Method for estimating a mechanical service interval for an open-type industrial compressor with alternating or continuous flow

Abstract

The invention relates to a method for estimating an actual service interval for an open-type industrial compressor with alternating or continuous flow, which comprises: - determining (1) the evaporation pressure P0 and the condensation pressure Pk of the compressor in operation; - determining (3) the actual service interval Ir by applying a starting coefficient Fd and a correction coefficient Fc to a general service interval Ig; the general service interval Ig depending on the evaporation pressure P0 and the condensation pressure Pk; the correction coefficient Fc being based on the load of the compressor in operation; and the starting coefficient Fd being based on a forecast number of starts and total hours of operation of the compressor over a predefined time interval; - updating (4) a future service time on the basis of the value of the actual service interval Ir determined and the date of the last service.

Description

[0001] DESCRIPTION

[0002] TITLE: Method for estimating a mechanical overhaul interval for an open-type industrial compressor with alternating or direct flow

[0003] technical field

[0004] The invention relates to the field of open industrial compressors, both piston (reciprocating) and screw (direct-flow). More specifically, the invention relates to the mechanical overhaul intervals of these compressors.

[0005] State of the art

[0006] To ensure optimal operation of an open reciprocating or direct-flow compressor, regular inspection and maintenance of its mechanical components must be performed. These preventive maintenance operations help guarantee proper functioning, extend the equipment's lifespan, and reduce unforeseen repair costs associated with corrective maintenance.

[0007] Maintenance operations are generally carried out after a certain number of compressor operating hours, and include, for example:

[0008] In the case of a "piston" compressor:

[0009] - replacing the oil filter,

[0010] - replacing the sealing gasket,

[0011] - the replacement of the suction and discharge valves and springs,

[0012] - the replacement of the segments,

[0013] - replacing the connecting rod bearings,

[0014] - etc. In the case of a screw compressor:

[0015] - replacing the oil filter,

[0016] - replacing the sealing gasket,

[0017] - the replacement of the thrust bearings,

[0018] - the replacement of bearing housings or plain bearings,

[0019] - etc.

[0020] In the case of a "single-screw" compressor:

[0021] - replacing the oil filter,

[0022] - replacing the sealing gasket,

[0023] - the replacement of carbon components in satellites,

[0024] - the replacement of the satellite thrust bearings,

[0025] - etc.

[0026] In practice, each manufacturer defines the recommendations and maintenance instructions for the various compressor parts. The frequency of intervention generally varies depending on the parts to be inspected, and some manufacturers define a general hourly inspection interval that serves as a basis for determining maintenance cycles.

[0027] The general overhaul interval depends on several parameters, such as the type of compressors (piston, screw or single-screw), the refrigerant used, specific operating conditions, etc.

[0028] For an open piston compressor, the manufacturer typically provides specific curves indicating, among other things, the maximum number of compressor operating hours between maintenance operations, depending on operating conditions. One such curve is illustrated in Figure 1, showing the maximum number of compressor operating hours as a function of condensing pressures (PC) and evaporating pressures (PE) for a given type of refrigerant. Thus, according to the curve in Figure 1, the general recommended overhaul interval would be 12,600 hours for operation involving a condensing pressure (PC) of 10 bar and an evaporating pressure (PE) of 5 bar, and the general recommended overhaul interval would be 7,000 hours for operation involving a condensing pressure (PC) of 35 bar and an evaporating pressure (PE) of 20 bar.

[0029] For an open screw compressor, the manufacturer usually gives a simple fixed value for the general overhaul interval, for example 30000 hours.

[0030] Furthermore, for open piston compressors, since the rotational speed impacts the friction of the components, the manufacturer recommends applying a correction factor F. c function of the compressor operating speed. The manufacturer provides a table like the one shown in Figure 2 giving the value of the correction factor F c to be applied according to the operating speed of the compressor. According to the table in figure 2, if the compressor operates at 970 rpm, for the general recommended overhaul interval of 12,600 hours, the actual corrected overhaul interval is 1.5 x 12,600 = 18,900 hours.

[0031] Thus, the equation giving the corrected revision interval is: I r = I g * F c, with: I r : the actual revision interval;

[0032] Ig: the general revision interval given by the manufacturer via curves;

[0033] F c : the correction coefficient provided by the manufacturer and a function of the compressor's operating speed, and can be defined as F c = 1460 / actual operating speed of the compressor (1460 rpm being considered by the manufacturer as the optimal operating speed of the compressor).

