 20 receives the RTD temperature signal on the lead wire 195 and the left and right sensor signals generated on the lead wire 100 carrying the left and right sensor signals 165l, 165r, respectively. The meter electronics 20 generates a drive signal on the lead wire 185 to the driver 180 to vibrate the conduits 130, 130'. The meter electronics 20 processes the left and right sensor signals and the RTD signal to calculate the mass flow rate and density of the material flowing through the meter assembly 10. This information, along with other information, is applied by the meter electronics 20 as a signal across the path 26.

[0033] According to the formula, the mass flow measurement value m' can be generated:

[0034]

Number

[0035] The Δt term includes an operationally derived (i.e., measured) time delay value that includes the time delay existing between pick-off sensor signals such as the time delay due to the Coriolis effect related to the mass flow through the vibrator 5. The measured Δt term ultimately determines the mass flow rate of the flowing material as flowing through the vibrator 5. Δt 0 The term includes the time delay in the zero flow calibration constant. Δt 0 The term is typically determined at the factory and programmed into the vibrator 5. Even when the flow state changes, the time delay of the zero flow Δt 0 The term does not change. The flow calibration factor FCF is proportional to the stiffness of the vibrator 5.

[0036] [Pressure of the fluid in the vibrator] Assuming an incompressible liquid under steady state, the velocity at which mass enters the control volume (e.g., a pipe) at the inlet (m' 1 ) is equal to the velocity at which it exits at the outlet (m' 3 ). This principle that the inlet mass flow rate (m' 1 ) must be equal to the outlet mass flow rate (m' 3 ) is shown by the following equation [2]. As it moves from the inlet to the outlet, the mass flow rate is maintained at each point along the pipe. However, there may be a decrease in the flow rate range between the inlet and the outlet. This decrease in the flow rate range requires the flow velocity to increase (vup) in order to maintain the same mass flow rate and follow the law of conservation of mass.

[0037]

Number

[0038] Here, m' is the mass flow rate of the fluid, v is the average flow velocity, ρ is the density of the fluid, A is the total cross-sectional area, The subscript 1 indicates the inlet, The subscript 3 indicates the outlet, The subscript 2 indicates the middle between the inlet and the outlet.

[0039] Furthermore, the total pressure in the flow system is equal to the sum of both the dynamic pressure and the static pressure:

[0040]

Equation

[0041] The dynamic pressure P dynamic can be defined as follows.

[0042]

Equation

[0043] Here, the terms ρ and v are defined above with respect to Equation [2].

[0044] Assuming a constant, incompressible, non-viscous, and irrotational flow, Bernoulli's equation becomes as follows:

[0045]

Equation

[0046] Here, P refers to the static pressure, and the term ρgz corresponds to the hydrostatic head pressure due to the elevation. More specifically, g is the gravitational constant and z is the height. The viscous part of the pressure drop can be handled as a separate loss term in Bernoulli's equation.

[0047]

Equation

[0048] Here, f is the coefficient of friction, L is the length of the pipe, D is the diameter of the pipe.

[0049] The following equation [7] is a version of Bernoulli's equation corresponding to the frictional losses associated with moving the pipe. As the fluid moves through the pipe, the fluid dissipates energy and the pressure decreases over a given length of the pipe. This pressure loss is irreversible because the energy from the fluid is consumed by frictional losses. Therefore, the following equation may explain this loss:

[0050] [Number]

[0051] This relationship can be applied to the above exemplary pipe with reference to Equation [2]. As the fluid moves from the inlet to the middle between the inlet and the outlet, there is a change in velocity to maintain the mass flow rate. Therefore, when maintaining the relationship shown in Equation [7], the dynamic pressure ρv 2 / 2 increases and the static pressure decreases. As the fluid moves from the middle between the inlet and the outlet to the outlet, the static pressure is restored by the same principle. That is, as it moves from the middle between the inlet and the outlet to the outlet, the flow rate range increases. Therefore, the flow velocity decreases, reducing the dynamic pressure while restoring part of the initial static pressure. However, due to the irreversible viscous losses, the static pressure at the outlet will be lower.

[0052] This is because while the static pressure between the inlet and the outlet is lower than the vapor pressure of the fluid, there is a possibility that it could cause the static pressures at the inlet and the outlet to be higher than the vapor pressure of the fluid. As a result, although the static pressures at the inlet and the outlet are both higher than the vapor pressure of the fluid, flashing or gas evolution may still occur within the pipe. Further, a vibration meter such as a Coriolis flow meter may be inserted into a pipeline having a diameter different from the diameter of one or more conduits within the vibration meter. As a result, if gas evolution is detected within the vibration meter, the pressure measured within the pipeline may not be the vapor pressure of the fluid within the vibration meter.

