Method for determining a compressor operating margin

Abstract

According to an embodiment, there is disclosed a method for determining an operating margin (206) of a compressor (102) comprising a cooling circuit (101), the method comprising iteratively performing the steps of measuring (200) one or more process variables indicative of an instantaneous operation of the compressor (102); estimating (201) the one or more process variables based on one or more setting parameters of the compressor (102) using a model (203) comprising a heat transfer characteristic between the compressor (102) and the cooling circuit (101), the heat transfer characteristic comprising a contamination parameter; matching (204) the estimated process variables (201) with the measured process variables (202) by changing the contamination parameter; wherein the operating margin (206) is determined (205) based on the contamination parameter.

Description

METHOD FOR DETERMINING A COMPRESSOR OPERATING MARGINTechnical Field

[0001] The present invention relates to a method for determining an operating margin of a compressor and / or peripherals in order to increase their availability.State of the art

[0002] A compressor is a mechanical machine, designed to provide a gas, such as ambient air, under higher pressure for applications in industrial processes and / or the medical sector. Depending on the required pressure, the desired application, a desired result, and other preconditions, it is possible to choose from a variety of compressor technologies, such as an axial compressor versus a centrifugal compressor, as well as an oil-free versus an oil-lubricated compressor.

[0003] Furthermore, compressors can be equipped with peripheral devices, also referred to as supporting devices, such as a cooler, an oil separator, a filter or air filter, a dryer, and so on.

[0004] It is also obvious that in most industrial environments and / or the medical sector, high compressor availability is expected without having to compromise on performance. However, like most mechanical machines, some form of degradation will inevitably occur over time due to, among other things, the presence of rotating parts, contamination in the ambient air around the machine, being subject to large temperature differences, the loss of oil and other internal or external influences that may prevent and / or deteriorate the proper functioning of the compressor.

[0005] This can cause the compressor to stop prematurely without prior notification to an operator. To avoid such an undesirable situation, a method is needed to determine the operating margin of a compressor. This allows to estimate the remaining availability and / or to timely take action to be able to guarantee its availability.

[0006] It is therefore an object of the present invention to provide a method for determining an operating margin of a compressor comprising a cooling circuit.Summary of the Invention

[0007] According to the present invention, the above-identified object is achieved by providing, according to a first aspect of the invention, a computer-implemented method according to claim 1 for determining an operating margin of a compressor comprising a cooling circuit, the method comprising iteratively performing the steps of:- measuring one or more process variables indicative of an instantaneous operation of the compressor;- estimating the one or more process variables based on one or more setting parameters of the compressor using a model comprising a heat transfer characteristic between the compressor and the cooling circuit, the heat transfer characteristic comprising a contamination parameter;- matching the estimated process variables with the measured process variables by changing the contamination parameter; wherein the operating margin is determined based on the contamination parameter and the one or more setting parameters of the compressor.

[0008] The step of measuring is understood to be the quantitative input of a quantity obtained from one or more observations, recordings, or sampling at a specific measuring location by means of suitable measuring instruments, such as sensors for expressing an observed quantity in a number with a relevant unit that can be compared with other values of the same quantity.

[0009] The step of estimating is understood to be the determination of a value of a quantity based on measured process quantities and / or setting parameters, using ascientific model representative of a technical process and / or apparatus with as input the measured process quantities and / or setting parameters, and as output the value that needs to be determined and is therefore estimated, based on one or more calculations.

[0010] The step of matching is understood to have a set of variables within a set of equations converge by changing one or more parameters of this set of equations to a set of certain desired values. The step of matching is therefore done based on one or more calculations.

[0011] Iteratively performing the steps means that the steps are performed repeatedly.

[0012] Later in the text, reference will be made to a machine, a compressor, and / or an apparatus, but further note that these terms are interchangeable for purposes of discussing the invention. When referring to the term machine, it can therefore refer to either a compressor, a supporting apparatus, or a combination of both.