[0034] However, the value of the correction factor F c may be too important in the case of a compressor operating with a variable speed drive and at low load which only requires a low rotational speed, inducing a high overhaul frequency.

[0035] Furthermore, the values ​​of the general revision interval I gThe manufacturer only provides the recommended service intervals in the form of curves, without indicating how these curves were obtained. Therefore, the service interval values ​​provided by manufacturers are intended to cover a wide range of operating conditions, which do not always reflect the actual operation of the compressor.

[0036] Thus, in certain situations where the compressor is under heavy load (operation at full load, significant variations in speed or load, mechanical variations without a variable speed drive, numerous starts, etc.), the recommended service interval may be insufficient, leading to premature wear of the components. Conversely, the compressor may sometimes be subjected to very little stress, and the manufacturer's recommended service frequency may be high, resulting in significant maintenance costs.

[0037] Description of the invention

[0038] The invention aims to provide an alternative solution for determining optimized overhaul intervals for an open-type industrial compressor, whether reciprocating or direct flow (piston or screw type). This optimization ensures optimal compressor operation and limits the risk of premature wear or unexpected failures that could lead to a complete and unforeseen compressor shutdown.

[0039] Adjusting the overhaul interval to the compressor's actual operating conditions impacts both the operating costs associated with compressor maintenance (ordering spare parts, personnel working on the compressor) and the compressor's energy efficiency. This adjustment also helps to limit unforeseen repair work during a mechanical overhaul that would otherwise require machining.

[0040] The invention relates to a method for estimating the actual mechanical overhaul interval of an open-type industrial compressor with reciprocating or direct flow (or a piston, screw, or single-screw compressor). The method comprises:

[0041] - the determination of the evaporation pressure Po and the condensation pressure Pk of the compressor in operation;

[0042] - the determination of the actual revision interval I r by applying a starting coefficient Fa and a correction coefficient F c at a general revision interval I g ;

[0043] . the general revision interval I g being dependent at least on the evaporation pressure Po and the condensation pressure Pk of the operating compressor;

[0044] the correction coefficient F c being a function of the compressor's operating load; and

[0045] . the start-up coefficient Fd being a function of a predicted number of compressor starts over a predefined time interval, for example over a given operating year, and of a predicted total number of compressor operating hours during the same predefined time interval, for example over the given operating year;

[0046] - the determination of a future overhaul time, by a compressor control unit, as a function of the value of the actual overhaul interval I r determined, and the date of the last revision (or update of revision times).

[0047] Thus, the service interval is determined taking into account the actual operating conditions of the compressor and in particular the load.

[0048] According to one embodiment, the actual revision interval I rcan be determined by further applying a reliability coefficient Ff to the general revision interval I g The reliability coefficient Ff is particularly representative of the mechanical reliability of the compressor model under consideration. In other words, when the compressor model is known and / or sufficient data relating to the compressor's operation or behavior over a long period is available, taking into account the compressor's reliability coefficient allows for the most accurate estimation of the overhaul interval.

[0049] In practice, the reliability coefficient Ff is specific to a compressor model and can be determined by taking into account metrological measurements relating to the compressor or its components. These measurements are collected beforehand over a predefined period, for example, 10 years. This metrological data might relate, for example, to the rotational play on a power control valve with a tolerance of 0.10 mm. For example, the reliability coefficient Ff of a compressor model can take into account an estimated or actual return rate for dismantling or repair of that compressor model, or a mean time between two failures of the compressor or a compressor component, over a predefined period (for example, 10 years). This return rate can be expressed as a notation with a value between 1 and 10.

[0050] Thus, the general overhaul interval is adjusted taking into account the actual operating conditions of the compressor, and in particular the variation of the compressor load, and the mechanical reliability of the compressor model considered.

[0051] Advantageously, the general revision interval I g can also be dependent on a precariousness coefficient i of negative value and a function of the determined evaporation pressure Po and condensation pressure Pk.