[0053] [Meter Electronics - Drive Gain] FIG. 2 is a block diagram of the meter electronics 20 of the vibration meter 5. During operation, the vibration meter 5 includes one or more of measured or average values of mass flow rate, volume flow rate, individual flow components, mass flow rate, volume flow rate, and total flow rate, and provides various measured values that can be output, including, for example, both the volume flow rate and the mass flow rate of the individual flow components.

[0054] The vibration meter 5 produces a vibration response. The vibration response is received and processed by the meter electronics 20 to generate one or more fluid measurement values. The values can be monitored, recorded, stored, aggregated, and / or output. The meter electronics 20 includes an interface 201, a processing system 203 that communicates with the interface 201, and a storage system 204 that communicates with the processing system 203. Although these components are shown as separate blocks, it should be understood that the meter electronics 20 can comprise various combinations of integrated components and / or separate components.

[0055] Interface 201 is configured to communicate with the meter assembly 10 of the vibration meter 5. Interface 201 may be coupled to the lead wire 100 (see FIG. 1) and configured to exchange signals with, for example, the driver 180, the pick-off sensors 170l and 170r, and the RTD 190. Interface 201 may be further configured to communicate over a communication path 26 to an external device or the like.

[0056] The processing system 203 can include any processing system. The processing system 203 is configured to search for and execute stored routines to operate the vibration meter 5. The memory system 204 can store routines including a flow meter routine 205, a valve control routine 211, a drive gain routine 213, and a vapor pressure routine 215. The memory system 204 can store measured values, received values, operating values, and other information. In some embodiments, the memory system stores a mass flow rate (m) 221, a density (ρ) 225, a density threshold 226, a viscosity (μ) 223, a temperature (T) 224, a pressure 209, a drive gain 306, a drive gain threshold 302, a gas mixture threshold 244, a gas mixture rate 248, and any other variables known in the art. Routines 205, 211, 213, 215 can include any of the described signals and other variables known in the art. Other measurement / processing routines are contemplated and are within the scope of the specification and claims.

[0057] As can be understood, the memory system 204 may store more or less values. For example, the vapor pressure may be measured without using the viscosity 223. For example, the viscosity may be estimated based on a pressure drop, or a function associating friction as a function of flow rate may be estimated. However, the viscosity 223 can be used to calculate a Reynolds number that can then be used to determine a friction coefficient. The Reynolds number and the friction coefficient can be used to determine the viscous pressure drop in conduits such as the conduits 130, 130, etc. described above with reference to FIG. 1. As can be understood, the Reynolds number may not always be used.

[0058] The flow meter routine 205 can generate and store fluid measurement values and flow measurement values. These values can include substantially instantaneous measurements, or can include total or cumulative values. For example, the flow meter routine 205 can generate a mass flow measurement value and store it, for example, in the mass flow storage device 221 of the storage system 204. The flow meter routine 205 can generate a density measurement value 225 and store it, for example, in the density storage device 225. The mass flow 221 and the density value 225 are already described and are determined from the vibration response as known in the art. The mass flow measurement value and other measurement values can include substantially instantaneous values, can include samples, can include average values over a time interval, or can include cumulative values over a time interval. The time interval can be selected to correspond to a particular fluid state, for example, a block of time during which only a liquid fluid state is detected, or alternatively, a fluid state including a liquid and entrained gas. Further, other mass flow and volume flow and related measurement values are contemplated and are within the scope of the specification and claims.

[0059] The drive gain threshold 302 may be used to distinguish between flow, no flow, the period of the single-phase / 2-phase boundary (where a fluid phase change occurs), and gas entrainment / mixed-phase flow. Similarly, the density threshold 226 applied to the density measurement value 225 may be used, separately or together with the drive gain 306, to distinguish gas entrainment / mixed-phase flow. The drive gain 306 may be utilized, for example, but not limited to, as a measurement criterion for the sensitivity of the conduit vibration of the vibrator 5 to the presence of fluids of different densities such as a liquid phase and a gas phase.

[0060] As used herein, the term "drive gain" refers to a measure of the amount of electrical power required to drive the flow tube to a particular amplitude, although any suitable definition may be used. For example, in some embodiments, the term "drive gain" may refer to a measurement or derived signal that indicates the amount of electrical power required to drive the drive current, pickoff voltage, or flow conduits 130, 130' to a particular amplitude. The drive gain may be used to detect a mixed-phase flow by taking advantage of drive gain characteristics such as, for example, noise level, standard deviation of the signal, attenuation-related measurements, and any other means known in the art for detecting a mixed-phase flow. These measurement criteria may be compared across the pickoff sensors 170l and 170r to detect a mixed-phase flow.

[0061] [Detection of Phase Change of Fluid] FIG. 3 shows a graph 300 depicting the relationship between the drive gain and the gas-liquid ratio that can be used to measure the vapor pressure using the vapor pressure gauge coefficient. As shown in FIG. 3, the graph 300 includes an average void fraction axis 310 and a drive gain axis 320. The average void fraction axis 310 and the drive gain axis 320 increase in percentage, although any suitable units and / or ratios may be used.

