阅读说明：本技术 使用蒸气压计因数确定蒸气压 (Determining vapor pressure using vapor pressure gauge factor ) 是由 霍埃尔·魏因施泰因 大卫·马丁内斯·莫雷特 于 2019-04-03 设计创作，主要内容包括：提供了用于使用蒸气压计因数确定蒸气压的计量器电子装置(20)。计量器电子装置(20)包括通信地耦接至计量器组件(10)的处理系统(200)。处理系统(200)被配置成：向具有流体的计量器组件(10)提供驱动信号；测量提供至计量器组件(10)的驱动信号的驱动增益；以及基于先前确定的驱动增益与参考气液比之间的关系来确定流体的蒸气压。(Meter electronics (20) for determining vapor pressure using a vapor pressure meter factor is provided. The meter electronics (20) includes a processing system (200) communicatively coupled to the meter assembly (10). The processing system (200) is configured to: providing a drive signal to a meter assembly (10) having a fluid; measuring a drive gain of a drive signal provided to the meter assembly (10); and determining a vapor pressure of the fluid based on a previously determined relationship between drive gain and reference gas-liquid ratio.)

1. A meter electronics (20) for determining vapor pressure using a vapor pressure meter factor, the meter electronics (20) comprising:

a processing system (200) communicatively coupled to the meter assembly (10), the processing system (200) configured to:

providing a drive signal to the meter assembly (10) with fluid;

measuring a drive gain of a drive signal provided to the meter assembly (10); and

the vapor pressure of the fluid is determined based on a previously determined relationship between drive gain and reference gas-liquid ratio.

2. The meter electronics (20) of claim 1, wherein the meter electronics (20) is further configured to determine a static pressure of a fluid in the meter assembly (10) while measuring the drive gain.

3. The meter electronics (20) of one of claims 1 or 2, wherein the vapor pressure is determined using the measured drive gain and a relationship between the previously determined drive gain and a reference gas-liquid ratio.

4. The meter electronics (20) of any one of the preceding claims 1-3, wherein the relationship between the previously determined drive gain and the reference gas-liquid ratio is a linear function relating 100% drive gain to true vapor pressure drive gain.

5. The meter electronics (20) of any one of the preceding claims 1 to 4, wherein at least one of the reference gas-liquid ratio and the measured drive gain is associated with a predetermined threshold value for detecting a phase change of the fluid.

6. The meter electronics (20) of any one of the preceding claims 1 to 5, wherein the determined vapor pressure is a true vapor pressure.

7. The meter electronics (20) of claim 6, wherein the meter electronics (20) is further configured to determine a Reid vapor pressure using the true vapor pressure.

8. A method of determining vapor pressure using a vapor pressure gauge factor, the method comprising:

providing a drive signal to the meter assembly having a fluid;

measuring a drive gain of a drive signal provided to the meter assembly; and

the vapor pressure of the fluid is determined based on a previously determined relationship between drive gain and reference gas-liquid ratio.

9. The method of claim 8, further comprising: determining a static pressure of the fluid in the meter assembly while measuring the drive gain.

10. The method of one of claims 8 or 9, wherein the vapor pressure is determined using the measured drive gain and the previously determined relationship between drive gain and reference gas-liquid ratio.

11. The method of any preceding claim 8-10, wherein the relationship between the previously determined drive gain and reference gas-liquid ratio is a linear function relating 100% drive gain to true vapor pressure drive gain.

12. A method according to any of the preceding claims 8-11, wherein at least one of the reference gas-to-liquid ratio and the measured drive gain is associated with a predetermined threshold value for detecting a phase change of the fluid.

13. The method according to any one of the preceding claims 8 to 12, wherein the determined vapor pressure is the true vapor pressure.

14. The method of claim 13, further comprising: the actual vapor pressure is used to determine the Reid vapor pressure.

15. A method of determining a vapor pressure gauge factor for determining vapor pressure, the method comprising:

determining a static pressure of a fluid in the meter assembly; and

determining a difference between the static pressure and the true vapor pressure of the fluid.

16. The method of claim 15, further comprising:

providing a drive signal to the meter assembly;

measuring a drive gain of a drive signal provided to the meter assembly; and

correlating the static pressure of the fluid in the meter assembly with the drive gain.

17. The method of one of claims 15 or 16, further comprising:

associating a drive gain threshold for detecting a phase change in the fluid with the measured drive gain; and

associating the difference with the drive gain threshold.

Technical Field

The embodiments described below relate to determining vapor pressure, and more particularly, to determining vapor pressure using a vapor pressure gauge factor.

Background

Vibration sensors, such as, for example, vibrating densitometers and coriolis flow meters, are generally known and are used to measure mass flow and other information of a material flowing through a conduit in a flow meter. Exemplary coriolis flowmeters are disclosed in U.S. patent 4,109,524, U.S. patent 4,491,025, and re31,450, all owned by j.e. smith et al. These flow meters have one or more conduits of straight or curved configuration. For example, each conduit structure in a coriolis mass flowmeter has a set of natural vibration modes, which may be simple bending, torsional, or coupled types. Each conduit may be driven to oscillate in a preferred mode.

The material flows into the flow meter from a connecting line on the inlet side of the flow meter, is directed through a conduit, and exits the flow meter through the outlet side of the flow meter. The natural vibration modes of the vibration system are defined in part by the combined mass of the conduit and the material flowing within the conduit.

When no flow is passing through the flowmeter, the driving force applied to the conduit causes all points along the conduit to oscillate with the same phase or a small "zero offset", which is the time delay measured at zero flow. As material begins to flow through the flowmeter, coriolis forces cause each point along the conduit to have a different phase. For example, the phase at the inlet end of the flow meter lags the phase at the central driver position, while the phase at the outlet leads the phase at the central driver position. A pickup on the conduit generates a sinusoidal signal representative of the motion of the conduit. Signals output from the pickups are processed to determine time delays between the pickups. The time delay between two or more pickups is proportional to the mass flow rate of the material flowing through the conduit.