[0013] In a first step, process variables are measured that are indicative of the instantaneous operation of the compressor. These process variables are an ambient temperature, cooling temperature, compressor temperature, electrical current, speed, inlet pressure, outlet pressure, ambient pressure, humidity, and / or flow rate. Furthermore, note that this list is non-exhaustive and that other process parameters, representative of the compressor operation, can also be measured. On the other hand, it should also be noted that not all process variables are measured, but some of them.

[0014] In a second step, these one or more process variables of the compressor are estimated. This estimation is made based on one or more setting parameters of the compressor that serve as input to a scientific model of the compressor, wherein the output of the model are the estimated process variables. Moreover, as already mentioned, this step can also be carried out according to an embodiment based on measurements carried out in the first step.

[0015] It should further be noted that the first and second steps can be performed in parallel and simultaneously. The used term 'first' and 'second' therefore serves todistinguish between the different steps, but does not indicate a specific chronology and / or hierarchy between the two steps. On the other hand, it must, of course, be understood that estimating process variables based on other measured process variables does imply that this measurement is carried out prior to the estimate.

[0016] The one or more process variables are estimated based on a model comprising a heat transfer characteristic between the compressor and the cooling circuit, wherein this heat transfer characteristic comprises a contamination parameter.

[0017] In the case of an oil-free compressor, the cooling circuit consists of several components, such as a pump, a housing of the compressor element of the compressor, a cooler, bearings, a gearbox and conduits connecting these components. Together, this whole forms a closed system, which means that the oil for the heat transfer, propelled by the oil pump, returns to the inlet of the same pump at a later time. Alternatively, with an oil-injected compression, the heat transfer can take place in the compressor element itself, and / or a cooling circuit can be provided with a coolant other than oil, such as water. It is important that a model is used that is representative of the cooling circuit used and described by a heat transfer characteristic. In the further discussion of the invention, reference will be made to oil as a coolant, but it should be understood that the use of another type of coolant is also possible.

[0018] During its operation, the compressor will generate heat that must be dissipated. For this purpose, oil will flow in the cooling circuit, whereby the cooling circuit is configured in such a way that this oil will absorb heat in order to cool the heated parts of the compressor. Stated differently, a specific mass of oil with a specific heat capacity will flow through the cooling circuit and the oil will absorb heat at certain locations in the circuit, for example at bearings, the gearbox, the compressor element, the element housing, and the pump, and will emit heat at other locations in the circuit, for example to a cooler or through radiation to the environment.

[0019] The heat transfer characteristic is then part of the model and is representative of the cooling circuit comprising a contamination parameter, as described further.

[0020] Initially, a model of an ideal machine is provided to estimate the process variables, i.e. a machine without any contamination and / or defects. The difference, also called a delta, between the measured and estimated process variables will in principle indicate deviating behaviour between an ideal or healthy machine and the actual machine. The greater this difference, the greater the deviating behaviour of the machine compared to a healthy machine. This difference will be further interpreted by this defined contamination parameter, present in the model used.

[0021] For example, the contamination parameter is a parameter with a value between zero and one, where a zero value is indicative of a completely clean compressor cooling circuit, i.e. in a healthy condition. Such condition can be further described as being a condition or state without the presence of dust and other contaminants. A value of one for the contamination parameter may then indicate a condition wherein the compressor cooling circuit is contaminated to such an extent that maintenance action is required. Moreover, this may further indicate a condition wherein the compressor is no longer suitable for further use due to contamination of the cooling circuit without carrying out such maintenance action.

[0022] It should be further understood that contaminants will mainly occur on the outside of the compressor, for example due to the accumulation of dust particles that can hinder the smooth passage of air to an air-oil heat exchanger. Furthermore, note that contamination of a mechanical machine such as a compressor, although undesirable, is unavoidable under normal operating conditions.

[0023] The contamination parameter can also take on a value, other than between zero and one, and can, for example, be further normalized to standardize further processing and control, based on the parameter. This normalization can be done, for example, based on a cooling surface of the cooling circuit.