[0062] The graph 300 includes a plot 330 that is a relationship between the drive gain and the gas-liquid ratio for various flow rates. As shown, the gas-liquid ratio is the average void fraction value of the plot 330, although any suitable gas-liquid ratio such as gas volume fraction ("GVF") or gas entrainment rate may be used and may be based on volume, cross-sectional area, etc. As can be understood, the plots 330 are similar even though they are associated with various flow rates. Also shown is a drive gain threshold line 340 that intersects the plot 330 at an average void fraction of about 0.20%, which may be the reference average void fraction 330a corresponding to a drive gain of 40%. Also shown is the true vapor pressure drive gain 332, which is about 10%. The true vapor pressure drive gain 332 has a static pressure at which a fluid phase change occurs and corresponds to the fluid within the meter assembly where the gas-liquid ratio is zero.

[0063] As can be seen, plot 330 varies from a drive gain of about 10% to about 100% over a range from an average porosity of 0.00% to about 0.60%. As can be understood, a relatively small change in the average porosity results in a significant change in the drive gain. This relatively small change can ensure that the start of vapor generation can be accurately detected with the drive gain.

[0064] A drive gain of 40% is shown as corresponding to an average porosity of 0.20%, but this correspondence may be specific to a certain process. For example, a drive gain of 40% may correspond to other average porosities for other process fluids and conditions. Different fluids may have different vapor pressures, so the vapor generation of the fluids may start at different flow rates. That is, a fluid with a relatively low vapor pressure will evaporate at a higher flow rate, and a fluid with a relatively high vapor pressure will evaporate at a lower flow rate.

[0065] Also as can be understood, the drive gain threshold line 340 may be an alternative / other drive gain. However, having a drive gain of 40% may be beneficial in order to eliminate false detection of the mixing / mixed-phase flow while also ensuring that the start of vapor generation is accurately detected.

[0066] Also, although plot 330 uses the drive gain, other signals such as the measured density may be used. The measured density may increase or decrease due to the presence of voids in the fluid. For example, the measured density may increase due to the voids of a relatively high-frequency vibrator for sonic effects in a counterintuitive way. With a relatively low-frequency meter, the measured density may decrease because the density of the voids is smaller than that of the liquid. These and other signals may be used alone or in combination to detect the presence of vapor in the meter assembly.

[0067] As described above, the average void fraction value of 0.20% may be the reference average void fraction 330a corresponding to a drive gain value of 40%, which may be the case where the drive gain threshold line 340 intersects the drive gain axis 320. Thus, when the measured drive gain is 40% with respect to the fluid within a meter assembly such as the meter assembly 10 described above, the average void fraction of the fluid can be approximately 0.20%. A void fraction of approximately 0.20% may correspond to the pressure of the fluid due to the gas present in the fluid. For example, a void fraction of approximately 0.20% may correspond to, for example, a static pressure value.

[0068] Due to the predetermined relationship between the drive gain, or other signals such as density, and the reference average void fraction 330a which can be a reference gas-liquid ratio, the vapor pressure may be related to the vapor pressure coefficient. For example, the meter assembly can be vibrated while the static pressure is increased or decreased until a fluid phase change is detected. Next, as will be described in more detail below with reference to FIG. 4, the vapor pressure may be measured from the static pressure. The measured vapor pressure may correspond to, for example, the static pressure of the drive gain threshold line 340. This measured vapor pressure can be adjusted by the vapor pressure coefficient so as to correspond to the true vapor pressure drive gain 332 where the phase change occurs or where the single-phase / 2-phase boundary is encountered. Thus, the presence of gas in the fluid may be detected at a static pressure different from the true vapor pressure of the fluid, but nevertheless, the true vapor pressure can be measured.

[0069] Using the reference average void fraction 330a as an example, the static pressure within the meter assembly can be reduced until the drive gain reaches 40%, which shows that the fluid within the meter assembly has an average void fraction of 0.20%. A processing system such as the above-described processing system 203 can determine that the fluid begins to evaporate at a static pressure that is proportionally higher than, for example, the static pressure corresponding to a 40% drive gain. For example, the true vapor pressure may be related to a drive gain of about 10%. As can be understood, due to uncertainties involved in the calculation of the static pressure (such as errors from the pressure sensor, flow measurement errors, etc.), the true vapor pressure can be proportionally lower than the calculated static pressure related to a 40% drive gain. The true vapor pressure corresponds to the static pressure of the fluid at which a fluid phase change occurs, but the gas-liquid ratio is zero.