Meter electronics connected to the driver generates drive signals to operate the driver and determines the mass flow rate and other properties of the material from the signals received from the pickup. The driver may comprise one of many well-known arrangements; however, magnets and reaction drive coils (opposing drive coils) have enjoyed great success in the flow meter industry. An alternating current is delivered to the drive coil for vibrating the conduit at a desired flow tube amplitude and frequency. It is also known in the art to provide the pick-up as a magnet and coil arrangement very similar to the driver arrangement. However, when the driver receives a current that causes motion, the pickup may use the motion provided by the driver to induce a voltage.

Vapor pressure is an important property in applications that handle the flow and storage of volatile fluids (e.g., gasoline, natural gas liquids, and liquefied petroleum gases). The vapor pressure provides an indication of how the volatile fluid may behave during processing and also indicates conditions under which bubbles will likely form and pressure will likely build. As such, vapor pressure measurements of volatile fluids increase safety and prevent damage to transport vessels and infrastructure. For example, if the vapor pressure of the fluid is too high, cavitation may occur during pumping and delivery operations. In addition, the vessel or process line vapor pressure can potentially rise above safe levels due to temperature changes. Therefore, it is often necessary to know the vapor pressure prior to storage and transport.

Typically, vapor pressure is determined by taking a sample and moving it to a laboratory for testing to determine values from the sample. This presents a challenge to the implementation of regulatory fuel quality standards due to delays in obtaining end results, the cost of maintaining the laboratory, and security and legal evidence leaks associated with sample processing. Accordingly, there is a need for an online device or system that can determine the vapor pressure of a fluid in a meter assembly on a continuous, real-time basis under process conditions. This is provided by the present embodiment and achieves an advance in the art. The field measurement is more reliable because it avoids the need for periodic sampling and completely eliminates the risk of fluid property changes between the time of sample collection and the time of laboratory determinations. Furthermore, security is increased by making real-time measurements, since unsafe conditions can be corrected immediately. In addition, money is saved because regulatory enforcement can be done via a simple field check, where inspection and enforcement decisions can be made with little delay or process interruption. These benefits can be enhanced by accurately determining the vapor pressure.

Disclosure of Invention

A meter electronics for determining vapor pressure using a vapor pressure meter factor is provided. According to an embodiment, the meter electronics include a processing system communicatively coupled to the meter assembly. The processing system is configured to: providing a drive signal to a meter assembly having a fluid; measuring a drive gain of a drive signal provided to the meter assembly; and determining a vapor pressure of the fluid based on a previously determined relationship between drive gain and reference gas-liquid ratio.

A method of determining vapor pressure using a vapor pressure gauge factor is provided. According to an embodiment, the method comprises: providing a drive signal to a meter assembly having a fluid; measuring a drive gain of a drive signal provided to the meter assembly; and determining a vapor pressure of the fluid based on a previously determined relationship between drive gain and reference gas-liquid ratio.

A method of determining a vapor pressure gauge factor for determining vapor pressure is provided. According to an embodiment, the method comprises: determining a static pressure of a fluid in the meter assembly; and determining the difference between the static pressure and the true vapor pressure of the fluid.

Aspects of the invention

According to one aspect, a meter electronics (20) for determining vapor pressure using a vapor pressure meter factor includes a processing system (200) communicatively coupled to a meter assembly (10). The processing system (200) is configured to: providing a drive signal to a meter assembly (10) having a fluid; measuring a drive gain of a drive signal provided to the meter assembly (10); and determining a vapor pressure of the fluid based on a previously determined relationship between drive gain and reference gas-liquid ratio.

Preferably, the meter electronics (20) is further configured to determine a static pressure of the fluid in the meter assembly (10) while measuring the drive gain.

Preferably, the vapor pressure is determined using the measured drive gain and a previously determined relationship between drive gain and reference gas-liquid ratio.

Preferably, the relationship between the previously determined drive gain and the reference gas-to-liquid ratio is a linear function relating 100% drive gain to true vapor pressure drive gain.

Preferably, at least one of the reference gas-to-liquid ratio and the measured drive gain is associated with a predetermined threshold for detecting a phase change of the fluid.

Preferably, the determined vapor pressure is the true vapor pressure.

Preferably, the meter electronics (20) is further configured to determine the reid vapor pressure using the true vapor pressure.

According to one aspect, a method of determining vapor pressure using a vapor pressure gauge factor, comprises: providing a drive signal to a meter assembly having a fluid; measuring a drive gain of a drive signal provided to the meter assembly; and determining a vapor pressure of the fluid based on a previously determined relationship between drive gain and reference gas-liquid ratio.

Preferably, the method further comprises determining a static pressure of the fluid in the meter assembly while measuring the drive gain.

Preferably, the vapor pressure is determined using the measured drive gain and a previously determined relationship between drive gain and reference gas-liquid ratio.

Preferably, the relationship between the previously determined drive gain and the reference gas-to-liquid ratio is a linear function relating 100% drive gain to true vapor pressure drive gain.

Preferably, at least one of the reference gas-to-liquid ratio and the measured drive gain is associated with a predetermined threshold for detecting a phase change of the fluid.

Preferably, the determined vapor pressure is the true vapor pressure.

Preferably, the method further comprises using the true vapor pressure to determine the reid vapor pressure.

According to one aspect, a method of determining a vapor pressure gauge factor for determining vapor pressure, comprises: determining a static pressure of a fluid in the meter assembly; and determining the difference between the static pressure and the true vapor pressure of the fluid.

Preferably, the method further comprises: providing a drive signal to a meter assembly; measuring a drive gain of a drive signal provided to the meter assembly; and correlating the static pressure of the fluid in the meter assembly with the drive gain.

Preferably, the method further comprises: associating a drive gain threshold for detecting a phase change in the fluid with the measured drive gain; and associating the difference with a drive gain threshold.

Drawings

Like reference symbols in the various drawings indicate like elements. It should be understood that the drawings are not necessarily drawn to scale.

Fig. 1 shows a vibrating meter 5.

Fig. 2 is a block diagram of the meter electronics 20 of the vibrating meter 5.

