METHOD AND SYSTEM FOR DOSING A DILUTE PRODUCT

Technical field

This invention relates to a method and a system for dosing release agents and in particular a system and a method for dosing release agents used in die casting installations and processes for moulding light alloys.

Background art

Die casting processes comprise a step of cooling and lubricating the mould by spraying, on the mould itself, a dilute product comprising, in brief, suitable lubricants and/or release agents, commonly referred to as “mould lubricants”, diluted with dilution or cooling water.

Most mould lubricants used in high pressure die casting processes are formulated as aqueous emulsions of active principles (oils, polymers, siloxanes, etc.) which are stably dispersed in water (continuous phase) as micro-droplets thanks to specific surfactants and additives, which also perform many other known functions in such processes.

The function of the dilute product is to form, by means of the mould lubricant, a film capable of lubricating and releasing the metal alloy injected into the mould cavity and of removing heat from the mould, with each cycle, by evaporation of the dilution water.

In general, in prior art solutions, once the composition of the dilute product has been established for a predetermined moulding installation or process, the quantity of mould lubricant in the dilution water remains fixed and, similarly, once the installation is running regularly, the quantity of the dilute product sprayed on the mould remains constant.

The chemical composition of the concentrate, together with other variables such as the level of dilution and the spraying parameters, mainly contribute, as already indicated, by means of evaporation of the dilution water, to the removal of heat from the mould so as to restore the“thermal equilibrium" and to the formation of a lubricating film on the hot surface of the mould.

The characteristics of this film, which is subject to rapid chemical and physical changes from the moment of spraying to actual adherence on the mould, are difficult to study and define, although they may to a great extent influence both the die casting process steps and the quality of the cast.

In other words, in high pressure die casting processes, the steps of cooling and lubricating the mould, by means of spraying dilute aqueous emulsions, are critical since they are poorly controlled.

Even by setting the application parameters, for example such as the type and number of nozzles, pressures, distances and spraying time, as well as those relating to chemical aspects, for example the formulation of the dilute product, the composition of the dilution water and the dilution ratio, the chemical and physical mechanisms for wetting the surface, heat exchange and depositing of the film are turbulent and locally depend on the temperature and the shape and may even modify some characteristics of the surface, in such a way that they do not guarantee correct “repeatability". Moreover, if the system is stopped and cooled, putting it back into service is extremely onerous in terms of energy and dilution water consumption, since the set-up of the lubricating system is designed for running regularly and not for transients.

In this context, the main purpose of this solution is to overcome the above- mentioned disadvantages.

Disclosure of the invention

The aim of this invention is to propose a method and a system for dosing the dilute product which allow effective lubricating of the mould and suitable cooling of it in any operating condition, whether during regular running or during any transients, thereby reducing both energy and water consumption. This invention relates to a system and a method for dosing the dilute product which allow improved control of the steps of cooling and lubricating the moulds in the die casting installations and processes for moulding light alloys.

According to one aspect of the invention, the invention relates to a method for dosing a dilute product comprising at least one active principle, such as, for example an oil, a polymer, or a siloxane, preferably in a mould lubricant concentrate, and dilution water to be sprayed on the mould in a die casting installation to facilitate detaching a cast from the mould and lowering at least one surface temperature of the mould.

According to one aspect of the invention, the invention relates to a dosing method which comprises a step of injecting in the dilute product, upstream of a spraying head, in a duct, or“piping”, for supplying dilute product to the spraying head, an anhydrous mould lubricant dissolvable in wafer, hereinafter also referred to simply as“anhydrous”, which dissolves in the dilute product before the dilute product is sprayed on the mould.

According to one aspect of the invention, the invention relates to a dosing method which comprises a step of injecting in the dilute product, upstream of a spraying head, in a duct, or“piping”, for supplying dilute product to the spraying head, at least one active principle, such as, for example, an oil, a polymer, or a siloxane which dissolves in the dilute product before the dilute product is sprayed on the mould.

According to one aspect of the invention, the invention relates to a dosing method which comprises a step of injecting in the dilute product, upstream of a spraying head, in a duct, or“piping”, for supplying dilute product to the spraying head, at least one lubricant and/or release agent, commonly referred to as“mould lubricants” in the form of an aqueous emulsion of active principles (oils, polymers, siloxanes, etc.) which are stably dispersed in water (continuous phase) as micro-droplets, for example thanks to specific surfactants and additives.