[0052] In other words, the actual revision interval I r can be defined by: [Math 1]

[0053] Ir being the actual revision interval; i being the precariousness coefficient, i < 0, a function of the determined evaporation pressure Po and condensation pressure Pk;

[0054] I g (i) being the general revision interval, a function of the precariousness coefficient i;

[0055] Ff being the compressor reliability coefficient;

[0056] F c being the correction coefficient; Fa being the starting coefficient. In practice, the determination of the actual revision interval I r can be achieved using two methods:

[0057] - by a static method (averaged over a one-year interval), that is to say, an average is determined for each of the variables involved in determining I r , over a year, so that the value of Ir is fixed for one year; or

[0058] - by a dynamic method (continuous, derivative over short periods), that is to say that we determine I r over short intervals and updating the value of I r , so that the value of I r may change over the course of the year.

[0059] Thus, determining the actual service interval between two mechanical overhauls takes into account measurements of parameters that can impact compressor operation. Furthermore, the service interval can be determined continuously, including in real time, or at predefined frequencies. In other words, the actual service interval can be a dynamic value.

[0060] According to one variant, the general revision interval I g (i) can be determined by further applying a technological factor F t of fixed value and indicative of the type of compressor, namely reciprocating or continuous flow compressor (piston or screw or single-screw compressor).

[0061] In practice, a screw compressor generally offers greater durability compared to a piston compressor, due to a smaller number of moving parts. For example, the technological factor F tcan be set to a value of 1 for a piston compressor, and to a value between 2 and 3 for a screw or single-screw compressor.

[0062] The precariousness coefficient i can be advantageously determined by the following formula:

[0063] [Math 3] i = (P k - n) / (Zn(P0) + fc) n being a constant between -23 and -21; k being a constant between -6 and -3.

[0064] Advantageously, for an open piston, screw, or single-screw compressor, the correction factor F c is determined with the following equation: [Math 4]

[0065] F c = [F v * (1 - )]

[0066] F v being a constant representing the existence or absence of premature wear due to the absence or presence of a speed variator in the compressor;

[0067] Ch being a compressor load in % (between 0 and 100%).

[0068] In practice, the load can be measured in the dynamic case, calculated in the static case, or predefined.

[0069] The correction factor F c is thus dependent on the presence or absence of a variable speed drive, as well as the compressor load during operation. In particular:

[0070] - without a speed variator: the variation will be carried out mechanically by the regulating slide valve for screw compressors and by the lifting of the valves for piston compressors. This variation in mechanical power causes premature wear of the compressor (due to friction, heating, vibrations, etc.);

[0071] - with variable speed drive: the variation will no longer be done mechanically by the power regulation spool and the rotation speed can be reduced or adapted to the compressor load, positively impacting the compressor's lifespan (related to the limitation of friction).

[0072] Thus the variation factor F v This reflects the possible existence of premature compressor wear induced by the absence of a speed variator in the compressor. In practice, the value of the variation factor F v can be determined via feedback from mechanics and by statistical analysis from metrological readings relating to the compressor or compressor parts, and previously collected over a predefined period, for example over 10 years.

[0073] For example, the factor of variation F vcan be a fixed positive value less than 1 when the compressor incorporates a variable speed drive, and F v can be a fixed negative value, with an absolute value less than 1 when the compressor does not incorporate a variable speed drive. For example:

[0074] - in the presence of a speed variator: F v can be between 0.1 and 0.5;

[0075] - in the absence of a speed variator: F v can be between -0.5 and -0.1.

[0076] The invention also relates to a system for estimating a mechanical overhaul interval of an open-type industrial compressor with alternating or continuous flow, the system comprising a compressor control module, the control module being coupled to at least means for determining the actual operating speed of the compressor, means for determining the evaporation pressure Po and the condensation pressure Pk of the compressor in operation, means for determining the compressor load, and a database, the module being configured to implement the estimation method described above.

[0077] The invention may also relate to a method of generating or constructing a virtual model, in the form of a digital twin, of the compressor or a more complete installation integrating the compressor, implementing the estimation method presented above.

[0078] In one variant, the construction of the virtual model may include the construction of an adjusted operating hour meter for the compressor, taking into account the vibratory behavior of the compressor, and the theoretical amount of oil consumed by the compressor, during a predefined time.