FIG. 3 shows a graph 300, the graph 300 illustrating the relationship between drive gain and gas-liquid ratio that can be used to determine vapor pressure using a vapor pressure gauge factor.

Fig. 4 shows a graph 400, which graph 400 shows how the static pressure of the fluid in the vibrating meter can be used to determine the vapor pressure.

Fig. 5 shows a system 500 for determining a vapor pressure of a fluid.

Fig. 6 shows a method 600 for determining vapor pressure using a vapor pressure gauge factor.

Fig. 7 shows a method 700 of determining a vapor pressure gauge factor for determining vapor pressure.

Detailed Description

Fig. 1-7 and the following description describe specific examples to teach those skilled in the art how to make and use the best mode of implementation for determining vapor pressure using a vapor pressure gauge factor. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form a variety of variations for determining vapor pressure using a vapor pressure gauge factor. Therefore, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

Fig. 1 shows a vibrating meter 5. As shown in fig. 1, the vibrating meter 5 includes a meter assembly 10 and meter electronics 20. The meter assembly 10 is responsive 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 100 to provide density, mass flow rate, temperature information, and/or other information on the path 26.

The gauge assembly 10 includes a pair of manifolds 150 and 150', flanges 103 and 103' having flange necks 110 and 110', a pair of parallel conduits 130 and 130', a driver 180, a Resistance Temperature Detector (RTD)190, and a pair of pickoff sensors 170l and 170 r. The conduits 130 and 130 'have two substantially straight inlet legs 131, 131' and outlet legs 134, 134 'which converge towards each other at the conduit mounting blocks 120 and 120'. The conduits 130, 130' are curved at two symmetrical positions along their length and are substantially parallel over their entire length. The support bars 140 and 140 'serve to define axes W and W about which each conduit 130, 130' oscillates. The branches 131, 131' and 134, 134' of the conduits 130, 130' are fixedly attached to the conduit mounting block 120 and the conduit mounting block 120', and these blocks are in turn fixedly attached to the manifolds 150 and 150 '. This provides a continuous closed material path through the gauge assembly 10.

When flanges 103 and 103' having holes 102 and 102' are connected via inlet end 104 and outlet end 104' into a process line (not shown) carrying a process material being measured, the material enters inlet end 104 of the meter through an aperture 101 in flange 103 and is directed through manifold 150 to conduit mounting block 120 having surface 121. Within the manifold 150, the material is separated and passed through the conduits 130, 130'. Upon exiting the conduits 130, 130', the process material is recombined into a single stream within the mounting block 120' having the surface 121' and the manifold 150' and thereafter directed to an outlet end 104' connected to a process line (not shown) by a flange 103' having holes 102 '.

The conduits 130, 130' are selected and suitably mounted to the conduit mounting blocks 120, 120' to have substantially the same mass distribution, moment of inertia, and young's modulus about the bending axes W-W and W ' -W ', respectively. These bending axes pass through the support rods 140, 140'. Since the young's modulus of the conduit changes with temperature, and this change affects the calculation of flow and density, the RTD 190 is mounted to the conduit 130' to continuously measure the temperature of the conduit 130 '. The temperature of conduit 130', and thus the voltage appearing across RTD 190 for a given current passing therethrough, is controlled by the temperature of the material passing through conduit 130'. The temperature dependent voltage appearing across the RTD 190 is used by the meter electronics 20 in a well known manner to compensate for changes in the modulus of elasticity of the conduits 130, 130' due to any changes in the conduit temperature. The RTD 190 is connected to meter electronics 20 by a lead 195.

The two conduits 130, 130 'are driven in opposite directions by the driver 180 about their respective bending axes W and W' and are in a so-called first out of phase bending mode of the flow meter. The driver 180 may comprise any one of a number of well-known arrangements, such as a magnet mounted to the guide tube 130 'and a counter-acting coil mounted to the guide tube 130, and through which an alternating current is passed for vibrating both guide tubes 130, 130'. An appropriate drive signal is applied by the meter electronics 20 to the driver 180 via the wire 185.

The meter electronics 20 receives the RTD temperature signal on lead 195, and the left and right sensor signals present on lead 100, which carry the left and right sensor signals 165l and 165r, respectively. The meter electronics 20 generates a drive signal to the driver 180 that appears on the wire 185 and vibrates 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 through the meter assembly 10. This information, along with other information, is applied as a signal to the path 26 by the meter electronics 20.

Mass flow rate measurementCan be generated according to the following equation:

the Δ t term includes an operatively derived (i.e., measured) time delay value that includes the time delay that exists between the pickoff sensor signals, such as where the time delay is due to the coriolis effect associated with the mass flow rate through the vibrating meter 5. The measured Δ t term ultimately determines the mass flow rate of the flowing material as it flows through the vibrating meter 5.Δ t₀The term includes the time delay at zero flow calibration constant. Δ t is typically determined at the factory₀The item and program it into the vibrating meter 5. Time delay at zero flow Δ t even in the case of changing flow conditions₀The items do not change. The flow calibration factor FCF is proportional to the stiffness of the vibrating meter 5.

Pressure in fluid in a vibrating meter

Assuming a liquid that is incompressible under steady conditions, the flow rate of mass into a controlled volume (e.g., a tube) at the inletEqual to the flow rate of the mass leaving at the outletInlet mass flow rateMust equal the outlet mass flow rateThe principle of (2) is represented by the following formula]Shown. Moving from the inlet to the outlet, the mass flow rate is conserved at each point along the tube. However, the flow area intermediate the inlet and the outlet may decrease. This reduction in flow area requires an increase in the velocity of the fluid (v ≠ g) to maintain the same mass flow rate and to comply with the mass conservation principle.

Wherein:

is the mass flow rate of the fluid;

v is the average fluid velocity;

ρ is the density of the fluid;

a is the total cross-sectional area;

subscript 1 represents the inlet;

subscript 3 denotes the outlet; and

the subscript 2 indicates the inlet to outlet.

