EP0827935B1 - Method for controlling the functioning of a load compensation device, and load compensation for carrying out the method - Google Patents

Description

The invention relates generally to hoists and more particularly to the use of such lifting devices in sensitive environments, such as nuclear power plant reactors. More specifically, the invention relates to a method of regulating the operation of a load compensating device of such a handling, as well as the load compensator implementing this process.

If the invention will more particularly be described in conjunction with its application to the nuclear field, it is understood that its scope cannot be limited to it.

The reactor core of a nuclear power plant is made up, so known, from a number of nuclear fuel assemblies put in place at the level of a box spring or heart plate at the bottom of the tank of the reactor.

These assemblies can be handled independently each other, after a certain period of irradiation, either replace irradiated assemblies or modify their positioning within said core, in order to homogenize the radiation of energy in the bottom of the heart.

The handling of these assemblies is carried out by means of a machine handling, also called loading machine, capable of to move in a horizontal plane above the pool covering the reactor core, said machine being provided with a control carriage, also likely to move in another horizontal direction at within the machine.

The trolley actually includes a lifting device, most often made up a vertical telescopic mast, capable of unfolding, at the end of which is located a grapple capable of engaging with the upper end nuclear fuel assemblies. The telescopic mast is capable of being moved in a vertical direction by a lifting means most often constituted by a motorized winch, on whose drum comes wind a cable or chain or any equivalent member, and comprising of one or more idler pulleys.

In general, nuclear fuel assemblies are made of pencils with fried fuel pellets proper, assembled together by means of spreader grids depending on the height of the assembly.

Whereas the different nuclear fuel assemblies are positioned juxtaposed within the heart plate, and come in contact with each other, in particular at the level of the spacer grids, we were able to observe collisions of the assemblies on the level of said grids, in particular during lifting or positioning operations of assemblies compared to neighboring assemblies.

As part of a lifting operation, i.e. removal or repositioning of an assembly, this attachment results in a overload on the hoist, and in particular on the cable, which must be detected immediately to ensure that the winch engine stops loading machine.

Indeed, in the event that such an overload is not detected, or, in one where the winch motor stops taking too long to intervene, the grids hanging assemblies are liable to deteriorate and the cohesion of the assembly itself may suffer.

The same phenomenon occurs when a assembly within the heart, with the proviso that the overload is transformed under load, so that the tension of the cable or chain decreases, no longer ensuring the positioning of the assembly according to a position vertical.

In order to overcome this serious drawback, it has been proposed, for example, in Document EP-B-0 292 413 from the Applicant, a load compensator intended to be positioned at the level of the carriage of the loading.

• une armature fixe, solidaire du chariot, et comportant deux butées extrêmes ;
• un coulisseau destiné à coulisser au sein de l'armature entre ces butées extrêmes ;
• une cloche extérieure, pourvue de moyens propres à coopérer avec le coulisseau ;
• un vérin de surcharge, disposé entre le coulisseau et l'armature, notamment l'une des butées extrêmes ;
• un vérin de souscharge disposé entre le coulisseau et la cloche extérieure.

Such a device basically comprises:

• a fixed frame, integral with the carriage, and comprising two extreme stops;
• a slide intended to slide within the frame between these extreme stops;
• an outer bell, provided with means suitable for cooperating with the slide;
• an overload cylinder, disposed between the slide and the frame, in particular one of the extreme stops;
• an underload cylinder arranged between the slide and the outer bell.

The end of the cable or chain of the hoist is fixed directly or indirectly to the outer bell.

In addition, an electro-pneumatic modulated supply circuit for cylinders are provided and act according to variations in the load.

These load variations are detected by means of a load cell which, in function of thresholds previously determined and set, induces the setting pressure of said cylinders, respectively underload and / or overload, according to discrete values.

These pre-established and therefore fixed pressures certainly make it possible to compensate positive or negative charge variations, but we also realized that, given the lack of effective movement control of the cable, the sum of the actions to which the fuel assembly is subjected handled, namely the movement which generated the grip and the reverse movement caused by the compensator, results in a absolute displacement of the fuel assembly in the opposite direction to the initial movement.

