Patent Application
20240027148
The invention relates to the technical field of heat exchangers equipped with measuring instruments. More particularly, the invention belongs to the field of industrial heat exchangers.
The invention relates to a heat exchanger equipped with measuring instruments and to a method for estimating the service life of the heat exchanger by means of measurements made by said measuring instruments.
Industrial heat exchangers are used in various industries.
As an illustration, in the oil, gas and petrochemical industries, production requires the use of heat exchangers for cooling or heating fluids. E.g., a gas is cooled for being liquefied and stored in a large volume for transporting by ship whereas the oil is heated for facilitating the movement thereof through the supply lines.
In such plants, heat exchangers play a central role in production. In the event of a failure of a heat exchanger, the production is affected or even stopped, generating significant financial losses on a daily basis.
In some cases, damage to the heat exchanger cannot be repaired. Replacement of the heat exchanger becomes necessary. Such industrial heat exchangers are specific and custom-made, so as to meet the needs of the plant. Sometimes large (a plurality of meters) and often complex in the inner architecture thereof, the manufacture of these heat exchangers requires a plurality of weeks or months to assemble, bake, cool and finally verify the leak-tightness. The delivery, often by boat, and finally the installation on site, extends the period during which production at the plant is interrupted or disrupted.
The initial service life of a heat exchanger is defined by the manufacturer. The service life is established for a normal use of the heat exchanger, i.e. at pressures and temperatures within a predefined range. The manufacturer also plans a provisional schedule for interrupting, for maintenance, the use of the heat exchanger. The schedule, like the initial service life, is established for a normal use of the heat exchanger.
However, it happens that industrial companies use heat exchangers outside of the predefined intervals. Such situations occur frequently in the oil and gas industry. Depending on the prices of each hydrocarbon, it can be interesting to produce a particular hydrocarbon. E.g. the same heat exchanger is used for producing a hydrocarbon in the morning and another hydrocarbon of a different type in the afternoon.
Such interruptions followed by resumptions of production to which are added different operating temperatures and pressures for each hydrocarbon lead to a premature wear of the heat exchangers. Such premature wear distorts the planned schedule of shutdowns for the maintenance of the heat exchanger and reduces the service life thereof.
The invention aims to remedy such drawbacks by enabling manufacturers to have, in real-time, a provisional schedule for maintenance and replacement of the heat exchanger, which is recalculated according the actual use of the heat exchanger. By following with the planned maintenance schedule and the replacement of the heat exchanger as determined according to the invention, the untimely shutdown of production due to a failure of the heat exchanger is prevented, and financial losses are controlled.
To this end, a heat exchanger is proposed in the first place, including:
Such a heat exchanger makes it possible to have, in real-time, a provisional schedule of maintenance and replacement of the heat exchanger which is recalculated according to the actual use of the heat exchanger.
Various additional features can be provided alone or in combination:
Secondly, an assembly comprising a heat exchanger as described hereinabove and a computer processing unit, is proposed.
Thirdly, a method is proposed for estimating a service life of a heat exchanger by means of an assembly as described hereinabove, the heat exchanger having a predetermined initial service life wherein the method comprises:
Other features and advantages of the invention will appear during reading the following description, the understanding of which will be supported by to the enclosed drawings, wherein:
The heat exchanger 1 comprises a plurality of frames 2. As can be seen, the frames 2 have a rectangular shape. Each frame 2 is made by assembling a plurality of substantially rectilinear bars 3 beveled at each of the ends thereof, so as to form a substantially right angle. The frames 2 are adjacent to each other. In other words, the frames 2 are overlaid one on top of the other. Each rectangular frame 2 defines an inner volume 4.
The heat exchanger 1 includes partition walls 5. A partition wall 5 is arranged between each rectangular frame 2. Thereby, a given rectangular frame 2 is not in immediate contact with an adjacent rectangular frame 2. A partition wall 5 separates the rectangular frames 2 from each other. The partition walls 5 separate the inner volume 4 of the rectangular frames 2 from one another, thereby creating compartments along the axis Z.
On either side of the heat exchanger 1, the latter includes an end frame 6, identical to the other rectangular frames 2 but located at the lower and upper ends 7, 8. A closing wall 9 is arranged on each end frame 6, for closing the inner volume 4 thereof.
As can be seen in
In the same way, each frame 2 except the end frames 6 has at least one fluidic outlet 31. Each fluidic outlet 31 of a given frame 2 is in fluidic communication with the inner volume 4 of the given frame 2.
As can be seen in the drawings, the fluidic inlets 10 are substantially aligned along the axis Z and the fluidic outlets 31 are also substantially aligned along the axis Z.