Furthermore, the total pressure (total pressure) in a flow system is equal to the sum of both dynamic pressure (dynamic pressure) and static pressure (static pressure):

P_total＝P_static+P_dynamic。 [3]

dynamic pressure P_dynamicCan be defined as:

wherein the terms ρ and v are defined above with respect to formula [2 ].

Assuming stable, incompressible, inviscid, no swirl, the bernoulli equation gives:

where P refers to static pressure and the term ρ gz describes the hydrostatic head due to elevation changes. More specifically, g is the gravitational constant and z is the height. The viscous part of the pressure drop (viscous port) can be handled with a separate loss term in the bernoulli equation.

Wherein:

f is the friction factor;

l is the length of the tube; and

d is the diameter of the tube.

Equation [7] below is a version of the Bernoulli equation that accounts for the frictional losses associated with traveling through a pipe. As the fluid travels through the tube, the fluid dissipates energy and the pressure drops over a given length of tube. This loss in pressure is not recoverable because the energy from the fluid has been dissipated through frictional losses. Thus, the following equation may account for this loss:

this relationship can be applied to the above reference equation [2]]Exemplary tubes are described. As the fluid moves from the inlet to intermediate the inlet and the outlet, there is a change in velocity to maintain the mass flow rate. Thus, in holding formula [7]Dynamic pressure in the relationship shown inIncreasing, resulting in a decrease in static pressure. When the fluid moves from the middle of the inlet and outlet to the outlet, the static pressure recovers by the same principle. I.e. moving from the middle of the inlet and outlet to the outlet, the flow area increases; thus, the fluid velocity is reduced, resulting in a reduction in dynamic pressure while restoring a portion of the initial static pressure. However, the static pressure at the outlet will be lower due to unrecoverable viscous losses.

This may allow the static pressure at the inlet and outlet to be greater than the vapor pressure of the fluid and the static pressure intermediate the inlet and outlet to be less than the vapor pressure of the fluid. Thus, although the static pressure at the inlet and outlet is greater than the vapor pressure of the fluid, flashing or degassing may still occur in the tubes. In addition, a vibrating meter, such as a coriolis meter, may be inserted into a conduit having a diameter different from the diameter of one or more conduits in the vibrating meter. Thus, when outgassing is detected in the vibrating meter, the pressure measured in the conduit may not be the vapor pressure of the fluid in the vibrating meter.

Meter electronics-drive gain

Fig. 2 is a block diagram of the meter electronics 20 of the vibrating meter 5. In operation, the vibrating meter 5 provides various measurements that may be output, including one or more of mass flow rates, volume flow rates, individual flow component mass flow rates and volume flow rates, and measurements or averages of total flow rates, including, for example, both volume flow rates and mass flow rates of individual flow components.

The vibrating meter 5 generates a vibratory response. The vibrational response is received and processed by the meter electronics 20 to generate one or more fluid measurements. These values may be monitored, recorded, saved, summed, and/or output. The meter electronics 20 includes an interface 201, a processing system 203 in communication with the interface 201, and a storage system 204 in communication with the processing system 203. While these components are shown as distinct blocks, it should be understood that the meter electronics 20 can include various combinations of integrated and/or discrete components.

The interface 201 is configured to communicate with the meter assembly 10 of the vibrating meter 5. Interface 201 may be configured to couple to lead 100 (see fig. 1) and exchange signals with, for example, driver 180, pickoff sensors 170l and 170r, and RTD 190. The interface 201 may also be configured to communicate with external devices, for example, via the communication path 26.

The processing system 203 may comprise any manner of processing system. The processing system 203 is configured to retrieve and execute stored routines to operate the vibrating meter 5. The storage system 204 may 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 storage system 204 may store the measurement results, the received values, the operating values, and other information. In some embodiments, the storage system stores mass flow (m)221, density (ρ)225, density threshold 226, viscosity (μ)223, temperature (T)224, pressure 209, drive gain 306, drive gain threshold 302, gas entrainment threshold 244, gas entrainment fraction 248, and any other variable known in the art. Routines 205, 211, 213, 215 may include any of the signals mentioned and other variables known in the art. Other measurement/processing routines are contemplated and are within the scope of the description and claims.

As can be appreciated, more or fewer values may be stored in the storage system 204. For example, vapor pressure can be determined without using viscosity 223. For example, viscosity is estimated based on pressure drop or friction related as a function of flow rate. However, the viscosity 223 may be used to calculate the Reynolds number (Reynolds number), which may then be used to determine the friction factor. The reynolds number and the friction factor may be used to determine a viscous pressure drop in a conduit (e.g., conduits 130, 130' described above with reference to fig. 1). As can be appreciated, the use of reynolds numbers may not be necessary.

The flow meter routine 205 may generate and store fluid volume and flow measurements. These values may comprise substantially instantaneous measurements or may comprise aggregated or accumulated values. For example, the flow meter routine 205 may generate mass flow measurements and store them in, for example, a mass flow 221 storage device of the storage system 204. The flow meter routine 205 may generate density 225 measurements and store them in, for example, a density 225 storage device. As previously discussed and as known in the art, the mass flow 221 value and the density 225 value are determined from the vibrational response. The mass flow rate and other measurements may include substantially instantaneous values, may include samples, may include averages over time intervals, or may include accumulated values over time intervals. The time interval may be selected to correspond to a time block during which certain fluid conditions (e.g., a fluid state of only liquid, or alternatively a fluid state including liquid and entrained gas) are detected. Additionally, other mass and volume flows and related quantities are also contemplated and are within the scope of the description and claims.

The drive gain threshold 302 may be used to distinguish between periods of flow, no flow, single/dual phase boundary (where fluid phase transition occurs), and gas entrainment/miscible flow. Similarly, the density threshold 226 applied to the density reading 225 may also be used alone or in conjunction with the drive gain 306 to differentiate gas entrained/mixed phase flow. The drive gain 306 may be used as a measure of, for example and without limitation, the sensitivity of conduit vibrations of the vibrating meter 5 to the presence of fluids of different densities (e.g., liquid and gas phases).