According to one aspect of the invention, the method preferably comprises a step of measuring the surface temperature of the mould to obtain a measured surface temperature;

a step of calculating a temperature error between at least one predetermined temperature and the measured surface temperature by a step of comparing the measured surface temperature with the predetermined temperature;

a step of generating at least one control signal as a function of the error by means of at least one proportional integral derivative RID regulator;

a step of regulating the quantity of dilute product to spray at the mould as a function of the control signal.

According to one aspect of the invention, the method comprises a step of regulating the quantity of anhydrous as a function of a respective control signal generated by a corresponding RID regulator as a function of the temperature error.

According to one aspect of the invention, the method comprises a step of regulating the quantity of dilute product as a function of a respective control signal generated by a corresponding RID regulator as a function of the temperature error.

According to one aspect of the invention, the method comprises a step of regulating the quantity of dilution water in the dilute product as a function of a respective control signal generated by a corresponding RID regulator as a function of the temperature error.

According to one aspect of the invention, the method comprises a step of regulating the quantity of the active principle in the dilute product as a function of the control signal generated by a corresponding RID regulator as a function of the temperature error.

According to one aspect of the invention, the active principle is preferably dispersed in an aqueous continuous phase and the regulation of the quantity of active principle occurs by means of a regulation of the quantity of the aqueous continuous phase, otherwise known as mould lubricant concentrate, in which it is dispersed.

According to one aspect of the invention, the regulation of the quantity of mould lubricant concentrate occurs by means of a corresponding RID regulator as a function of the temperature error.

According to one aspect of the invention, the dosing system may comprise a RID regulator operating on the basis of the temperature error to regulate the quantity of dilute product to be sprayed on the mould.

According to one aspect of the invention, the dosing system may comprise a RID regulator operating on the basis of the temperature error to regulate the quantity of anhydrous injected in the dilute product.

According to one aspect of the invention, a second duct is connected to the dilute product duct, the second duct being dedicated to a concentrated or anhydrous or anhydrous lubricant fluid which is dosed by means of a proportional valve.

During a system restart, a RID logic defines the quantities of dilute product and anhydrous as a function of the temperature error between a detected temperature and a target temperature.

According to one aspect of the invention, the mould will be sprayed with: a“large quantity” of anhydrous when the surface of the mould is cold;

a“large quantity” of dilute product when the surface of the mould heats up.

The anhydrous fluid, as soon as it comes into contact with the dilute product, dissolves, for example emulsifies in it; the anhydrous may also, for example, be soluble in water.

In that way the following is obtained:

use of a single lubricating head, with a single set of delivery nozzles and a single distribution duct;

a modulatable capacity for cooling and detaching of the lubricants used; doses managed by the system with RID logic (rapid reaching and maintaining of the target temperature).

According to one aspect of the invention, the dosing system may comprise a P!D regulator operating on the basis of the temperature error to regulate the quantity of dilution water in the dilute product.

According to one aspect of the invention, the dosing system may comprise a RID regulator operating on the basis of the temperature error to regulate the quantity of mould lubricant concentrate in the dilute product.

According to one aspect of the invention, the quantities of dilute product, dilution water and mould lubricant concentrate may be regulated by acting on the length of time the dilute product, dilution water and mould lubricant concentrate are supplied.

According to one aspect of the invention, in a step of heating the mould, the quantity of dilution wafer may be reduced to 0, in such a way that a mould lubricating head actually sprays mould lubricant concentrate.

According to one aspect of the invention, the invention relates to a system for dosing the dilute product sprayed on the mould.

According to one aspect of the invention, the system comprises one or more dosers for dosing the anhydrous, the dilute product or the dilution water or mould lubricant concentrate which may each be driven by a respective RID regulator as a function of the error between the surface temperature of the mould and a reference temperature which is preferably the optimum temperature of the mould when running regularly.

According to one aspect of the invention, each doser may be mounted along a respective duct for supplying the dilute product or the concentrate or the dilution water.

Further characteristics and advantages of this invention will be more apparent from the indicative, non-limiting description, of a preferred, non- limiting embodiment of a system and a method for dosing dilute products which comprise mould lubricants and dilution water as illustrated with reference to the accompanying drawings in which:

Figure 1 is a schematic block diagram of a dosing system according to this invention;

- Figure 2 is a schematic block diagram of a dosing system according to this invention;

Figure 3 is a schematic block diagram of a dosing system according to this invention;

Figure 4 is a schematic block diagram detail of a dosing system according to this invention;

Figure 5 is a schematic block diagram of a dosing system according to this invention.

