Method and apparatus for the measurement of flow in gas or oil pipes

Abstract

The present disclosure relates to a method and an apparatus for measuring a flow rate through a vessel, such as a conduit or pipeline. The method comprises providing a reference parameter, measuring a first parameter at a first position at the vessel and determining a difference between the first parameter and the reference parameter. The flow rate through the vessel is determined based on the difference between the first parameter and the reference parameter.

Claims

1. A method for measuring a storage volume in a storage tank, the method comprising: providing a surrounding environment reference temperature; measuring a first temperature using an infrared radiation sensor at a position at the storage tank; determining a difference between the first temperature and the reference temperature; and determining the storage volume in the storage tank based on the determined temperature difference, wherein the measuring of the first temperature is at a distance from the storage tank to the position at the storage tank; and wherein the measuring the surrounding environment reference temperature comprises measuring a ground temperature as the surrounding environment reference temperature.

2. The method of claim 1, wherein the providing the surrounding environment reference temperature comprises measuring the surrounding environment reference temperature at the position, and wherein the first temperature is measured at a first time and the surrounding environment reference temperature is measured at a reference time.

3. The method of claim 1, wherein the providing the surrounding environment reference temperature comprises measuring the surrounding environment reference temperature at a reference position.

4. The method of claim 1, wherein measuring the first temperature comprises measuring a temperature pattern.

5. The method of claim 1, further comprising measuring a second temperature at a second position.

6. The method of claim 1, wherein the step of measuring a first temperature using an infrared radiation sensor at a position at the storage tank comprises measuring the first temperature at the position only without direct contact with the storage tank.

7. The method of claim 1, wherein the measuring of the first temperature comprises measuring a plurality of first temperatures at different ones of the positions at the storage tank.

8. An apparatus for measuring a storage volume in a storage tank, the apparatus comprising: a first sensor for measuring a first temperature at a first position of the storage tank; a second sensor for measuring a surrounding environment reference temperature, wherein the second sensor is positioned to measure a ground temperature outside the storage tank as the surrounding environment reference temperature; and a calculation unit for determining a difference between the first temperature and the surrounding environment reference temperature and for determining the storage volume in the storage tank based on the determined temperature difference; wherein the first sensor is an infrared radiation sensor.

9. The apparatus of claim 8, wherein the calculation unit and the first sensor are arranged at a distance with respect to each other.

10. A method for measuring a storage volume in a storage tank, the method comprising: providing a reference temperature of an environment outside the storage tank, wherein the reference temperature comprises a ground temperature outside the storage tank; measuring a first temperature at a first position at the storage tank; determining a difference between the first temperature and the reference temperature; and determining the storage volume in the storage tank based on the determined temperature difference; wherein the measuring of the first temperature is at a distance from the storage tank to the first position by means of an infrared radiation sensor.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a first aspect for measuring the flow rate through a vessel, such as a conduit.

(2) FIG. 2 shows a second aspect for measuring the flow rate through the vessel.

(3) FIG. 3 shows a third aspect for measuring the flow rate through the vessel.

(4) FIG. 4 shows a flow diagram of the method of the present disclosure.

(5) FIG. 5 shows a forth aspect for measuring volume of a fluid in a storage vessel.

DETAILED DESCRIPTION

(6) The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will also be understood that a feature of one aspect can be combined with the features of another aspect or other aspects.

(7) The present invention is based on the observation that a tubing or pipe (collectively called a conduit) conducting a hot fluid will be warmed up as long as the fluid flows through the tubing. If the flow is stopped the temperature of the conduit will decrease to the temperature of the environment of the conduit. A simple example of such a conduit is the household water pipe. Equally it has been observed that the temperature of a storage vessel, such as a tank, varies when a fluid is stored in the storage vessel and in particular the temperature of the storage vessel is different in the air space above a liquid (the fluid) compared to the liquid volume.