As used herein, the term drive gain refers to a measure of the amount of power required to drive a flow tube to a specified amplitude, although any suitable definition may be used. For example, in some embodiments, the term drive gain may refer to a drive current, a pickup voltage, or any measured or derived signal indicative of the amount of power required to drive the flow conduits 130, 130' at a particular magnitude. The drive gain can be used to detect multiphase flow by utilizing characteristics of the drive gain (e.g., such as noise level, standard deviation of the signal, damping related measurements, and any other method known in the art for detecting a mixed phase flow). These metrics may be compared between the pickup sensor 170l and the pickup sensor 170r to detect the mixed phase flow.

Detecting a phase change of a fluid

FIG. 3 shows a graph 300 illustrating the relationship between drive gain and gas-liquid ratio, which may be used to determine vapor pressure using a vapor pressure gauge factor. As shown in fig. 3, 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 are incremented by a percentage, although any suitable units and/or ratios may be used.

Graph 300 includes a curve 330, where curve 330 is the relationship between drive gain and gas-liquid ratio for various flow rates. As shown, the gas-to-liquid ratio is an average void fraction value of curve 330, although any suitable gas-to-liquid ratio (e.g., gas volume fraction ("GVF") or gas entrainment fraction) may be used, and may be based on volume, cross-sectional area, or the like. As can be appreciated, the curves 330 are similar, although associated with different flow rates. Also shown is a drive gain threshold line 340 that intersects curve 330 at about 0.20% average void fraction, which may be a reference average void fraction 330a corresponding to 40% drive gain. A true vapor pressure drive gain 332 of about 10% is also shown. The true vapor pressure drive gain 332 corresponds to the following fluids in the gauge assembly: the fluid has a static pressure at which the fluid changes phase and has a gas-to-liquid ratio of zero.

As can be seen, curve 330 varies from a drive gain of about 10% to a drive gain of about 100% over a range of average void fractions from 0.00% to about 0.60%. As can be appreciated, a relatively small change in average void fraction produces a significant change in drive gain. This relatively small variation may ensure that the onset of vapor formation may be accurately detected using the drive gain.

Although a drive gain of 40% is shown to correspond to an average void fraction of 0.20%, the correspondence may be process specific. For example, a drive gain of 40% may correspond to other average voidages in other process fluids and conditions. Different fluids may have different vapor pressures, and thus the onset of vapor formation for a fluid may occur at different flow rates. That is, a fluid having a relatively low vapor pressure will evaporate at a higher flow rate, while a fluid having a relatively high vapor pressure may evaporate at a lower flow rate.

As can also be appreciated, the drive gain threshold line 340 may increase benefits at alternative/other drives. However, it may be beneficial to have the drive gain at 40% to eliminate false detection of entrained/mixed phase flow while also ensuring that the onset of vapor formation is correctly detected.

Further, curve 330 uses drive gain, but other signals may be used, such as measured density, etc. The measured density may increase or decrease due to the presence of voids in the fluid. For example, due to the acoustic velocity effect, the measured density may increase counter-intuitively due to voids in the relative dither meter. In relatively low frequency gauges, the measured density may decrease because the density of the voids is less than the density of the fluid. These and other signals may be used alone or in combination to detect the presence of vapor in the gauge assembly.

As discussed above, the 0.20% average void fraction value may be the reference average void fraction 330a corresponding to the 40% drive gain value, which may be the location where the drive gain threshold line 340 intersects the drive gain axis 320. Thus, when the drive gain measured for the fluid in a meter assembly (e.g., meter assembly 10 described above) is at 40%, then the average void fraction of the fluid may be about 0.20%. A void fraction of about 0.20% may correspond to the pressure of the fluid due to the presence of gas in the fluid. For example, a void fraction of about 0.20% may correspond to a static pressure value, for example.

Vapor pressure values may be associated with vapor pressure gauge factors due to a previously determined relationship between drive gain or other signal (e.g., density) and a reference average void fraction 330a (which may be a reference gas-liquid ratio). For example, the meter assembly may be vibrated while increasing or decreasing the static pressure until a fluid phase change is detected. The vapor pressure value may then be determined from the static pressure, as will be described in more detail below with reference to fig. 4. The determined vapor pressure value may correspond to, for example, the static pressure at drive gain threshold line 340. This determined vapor pressure value may be adjusted by a vapor pressure gauge factor to correspond to the true vapor pressure drive gain 332, where the phase change occurs or a single/dual phase boundary is encountered, 332. Thus, while the presence of a gas in a fluid can be detected at a static pressure different from the true vapor pressure of the fluid, the true vapor pressure value can still be determined.

Using reference average void fraction 330a as an example, the static pressure in the meter assembly may be reduced until the drive gain reaches 40%, indicating that the fluid in the meter assembly has an average void fraction of 0.20%. A processing system, such as processing system 203 described above, may determine that the fluid begins to evaporate at a static pressure that is, for example, proportionally higher than the static pressure corresponding to the 40% drive gain. For example, a true vapor pressure value may be associated with a drive gain of about 10%. As can be appreciated, due to uncertainties involved in calculating the static pressure (e.g., errors from pressure sensors, flow rate measurement errors, etc.), the true vapor pressure may be proportionally lower than the calculated static pressure associated with a 40% drive gain. The true vapor pressure corresponds to the static pressure of the fluid where the fluid phase change occurs but the gas-liquid ratio is zero.

Thus, the measured drive gain can be used to detect gases, but can still produce highly accurate true vapor pressure values. More specifically, at the instant when outgassing first occurs, the drive gain may not increase beyond the drive gain threshold line 340 for detection due to the presence of some micro-bubbles. For example, the dynamic pressure may be increased by a pump that continues to increase the flow rate until the static pressure drops, causing the drive gain to pass through the drive gain threshold line 340. Depending on the application, this calculated static pressure (e.g., uncorrected vapor pressure) may be corrected (e.g., adjusted-decreased or increased) by a vapor pressure gauge factor (e.g., 1psi) to account for delays in detecting a phase change of the fluid. That is, a vapor pressure gauge factor may be determined and applied to an uncorrected vapor pressure measurement according to a drive gain to account for differences in the drive gain when gas is detected from the true vapor pressure to detect trace amounts of gas.