[0070] Therefore, the measured drive gain can be used to detect gas, but still, it can result in a highly accurate true vapor pressure. More specifically, at the moment when gas evolution first occurs and there are a few small bubbles present, the drive gain may not increase beyond the drive gain threshold line 340 for detection. The dynamic pressure may be increased, for example, by a pump that continues to increase the flow rate until the static pressure decreases such that the drive gain passes the drive gain threshold line 340. Depending on the application, this calculated static pressure (e.g., uncorrected vapor pressure) can be corrected (e.g., adjusted - increased or decreased) by, for example, a vapor pressure gauge coefficient of 1 psi that causes a delay in the detection of the fluid phase change. That is, the vapor pressure gauge coefficient is determined and can be applied to the uncorrected vapor pressure measurement as a function of the drive gain that causes the difference between the drive gain at which gas is detected and the true vapor pressure to detect a trace amount of gas.

[0071] Referring to FIG. 3 as an example, 40% of the measured drive gain may correspond to a static pressure of the fluid within the meter assembly that is 1 psi less than the static pressure corresponding to the true vapor pressure, i.e., the static pressure associated with the drive gain. Thus, the vibration meter 5, or the meter electronics 20, or any suitable electronics can determine that the vapor pressure coefficient is 1 psi and add this value to the static pressure associated with the 40% drive gain. As a result, since the vibration meter 5 can accurately detect the phase change of the fluid, it can also accurately measure the vapor pressure of the fluid using the drive gain.

[0072] However, other means of detecting the phase change that do not use the drive gain may be used. For example, the phase change may be detected by acoustic measurements, X-ray based measurements, optical measurements, etc. Combinations of the above implementations can also be considered. For example, a bypass line that extends vertically within a loop in which the acoustic and / or optical measurement values are vertically distributed is for determining where the gas first escapes. This height will provide the input necessary to calculate the vapor pressure of the fluid within the vibration meter 5, as described below.

[0073] [Pressure Drop in the Vibration Meter] FIG. 4 shows a graph 400 illustrating a method by which the vapor pressure can be measured using the static pressure of the fluid within the vibration meter. As shown in FIG. 4, the graph 400 includes a position axis 410 and a static pressure axis 420. The position axis 410 is not shown in terms of any particular unit of length and may be in inches, although any suitable unit may be used. The static pressure axis 420 is in units of pounds per square inch (psi), although any suitable unit may be used. The position axis 410 ranges from the inlet ("IN") to the outlet ("OUT") of the vibration meter.

[0074] Accordingly, the position from IN to OUT may correspond to the fluid within the meter assembly 10 shown, for example, in FIG. 1. In this example, the region from IN to around A may correspond to a portion of the meter assembly 10 between the flange 103 and the conduit mount 120. The region from around A to around G may correspond to the conduits 130, 130' between the mounts 120, 120'. The region from G to OUT may correspond to a portion of the meter assembly 10 from the mount 120' to the flange 103'. Thus, the fluid within the meter assembly 10 (e.g., the position ranging from IN to OUT) may not include, for example, the fluid within the pipeline into which the meter assembly 10 is inserted. The fluid within the meter assembly 10 may be the fluid within the conduits 130, 130'.

[0075] Graph 400 also includes a zero dynamic pressure plot 430 and a dynamic pressure change plot 440. The zero dynamic pressure plot 430 shows no change in dynamic pressure - the pressure is assumed to drop linearly from the inlet to the outlet of the vibrator. The dynamic pressure change plot 440 may represent the actual pressure within a vibrator inserted into a pipeline where the diameter of one or more conduits of the vibrator is smaller than the diameter of the pipeline. An exemplary vibrator 5 is shown in FIG. 1, but any suitable vibrator may be used. Thus, the fluid within a meter assembly such as the meter assembly 10 described above may have a reduced static pressure due to an increase in dynamic pressure. Also shown is a vapor pressure line 450 representing the vapor pressure of the fluid within the vibrator.

[0076] The dynamic pressure change plot 440 includes a static pressure drop portion 440a, a viscous loss portion 440b, and a static pressure rise portion 440c. The dynamic pressure change plot 440 also includes a minimum static pressure 440d. The static pressure drop portion 440a may be due to an increase in the flow rate that causes a corresponding increase in the dynamic pressure at this part of the vibrator. The viscous loss portion 440b may correspond to a constant diameter portion of one or more conduits within the vibrator. Thus, since the viscous loss portion 440b does not reflect an increase in the flow rate, it may not reflect an increase in the dynamic pressure. The static pressure rise portion 440c may recover the static pressure drop in the static pressure drop portion 440a due to a decrease in the flow rate. The static pressure drop portion 440a and the static pressure rise portion 440c may be static pressure changes within the meter assembly.