However, it is now established that fuel assemblies coexisting within the same heart, can be of type and brand that, in particular, the level of positioning of the spacer grids at the level of each of the assemblies is different and therefore, can induce reverse and uncontrolled snaps, taking into account the absolute movement of the fuel assembly handled in the direction reverse of the initial movement.

Furthermore, it appeared that, given the speed of the movement of the compensator, a relative movement between assemblies is generated fuels, whose instantaneous speed is higher than the allowed speed in handling these assemblies.

It followed that the implementation of a control appeared essential precise operation of the compensator, and in particular the removal of any reverse movement of the fuel assembly handled.

The object of the invention is therefore to propose a method for regulating the operation of such a load compensating device, susceptible avoid this absolute reverse movement of the load after being put in artwork.

• une cloche interne fixe, solidaire du bâti sur lequel repose l'engin de manutention, et au sein de laquelle est susceptible de se translater un piston supérieur et un piston inférieur, respectivement entre des butées ménagées au sein de ladite cloche, et entre le piston supérieur et le fond de ladite cloche;
• une cloche externe mobile, susceptible de coopérer avec le piston inférieur, et à laquelle est solidarisée l'une des extrémités de l'organe de manutention, notamment câble ou chaíne, à l'autre extrémité duquel est suspendue la charge ;
• un vérin pneumatique de surcharge, s'étendant entre le piston supérieur et la cloche interne fixe et un vérin pneumatique de souscharge, s'étendant entre le piston supérieur et le piston inférieur, lesdits vérins étant reliés à une source de pression ou mis à l'échappement par un ensemble d'électro-distributeurs.

This method, for regulating the operation of a load compensating device of a handling machine, comprises:

• a fixed internal bell, integral with the frame on which the handling machine rests, and within which is likely to translate an upper piston and a lower piston, respectively between stops formed within said bell, and between the piston upper and the bottom of said bell;
• a movable external bell, capable of cooperating with the lower piston, and to which is secured one of the ends of the handling member, in particular cable or chain, at the other end from which the load is suspended;
• a pneumatic overload cylinder, extending between the upper piston and the fixed internal bell and a pneumatic overload cylinder, extending between the upper piston and the lower piston, said cylinders being connected to a pressure source or set to exhaust by a set of solenoid valves.

It consists in controlling the pressure within said cylinders so continuous, so as to modify the position setpoint of the external bell corresponding to the state of equilibrium as a function of the measured pressure variations on the cylinders to eliminate any overload or underload effect on the load, and to bring the compensator back to its equilibrium state corresponding to normal operation of the lifting device, i.e. in the absence of any overload or underload, after elimination of the cause having caused such a state of overload or underload.

In other words, the invention consists in piloting so pressure inside the cylinder chambers pneumatic, to result in very small variations in pressure within said chambers in order to tend towards a constant pressure, in order to maintain the initial position of the compensating device, and therefore limit efforts in the event of overload or underload, and in particular in the event of of fuel assemblies, but also to avoid any phenomenon of "backtracking" of the load, after operation of the compensating device.

According to the invention, the control being carried out so permanent, the lifting function stops on incident (grid hooking) is triggered by the detection of the change of position of the compensator, and more precisely of the external bell. It is also possible to deduct from this change of position, the speed of movement of the external bell, by simple derivation from time of this change of position, said speed being compared to a determined threshold representative of a characteristic of an overload, underload, and more specific of a hanging. In fact, through this it becomes possible to detect such a situation before the detection of the threshold admitted for the charge, by traditional dynamometric means.

In this way, such detection makes it possible to trigger very quickly stopping the movement that led to this situation, effectively avoiding inconvenience and disorder inherent in a late stop.

Advantageously, an overload, underload, and detection signal more particularly of attachment by detection of the value of the threshold of overload or underload delivered by a traditional weighing system, and notably dynamometric, also comes to close on the stop of the movement having brought about this situation, giving the system a redundancy, optimizing the operating conditions of such a device load compensator.