(8) The present disclosure uses this observation for measuring the following parameters related to a flow rate of the liquid in the tubing, pipe or other type of conduit: a) If the temperature of the conduit is higher than the temperature of the environment, a hot fluid is flowing through the conduit. b) If the temperature of the conduit increases, there is an increasing flow of hot fluid and the flow rate is increased. c) If the temperature of the conduit is stable at a higher temperature than the environment over a time interval, there is a stable flow of hot fluid at a constant flow rate through the conduit. d) If the temperature of the conduit decreases from a higher temperature towards the temperature of the environment, the flow rate of the hot fluid has been decreased or stopped.

(9) The same principle may be applied inversely if the fluid in the conduit is colder than the environment.

(10) While the examples given above assume that the temperature differences between the fluid in the conduit and the environment are rather high, it has been found that the same principle can be applied if the temperature differences are small. For example, the temperature differences may be 1 C. or less.

(11) The flow rate in the conduit may be calculated in a first approximation by the equation:
Flow=(T.sub.cT.sub.r)*k(1)

(12) Where the parameter Flow is the flow through the conduit in volume per time, T.sub.c is the temperature measured from the conduit, T.sub.r is a reference temperature and k is a constant. More advanced formulas can be applied using adding offsets, a variable heat capacitance of the fluid, a heat capacity of the conduit.

(13) In a multiflow system, for example a system in which oil and gas are both present, the heat capacity of the fluid (oil and gas together) will be a function of the individual heat capacities of the mixture of oil and gas. The constant k in the multiflow system will therefore be a function of the effective volume of the mixture and the method of this disclosure can be used for measurement of the multiflow of the fluid.

(14) An extreme example of the multiflow system is a cavity or a storage vessel, which can be considered to be a subpart of the pipe or the conduit. The liquid medium of the multiflow system will normally be present at the bottom of the storage vessel and the gaseous medium will be at the top of the storage vessel.

(15) FIG. 1 shows an example of how a flow rate of fluid in a conduit is measured in one aspect of this invention. The conduit may be a pipeline used for transporting fluids 13 such as gas or oil. The term fluid used in this disclosure also comprises compressible liquids or mixtures of gasses and liquids and solid grain materiel. FIG. 1 shows a pipeline 10 exiting from the sea 2. Such an exit point 11 can be found, for example, where the pipeline 10 crosses out from the sea 2 at the coast. Alternatively, the pipeline 10 may exit at the exit point 11 from the ground or soil. The method and the apparatus of the present disclosure can be used at such exit points 11 because the pipelines 10 are easily accessible. The pipeline 10 and the fluid 13 flowing through the pipeline 10 are at a constant temperature at the exit point 11 from the sea 2 or from the ground. This constant temperature corresponds to the temperature of the sea 2 or of the ground. The ground temperature or a sea temperature can be easily may be used for the determination of the flow rate but it is not necessary for the present invention to measure or know this ground or sea temperature.

(16) A first temperature sensor 20 may be arranged at a first position 12 of the pipeline 10 and the temperature of the pipeline at the first position 12 can be measured as a first temperature T.sub.c. The first temperature sensor 20 may be in direct contact with the pipeline 10, as shown in FIG. 1. No access to the inside of the pipeline 10 is necessary and the first temperature sensor 20 may be removable attached to the pipeline 10. For example the first temperature sensor 20 may be attached to the pipeline 10 using a magnet, a tape or other means for fixing the temperature sensor 20 to the pipeline 10. The temperature sensor 20 may be removably arranged at the pipeline 10 or may be fixedly installed.

(17) The first temperature sensor 20 may be a commercially available temperature sensor. The first temperature sensor 20 may have an accuracy of about 1% depending of the site and number of sensors.