[0077] A portion of the dynamic pressure change plot 440 that includes the minimum static pressure 440d and is lower than the vapor pressure line 450 may correspond to a location (e.g., from around position E to slightly after position G) where a fluid phase change occurs in the fluid within a meter assembly such as the meter assembly 10 described above. As can be seen in FIG. 4, the minimum static pressure 440d is below the vapor pressure line 450. This indicates that the dynamic pressure change plot 440 may move upward by increasing the static pressure of the fluid within the meter assembly. However, if the static pressure is increased by about 5 psi so that the dynamic pressure change plot 440 moves up until the minimum static pressure 440d reaches the vapor pressure line 450, a fluid phase change can be detected. Due to the increase in the static pressure, gas or vapor in the fluid within the meter assembly may become liquid. Conversely, if the dynamic pressure change plot 440 is above the vapor pressure line 450 and the static pressure of the fluid within the meter assembly decreases until the minimum static pressure 440d reaches the vapor pressure line, the fluid phase change can be the generation of gas or vapor in the fluid.

[0078] As can be seen in FIG. 4, the viscous loss portion 440b decreases from a static pressure of about 68 psi at position A to a static pressure of about 55 psi at position G. As can be understood, the static pressure of about 55 psi at position G is less than the vapor pressure line 450 which is about 58 psi. As a result, even though the static pressures at the inlet and outlet are greater than the vapor pressure line 450, the fluid within the vibrator may still flow vigorously or leak out.

[0079] Therefore, the static pressures at the inlet and outlet do not directly correspond to the vapor pressure of the fluid. That is, the vapor pressure of the fluid may not be directly determined from the static pressure of the fluid within the pipeline or external to the meter assembly. The static pressure within the meter assembly 10, or more specifically, within conduits 130, 130' can be accurately measured, for example, by inputting the dimensions of the vibrator 5 (e.g., the diameter and length of conduits 130, 130') using the inlet and outlet pressure measurements. However, in order to accurately measure the vapor pressure, it may be necessary to induce a phase change of the fluid within the vibrator 5, which can be caused by changing the static pressure of the fluid within the vibrator 5.

[0080] [Change in Static Pressure of Fluid] FIG. 5 shows a system 500 for measuring the vapor pressure of a fluid. As shown in FIG. 5, the system 500 is a bypass that includes a bypass inlet and a bypass outlet coupled to a pipeline 501. The system 500 includes a pump 510 in fluid communication with the outlet of a vibrator 5 illustrated as a Coriolis flow meter, and the bypass outlet. An inlet pressure sensor 520 is in fluid communication with the inlet of the vibrator 5 and the bypass inlet. An outlet pressure sensor 530 is disposed between the outlet of the vibrator 5 and the pump 510 and is configured to measure the static pressure of the fluid at the outlet of the vibrator 5. A flow control device 540 shown as a valve is disposed between the bypass inlet and the inlet pressure sensor 520.

[0081] The pump 510 may be any suitable pump that can increase, for example, the velocity of the fluid within the vibrator 5. The pump 510 may include, for example, a variable frequency drive. The variable frequency drive may enable the pump 510 to control the flow rate of the fluid within the system 500. For example, the variable frequency drive can increase the flow rate of the fluid through the vibrator 5, although the flow rate can be increased by any suitable pump. The pump 510 can increase the dynamic pressure of the fluid within the vibrator 5 by increasing the flow rate.

[0082] Therefore, the static pressure of the fluid within the vibrator 5 may decrease. By way of example, referring to FIG. 4, the pump 510 may move the dynamic pressure change plot 440 downward. Thus, although not shown in FIG. 4, if the dynamic pressure change plot 440 is above the vapor pressure line 450, the pump 510 may induce flashing or gas evolution by moving the dynamic pressure change plot 440 downward. Similarly, by moving the dynamic pressure change plot 440 above the vapor pressure line 450, gas or vapor within the fluid may become liquid.

[0083] The inlet pressure sensor 520 and the outlet pressure sensor 530 may be any suitable pressure sensors configured to measure any pressure of the fluid. For example, the inlet pressure sensor 520 and the outlet pressure sensor 530 may measure the static pressure of the fluid within the system 500. Additionally or alternatively, the inlet pressure sensor 520 and the outlet pressure sensor 530 may measure the total pressure of the fluid within the system 500. In one example, the dynamic pressure of the fluid may be determined by taking the difference between the total pressure and the static pressure of the fluid within the system 500 according to Equation [3] above. For example, the inlet pressure sensor 520 may measure the total pressure and the static pressure of the fluid proximate to or at the inlet of the vibrator 5. The inlet pressure sensor 520 and / or the meter electronics 20 within the vibrator 5 may measure the dynamic pressure at the inlet of the vibrator 5.

[0084] The flow control device 540 can increase the flow velocity of the fluid within the system 500 when the position of the flow control device 540 is moved from a partially closed position to a fully open position. For example, by reducing the flow restriction of the system 500 at the inlet of the vibrator 5, the velocity of the fluid may increase according to Equation [2] above. This can move the dynamic pressure change plot 440 downward to induce flashing or gas evolution. Conversely, the flow control device 540 can decrease the flow velocity of the fluid within the system 500, thereby moving the dynamic pressure change plot 440 upward, thereby condensing gas or vapor.