With reference to the figures, the numeral 1 denotes a dosing system for dosing a dilute product comprising at least one mould lubricant and dilution water in a die casting installation 1 00 for moulding light alloys, for example aluminium, iron or magnesium alloys.

The installation 100 is of the substantially known type and, schematically, comprises a mould 101 , of which for simplicity only one half mould is illustrated, having a cavity 102 for receiving the molten alloy. Hereinafter use will be made of the following terms which are well known in the reference technical sector:

mould lubricant or mould lubricant concentrate or concentrate: an aqueous emulsion of active principles (oils, polymers, siloxanes, etc.) which are stably dispersed in water (continuous phase) as micro-droplets thanks to specific surfactants and additives which are also present; the mould lubricant is concentrated and guarantees detaching of the parts from the mould;

dilution water, diluent: is the diluent used to dilute the concentrate and to obtain the dilute product; the dilution water serves, not just to dilute, but also to remove heat from the mould by evaporation; dilute product or mould lubricant dilute product: is what is sprayed on the mould and is obtained, at least, from dilution of the mould lubricant with the dilution water.

Hereinafter use will also be made of the following terms in accordance with this solution:

anhydrous mould lubricant dissolvable in water or anhydrous or anhydrous lubricant or anhydrous fluid: what is injected, as explained in more detail below, in the dilute product before if is sprayed on the mould.

In use, the anhydrous mould lubricant, by not contributing water to the dilute product, does not contribute to cooling of the mould, instead only lubricating it.

In fact, in general it is the water, present in the dilute product as dilution water or in the concentrate as continuous phase, which cools the mould by evaporating.

The dosing system 1 serves, for example, to determine the doses of concentrate and diluent in the dilute product which is usually sprayed on the mould, and their appropriate ratio for facilitating detaching of a cast, not illustrated, from the mould and lowering of the surface temperature of the mould.

In general, the dosing system 1 serves to define a formulation of the dilute product which is usually sprayed on the mould and which, as explained in more detail below, also comprises, at least under predetermined circumstances, for example during system restarting, a fluid, preferably anhydrous, which may also be indicated as anhydrous lubricant, injected in the dilute product immediately upstream of the spraying.

As is clarified below, this invention also relates to a configuration in which the mould lubricant concentrate is sprayed on the mould.

The system 1 is described below with reference to the parts essential for an understanding of this invention.

With reference to Figures 1 , 2, 3 and 5, it should be noticed that the system 1 comprises a lubricating or spraying head, schematically illustrated with a block 103, for spraying the suitably formulated dilute product, in the cavity 102, against the surface of the mould 101 , and a duct 2 for supplying dilute product to the head 103

In the example illustrated, the system 1 comprises a system or sub-system for preparing the dilute product which is schematically illustrated, using a dashed line, by a block 1 10.

The duct 2 for supplying the dilute product to the head 103 comes directly out of the system 1 10 and communicates with the head 103.

The system 1 10 schematically indicates the portion of the system 1 in which the dilute product is prepared or even the dilute product is only stored and from which it is supplied and which must be used by the head 103.

In the examples illustrated, a doser of the dilute product, which may be absent in embodiments of the type illustrated in Figures 2 and 3 (therefore illustrated with a dashed line in those figures), schematically illustrated with a block 3, doses the mould lubricant dilute product in the duct 2 and therefore to the head 103.

Preferably, the system 1 comprises a non-return valve for the dilute product, schematically illustrated with a block 3b in Figure 5, located along the duct 2 immediately upstream of the head 103. Advantageously, even the other embodiments illustrated preferably comprise the valve 3b which is not illustrated for the sake of simplicity.

The doser 3 may be, for example, a solenoid valve, in the case of a pressurised system 1 , or even a pump, and determines the quantity of dilute product which reaches the head 103 and therefore the mould 101. The doser 3, or if necessary directly the duct 2 for supplying the dilute product, are in fluid communication with a diluting system 4 in which the mould lubricant concentrate is diluted with the dilution water, in particular if the installation 101 comprises a dilution water supply line and a mould lubricant concentrate supply line, as shown for example in Figures 1 to 3. The diluting system 4 is schematically illustrated with a diluting duct. J. U

A duct 5 for supplying dilution water joins the diluting system 4 to supply it with the dilution water.