Referring to fig. 3, by way of example, a measured drive gain of 40% may correspond to a static pressure of the fluid in the gauge assembly that is, for example, 1psi less than the static pressure corresponding to the drive gain associated with the true vapor pressure. Accordingly, the vibrating meter 5 or meter electronics 20 or any suitable electronics may determine that the vapor pressure gauge factor is 1psi and add this value to the static pressure associated with the 40% drive gain. As a result, the vibrating meter 5 can accurately detect the phase change of the fluid, and thus also accurately determine the vapor pressure of the fluid using the drive gain.

However, other methods of detecting phase change without using a driving gain may be employed. For example, the phase change may be detected by acoustic measurements, x-ray based measurements, optical measurements, and the like. Further, combinations of the above implementations are contemplated. For example, a bypass line running vertically in the circuit utilizes vertically distributed acoustic and/or optical measurements to determine the location of the first degassing of the gas. This height will then provide the required input to calculate the vapor pressure of the fluid in the vibrating meter 5, as described below.

Pressure drop in a vibrating meter

Fig. 4 shows a graph 400 illustrating how the static pressure of the fluid in the vibrating meter can be used to determine the vapor pressure. As shown in fig. 4, graph 400 includes a position axis 410 and a static pressure axis 420. The position axis 410 is not shown in any particular unit of length, but may be in inches, although any suitable unit may be used. The hydrostatic shaft 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 vibrating meter.

Thus, the position from IN to OUT may correspond to fluid IN the meter assembly 10 shown IN fig. 1, for example. IN this example, the area from IN to about a may correspond to the portion of the gauge assembly 10 between the flange 103 to the conduit mounting block 120. The region from about a to about G may correspond to the conduit 130, 130 'between the mounting blocks 120, 120'. The area from G to OUT may correspond to the portion of the meter assembly 10 from the mounting block 120 'to the flange 103'. Thus, fluid IN the meter assembly 10 (e.g., IN locations ranging from IN to OUT) may not include, for example, fluid IN a pipe into which the meter assembly 10 is inserted. The fluid in the meter assembly 10 may be the fluid in the conduits 130, 130'.

Graph 400 also includes a zero dynamic pressure curve 430 and a dynamic pressure change curve 440. The zero dynamic pressure curve 430 shows no change in dynamic pressure — assuming a linear decrease in pressure from the inlet to the outlet of the vibrating meter. The dynamic pressure change curve 440 may represent the actual pressure in a vibrating meter inserted into a pipe, where the diameter of one or more conduits of the vibrating meter is less than the diameter of the pipe. An exemplary vibrating meter 5 is shown in fig. 1, although any suitable vibrating meter may be used. Thus, the fluid in a gage assembly (e.g., the gage assembly 10 described above) may have a reduced static pressure due to an increase in dynamic pressure. A vapor pressure line 450 representing the vapor pressure of the fluid in the vibrating meter is also shown.

The dynamic pressure change curve 440 includes a static pressure decreasing section 440a, a viscous loss section 440b, and a static pressure increasing section 440 c. The dynamic pressure profile 440 also includes a minimum static pressure 440 d. The static pressure drop segment 440a may be due to an increase in fluid velocity resulting in a corresponding increase in dynamic pressure for that segment of the vibrating meter. The viscous loss section 440b can correspond to a constant diameter portion of one or more conduits in the vibrating meter. Therefore, the viscosity loss section 440b may not reflect an increase in fluid velocity, and thus may not reflect an increase in dynamic pressure. The static pressure increasing section 440c may be due to a decrease in fluid velocity and, therefore, the static pressure decrease during the static pressure decreasing section 440a may be restored. The static pressure dropping section 440a and the static pressure increasing section 440c may be static pressure variations in the gage assembly.

The portion of the dynamic pressure profile 440 below the vapor pressure line 450, which includes the minimum static pressure 440d, may correspond to a location (e.g., from about location E to slightly after location G) where a fluid phase change occurs in the fluid in a gage assembly (e.g., the gage assembly 10 described above). As can be seen in fig. 4, the minimum static pressure 440d is lower than the vapor hold-down line 450. This indicates that the dynamic pressure profile 440 can be moved upward by increasing the static pressure of the fluid in the meter assembly. However, if the static pressure is increased by approximately 5psi to move the dynamic pressure profile 440 upward until the minimum static pressure 440d is above the vapor pressure line 450, a fluid phase change may be detected. As the static pressure increases, the gas or vapor in the fluid in the gauge assembly may become liquid. Conversely, if the dynamic pressure change curve 440 is above the vapor pressure line 450 and the static pressure of the fluid in the gage assembly decreases until the minimum static pressure 440d is on the vapor pressure line, the fluid phase change may be the formation of gas or vapor in the fluid.

As can be seen in FIG. 4, the viscous loss section 440b decreases from a static pressure of about 68psi at position A to a static pressure of about 55psi at position G. As can be appreciated, the static pressure of about 55psi at location G is less than the vapor pressure line 450 of about 58 psi. Thus, even if the static pressure at the inlet and outlet is greater than the vapor hold-down line 450, the fluid in the vibrating meter may still flash or outgas.

Therefore, the static pressure at the inlet and outlet does not directly correspond to the vapor pressure of the fluid. That is, the vapor pressure of the fluid may not be determined directly from the static pressure of the fluid in the conduit or outside the meter assembly. The static pressure in the meter assembly 10, or more specifically in the conduits 130, 130', can be accurately determined by, for example, using pressure measurements at the inlet and outlet and inputting the dimensions of the vibrating meter 5 (e.g., the diameter and length of the conduits 130, 130'). However, in order to accurately determine the vapor pressure, it may be necessary to cause a phase change of the fluid in the vibrating meter 5, which may be caused by changing the static pressure of the fluid in the vibrating meter 5.