[0024] Therefore, the model is representative of the compressor comprising the cooling circuit and is, for example, a physical or multi-physical model comprising a set of differential equations, and / or physical relations, and / or empirical relations, describing the different physical parts of the compressor and the cooling circuit and depend on each other through one or more common variables. The set of differential equationsfurther comprises one or more parameters, such as the contamination parameter as mentioned above, and one or more variables. Alternatively, the contamination parameter can also be a parameter in an empirical model and / or a physical relationship.

[0025] In a third step, the estimated process quantities are matched with the measured quantities by changing the contamination parameter within the model. In other words, the other parameters within the differential equations describing the compressor are maintained constant, while the contamination parameter is changed to bring the estimated process quantities into agreement with the measured process quantities. When the model is an empirical model and / or comprises a physical relationship, the parameters other than the contamination parameter can be maintained constant to determine the value of the contamination parameter. It should further be understood that there may still be a deviation between the measured and matched process variables as a result of the sensors used, as well as the method used for matching to converge the values to the measured values.

[0026] Finally, the operating margin of the compressor is determined, based on the contamination parameter and one or more compressor setting parameters. In other words, by matching the estimated process variables with the measured process variables by changing the contamination parameter in the model, this parameter will be adjusted in a range of zero and one, whether or not normalized, as described above. As already mentioned, this corresponds to a completely healthy versus completely contaminated situation, and therefore gives an idea of what the operating margin and therefore the future availability of the compressor is given a certain use.

[0027] As already mentioned, the different steps are done iteratively, in other words, the steps are performed repeatedly, providing a successive estimate of the operating margin over time.

[0028] This operating margin can then be further monitored so that it can be estimated under which operating conditions a failure or shutdown will occur. Such failures can occur, for example, when the oil temperature of the oil present in the oil circuit exceeds a predefined safety limit. This exceedance may then be attributed to an excessivelycontaminated situation in the compressor and / or the cooling circuit and can therefore be derived from the value of the contamination parameter.

[0029] A further advantage is that, instead of estimating when a failure will occur, it is also possible to estimate the further operational availability of the compressor, based on this contamination parameter. It is then possible to anticipate, for example, by limiting a range of compressor setting parameters. These setting parameters of the compressor are, for example, a pressure, a flow rate, a power, and / or optionally a humidity level. This limitation can then extend the availability or the time during which the compressor can continue to run. This is possible because it is possible to take into account undesirable but expected contamination of the compressor under normal operating conditions.

[0030] Formulated differently, if it can be deduced that the machine is working subop- timally or that there is a risk that the machine is going to work suboptimally due to contamination, this can already be anticipated by limiting the range of the setting parameters. This avoids the risk of a sudden failure or shutdown, as well as prevents any further damage to the machine if it continues to operate, based on setting parameters that could have a negative influence on its further operation. As a result thereof, the availability of the compressor can be optimized. Although the machine will run suboptimally, it will be possible to ensure that it indeed remains in operation.

[0031] According to an embodiment, the heat transfer characteristic further comprises a heat dissipation component comprising a power efficiency factor of the compressor.

[0032] In addition to modelling the cooling circuit itself, the heat transfer characteristic model can further comprise a heat dissipation component of the compressor, expressed via a power efficiency factor. This means that the model takes into account the expected heat, generated by the compressor in normal operation. Since losses always occur with every machine, expressed in a return or efficiency factor, the model will be more accurate if this is taken into account.

[0033] According to an embodiment, the heat dissipation component may further comprise an instantaneous speed factor of the compressor.

[0034] The heat generated during normal operation also depends on the speed at which the compressor elements rotate and is expressed by the instantaneous speed factor. This factor then ensures further accuracy of the model.

[0035] According to an embodiment, the heat transfer characteristic further comprises a heat elimination component comprising a cooling capacity of the cooling circuit.

[0036] Not only the heat generated by the compressor during operation is taken into account, but also the cooling capacity of the cooling circuit, whereby the cooling capacity model may further comprise a heat transfer coefficient of the cooling circuit.