A dilution water doser, for example a solenoid valve or a pump, schematically illustrated with a block 6, doses the diluent to the duct 5 and therefore to the system 4.

The system 1 comprises a system, schematically illustrated with a block 7, for supplying the dilution water to the doser 8, for example a pumping system.

Downstream of the system 1 10, irrespective of how the dilute product is obtained, the system 1 comprises a system 200 for injecting a mould lubricant which is dissolvable in water in communication with the duct 2 for supplying dilute product to the head 103.

In one embodiment, the mould lubricant which is injected in the dilute product is a mould lubricant concentrate, that is to say, an aqueous emulsion of active principles (oils, polymers, siloxanes, etc.) which are stably dispersed in water (continuous phase) as micro-droplets thanks to specific surfactants and additives which are also present.

II mould lubricant concentrate which is injected in the dilute product immediately upstream of the spraying is, for example, the same mould lubricant concentrate diluted with the dilution water to form the dilute product.

In one embodiment, the mould lubricant which is injected in the dilute product is an anhydrous mould lubricant, that is to say, without water, in such a way as to contribute to detaching parts from the mould but not to cooling of the mould, since, as indicated, it contains no water.

Use of an anhydrous mould lubricant, for example of the type which can be emulsified in water or which is soluble in water, is particularly advantageous, for example, during system 1 restarts, when it is necessary to guarantee detaching of parts from the mould but also to allow the mould to reach the operating temperature. The system 200 is configured to inject in the duct 2, upstream of the spraying head 103, the mould lubricant, concentrate or anhydrous, by means of a corresponding duct 204. For simplicity, hereinafter, that mould lubricant will be referred to as mould lubricant injected.

Preferably, the system 200 comprises a non-return valve, schematically illustrated with a block 201 , substantially at the entry of the system 200 in the duct 2 along the duct 204.

Preferably, the system 200 is in fluid communication with the duct 2 downstream of the non-return valve 3b, as illustrated in Figure 5.

In accordance with what is illustrated, the system 200 comprises a doser

202, provided for example with a proportional solenoid valve 202a, for the lubricant injected.

In alternative embodiments, the doser 202 comprises an on/off valve combined with a related flowmeter.

The system 200 comprises a supply, schematically illustrated with a block

203, of the mould lubricant to be injected to the doser 202.

As illustrated, the system 1 comprises a temperature measuring device, schematically illustrated with a block 1 1 , for measuring the surface temperature of the mould and obtaining a measured surface temperature tmis.

The measuring device 1 1 may be, for example, a pyrometer which is facing the mould 101 , an infra-red thermometer, one of the thermocouples usually embedded in the moulds 101 of die casting installations 100.

The system 1 comprises a control system 12, schematically illustrated in more detail in Figure 4, in communication with the measuring device 1 1 to receive as input the measured surface temperature tmis.

The control system 12 also receives as input a predetermined temperature or reference temperature and is configured to generate a control signal as a function of the measured surface temperature tmis and the reference temperature tret. The predetermined temperature or reference temperature is preferably the optimum temperature of the mould 101 when it is running regularly.

The control system 12 comprises an adder 13 configured to calculate a temperature error e(t) between the predetermined temperature and the measured surface temperature tmi _S ; the error e(t) is in particular calculated as the difference between and tmis.

According to this invention, the control system 12 comprises one or more proportional integral derivative or RID regulators in communication with the adder, or with a respective adder, and which are configured to generate a control signal as a function of the error e(t) to drive the dosing system 1 With reference to Figures 1 , 2, 3 and 5, the control system 12 is in communication with the doser 202 to which it sends a control signal SO. The signal SO is generated by a respective, suitably programmed proportional integral derivative regulator 12d.

The doser 202 comprises, for example, the proportional solenoid valve 202a which is driven by the signal SO as a function of the temperature error e(t), to regulate the quantity of mould lubricant injected in the duct 2, that is to say, in the dilute product, and therefore supplied to the head 103. In use, connected in the duct for supplying the dilute product, which is usually composed of mould lubricant concentrate diluted in water, there is the duct 204 dedicated to injecting further mould lubricant, concentrate or anhydrous, which is dissolvable in water, which is dosed by means of the doser 202 and, for example, the proportional valve 202a.