Varying hydrostatic pressure of fluid

Fig. 5 shows a system 500 for determining a 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 conduit 501. The system 500 includes a pump 510 in fluid communication with an outlet of the vibrating meter 5 (shown as a coriolis meter) and a bypass outlet. The inlet pressure sensor 520 is in fluid communication with the inlet of the vibrating meter 5 and the bypass inlet. The outlet pressure sensor 530 is arranged between the outlet of the vibrating meter 5 and the pump 510, and is configured to measure the static pressure of the fluid at the outlet of the vibrating meter 5. A flow control device 540 (shown as a valve) is disposed between the bypass inlet and the inlet pressure sensor 520.

The pump 510 may be, for example, any suitable pump capable of increasing the velocity of the fluid in the vibrating meter 5. The pump 510 may, for example, comprise a variable frequency drive. The variable frequency drive may enable the pump 510 to control the fluid velocity of the fluid in the system 500. For example, the variable frequency drive may increase the fluid velocity of the fluid through the vibrating meter 5, although the fluid velocity may be increased by any suitable pump. By increasing the fluid velocity, the pump 510 can increase the dynamic pressure of the fluid in the vibrating meter 5 by increasing the fluid velocity.

Therefore, the static pressure of the fluid in the vibrating meter 5 may decrease. By way of illustration, referring to fig. 4, the pump 510 may move the dynamic pressure variation curve 440 downward. Thus, although not shown in fig. 4, if the dynamic pressure change curve 440 is higher than the vapor pressure line 450, the pump 510 may cause flashing or degassing by moving the dynamic pressure change curve 440 downward. Similarly, by moving the dynamic pressure profile 440 up to or above the vapor hold-down line 450, the gas or vapor in the fluid may become liquid.

Inlet pressure sensor 520 and outlet pressure sensor 530 may be any suitable pressure sensors configured to measure any pressure of a fluid. For example, the inlet pressure sensor 520 and the outlet pressure sensor 530 may measure the static pressure of the fluid in the system 500. Additionally or alternatively, inlet pressure sensor 520 and outlet pressure sensor 530 may measure the total pressure of the fluid in 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 in the system 500 according to equation [3] above. For example, the inlet pressure sensor 520 may measure the total and static pressures of the fluid proximate to or at the inlet of the vibrating meter 5. The inlet pressure sensor 520 and/or the meter electronics 20 in the vibrating meter 5 may determine the dynamic pressure at the inlet of the vibrating meter 5.

The flow control device 540 may increase the fluid velocity of the fluid in the system 500 as the position of the flow control device 540 moves from the partially closed position to the fully open position. For example, by reducing the flow restriction of the system 500 at the inlet of the vibrating meter 5, the velocity of the fluid may be increased according to equation [2] above. This may move the dynamic pressure profile 440 downward to cause flashing or outgassing. Conversely, the flow control device 540 may decrease the fluid velocity of the fluid in the system 500, thereby moving the pressure change curve 440 upward, thereby condensing the gas or vapor.

When the flow control device 540 is opened, the fluid velocity will increase, but the static pressure at the inlet of the vibrating meter 5 will also increase, and vice versa. The combination of flow control device 540 and pump 510 may provide preferred processing conditions by partially closing flow control device 540 (e.g., restricting flow and reducing pressure downstream of flow control device 540) and increasing pump speed (e.g., increasing flow rate) to achieve a desired lower static pressure and higher speed.

While the static pressure of the fluid in the vibrating meter 5, or more specifically the static pressure of the fluid in the meter assembly 10 in the vibrating meter 5, may be varied by using the pump 510 or the flow control device 540, or a combination of both described above, other methods of varying the static pressure may be used. For example, the height z of the vibrating meter 5 may be changed. To reduce the static pressure of the fluid in the vibrating meter 5, the height z may be increased. To increase the static pressure of the fluid in the vibrating meter 5, the height z may be reduced. The height z of the vibrating meter 5 may be varied by any suitable means, such as an electric lift between the vibrating meter 5 and the pipe 501 and, for example, a bellows between the vibrating meter 5, the flow control device 540 and the pump 510. Other devices may be used, as well as combinations of various devices (e.g., pump 510, flow control device 540, and/or a motorized lift).

For example, if the flow rate through the bypass is sufficient, the pump may not necessarily be used. Only the flow control device 540 may be used. The flow control device 540 may be mounted in other locations, such as downstream of the vibrating meter 5. Alternatively, the flow control device 540 may not be used, for example, where a pump 510 and/or a motorized lift are used. In another alternative example, the meter may be installed in the main line rather than the bypass. Additionally or alternatively, only a single pressure sensor may be used. For example, only the outlet pressure sensor 530 may be used. The inlet pressure sensor 520 and/or the outlet pressure sensor 530 may be located at alternative locations. The outlet pressure sensor 530 and its location may be beneficial because the static pressure at the location of the outlet pressure sensor 530 may be substantially stable with respect to the fluid velocity once the fluid in the gauge assembly 10 is under vapor pressure. That is, any additional increase in fluid velocity may not cause a significant decrease in the static pressure measured by outlet pressure sensor 530.

True vapor pressure and Reid (Reid) vapor pressure

As discussed above, a coriolis meter based system can provide a true vapor pressure at a gas-to-liquid ratio of 0:1, which may be a more useful parameter for engineering calculations. In addition, coriolis-based systems can measure "live samples" that may still contain components with low vapor pressures ("light ends"). This can be a potential benefit when compared to methods that use "dead samples" where light fractions are evaporated and lost during sampling. In addition, safety benefits can be realized that eliminate the need to transport sample containers filled with vapor for laboratory analysis.

As with other vapor pressure measurements, the meter electronics 20 can be configured to back-calculate the reid vapor pressure at 4:1 or some other V/L ratio using other correlations. For example, to obtain the Reid vapor pressure from a true vapor pressure measurement of gasoline, the following equation can be used:

A＝A₁-A₂ln(TVP) [8]

B＝B₁-B₂ln(TVP) [9]

similarly, to obtain the Reid vapor pressure from a true vapor pressure measurement of the crude oil, the following formula can be used:

A＝A₁-A₂ln(TVP)-A₃(T+C) [11]

B＝B₁-B₂ln(TVP)-B₃[ln(TVP)]² [12]

wherein:

t is temperature (. degree. C.);

TVP is true vapor pressure (kPa);

RVP is the Reid vapor pressure (kPa); and is

A₁、A₂、A₃、B₁、B₂、B₃And C is a parameter for converting between reed vapor pressure and true vapor pressure, and depends on the composition of the fluid.