The heat exchanger 1 includes at least one distributor 11 of fluids and at least one collector 12 of fluids. The distributor 11 and the collector 12 of fluids have a substantially identical shape. Same is a curved sheet metal part defining a closed volume. The distributor 11 and the collector 12 are provided with a supply line 13 and with a discharge line 14, respectively, opening onto the closed volume. The supply pipe 13 is used for conveying the fluid into the closed volume of the distributor 11 and the discharge pipe 14 is used for discharging the fluid from the closed volume of the collector 12.
Hereinafter, distributors and collectors are referred to, indistinctly, by the expression “heads”.
The rectangular frames 2 define faces 16, 17, namely two lateral faces 16 extending along the axis X and two transverse faces 17 extending along the axis Y. The heads can be attached to the lateral faces 16 and/or to the transverse faces 17, defining a junction between said heads 11, 12 and said faces 16, 17. The heads 11, 12 extend over the entire height H, measured along the axis Z, of the heat exchanger 1. Thus, the heads 11, 12 are attached both to the rectangular frames 2 via a first junction 18 which extends substantially along the axis Z and to the closing walls 9 via a second junction 19 which extends substantially along the axis X or Y along the face 16, 17 on which said heads 11, 12 are positioned. Hereinafter, the first junctions 18 and the second junctions 19 are called lateral junctions 18 and end junctions 19, respectively.
The distributor 11 of fluid thus arranged is used for distributing the fluid towards the fluidic inlets 10. The collector 12 of fluids thus arranged is used for collecting the fluid leaving the fluidic outlets 31.
According to a preferred embodiment, the junction is welded so as to rigidly attach the heads 11, 12 to the rectangular frames and to the closing walls.
Advantageously, the heat exchanger 1 comprises at least one temperature gage 20 apt to measure a temperature of the fluid.
Advantageously, the heat exchanger 1 comprises at least one pressure gage 21 apt to measure a pressure of the fluid.
Advantageously, the heat exchanger 1 includes a plurality of strain gages 22 apt to measure deformations on the heat exchanger 1.
The heat exchanger 1 further includes a communication device 23 apt to receive the measurements from the different gages 20, 21, 22 and to send said measurements to a computer processing unit 24.
Advantageously, the invention also relates to an assembly 25 comprising a heat exchanger 1 and a computer processing unit 24.
As can be seen in the drawings, the strain gages 22 are advantageously arranged on the closing walls 9. The heat exchanger 1 includes so-called “junction” strain gages 22, hereinafter called junction gages 26. The junction gages 26 are situated in the vicinity of the end junctions 19 and arranged on the closing walls 9. The junction gages 26 are situated at a first gap distance D1 from the end junctions 19, comprised between 44 and 150 millimeters. The first gap distance D1 is measured along the longitudinal axis X.
Such arrangement of the junction gages 26 is advantageously used for obtaining measurements of the deformation stresses in a zone of the heat exchanger 1 prone to mechanical rupture and hence to leak.
Advantageously, the heat exchanger 1 can comprise a plurality of junction gages 26 arranged on the closing walls 9. The junction gages 26 are spaced apart from each other by a first gap distance D2 comprised between 10 and 500 millimeters. The first gap distance D2 is measured along the axis X when the head 11, 12 is situated on one of the lateral faces 16 and along the axis Y when the head 11, 12 is situated on one of the transverse faces 17.
In a preferred embodiment, the first gap distance D2 is substantially equal to 50 millimeters.
Such a first gap distance D2 makes it possible to obtain a precise distribution of the stress in the vicinity of the end junction 19.
The end junctions 19 extend over a length substantially equal to a width of the heads 11, 12. As can be seen in the drawings, the junction gages 26 are arranged substantially parallel to the end junctions 19 in a zone corresponding to the length of the end junction 19.
Advantageously, junction gages 26 can be arranged beyond the length of the end junctions 19. An additional junction gage 26 can be arranged beyond the length of the end junction 19.
Hereinafter, reference is made to
As can be seen in particular in
Advantageously, a so-called central strain gage is arranged on the closing walls 9 at the intersection of two diagonals d of the rectangle formed by each of said closing walls 9.
The central strain gage 27 is used for measuring the stresses in a zone of the closing walls 9 where the deformations are particularly significant.
Advantageously, a plurality of strain gages 22 are arranged on the closing walls 9. The strain gages 22 are aligned along the axis X.
The aligned arrangement of a plurality of strain gages 22 including the central strain gage 27 makes it possible to measure the stresses along the heat exchanger 1 along the axis X. The applicant determined that the deformations along the exchanger 1 along the longitudinal direction thereof and passing through the center of the closing walls 9 are particularly likely to reduce the service life thereof.
Advantageously, the strain gages 22 aligned with the closing walls 9 are spaced apart from each other by a second gap distance D3 measured along the axis X. The second gap distance D3 is between 0.6 meters and 1.6 meters. Preferentially, the second gap distance D3 is substantially equal to 1 meter.
The strain gages 22 thus arranged make it possible to mesh the closing walls 9 in order to obtain reliable measurements.