(18) The first temperature sensor 20 may transmit the measured parameter (in this case temperature data) to a calculation unit 30. A simple wire connection or a radio connection may be used to transmit temperature data measured by the first temperature sensor 20 to the calculation unit 30. The calculation unit 30 can be a handheld device for in-field measurements. The calculation unit 30 can also be arranged at some distance from the temperature sensor 20 and the temperature data can be transmitted via a radio connection, the internet or other known means for data transfer. The calculation unit 30 may be a separate device or may be implemented in a computer program running on a commercially available computer close to the site or far remote from the site. The calculation unit 30 determines the difference between the first temperature T.sub.c at the first position 12 of the pipeline 10 and the reference temperature T.sub.R as outlined above (equation 1).

(19) The reference temperature T.sub.R may be obtained from a reference temperature sensor 25. The reference temperature sensor 25 may measure the temperature of the environment, for example the air surrounding the pipeline 10. The temperature measured at the reference temperature sensor 25 may be equal to or may be used to derive the reference temperature T.sub.R corresponding to the temperature at the first position 12, if no fluid flow is present in the pipeline 12.

(20) The calculation unit 30 may in some applications receive further temperature information from further temperature sensors arranged at different positions at or along the pipeline 10 or elsewhere. If several different ones of the temperature sensors are used, the measurement accuracy may be improved.

(21) In some applications, the reference temperature sensor may be omitted and the reference temperature T.sub.R may be determined or known from other sources.

(22) In one example, the reference temperature T.sub.R can also be measured using the first temperature sensor 20. In this case, the reference temperature T.sub.R can be measured at a reference time tr, for example when there is no flow in the pipeline 12, but the invention is not limited thereto. The first temperature T.sub.1 can then be measured at time t1, which is at a different time than tr, also using the first temperature sensor 20. Only one temperature sensor is required in this aspect of the disclosure.

(23) An additional aspect is shown in FIG. 2. The example of FIG. 2 is identical to the example shown in and described with respect to FIG. 1 and the same measurement principles may be applied. The examples of FIG. 2 and FIG. 1 differ in that FIG. 2 uses a radiation sensor 21 to measure the first temperature T.sub.1 at the first position 12. Using the radiation sensor 21, such as an infrared (IR) radiation sensor, has the advantage that the first temperature T.sub.1 can be measured at a distance from the first position 12 and that no direct access to the pipeline 10 is necessary. This makes it possible to determine the flow rate of the fluid 13 inside the pipeline 10 without having direct access to the pipeline 10.

(24) The aspect of FIG. 2 further differs from FIG. 1 f in that the reference temperature sensor 25 is omitted as explained above. It is obvious that the example of FIG. 2 can be used with a reference sensor 25.

(25) FIG. 3 shows a further aspect of the present invention. If there is a compressible fluid inside the conduit 10, the temperature will also change if there is a change of pressure inside the conduit 10. This temperature difference may be measured and the flow rate of the fluid may be derived. A change or pressure in the pipeline 10 may be changed by an element 40 in the pipeline. The element 40 may be a pump, a valve, a bend, a choke, or just a heating element which is turned on.

(26) If, for example, a valve 40 is present is used, the compressible fluid may be expanded and the compressible fluid 13b behind the valve may have a lower temperature compared to the temperature of the compressible fluid 13a in front of the valve 40. The temperature of the compressible fluid 13b behind the valve 40 may be measured with the first temperature sensor 20 and may be compared to the temperature of the compressible fluid 13a in front of the valve 40 measured by reference temperature sensor 25.

(27) The example shown in FIG. 3 can also be used to determine pressure differences in the pipeline 10, if the flow rate is known. From the pressure difference further parameters of the element 40 such as the setting of the valve or the pumping level of a pump.

(28) While the examples given above have been described by comparing a first temperature with a reference temperature, the present disclosure is not limited thereto. As noted previously, a plurality of temperature measurements can be made at different places along the conduit or pipeline 10.

(29) It is also possible to set up more advanced and accurate measurements of the flow and to determine several unknown parameters, example the mass flow/time, the volume flow/time, the pressure inside the conduit, the heat capacity of the fluid inside the conduit, the volume mixture of the material inside the conduit, the mass mixture of the material inside the conduit, either static or change per time.