The RID logic defines at least the quantity of mould lubricant injected as a function of the temperature error e(t).

Preferably, the system 200 injects a relatively“large quantity” of mould lubricant when the surface of the mould 101 is cold, in such a way as to guarantee detaching of the parts being worked.

To facilitate heating of the mould, the anhydrous mould lubricant is preferably injected, which does not contribute water to the dilute product and therefore does not contribute to mould cooling. In particular with reference to Figures 1 to 3, a duct 8 for supplying mould lubricant concentrate for defining the dilute product joins the diluting system 4 in order to supply the concentrate to it.

A concentrate doser, for example a solenoid valve or a pump, schematically illustrated with a block 9, doses the diluent to the duct 8 and therefore to the system 4.

The system 1 comprises a system, schematically illustrated with a block 10, for supplying the mould lubricant to the doser 9, for example a concentrate storage device or pumping system.

With reference to Figure 1 , in the embodiment illustrated, the control system 12 is in communication with the doser 3 to which it sends a control signal S1.

The signal SI is generated by a respective, suitably programmed proportional integral derivative regulator 12a.

The doser 3 comprises, for example, a proportional solenoid valve 3a, driven by the signal S1 as a function of the temperature error e(t), to regulate the quantity of dilute product supplied to the head 103.

In alternative embodiments, the doser 3 comprises an on/off valve combined with a related flowmeter.

In this case, a proportional integral derivative type logic defines the quantities of both of the fluids (dilute product and mould lubricant to be injected) as a function of the temperature error.

Preferably, when the surface of the mould is cold a“large quantity” of mould lubricant will be injected for spraying on the mould 101.

Once the surface of the mould 101 heats up, a“large quantity” of dilute product will be sprayed on it.

In particular, the anhydrous fluid, as soon as it comes into contact with the dilute product, dissolves, for example emulsifies in it and is sprayed on the mould 101.

Advantageously, therefore only one lubricating head is used, with a single set of delivery nozzles and a single distribution. Moreover, the capacities for cooling and detaching of the lubricants used are modulatab!e.

The doses managed by a system with RID logic allow rapid reaching and maintaining of the target temperature.

With reference to Figure 2, in the embodiment illustrated, the control system 12 is in communication with the doser 6 to which it sends a control signal S2

The signal S2 is generated by a respective, suitably programmed proportional integral derivative regulator 12b.

The doser 6 comprises, for example, a proportional solenoid valve 6a, driven by the signal S2 as a function of the temperature error e(t), to regulate the quantity of dilution water supplied to the diluting system 4.

In alternative embodiments, the doser 6 comprises an on/off valve combined with a related flowmeter.

With reference to Figure 3, in the embodiment illustrated, the control system 12 is in communication with the doser 9 to which it sends a control signal S3.

The signal S3 is generated by a respective, suitably programmed proportional integral derivative regulator 12c.

The doser 9 comprises, for example, a solenoid valve 9a, driven by the signal S3 as a function of the temperature error e(t), to regulate the quantity of mould lubricant concentrate supplied to the diluting system 4.

In alternative embodiments, the doser 9 comprises an on/off valve combined with a related flowmeter.

In use, the method for dosing the dilute product comprises

a step of injecting in the dilute product, upstream of the spraying head, in the duct 2 for supplying dilute product to the spraying head, the mould lubricant dissolvable in water which dissolves in the dilute product, for example emulsifies in it, before the dilute product is sprayed on the mould. In one embodiment, the mould lubricant injected in the dilute product upstream of the spraying head in the duct 2 for supplying dilute product to the head 103 is an anhydrous mould lubricant.

In one embodiment, the mould lubricant injected in the dilute product upstream of the spraying head in the duct 2 is an aqueous emulsion of at least one active principle, such as, for example, an oil, a polymer, or a siloxane, stably dispersed in water or as micro-droplets or a mould lubricant concentrate, for example of the type diluted in the dilute product. Preferably, the method comprises

a step of measuring the surface temperature to obtain the measured surface temperature tmi _S ;

a step of calculating the temperature error e(t) between the predetermined reference temperature and the measured surface temperature by a step of comparing the measured surface temperature tmis with the predetermined temperature tret;

a step of generating at least one first control signal SO as a function of the temperature error eft) by means of at least a first proportional integral derivative regulator 12d;

a step of regulating the quantity of the lubricant to be injected in the dilute product in the injecting step as a function of the control signal SO. The quantity of the lubricant injected in the dilute product is preferably regulated by increasing or decreasing or keeping constant the length of time the anhydrous lubricant is supplied to the duct 2.