Hereinafter, reference is made to
The heat exchanger 1 includes sealing bars 28. The sealing bars 28 separate the inner volume 4 of a frame 2, into two sub-volumes. In other words, the sub-volumes form sealed compartments. The sealing bars 28 thus allow a first fluid to flow through a first compartment 29 and a second fluid to enter a second compartment 30, without the fluids mixing.
In the drawing shown in
When the heat exchanger 1 comprises sealing bars 28, as is the case in the second embodiment, a plurality of strain gages 22 are arranged on the closing walls 9, around the sealing bars 28.
Advantageously, the strain gages 22 are situated at a second gap distance D4 from the sealing bar 28, which is comprised between 10 and 50 millimeters. When the sealing bar 28 is arranged along the axis Y, as is the case in the second embodiment, the second gap distance D4 is measured along the axis X. When the sealing bar 28 is arranged along the axis X (not shown), the second gap distance D4 is measured along the axis Y.
The strain gages 22 thus arranged make it possible to measure the stresses around the sealing bar 28. Indeed, the zone surrounding the sealing bar 28 can be the seat of leaks.
The strain gages 22 located around the sealing bar 28 are spaced apart from each other by a third gap distance D5 comprised between 10 and 500 millimeters. The third gap distance D5 is measured along the axis Y when the sealing bars 28 are arranged along the axis Y as is the case in
The strain gages 22 thus arranged make it possible to mesh the zone around the sealing bars 28 in order to detect as well as possible excesses which are potentially dangerous for the heat exchanger 1 and useful in the calculation of the service life of said heat exchanger 1. Indeed, analyses carried out by the applicant were used for demonstrating the fact that the zones around the sealing bars 28 cause deformations on the closing wall 9.
As can be seen in
Each sub-rectangle corresponds to an inner sub-volume within a frame.
It has been determined by the applicant that deformations in the central zone of each sub-rectangle have an impact on the service life of the heat exchanger 1. The central strain gage 27 arranged at said place advantageously makes it possible to measure the deformations in said zone.
As can be seen in
The aligned arrangement of a plurality of strain gages 22 including the central strain gage 27 makes it possible to measure the stresses along each sub-rectangle on the closing walls 9. The applicant determined that the deformations of the sub-rectangles on the closing wall 9 along the longitudinal direction of the latter and passing through the center of the sub-rectangles are particularly likely to reduce the service life thereof.
The strain gages 22 are spaced apart from each other by a fourth gap distance D6 comprised between 0.6 meters and 1.6 meters. The fourth gap distance D6 is substantially equal to 1 meter.
The strain gages 22 thus arranged make it possible to mesh the closing walls 9 in order to obtain reliable measurements.
Hereinafter, a method 35 for estimating a service life of the heat exchanger 1 will be described. The estimation method 35 applies to the heat exchanger 1 described hereinabove whichever embodiment described. The heat exchanger 1 has a known initial service life. The initial service life is calculated by the manufacturer of the heat exchanger 1.
The estimation method comprises a first step E1 of measurement of the temperature of the fluid, by means of the temperature gages 20.
During a second step E2, the computer processing unit 24 calculates, in real-time, a thermo-mechanical stress for each temperature measurement performed. The thermo-mechanical stress is calculated using the following formula:
σth(T)=E·α·ΔT
In a third step E3, the calculated thermo-mechanical stresses are stored in a computer memory.
The method 35 further comprises a fourth step E4 of continuous measurement of the pressure, by means of the pressure gages 21.
During a fifth step E5, the computer processing unit 24 calculates, in real-time, a mechanical pressure stress for each pressure measurement performed.
In a sixth step, the calculated mechanical pressure stresses are stored in a computer memory.
The method comprises a seventh step E7 of continuous measurement of the mechanical stresses on the closing walls 9, by means of the strain gages 22.
In an eighth step E8, the measured mechanical stresses are stored.
The method further comprises a ninth step E9 of determining a series of ranges of mechanical stress values. Such ranges of values are determined by taking the interval between the maximum value and the minimum value of the previously calculated and measured stresses. The interval between the minimum and maximum is discretized so as to obtain ranges of values. The discretization can be variably coarse depending on the precision sought. As an example, a discretization can be performed with a step equal to 10. According to such example, but not limited to, the interval between extrema is divided into 10 ranges of values.
The method includes a tenth step E10 during which the stress calculated and stored in memory are associated with a range of values. In other words, whenever a stored stress has a value within a range of values, the stored stress being associated with the corresponding range of values.
The method 35 comprises an eleventh step E11 during which the number of occurrences for each range of values is determined. In other words, for a given range of values, it is determined how many times the previously calculated and measured stresses fall within the given range of values.
In this way, it is possible, in a twelfth step E12 of the method, to determine an estimation of a service life. The above is done in a comparative way with a database empirically developed by performing many laboratory tests.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012926 | Dec 2020 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/085007 | 12/9/2021 | WO |