By way of example, parameter A is converted₁、A₂、A₃、B₁、B₂、B₃And C may have the following values (for international system of units (SI) units):

parameter(s)	Gasoline (gasoline)	Crude oil
			A1	9.4674	16.62
A2	-0.9445	0.9875
			B1	5211.0	5339
B2	16.014	675.7
			C	459.67	273.15

An example of the benefit of measuring vapor pressure at a near zero gas to liquid ratio can be seen in the rail transport of crude oil. Most vapor pressure test methods require a gas to liquid ratio of 4:1 and a measured temperature of 37.8 ℃. However, crude oil can be transported at 80 ℃ and gas to liquid ratios close to 0: 1. Under these conditions, the light fraction may start to vaporize even in "dead" crude oil and produce a gas mixture with an exponential pressure increase. This point may not be foreseen if the vapour pressure is measured at a gas to liquid ratio of 4:1 and a temperature of 37.8 ℃. For safety calculations, it may be important to measure the vapor pressure delivered in the conduit at process temperatures and gas-liquid ratios close to 0:1, which may be accomplished using methods consistent with the description of FIG. 6, exemplary methods of which are described below.

Using vapor pressure gauge factor

Fig. 6 shows a method 600 for determining vapor pressure using a vapor pressure gauge factor. As shown in fig. 6, the method 600 begins with step 610, which provides a drive signal to a meter assembly having a fluid. The meter assembly used by the method 600 may be the meter assembly 10 described above, although any suitable meter assembly may be used. In step 620, a drive gain of the drive signal provided to the meter assembly is measured. In step 630, the vapor pressure of the fluid is determined based on the previously determined relationship between drive gain and reference gas-liquid ratio.

Method 600 may include additional steps. For example, the static pressure may be determined when the drive gain is measured. For example, the static pressure may be determined while measuring the drive gain. As described above with reference to fig. 3, the measured drive gain may be associated with a drive gain threshold (e.g., drive gain threshold line 340) for detecting phase transitions. The method 600 may also determine a static pressure of the fluid in the meter assembly when the drive gain is measured at the drive gain threshold. Thus, the measured static pressure may be an uncorrected vapor pressure. The uncorrected vapor pressure can be adjusted using a vapor pressure gauge factor to determine the true vapor pressure.

In step 610, the drive signal may be provided by the meter electronics 20 described above, although any suitable electronics may be used. The fluid may or may not have a gas or vapor, such as entrained gas, bubbles, slugs, and the like. The velocity of the fluid may vary due to, for example, a pump in line with the vibrating meter 5, although any suitable configuration may be used. By varying the velocity of the fluid in the meter assembly, the static pressure of the fluid in the meter assembly may be increased or decreased. For example, increasing the velocity of the fluid may decrease the static pressure of the fluid in the meter assembly.

The relationship between the previously determined drive gain and the reference gas-to-liquid ratio may be a direct relationship or an indirect relationship. For example, the relationship between the direct previously determined drive gain and the reference gas-to-liquid ratio may be a linear relationship relating drive gain to gas-to-liquid ratio over a range. The range may be from a drive gain associated with true vapor pressure to a drive gain of 100%. In an example, the drive gain associated with the true vapor pressure can be about 10%, although any suitable value can be used.

In an exemplary indirect relationship, the reference gas-to-liquid ratio may be associated with the static pressure minus a vapor pressure gauge factor. Thus, the vapor pressure gauge factor may also be associated with a drive gain threshold associated with an uncorrected vapor pressure. Thus, the value of the gas-liquid ratio may not necessarily be used to calculate vapor pressure, e.g., true vapor pressure, but the previously determined relationship between drive gain and gas-liquid ratio may still be the basis for determining vapor pressure.

Fig. 7 shows a method 700 of determining a vapor pressure gauge factor for determining vapor pressure. As shown in FIG. 7, in step 710, the method 700 determines a static pressure of a fluid in the meter assembly. In step 720, the method 700 determines the difference between the static pressure and the true vapor pressure of the fluid.

The method 700 may also include providing a signal to the meter assembly, measuring a drive gain of a drive signal provided to the meter assembly, and/or correlating a static pressure of a fluid in the meter assembly with the drive gain. Additionally or alternatively, the method 700 may include associating a drive gain threshold for detecting a phase change in the fluid with the measured drive gain, and the difference is associated with the drive gain threshold.

The vibrating meter 5, and in particular the meter electronics 20, and the method 600 of determining vapor pressure using a vapor pressure meter factor are described above. By using a vapor pressure gauge factor, a threshold value, such as drive gain threshold line 340, may be considered. More specifically, the vapor pressure value associated with drive gain threshold line 340 may be corrected by a vapor pressure gauge factor to obtain a true vapor pressure value. The true vapor pressure value may correspond to a situation where a phase change occurs in the fluid but there is no vapor in the fluid. Thus, the determined vapor pressure may be more accurate. As a result, the operation of the vibrating meter 5 and the meter electronics 20 is improved because the values provided by the vibrating meter 5 and the meter electronics 20 are more accurate. More accurate measurements in the technical field of vapor pressure measurement may improve other technical fields, such as fluid process control, etc.

The above detailed description of the embodiments is not an exhaustive description of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be combined or eliminated in various ways to produce other embodiments, and that such other embodiments fall within the scope and teachings of the specification. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present specification.

Thus, while specific embodiments are described herein for purposes of illustration, various equivalent modifications are possible within the scope of the description, as those skilled in the relevant art will recognize. The teachings provided herein can be applied to other methods of determining vapor pressure using vapor pressure gauge factors, not just to the embodiments described above and shown in the figures. Accordingly, the scope of the embodiments described above should be determined by the appended claims.