[0037] According to a second aspect of the invention, there is disclosed a data processing system comprising a processing unit configured to perform the method according to the first aspect of the invention.

[0038] According to a third aspect of the invention, there is disclosed a computer program product containing computer-executable instructions for performing the method of the first aspect when this program is executed on a computer.

[0039] According to a fourth aspect of the invention, there is disclosed a computer- readable storage means containing the computer program product of the third aspect.

[0040] According to a fifth aspect of the invention, there is disclosed a compressor comprising the data processing system according to the second aspect of the invention.

[0041] According to a sixth aspect of the invention, there is disclosed a method for determining an operating margin of a compressor comprising a cooling circuit, the method comprising iteratively performing the steps of:- measuring one or more process variables indicative of instantaneous operation of the compressor;- estimating the one or more process variables based on one or more setting parameters of the compressor using a model comprising a heat transfercharacteristic between the compressor and the cooling circuit, the heat transfer characteristic comprising a contamination parameter;- matching the estimated process variables with the measured process variables by changing the contamination parameter; where the operating margin is determined based on the contamination parameter and the one or more setting parameters of the compressor.

[0042] Furthermore, the estimation may be done based on one or more measured process variables of the one or more measured process variables.

[0043] Furthermore, the heat transfer characteristic may comprise a heat dissipation component comprising a power efficiency factor of the compressor.

[0044] The dissipation component may further comprise an instantaneous speed factor of the compressor.

[0045] The heat transfer characteristic may further comprise a heat elimination component comprising a cooling capacity of the cooling circuit.

[0046] The cooling capacity may further comprise a heat transfer coefficient of the cooling circuit.

[0047] The cooling circuit may further comprise an oil circuit comprising a coolant, and wherein the heat elimination component further comprises a temperature difference between the coolant and inlet air.

[0048] Furthermore, the method may comprise the step of:- normalizing the contamination parameter based on a cooling surface of the cooling circuit.

[0049] Furthermore, the method may comprise the step of:- limiting a range of setting parameters of the compressor based on the contamination parameter.

[0050] The process variables comprise one or more of the group comprising an ambient temperature, cooling temperature, compressor temperature, flow, speed, inlet pressure, outlet pressure, ambient pressure, humidity, and / or flow rate.

[0051] The setting parameters comprise one or more of the group of a pressure, a flow rate, a humidity level, a power.Brief description of the drawings

[0052] The invention will be further illustrated with reference to the figures, wherein

[0053] Fig. 1 schematically illustrates a compressor with a cooling circuit monitored by a controller;

[0054] Fig. 2 schematically illustrates the steps of the method of the invention for determining an operating margin of the compressor and the cooling circuit according to an embodiment in Fig. 1 ;

[0055] Fig. 3 illustrates in more detail the cooling circuit as illustrated in Fig. 1;

[0056] Fig. 4 illustrates a model comprising a set of inputs representative of a compressor and / or cooling circuit; and

[0057] Fig. 5A and 5B illustrate the evolution of oil temperature and operating margins under different conditions.Detailed description of the embodiments

[0058] The present invention will be described with respect to certain embodiments and with reference to certain drawings, but the invention is not limited thereto and is determined only by the claims. The drawings described are only schematic and nonlimiting. In the drawings, the size of certain elements may be exaggerated and notdrawn to scale for illustrative purposes. The dimensions and relative dimensions do not necessarily correspond to actual practical embodiments of the invention.

[0059] Furthermore, the terms first, second, third and the like, are used in the description and in the claims to distinguish between similar elements and not necessarily to describe a sequential or chronological order. The terms are interchangeable under appropriate circumstances and the embodiments of the invention may be practiced in sequences other than those described or illustrated herein.

[0060] In addition, the terms top, bottom, over, under and the like in the description and claims are used for illustrative purposes and not necessarily to describe relative positions. The terms thus used are interchangeable under appropriate circumstances and the embodiments of the invention described herein may be employed in orientations other than those described or illustrated herein.