[0085] When the flow control device 540 is opened, the flow velocity increases, but the static pressure at the inlet of the vibration meter 5 is the same, and vice versa. The combination of the flow control device 540 and the pump 510 preferably partially closes the flow control device 540 (e.g., to restrict the flow downstream of the flow control device 540 and reduce the pressure) and increases the pump speed (e.g., to increase the flow rate) in order to obtain a lower static pressure and a higher speed, thereby providing favorable process conditions.

[0086] The static pressure of the fluid in the vibration meter 5, or more specifically, in the meter assembly 10 within the vibration meter 5, can be changed by using the pump 510 or the flow control device 540, or a combination of both, although other means for changing the above-mentioned static pressure may be used. For example, the height z of the vibration meter 5 may be changed. To decrease the static pressure of the fluid within the vibration meter 5, the height z may be increased. To increase the static pressure of the fluid within the vibration meter 5, the height z may be decreased. The height z of the vibration meter 5 may be changed by any suitable means such as an electric lift between the vibration meter 5 and the pipeline 501, and a bellows between the vibration meter 5 and, for example, the flow control device 540 and the pump 510. Other means, as well as combinations of various means (e.g., the pump 510, the flow control device 540, and / or the electric lift), may be used.

[0087] For example, if the flow rate through the bypass is sufficient, the pump does not necessarily have to be used. Only the flow control device 540 may be used. The flow control device 540 may be attached at other positions such as downstream of the vibration meter 5. Alternatively, the flow control device 540 may not be used, such as where the pump 510 and / or the electric lift is used. In another alternative, the meter may be attached to the main line instead of the bypass. Additionally or alternatively, only a single pressure sensor may be used. For example, the outlet pressure sensor 530 may be used. The inlet and / or outlet pressure sensors 520, 530 may be arranged at alternative positions. The outlet pressure sensor 530 and its position may be beneficial because when the fluid in the meter assembly 10 is at vapor pressure, the static pressure at the position of the outlet pressure sensor 530 can be substantially stable with respect to the flow velocity. That is, any additional increase in the flow velocity may not cause a substantial decrease in the static pressure measured by the outlet pressure sensor 530.

[0088] [Measurement of Vapor Pressure Using Density] FIG. 6 shows a graph 600 showing the vapor pressure of a multi-component fluid. As shown in FIG. 6, the multi-component fluid contains hydrocarbons. The graph 600 includes a liquid density axis 610 and a logarithmic vapor pressure axis 620, which are in units of kilograms per cubic meter (kg / m 3 ) and pounds per square inch absolute (psia), respectively, although any suitable units may be used. The graph 600 also includes a density-versus-pressure plot 630 showing the relationship between the density and vapor pressure of the hydrocarbon. The density-versus-pressure plot 630 is shown as including a propane density-versus-pressure plot 630a, a butane density-versus-pressure plot 630b, and a hexane density-versus-pressure plot 630c. The temperature of the multi-component fluid is in the range of 34°C to 48°C.

[0089] If the fluid within the meter assembly contains two components, such as propane and butane for example, the density of the fluid can be between the densities of the two components. This density can be used to measure the vapor pressure of the mixture. For example, the density of propane and butane fluids can be correlated to the vapor pressure by interpolation. In one example, linear interpolation can be used to estimate the vapor pressure of the mixture from the density. As an example, a multi-component fluid containing propane and butane can have a density of about 500 kg / m 3 and this can potentially correspond to a vapor pressure of about 130 psia. This vapor pressure can be used to verify the vapor pressure measured by detecting the phase change within the meter assembly as described above.

[0090] Figure 6 can be understood to be a simplified representation with only three components. Alternative density versus temperature plots can be different. For example, more components and properties typical of crude oil or processed hydrocarbons can be used, which can result in alternative density versus temperature plots. By way of illustration and not limitation, when additional propane is used, an increase in vapor pressure may be observed, but if other components (e.g., crude oil) are heavy, the density can be similar. Still, a general relationship such as the higher the density, the lower the vapor pressure and vice versa may still hold true.

[0091] Furthermore, the slope or curve of the alternative plot is not always constant. For example, in certain applications where the fluid composition may not change significantly, once calibrated, a calibrated vapor pressure versus density plot can be used as in the following illustration.

[0092] Figure 7 shows a method 700 for verifying vapor pressure using measured values of fluid density. As shown in Figure 7, in step 710, method 700 measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly. The meter assembly used by method 700 may be the meter assembly 10 described above, although any suitable meter assembly may be used. In step 720, method 700 measures the density of the fluid based on the resonant frequency of the meter assembly. The density of a fluid, such as a multi-component fluid, can be determined, for example, by measuring the resonant frequency of the meter assembly and measuring the corresponding density associated with the resonant frequency. In step 730, method 700 derives the vapor pressure from the measured density. In step 740, method 700 compares the measured vapor pressure with the derived vapor pressure.