In alternative embodiments, the step of injecting the mould lubricant is regulated by acting directly, for example, on the length of injecting time, without control by feedback as a function of the temperature.

The dosing method preferably comprises

a step of generating at least one control signal SI , S2, S3 as a function of the error eft) by means of a respective proportional integral derivative RID regulator 12a, 12b, 12c; a step of regulating the quantity of dilute product supplied to the head 103 and/or the quantity of dilution water in the dilute product and/or the quantity of mould lubricant concentrate in the dilute product, as a function of the respective control signal S1 , S2, S3, to be sent to the lubricating head 103.

Without prejudice to the regulations of the mould lubricant injected in the dilute product, in general, given that it is substantially the active principle which guarantees detaching of the cast from the mould, the system 10 may, in one embodiment, deliver the active principle and the regulation affects the active principle.

Preferably, the quantity of mould lubricant concentrate in the dilute product is regulated in order to regulate the quantity of active principle in the dilute product; for simplicity, hereinafter reference is made to that situation, without thereby limiting the scope of the invention.

With reference to Figure 1 , the quantity of dilute product in the duct 2 for supplying the spraying head 103 is regulated by the doser 3.

The regulation of the quantity of dilute product occurs by increasing or decreasing or keeping constant the length of time the dilute product is supplied to the spraying system or the length of time for which the doser 3 operates.

In that way, the quantities of both the mould lubricant injected in the dilute product and the dilute product supplied to the spraying head are regulated. With reference to Figure 2, the quantity of dilution water in the supply duct 5, upstream of the diluting duct 4, is also regulated by the doser 6.

The regulation of the quantity of dilution water occurs by increasing or decreasing or keeping constant the length of time the dilution water is supplied to the diluting duct or the length of time for which the doser 6 operates.

For example, during a mould heating transient the quantity of dilution water supplied to the head 103 may be decreased in order to remove less heat from it. In particular, the quantity of dilution water in the dilute product may be zeroed, during heating of the mould, in such a way that, in use, the mould lubricant is sprayed on the mould 101 in concentrated form, if necessary together with the further mould lubricant injected in the duct 2

The quantity of the dilution water may be controlled, again by a RID regulator, by acting in any section of the line for supplying water to the head 103, for example by modifying the operating or opening times of the pumps or of the solenoid valves present along the line.

In any case it is possible to reduce the quantity of dilution water in the dilute product, in particular during mould heating steps, therefore reducing both energy and diluent consumption.

Reducing the quantity of water sprayed on the mould results in acceleration of the times for bringing the mould to the regular running temperature.

With reference to Figure 3, there is also regulation of the quantity of mould lubricant concentrate supplied to the supply duct 8, upstream of the diluting duct 4, by the doser 9.

The regulation of the quantity of concentrate may occur by increasing or decreasing or keeping constant the length of time the concentrate is supplied to the diluting duct or the length of time for which the doser 9 operates.

In alternative embodiments not illustrated, the system 1 may comprise none, one, two or three RID regulators 12a, 12b, 12c based on the management requirements of the installation 100.

Each RID regulator 12a, 12b, 12c, 12d is programmed, with its own algorithm, for a predetermined follower function so as to generate the respective control signal SO, S1 , S2, S3.

The surface temperature of the mould is an input parameter for the control system which therefore allows the dosing system to effectively act in reaching and maintaining the optimum temperature of the mould, in particular by regulating the quantity of mould lubricant injected in the dilute product.

Moreover, in particular embodiments, the control system allows effective action in reaching and maintaining the optimum temperature of the mould, by also regulating the quantity of concentrate and/or the quantity of diluent and/or the quantity of dilute product sprayed on the mould by the lubricating head.

The surface temperature of the mould may be measured in one or more regions of interest and the separate values used on their own or in combination to control corresponding RID controllers.

The system 1 may comprise, not illustrated, flowmeters for measuring the flow rates of the diluent, the concentrate and the dilute product which may be controlled by corresponding on/off valves preferably driven by the corresponding control logics.