[0061] Furthermore, the various embodiments, although referred to as "preferred embodiments", are to be construed as exemplary means of carrying out the invention rather than as a limitation on the scope of the invention.

[0062] The term “comprising”, used in the claims, should not be construed as being limited to the means or steps set forth thereafter; the term does not exclude other elements or steps. The term should be interpreted as specifying the presence of the mentioned features, elements, steps or components referred to, but does not exclude the presence or addition of one or more other features, elements, steps or components, or groups thereof. The scope of the expression “a device comprising means A and B” should therefore not be limited to devices consisting only of components A and B. The meaning is that, with respect to the present invention, only components A and B of the device are listed, and the claim is further construed to also include equivalents of these components.

[0063] Fig. 1 schematically illustrates a compressor 102 comprising a compressor element 100. The compressor element 100 is, for example, a screw when the compressor 102 is of the screw compressor type. Furthermore, the compressor can be of theoil-free or oil-lubricated type - also called oil-injected. However, given the steps of the method, it is essential that a cooling circuit 101 is present.

[0064] With reference to Fig. 3, this cooling circuit 101 is schematically illustrated in further detail. The illustrated cooling circuit 101 is a closed cooling circuit, which means that the cooling liquid, in this case oil, circulates in a closed circuit and exchanges heat with various components of the compressor 102. The oil circulates by means of a pump 300 to one or more machine components 301 , such as the compressor element 100, where heat is removed to the oil. The oil is then cooled again in a cooler 302, for example by means of a fan 303, and thus exchanges heat with the ambient air. The oil can then be further used as lubrication 304 of machine components, such as a gearbox, and recirculated through the pump 300 in the cooling circuit 101.

[0065] The fan 303, as schematically illustrated in Fig. 3, should be regarded as a component of an air-oil heat exchanger wherein heat can be removed from the oil to the environment, such as already mentioned above. Dust particles, present in the ambient air, can contaminate the fan 303 and / or air-oil heat exchanger by accumulating these dust particles, causing damage to the fan 303 and / or preventing smooth air passage to the air-oil heat exchanger.

[0066] The compressor element 100, and more generally the compressor 102, will further generate heat during operation, this heat being referred to as Qheatgenerated - The heat is generated by various physical processes. A first process is heat release from the compressor due to the compression process, a function of a power efficiency factor rj, an instantaneous speed factor o)unit, and a compressor power PCOmpr- The compressor power can be determined using a compression model. A second process is the generation of heat by friction and depends on the speed at which the compressor rotates. Thus, the heat output due to friction is a function of a gain factor africrepresentative of a friction factor for the compressor element 100 when the compressor 102 is operational and an instantaneous speed factor o)unit. Therefore, for the heat generated, the general expression is Qheatgenerated■■■ )■

[0067] The cooling circuit 101 , in turn, is characterized by a cooling capacity Pcooierasthe power the circuit 101 can discharge via the oil from the compressor 102. This cooling capacity is also the heat Qheatremoved removed during the operation of the compressor 102 and is proportional to the difference between an oil temperature ToUin the circuit and a cooling air temperature Tair inietsupplied by the fan 303, the proportionality factor being equal to a heat transfer coefficient UA of the cooler. Furthermore, the cooling capacity also depends on whether or not forced ventilation by the fan 303 is active. The cooling air temperature itself can be modelled as a correction on top of the temperature in the compressor casing of the compressor 102. The cooling capacity Pcooier which corresponds to the discharged heat, then becomes

[0068] As long as it can be assumed that the cooling circuit 101 is healthy, in other words not contaminated, the above model can be used to determine the efficiency of the cooling circuit 101 and the compressor 102 in general. Moreover, the operating margin of the compressor 102 can also be determined therefrom. Note that the operating margin is understood as being the amplitude by which a process variable can increase while the compressor 102 can still remain operational in a safe and efficient manner. When the cooling circuit 101 is healthy, measurements and estimates via the calculations will be in accordance with each other. However, when the cooler begins to clog up, the heat transfer coefficient UA of the cooler will decrease. This degradation can be included in the model by introducing an additional factor f>a, further referred to as a contamination parameter, wherein the value ranges between 1 , corresponding to a healthy cooling circuit 101 , and 0, wherein no heat transfer takes place at all. Then, the capacity of the cooler Pcooler(fanstate, UA, Toil, Tair inlet, fu') = Qheatgeneratedis obtained.