[0079] Brief description of the drawings The present invention and its advantages will become clearer from the following description of several embodiments given by way of non-limiting examples, with reference to the accompanying drawings, in which:

[0080] [Fig 1] is an example of a curve diagram showing the maximum number of compressor operating hours between maintenance operations, as a function of condensation and evaporation temperatures;

[0081] [Fig 2] is an example of a table giving the correction factor as a function of the compressor rotation speed;

[0082] [Fig 3] is an example of a curve diagram showing the general revision interval I r (i), depending on the condensation pressures Pk and evaporation pressures Po; [Fig 4] is a simplified flowchart representing the steps of the process for determining the actual revision interval according to one embodiment;

[0083] [Fig 5] is a simplified block diagram of the system according to one embodiment;

[0084] [Fig 6] presents curves representing the evolution of the hours accumulated by the hour meters, and the theoretical oil leakage rate, according to one embodiment;

[0085] [Fig 7] presents curves representing the evolution of the hours accumulated by the hour meters, and their difference, according to one embodiment.

[0086] Description of the implementation methods

[0087] Determining the actual revision interval I rof an open-type industrial compressor with piston, screw or single-screw, according to an embodiment that takes into account a precariousness coefficient i, a correction factor F c but also a reliability factor Ff, and / or a starting factor Fa.

[0088] Thus, with reference to Figure 4, the method for determining the actual revision interval I r In one embodiment, it may thus include the following operations:

[0089] - the determination 1 of the evaporation pressure Po and the condensation pressure Pk of the compressor in operation;

[0090] - the determination of the different coefficients necessary for the calculation of I r ; - the determination 3 of the actual revision interval I r by applying the different coefficients to a general revision interval I g ;

[0091] - the determination 4 of a future overhaul time, by a compressor control unit, as a function of the value of the actual overhaul interval I r determined, and the date of the last revision (or update of revision times).

[0092] In one embodiment, the actual revision interval I r can be determined via the following general equation:

[0093] [Math 5]

[0094] Ir being the actual revision interval; i being a precariousness coefficient;

[0095] I g (i) being a general revision interval, a function of the precariousness coefficient i;

[0096] Ff being a factor in compressor reliability;

[0097] F c being a correction coefficient;

[0098] Fa being a starting coefficient.

[0099] The different factors and coefficients will be presented below.

[0100] Precariousness coefficient i

[0101] The precariousness coefficient i can be determined by the following formula: [Math 6] i = (P k - n) / (Zn(P0) + fc) i < 0

[0102] Po is the evaporation pressure of the compressor in operation, and which can be measured by a sensor;

[0103] Pk is the compressor's operating condensation pressure, which can also be measured via a sensor; n is a constant between -23 and -21; k is a constant between -6 and -3. General overhaul interval Ig(i)

[0104] The general revision interval I g (i) can be determined via the following formula: [Math 7] i is the precariousness coefficient defined above;

[0105] F tis a fixed-value technological factor indicating the type of compressor, namely piston compressor or screw compressor or single-screw compressor; a, b, c and d being constants.

[0106] In particular, the technological factor F t can be set to a value of 1 for a piston compressor, and to a value between 2 and 3 for a screw or single-screw compressor.

[0107] The constant a can be between 0.2 and 1.

[0108] The constant b can be between 35 and 40.

[0109] The constant c can be between 1265 and 1275.

[0110] The constant d can be between 20725 and 20735.

[0111] In practice, the value of the general revision interval I g (i) can be given via a curve diagram like the one shown in Figure 3 giving the value of the general revision interval I gdepending on the evaporation pressure Po and the condensation pressure Pk. Thus, according to figure 3, the general overhaul interval Ig is 8000 hours for compressor operation corresponding to the curve Co.

[0112] This formula for determining the general revision interval I g (i) is valid for all types of refrigerant.

[0113] Reliability Factor Ff: The reliability factor Ff represents the mechanical reliability of the compressor model under consideration and is a function, for example, of an estimated or actual return rate for dismantling or repair of that compressor model. It can be determined by taking into account metrological measurements relating to the compressor or compressor parts, collected beforehand over a predefined period, for example, 10 years. This reliability coefficient Ff can be obtained by applying reliability calculation laws for mechanical systems, or be based on the study of the behavior of the compressor or compressor components, taking into account feedback from qualified personnel involved in compressor maintenance over a predefined period, for example, 10 years. The return rate can be expressed as a rating from 1 to 10.