[0093] In step 710, the vapor pressure of the fluid may be measured, for example, by changing the total pressure or static pressure of the fluid within the meter assembly 10 until a fluid phase change is detected. For example, the static pressure of the fluid may decrease until no vapor is detected anymore. Conversely, the static pressure can be increased until vapor is detected. The fluid phase change may be detected by any suitable means based on a sensor signal, such as detecting a change in the drive gain or drive signal as described above with reference to Figure 3.

[0094] When a fluid phase change is detected, such as when a change in the drive gain is detected, the vibrometer 5, or electronics coupled to the vibrometer 5, can measure the pressure at the inlet and / or outlet of the meter assembly 10. For example, referring to Figure 5, the inlet pressure sensor 520 may measure the static pressure of the fluid at the inlet of the meter assembly 10, and the outlet pressure sensor 530 may measure the static pressure of the fluid at the outlet of the meter assembly 10. Thus, the inlet static pressure and / or the outlet static pressure may be associated with the fluid phase change.

[0095] The inlet static pressure and the outlet static pressure can be used in the above equation [7] to determine the static pressure within the meter assembly. For example, the outlet pressure is P 1 , P 2 can be the pressure of the fluid within the meter assembly. The height-related terms, ρgz 1 and ρgz 2 are used to explain, for example, changes in the height of the fluid within the meter assembly due to the conduit shape. For example, an arcuate conduit such as the conduit of the above-described meter assembly 10 may have a step. The dynamic velocity terms (ρv 1 2 ) / 2, (ρv 2 2 ) / 2 can likewise have their values determined by measuring the density and flow rate of the fluid and knowing the dimensions of the conduits and the pipes coupled to the inlet and outlet of the conduits. Similarly, the viscous pressure drop term, -(ρv 2 ) / 2fL / D can also be determined.

[0096] In step 730, the derivation of the vapor pressure may be based on a predetermined correlation between a plurality of vapor pressures and densities. For example, referring to FIG. 6, the plurality of vapor pressures may include measured values of the vapor pressures of various hydrocarbons. The density can be the density of the hydrocarbon. Although FIG. 6 shows hydrocarbons of propane, butane, and hexane, more or less alternative hydrocarbons may be used.

[0097] The correlation between the plurality of vapor pressures and densities may be a density-versus-pressure plot 630 including a propane density-versus-pressure plot 630a, a butane density-versus-pressure plot 630b, and a hexane density-versus-pressure plot 630c, as shown in FIG. 6. Also, the correlation between the plurality of vapor pressures and densities may include interpolation such as mathematical formulas and data points between the propane density-versus-pressure plot 630a, the butane density-versus-pressure plot 630b, and / or the hexane density-versus-pressure plot 630c.

[0098] These interpolations may correspond to the correlation between multiple vapor pressures and densities for multi-component fluids. For example, referring to FIG. 6, the interpolation between the propane density vs. pressure plot 630a and the butane density vs. pressure plot 630b can correlate a density of 500 kg / m 3 to a vapor pressure of approximately 120 psia. This interpolation can correlate density and vapor pressure for a mixture of propane and butane. As described above, density vs. pressure plots alternative to those shown in FIG. 6 may vary depending on the number and concentration of components.

[0099] Thus, since the vapor pressure of a liquid is a function of temperature and composition, and the density of a liquid is a strong function of temperature and composition, the vapor pressure of a pure or multi-component liquid can be correlated to its density. This is shown in FIG. 6 where the vapor pressures of selected hydrocarbons are plotted against their liquid densities. Using density measurements and temperature measurements from a Coriolis flow meter, an approximate saturation pressure of the hydrocarbon can be determined. This correlation can be used as an indirect reference for vapor pressure and will be used as a quality check against the direct pressure measurements described above with reference to FIGS. 3 to 5. Since density and temperature are measured, and standard hydrocarbons exhibit a consistent relationship between vapor pressure and these variables, it can serve as an approximate indicator of vapor pressure for any hydrocarbon in any device, without the need for bypass lines, pumps, valves, pressure measurements, or other components, simply by measuring the density. However, depending on whether the individual components change during the flow, additional information may be needed, and additional components may need to be used.

[0100] Furthermore, calibration services can be provided that are tailored to specific applications, fluids, and process conditions. During calibration, the density (of pure or multi-component liquids) can be correlated to the vapor pressure, potentially eliminating the need to perform pressure measurements. A typical composition of hydrocarbon liquids from an intermediate plant includes a mixture of about 30 components. Measuring the vapor pressure of a mixture with 30 components using only density can be sufficiently accurate. For example, if the expected variation in the concentration of each component is minimal, the vapor pressure can be sufficiently accurate.