The invention also relates to the load compensating device implementing this process.

The manner in which the invention can be carried out and the advantages thereof will emerge more clearly from the example of embodiment which follows given to indicative and non-limiting in support of the attached figures.

Figure 1 is a schematic view showing a machine for load fitted with load compensating device in accordance with the invention.

Figures 2 to 4 show different operating phases of the load compensating device according to the invention, respectively equilibrium, in a state of overload, and in a state of underload.

FIG. 1 shows the carriage (1) of a machine for loading of nuclear fuel assemblies from a nuclear reactor nuclear plant. This carriage moves on a raceway (2) at roller means (3), and to which a lifting device, consisting of a motorized winch (4) (5) on which a cable (6) is wound. The other end of the cable (6) is fixed to a load compensating device (7), also integral with the carriage (1).

The cable (6) surrounds a pulley mounted madly in rotation (8) on a bracket (9) integral with the carriage (1) and, it cooperates with a load cell (10) of the type dynamometer with strain gauge (such as for example marketed by TELEMECANIQUE) and connected to a weight indicator, the weight information being transmitted to the programmable controller (not shown) managing the loading machine.

The load (11) is attached to the hook (12a) of a movable block (12), whose pulley (12b) is surrounded by the cable (6) before it goes surround yourself with the winch drum (4).

As already stated, the invention is more particularly described in liaison with the electro-nuclear industry. In fact, the charge (11) in question is here constituted by an assembly of nuclear fuels, which one wishes to handle within the core of a reactor, this handling may be constituted by the establishment of said assembly within the heart plate, but also by its replacement or its repositioning.

The load compensator (7) will now be described in more detail, without being too weightless, since this one is everything particularly described in the document EP-B-0 292 413 already mentioned.

This load compensator firstly has an internal bell fixed, integral with the carriage (1), and composed of at least two columns (13), each of the two columns having two sections (13b) and (13c) of different diameters, the variation of these sections generating a shoulder (13a). The free ends of the two portions (13c) are joined by a crosspiece (14) also forming a stop.

An upper piston (15) is capable of translating between the stops (13a) and (14) and, a lower piston (16), is also capable of move between the piston (15) and substantially the lower end or bottom of the internal bell.

Each piston receives a flexible pneumatic cylinder, respectively overload cylinder (17) and underload cylinder (18), supplied separately by a flexible line from a source of compressed air (not shown).

The connection with the load to be balanced, shown in Figures 2 to 4 by the arrow, and representing in fact, the departure of the cable (6), is produced by via a movable external bell (19), therefore in translation vertical, and likely to be supported at the base of the lower piston (16) using a ball joint (20).

Advantageously, the load to be balanced is linked to a counterweight (21), capable of sliding freely on vertical columns (22) extending from the upper end of the external bell (19), and therefore integral with it. It should be noted that the displacement of the counterweight (21) within the columns (22) is limited in the upper zone by stops (23).

The operation of this compensator (7) is as follows.

When the system is in equilibrium (see FIG. 2), that is to say when no obstacle is encountered by the load, the respective pressures in the jacks (17) and (18) are respectively PU ₁ and PO ₁ . The pressure PO ₁ is fixed so that it cannot induce the displacement of the upper piston (15), and that the latter rests in fact on the stops (13a) formed at the level of the internal bell (13).

This balance remains as long as the cable tension remains substantially constant, and in particular that it does not exceed a determined threshold. In fact, the external bell is located at a height h relative to the base of the internal bell, as shown in FIG. 2.

In the event of an overload (Figure 3), the additional voltage is absorbed by the load compensator by inducing the rise of the external bell (19) to a height h ₁ , by reducing the pressure inside the overload cylinder according to a new value PU ₂ less than FU ₁ .

At the same time, in the event of an underload (figure 4), the reduction in cable tension is absorbed and therefore the tension is kept at equilibrium by lowering the external bell by inducing a pressure PO ₂ inside the underload cylinder greater than PO ₁ .