[0069] In Fig. 1 , a controller 103 is further illustrated which is configured to carry out the method for determining an operating margin of the compressor 100 comprising the cooling circuit 101 , based on the aforementioned contamination parameter and a set of possible setting parameters fu of the compressor 102. As illustrated in Fig. 1 , the controller 103 is configured to exchange information 104 with the compressor 102, butit should be further understood that the controller 103 may also be an integral part of the compressor 102.

[0070] With reference to Fig. 2, the steps, performed by the controller 103, are further illustrated. In a first step, process variables 200 are measured by the measuring module 202 that are representative and / or indicative for the operation of the compressor 102. In a second step 201 , based on one or more setting parameters of the compressor 102, these measured process variables are estimated, based on a model illustrated by module 203. Furthermore, as illustrated in Fig. 2, the estimation may also be done based on one or more measured process variables. The outcome of module 202, for example, is the measured oil temperature, and the outcome of model 203 is the estimated oil temperature in the same example.

[0071] In measuring module 202, the calculations are then carried out based on the above equations and based on the measured values 200 to further determine the cooling capacity of the cooling circuit 101. In module 203, the expected cooling capacity is also estimated as well as the heat generated based on the setting parameters of the compressor 102. Therefore, this module 203 carries out the necessary calculation steps to predict the temperature. Note further that Fig. 2 serves to illustrate the steps of the disclosed method, and that all calculations can also be performed by module 203.

[0072] In Fig. 4 further illustrates the modules 202 and 203 schematically. Here, a set of inputs 401-405 is shown, for example a speed 401 , a pressure 402, an inlet temperature 403, a ventilation condition 404 of the fan 303, and an oil temperature at a certain time 405, whereby it is possible, with a set of equations 406 such as in the above model, to determine and estimate the cooling capacity as the outcome of the calculations.

[0073] Furthermore, the difference 204 between the measurement and the estimate will then be determined, after which the contamination parametercan be determined via module 205, whether or not normalized, and based on this and a set of setting parameters of the compressor 102, the operating margin 206 may be derived.

[0074] With reference to Fig. 5A and 5B, an illustration is shown for graphs 511-514 and 521-524 in which the oil temperature 500 is expressed in °C on the y-axis 500 as a function of time 501 . The graphs of Fig. 5A, being 511-514, are representative of a compressor 102 with a clean or healthy cooling circuit 101. Furthermore, there is a variation of the temperature of the oil at an ambient temperature of 20°C 511-512 and 40°C 513-514, respectively, and the compressor 102 running at a minimum 511 , 513 and a maximum 512, 514, respectively. Furthermore, there is a limit 502 that can be selected as being the limit value within which the compressor 102 can remain operational in a safe manner. In this example, this limit value is set at 70°C, and the corresponding zone above the limit value 502 is the Shutdown Limit, i.e. the zone within which the compressor 102 must be switched off because the oil temperature 500 has increased too much. In the example of graphs 511-514, there are different operating modes in which the threshold value or limit value is not reached.

[0075] With further reference to graphs 521-524 in Figs. 5B, an example of a compressor 102 with a contaminated cooling circuit 101 , in this example a contamination of 85%, which corresponds to a normalized contamination parameterof 0.85 is shown.

[0076] Once again, there are four operating modes, namely the compressor 102 running at a minimum power at an ambient temperature of 20°C 521 , the compressor 102 running at a maximum power at an ambient temperature of 20°C 522, the compressor 102 running at a minimum power at an ambient temperature of 40°C 523, and the compressor 102 running at maximum power at an ambient temperature of 40°C 524. It can then be noted that a compressor 102 with a dirty cooling circuit 101 corresponding to a contamination parameterof 0.85 and an ambient temperature of 40°C will have to be switched off over time because the operating point will then be in the range of the Shutdown Limit.