[0101] The above describes the vibration meter 5, particularly the meter electronics 20, and the method 700 of using density to verify the vapor pressure. Therefore, the accuracy of the vapor pressure can be guaranteed. The density can include the density of multi-component fluids. Thus, if the vapor pressure includes multiple partial vapor pressures, the density may still be used to verify the vapor pressure. Furthermore, since the density can be measured with the vibration meter 5 that can also measure the vapor pressure, the vapor pressure can be verified, for example, within the meter electronics 20 before being provided across the path 26.

[0102] The detailed description of the above embodiments is not an exhaustive description of all embodiments that the inventors consider to be within the scope of this specification. In fact, those skilled in the art will recognize that they can create additional embodiments by variously combining or omitting specific elements of the above embodiments, and such additional embodiments will fall within the scope and teachings of this specification. It will also be apparent to those skilled in the art that additional embodiments can be created by combining the above embodiments in whole or in part within the scope and teachings of this specification.

[0103] Accordingly, specific embodiments of the present invention are described herein for purposes of illustration, but as will be recognized by those of ordinary skill in the relevant art, various equivalent modifications are possible within the scope of the present invention. The teachings provided herein can be applied not only to the embodiments shown above and in the accompanying figures, but also to other methods of verifying vapor pressure using fluid density measurements. Accordingly, the scope of the above embodiments should be determined from the following claims.

Claims

1. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such. A meter electronic device (20) for verifying vapor pressure using a measured value of the density of a fluid, comprising a processing system (200) communicatively coupled to a meter assembly (10) having the fluid, wherein the processing system (200) measures the vapor pressure of the fluid by detecting a phase change of the fluid within the meter assembly (10), measures the density of the fluid based on a resonance frequency of the meter assembly (10), derives a vapor pressure from the measured density, and compares the measured vapor pressure with the derived vapor pressure, and is configured as such.

2. The meter electronic device (20) according to claim 1, wherein the fluid is a multi-component fluid containing a hydrocarbon component.

3. The meter electronic device (20) according to claim 2, wherein the hydrocarbon component contains at least two of propane, butane, and hexane.

4. The meter electronic device (20) according to any one of claims 1 to 3, comprising a processing system (200) configured to utilize a predetermined correlation between a plurality of vapor pressures and a plurality of densities, wherein the processing system (200) configured to derive a vapor pressure from the measured density is configured to utilize the predetermined correlation between the plurality of vapor pressures and the plurality of densities.

5. The meter electronic device (20) according to claim 4, comprising a processing system (200) configured to interpolate between the predetermined correlations, wherein the processing system (200) configured to utilize the predetermined correlation between the plurality of vapor pressures and the plurality of densities is configured to interpolate between the predetermined correlations.

6. The meter electronic device (20) according to any one of claims 1 to 5, comprising a processing system (200) configured to determine whether the measured vapor pressure is within a predetermined range of the derived vapor pressure, wherein the processing system (200) configured to compare the measured vapor pressure with the derived vapor pressure is configured to determine whether the measured vapor pressure is within a predetermined range of the derived vapor pressure.

7. The meter electronic device (20) according to any one of claims 1 to 6, wherein the processing system (200) is further configured to measure the vapor pressure of the fluid by detecting a phase change of the fluid using a drive gain.

8. A method for verifying vapor pressure using a measured value of the density of a fluid, comprising the step of measuring the vapor pressure of the fluid by detecting a phase change of the fluid within a meter assembly. A method for verifying vapor pressure using a measured value of the density of a fluid, comprising the step of measuring the vapor pressure of the fluid by detecting a phase change of the fluid within a meter assembly. Measuring the density of the fluid based on the resonance frequency of the meter assembly; Deriving the vapor pressure from the measured density; Comparing the measured vapor pressure with the derived vapor pressure; A method comprising.

9. The method according to claim 8, wherein the fluid is a multi-component fluid containing a hydrocarbon component.

10. The method according to claim 9, wherein the hydrocarbon component contains at least two of propane, butane, and hexane.

11. The method according to any one of claims 8 to 10, wherein the step of deriving the vapor pressure from the measured density includes utilizing a predetermined correlation between a plurality of vapor pressures and a plurality of densities.

12. The method according to claim 11, wherein the step of utilizing the predetermined correlation between the plurality of vapor pressures and the plurality of densities includes interpolating between the predetermined correlations.

13. The method according to any one of claims 8 to 12, wherein the step of comparing the measured vapor pressure with the derived vapor pressure includes determining whether the measured vapor pressure is within a predetermined range of the derived vapor pressure.

14. The method according to any one of claims 8 to 13, further comprising measuring the vapor pressure of the fluid by detecting a phase change of the fluid using a drive gain.

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