As already mentioned, the load compensator known in the art previous operated from overload detection thresholds or underload, these detection thresholds being detected by the load cell (10).

We have also shown the drawbacks linked to this mode of compensator operation.

In fact, and in accordance with the invention, each of the chambers of the jacks tires, respectively overload (17) and underload (18), is fitted with a pressure sensor capable of permanently indicating the prevailing pressure inside these chambers, and whose data as well measurements are transferred to the aforementioned programmable controller, acting at the level of a set of solenoid valves ensuring the admission or exhaust of a compressed air source.

In fact, in the event of an overload, the pressure detected within the actuator overload (17) will increase taking into account on the one hand, the inexpansibility of the volume of said cylinder, and on the other hand, of the overvoltage transmitted by the cable (6) and relayed by the external bell (19).

This overpressure is immediately evacuated at one or more of the two chambers simultaneously, until returning to equilibrium pressure, ie in order to keep the same pressure as that of the state of balance, while observing the rise of the external bell of the height h at height h1.

In other words, the internal pressure sensor associated with its PLC of operation will simply reduce the inherent excess pressure at the overload at the original pressure, when the compensator was in equilibrium position.

Conversely, in the event of underloading, there will be a decrease in the tension of the cable and consequently, tendency of the external bell (19) to drop so that the pressure inside the pneumatic chamber of the jack underload (18) will decrease and, simultaneously, taking into account the automaton, this reduction will be compensated by the introduction of compressed air until returning to the initial equilibrium pressure. In parallel, there is a descent of the external bell from the height h to the height h ₂ , until returning to the equilibrium conditions of the compensator.

In other words, this pressure regulation, which in addition can be modulated simultaneously at the level of one or both chambers, will generate at the cable variation of effort reduced to a minimum and in addition, maintaining physical contact between the elements concerned, especially fuel assemblies.

Furthermore, by the almost constant maintenance of efforts exerted at the level of the cable, and in particular of the tension, and moreover, by the variations pressure continues, we avoid return phenomena backward observed when the compensator operates with thresholds of pressure.

According to the invention, the installation is equipped with sensors for detecting the position of the load compensator, and more precisely of the position of the external bell (19).

These position sensors are sensors per se known, in particular from optical or differential transformer technologies, which range ensure the measurement for the position control of the external bell. The corresponding signals are further processed, in order to determine, by deriving with respect to time the distance of the displacement of the bell thus measured, the speed of this movement. This speed is characteristic of a situation of overload, underload, and more specifically hooking, and its determination allows the winch (4) to be stopped very quickly, to say the stop of the movement having caused this situation.

According to an advantageous characteristic of the invention, a signal overload, underload, and more particularly snag detection by detection of the value of the overload or underload threshold delivered by the load cell (10), also comes to buckle on the programmable automaton or on the hoist management unit, giving the system a redundancy, optimizing the operating conditions of such a device load compensator.

• le maintien des vérins à pression constante entraine l'existence d'un effort lors des surcharges ou souscharges proche de l'effort existant à l'équilibre ;
• le maintien des vérins à pression constante, avec une légère variation de la force qui en découle, assure la conservation du contact entre le câble et la charge, sans phénomènes de mouvement inverse, de sorte qu'il n'y a plus interférence inverse entre les grilles-entretoises d'assemblages de combustibles de types différents ;
• la continuité de la régulation de pression se traduit par l'absence d'à-coups ;
• le contrôle de position du compensateur permet un retour de celui-ci à sa position initiale après suppression de l'effet d'accrochage ;
• la souplesse et la précision de ce système permettent de réduire les seuils de détection à des valeurs plus basses, typiquement 40 à 60 daN au lieu de 80 daN.

It results from the mode of operation and regulation of the load compensating device according to the invention a certain number of consequences and advantages, among which we can cite:

• maintaining the cylinders at constant pressure results in the existence of an effort during overloads or underloads close to the effort existing at equilibrium;
• maintaining the cylinders at constant pressure, with a slight variation in the resulting force, ensures the conservation of the contact between the cable and the load, without reverse movement phenomena, so that there is no longer any reverse interference between spacer grids of fuel assemblies of different types;
• the continuity of the pressure regulation results in the absence of jerks;
• the position control of the compensator allows the latter to return to its initial position after removal of the latching effect;
• the flexibility and precision of this system make it possible to reduce the detection thresholds to lower values, typically 40 to 60 daN instead of 80 daN.