[0077] Furthermore, note that for other values of the contamination parameter Pu similar graphs can be drawn up.

[0078] When then the contamination parameter is determined, based on the method described above, the operating margin 206 can then be determined based on these different models for different values of the contamination parameterand a set of setting parameters of the compressor 102. Not only it can be estimated what the remaining operating margin will be over time at a certain ambient temperature, but also what the influence may be when the ambient temperature rises or when there is an increase in the exhaust pressure or the consumption of compressed air.

[0079] At an ambient temperature of 20°C and a contamination parameterof 0.85, the compressor 102 will remain operational because it will not end up in the zone in which a breakdown is expected - i.e. above the limit of 70°C 502. If the ambient temperature is expected to rise to 40°C, for example during the summer months, it is then possible to estimate what the operating margin is, and therefore to estimate the time remaining until the operating point exceeds the limit value of 70°C at a certain con- tamination parameterand a set of setting parameters of the compressor 102. It will therefore be possible to take timely action, for example by carrying out maintenance of the cooling circuit 101 and / or of the compressor 102 as a whole.

Claims

CLAIMS1.- A computer-implemented method for determining an operating margin (206) of a compressor (102) comprising a cooling circuit (101), the method comprising iteratively performing the steps of:- measuring (200) one or more process variables indicative of an instantaneous operation of the compressor (102);- estimating (201) the one or more process variables based on one or more setting parameters of the compressor (102) using a model (203) comprising a heat transfer characteristic between the compressor (102) and the cooling circuit (101), the heat transfer characteristic comprising a contamination parameter;- matching (204) the estimated process variables (201) with the measured process variables (200) by changing the contamination parameter; wherein the operating margin (206) is determined (205) based on the contamination parameter and the one or more setting parameters of the compressor (102).2.- The computer-implemented method according to claim 1 , wherein the estimation (201) is further done based on one or more measured process variables (200) of the one or more measured process variables.3.- The computer-implemented method according to any one of the preceding claims, the heat transfer characteristic further comprising a heat dissipation component comprising a power efficiency factor of the compressor (102).4.- The computer-implemented method according to claim 3, the dissipation component further comprising an instantaneous speed factor of the compressor (102).5.- The computer-implemented method according to any one of the preceding claims, the heat transfer characteristic further comprising a heat elimination component comprising a cooling capacity of the cooling circuit (101).6.- The computer-implemented method according to claim 5, the cooling capacity comprising a heat transfer coefficient of the cooling circuit (101).7.- The computer-implemented method according to claim 6, the cooling circuit (101) comprising an oil circuit comprising a coolant, and wherein the heat elimination component further comprises a temperature difference between the coolant and inlet air.8.- The computer-implemented method according to any one of the preceding claims, further comprising the step of:- normalizing (205, 206) the contamination parameter based on a cooling surface of the cooling circuit (101).9.- The computer-implemented method according to any one of the preceding claims, further comprising the step of:- limiting a range of setting parameters of the compressor (102) based on the contamination parameter.10.- The computer-implemented method according to any one of the preceding claims, the process variables comprising one or more of the group of an ambient temperature, cooling temperature, compressor temperature, flow, speed, inlet pressure, outlet pressure, ambient pressure, humidity, and / or flow rate.11.- The computer-implemented method according to any one of the preceding claims, the setting parameters comprising one or more of the group of a pressure, a flow rate, a humidity level, a power. 12.- A data processing system (103) comprising a processing unit configured to perform the method according to any one of the preceding claims.13.- A computer program product containing computer-executable instructions for performing the method according to any one of claims 1 to 11 when this program is exe- cuted on a computer.14.- A computer-readable storage means containing the computer program product according to claim 13.

15. - A compressor (102) comprising the data processing system according to claim14.

Images