[0114] For example, the reliability factor Ff can be determined by the following equation: [Math 8] nt being a notation of the compressor model considered, and generally takes a value between 1 and 10. This notation is an objective data representative of the return rate for dismantling or repair of the compressor: a being a constant between 0.02 and 0.06;

[0115] P being a constant between 0.5 and 0.7

[0116] The determination of the reliability coefficient of a compressor model can be based on the causes and / or consequences of failures or returns of the compressor to the factory or for repair, as well as on the metrological deviations observed between machines of the same model in ideal regimes.

[0117] For example, the reliability coefficient can be based on data relating to the impact of water hammer on the premature wear of a given compressor model, under different operating conditions (e.g., compressor operating with or without an economizer, with an economizer, without an economizer). A statistical rule, such as the binomial distribution, can be implemented to highlight the significance or importance of a physical phenomenon observed in the compressor.

[0118] Correction factor Fc

[0119] The correction factor F c allows taking into account the presence or absence of a speed variator, as well as the compressor load.

[0120] The correction factor F c can be determined with the following equation: [Math 9]

[0121] F c = (F v * (1 - ))

[0122] F va variation factor representative of the existence or absence of premature wear due to the absence or presence respectively of a speed variator in the compressor;

[0123] Ch is the compressor load in % (between 0 and 100%).

[0124] For example :

[0125] - in the presence of a speed variator: F v can be between 0.1 and 0.5, for example equal to 0.2;

[0126] - in the absence of a speed variator: F v can be between -0.5 and -0.1, for example equal to -0.2.

[0127] Starting coefficient Fd

[0128] The starting coefficient Fa depends on the predicted number of compressor starts over a predefined time interval, for example over the operating year considered, and can be expressed as follows:

[0129] [Math 10] nba being the number of compressor starts during the predefined time interval, for example per year; nbh being the number of compressor operating hours during the predefined time interval, for example per year; m being a constant equal to 7.5 corresponding to the number of minutes to be subtracted from the general overhaul interval I g ; h being a constant equal to 60.

[0130] Expanded form of the real interval Ir

[0131] The real interval I r can thus be the product of the general interval I g (i) with the reliability factor Ff, adjusted with the correction coefficient F c and the starting coefficient Fd.

[0132] Thus, according to one embodiment, the revision interval Ir is given by the following equation:

[0133] [Math 11]

[0134] Estimation system

[0135] All of these operations can be implemented in a control module of an estimation system, illustrated in Figure 5. The control module 5 can be coupled, for example, to means 6 for determining the actual operating speed of the compressor, means 7 for determining the evaporation pressure Po and the condensation pressure Pk of the operating compressor, means 8 for determining the load of a compressor 9, and a database 10 or memory. The various parameters (curve diagram, the different constants, a table giving the notation nt for different compressor models, the variation factors, etc.), as well as the equations involved in determining the actual interval I r revisions can be stored in the database.

[0136] Control module 5 is configured to determine the actual revision interval I rby applying the equations above, and to determine future revision times based on the actual revision interval I r determined and the date of the last revision.

[0137] Digital twin

[0138] The estimation process described above can also be implemented for the generation or construction of a virtual model, in the form of a digital twin, of the compressor or a more complete installation incorporating the compressor.

[0139] Thus, in addition to the data required for estimating the revision interval according to the invention, other data or measurements can be used for simulating the life cycle of the compressor or installation.

[0140] Such data can be quantitative data, such as, for example, the vibration behavior of compressors via a vibration sensor, the theoretical amount of oil consumed by the compressor, etc.

[0141] Such data can also be qualitative data, such as, for example:

[0142] - the rating of compressors which results from an expertise of the Applicant benefiting from global feedback concerning different models of compressors;

[0143] - The rating of actual oil consumption at the compressor seals compared to theoretical consumption during operation. In practice, this modeling can enable anomaly detection and / or assist in the control of compressors or the system, and identify areas for improvement in operating conditions. For example, it is possible to adjust the rotation speed, modify the number of daily starts allowed, reduce the compression ratio, put the compressor in backup mode, etc., in order to operate the compressor under more favorable conditions.

[0144] In one variation, the modeling can also include the construction or generation of an adjusted compressor operating hour meter. The modeling of the actual adjusted hour meter can take into account the quantitative data mentioned above.

[0145] The hour meter defines the number of hours the compressor can operate in a day. This hour meter is separate from the hourly maintenance interval. Thus, the hourly maintenance interval can be determined according to the method of the invention, and the hour meter can be adjusted.