Claims (6)

1. Method of regulating the operation of a load compensation device for handling gear, of the type comprising :

   a stationary internal bell housing (13) secured to the bed on which the handling gear rests, and inside which an upper piston (15) and a lower piston (16) can move in translation between stops (13a, 14) formed within said bell housing, and between the upper piston (15) and the bottom of said bell housing, respectively;

   a mobile external bell housing (19) that can cooperate with the lower piston (16) and to which is secured one of the ends of the handling member (6), especially a cable or a chain, from the other end of which the load (11) is hung ;

   an overload pneumatic cylinder (17) which extends between the upper piston (15) and the stop (14) of the stationary internal bell housing (13), and an underload pneumatic cylinder (18) which extends between the upper piston (15) and the lower piston (16), said cylinders being connected to a source of pressure or exhausted by a series of electric directional control valves,

   characterized in that it consists in actively controlling the pressure within said cylinders (17, 18) continuously so as to alter the datum position of the external bell housing (19) which corresponds to the state of equilibrium as a function of the variations in pressure which are measured at the cylinders in order to cancel out any overload or underload effect on the load (11) and return the compensator to its state of equilibrium that corresponds to the lifting gear operating in the normal way, that is to say operating in the absence of any overload or underload after the cause which led to such an overload or underload condition has been eliminated.
2. Method for regulating the operation of a load compensation device of handling gear according to Claim 1, characterized in that the pressure regulation carried out at the cylinders is performed by detecting the change in pressure in the cylinders.
3. Method for regulating the operation of a load compensation device of handling gear according to Claim 2, characterized in that the signals relating to the displacement of the external bell housing (19) are processed in such a way as to deduce the rate of displacement of said external bell housing, simply by differentiating said displacement with respect to time, said rate being compared with a determined threshold that represents a characteristic of an overload or underload situation and, depending on this comparison, to trigger the stopping of the lifting movement.
4. Method for regulating the operation of a load compensation device of handling gear according to one of Claims 1 to 3, characterized in that an overload or underload detection signal, by detecting the value of the overload or underload threshold, and delivered by a conventional weighing system (10) installed at the cable (6), especially a dynamometric one, is also fed back to the programmable automaton or to the lifting gear management unit in such a way as to give the system a degree of redundancy in order to achieve the end result of stopping the movement that led to this overload or underload situation.
5. Load compensation device for handling gear, of the type comprising :

   a stationary internal bell housing (13) able to be secured to the bed on which the handling gear rests, and inside which an upper piston (15) and a lower piston (16) can move in translation between stops (13a, 14) formed within said bell housing, and between the upper piston (15) and the bottom of said bell housing, respectively ;

   a mobile external bell housing (19) that can cooperate with the lower piston (16) and to which is able to be secured one of the ends of the handling member (6), especially a cable or a chain, from the other end of which the load (11) is hung ;

   an overload pneumatic cylinder (17) which extends between the upper piston (15) and the stop (14) of the stationary internal bell housing (13), and an underload pneumatic cylinder (18) which extends between the upper piston (15) and the lower piston (16), said cylinders being connected to a source of pressure and to a partial vacuum volume ;

   a programmable automaton or a management unit ;

   characterized in that each of the cylinders (17, 18) comprises a built-in pressure sensor, the signals from which are transmitted to said programmable automaton or to said management unit in such a way as to cause the pressure within said cylinders to be regulated in order to keep the pressure within the cylinders constant during overloads or underloads.
6. Load compensation device for handling gear according to Claim 5, characterized in that it is fitted with position sensors capable of detecting the displacement of the external bell housing (19), the signals transmitted by said sensors furthermore being processed in conjunction with a clock signal in order to determine the rate of displacement of said external bell housing.

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