(30) While the aspects given above have been described by measuring the temperatures at one or two points in time only, the invention is not limited thereto. A series of temperature measurements may be performed or the first temperature T.sub.1 and/or the reference temperature T.sub.R may be continuously measured and monitored and a temperature pattern may be obtained. This allows the determination of the change of flow rate over time.

(31) Another example of the present disclosure may be applied if the flow in the pipeline 10 is at a constant flow rate and if the temperature of the fluid changes over time. The first temperature sensor 20 may be arranged at a first position 12 at the pipeline 10 and the reference temperature sensor 25 is arranged at a reference position at some known distance at the pipeline 10. If the fluid 13 inside the pipeline is cooled or heated before the reference temperature sensor 25, for example by a door which is opened towards a cold room the pipeline 10 becomes slightly cooled for a short time. Another example would be the switching on of a heating element attached to the pipeline 10 in front of the reference temperature sensor 25. The source of temperature change can either be random or forced by purpose by the measurement system. The reference temperature sensor 25 will then measure a change in the reference temperature T.sub.R at a reference time tr. The first temperature sensor 20 will also measure a change in the first temperature T.sub.1 at a first time t1. If the distance between the first temperature sensor 20 and the reference temperature sensor 25 is known, the flow velocity can be calculated from the difference between tr and t1 and the corresponding flow rate can be derived. For example if the first temperature sensor 20 and the reference temperature sensor 25 are arranged at a distance of 8 m and a similar temperature change is measured 60 s later, the fluid flows at a velocity of 8 m/60 s. Multiplying this velocity with the cross sectional area of the pipe, for example 60 cm.sup.2, the flow is 800 cm.sup.3/s.

(32) The above examples have been described with respect to temperature differences between a first temperature and a reference temperature. The present invention may also be applied to other parameters of the pipeline. For example the circumference and the diameter of the pipeline 10 change if the fluid flows through the pipeline 10. This change in dimension can be measured and compared to a reference value. The reference value may be measured when no flow is present in the pipeline 10 or may be measured at a model of the pipeline 10.

(33) The present disclosure may be used with pipelines transporting fluids such as natural gas, oil or other similar liquids for energy companies, as well as other chemical and petrochemical products. The teachings of the present disclosure can also be used for multiflow systems including mixtures of oil and gas, as well as sand, mud and water, but this is not limiting of the invention.

(34) Knowledge of the type of the fluid 13 transported in the pipeline 10 may increase the accuracy of the flow rate measurement as further parameters such as viscosity, heat coefficient and others can be used in determining the flow rate.

(35) FIG. 5 shows an example of a storage vessel 500 containing a liquid 505, which enters the storage vessel 500 through a liquid inlet 540 and exits the storage vessel 500 through a liquid outlet 530. It will be noted that the liquid inlet 540 and the liquid outlet 530 can be the identical. The top surface 507 of the liquid 505 will move up and down through an air space 515 as the liquid 505 enters and/or exits the storage vessel 500. A first sensor 510 is able to measure the temperature of the outer surface 508 of the storage vessel 500 and scan up and down the outer surface 508 in order to determine the approximate position of the top surface 507 of the liquid 505. A line detector (a one-dimensional array) or a matrix of sensors in an IR cameral can be used instead of mechanically scan up and down. A second sensor 520 is a reference sensor and can be used to calibrate the first sensor 510, for example by measuring the temperature of the storage vessel 500 near the ground 525. Both the first sensor 510 and the second sensor 520 are connected to a processing unit 550, which is able to use the data from the first sensor 510 and the second sensor 520 in order to calculate the volume of the liquid 505 in the storage vessel 500. The total volume of the storage vessel 500 can be calculated by measuring the external dimensions of the storage vessel 500, which can be obtained either from physical measurements on the ground or by calculation from aerial photographs.

(36) Although the present disclosure has been described with respect to combustible fluids in pipelines it is obvious to a person skilled in the art that the present disclosure may applied to any fluid transported in any type of vessels. The present disclosure can be applied to any dimension of the vessel.