[0146] In practice, it is possible to adjust the speed of the counter. For example, the actual counter can advance faster if the actual operating conditions of the compressor are considered unfavorable and advance more slowly if the actual operating conditions of the compressor are considered favorable.

[0147] An example illustrating the evolution of the hour meters is shown in figures 6 and 7. The dates are given on the x-axis, and the quantity of oil leakage (ml), the number of hours on the hour meters (h) and the difference between the hour meters (Nh) are given on the y-axis.

[0148] The curve Cl (solid line curve) represents the evolution of the number of hours (h) of the theoretical hour meter of the compressor;

[0149] Curve C2 (dashed curve) represents the evolution of the number of hours (h) of the adjusted real hour meter generated by the modeling (digital twin); Curve C3 gives the theoretical oil leakage rates;

[0150] Curve C4 represents the evolution of the difference in number of hours (Nh) between the two curves Cl and C2. The solution presented above can be implemented in a more comprehensive Intelligent Collaborative Factory solution.

Claims

Demands 1. A method for estimating the actual mechanical overhaul interval of an open-type industrial compressor with alternating or direct flow, comprising: - the determination (1) of the evaporation pressure Po and the condensation pressure Pk of the compressor in operation; - the determination (3) of the actual revision interval I r by applying a starting coefficient Fa and a correction coefficient F c at a general revision interval I g ; . the general revision interval I g being dependent at least on the evaporation pressure Po and the condensation pressure Pk of the operating compressor; the correction coefficient F c being a function of the compressor's operating load; and . the start-up coefficient Fa being a function of a predicted number of compressor starts over a predefined time interval, for example over a given operating year, and of a predicted total number of compressor operating hours during the same predefined time interval, for example over the given operating year; - the update (4) of a future revision time based on the value of the actual revision interval I r determined, and the date of the last revision.

2. Estimation method according to claim 1, wherein the actual revision interval I r is determined by further applying a reliability coefficient Ff to the general revision interval I g The reliability coefficient Ff is representative of the mechanical reliability of the compressor or a set of compressor parts.

3. Estimation method according to claim 1 or 2, wherein the general revision interval I g can also be a function of a precariousness coefficient i of negative value and a function of the evaporation pressure Po and the condensation pressure Pk determined, of the compressor in operation.

4. Estimation method according to claim 3, wherein the actual revision interval is determined by applying the following equation: I r being the actual revision interval; i being the precariousness coefficient, i < 0, a function of the determined evaporation pressure Po and condensation pressure Pk; I g (i) being the general revision interval, a function of the precariousness coefficient i; Ff being the compressor reliability factor; F c being the correction factor; Fa being the starting factor.

5. An estimation method according to any one of claims 1 to 4, wherein the general revision interval I g (i) is determined taking into account a technological factor F t indicative of the type of compressor, namely reciprocating or direct flow compressor.

6. Estimation method according to any one of claims 1 to 5, wherein the precariousness coefficient i can be advantageously determined by the following formula: i = (Pk - ri) / (ln( o) + kn being a constant between -23 and -21; k being a constant between -6 and -3.

7. Estimation method according to any one of claims 2 to 6, wherein the reliability coefficient Ff is given by: Ff = (0.05 * nt) + 0.65, nt being a notation of the compressor model considered, and has a value between 1 and 10.

8. An estimation method according to any one of claims 1 to 7, wherein the correction factor F cis determined using the following equation: F c = Fv * (1 - Ch) F v being a constant representing the existence or absence of premature wear due to the absence or presence of a speed variator in the compressor; Ch being a compressor load in %.

9. Estimation method according to claim 8, wherein the variation factor F v is representative of the presence or absence of premature wear due to the presence or absence of a speed variator in the compressor, the variation factor F v being equal to a fixed positive value less than 1 when the compressor incorporates a speed variator, and equal to a fixed negative value, with an absolute value less than 1 when the compressor does not incorporate a speed variator.

10. System for estimating a mechanical overhaul interval of an industrial open-type compressor (9) with alternating or continuous flow, the system comprising: a compressor control module (5) coupled at least to means (6) for determining the actual operating speed of the compressor, means (7) for determining the evaporation pressure Po and the condensation pressure Pk of the operating compressor, means (8) for determining the load of the compressor (9), and a database (10), the control module (5) being configured to implement the estimation method according to any one of claims 1 to 9.

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