Device for transporting solder flux without moisture absorption

Abstract

Device for transporting recycled solder flux for the purpose of preventing moisture re-entry, according to the mechanical design of patent FR 1501661, characterized in that: - an air heater (a) placed upstream of the transfer box, heater equipped with a servo (b) and a temperature probe (c) at the inlet of the flux distribution box, - a second sub-assembly provided with insulation (g) and a heating cord (h) over the entire length of the piping between the flux distribution box and the head hopper (e), a temperature probe (d) at the inlet of the head hopper (e), and a servo (f) controlled by the temperature probe (d), - a third sub-assembly consisting of a motorized fresh air intake valve (k) at the inlet of the filter (j) associated with a servo (l) controlled by a temperature probe (i) at the inlet of the filter (j). Figure for abstract [Fig. 1]

Description

Title of the invention: Device for transporting solder flux without moisture absorption

[0001] The present inventor had designed a welding flux treatment device in a compact and manageable block (patent application No. FRI800706) called “Cerf”®, to be moved in a boilermaking workshop for the purpose of providing a flow of powders to the welding head of 60 liters per hour over 72 continuous hours according to the prerogatives of welding in a nuclear environment: - integrating the cumulative functions of: = recovery of excess solder flux, = sieving of the latter, = mixing of these flows with new flow, = steaming and preservation, = and release of the reprocessed flux to the welding head, - receiving other devices patented by the same applicant: = No. 1200997 of April 4, 2012 relating to a continuous flux drying module with unlimited capacity intended for drying powdered products, = No. 1400960 relating to a solder flux steaming and preservation module intended for installations meeting the standards for solder flux treatment in a nuclear environment, = No. 1402232 of October 2014 relating to a module for coupling accelerated treatment ovens and solder flux preservation ovens, = No. 1501661 of October 2015 relating to a module for transporting new / and / or recycled welding flux to the head hopper of the welding torch, based on a principle of supply by several steaming and conservation modules, = No. 1600710 of April 26, 2016 relating to a solder flux recovery module, = No. 1700193 of February 27, 2017 relating to a pneumatic suction recycling device mixing new solder flux and recovered flux.

[0002] A problem remained with the “Cerf”® devices (patent application no. FRI800706) relating to the transport of the welding flux to the welding head, fluxes intended to be used in a nuclear environment. Indeed, the current “Cerf”® device uses a pulsed air technology which pushes the flux towards the welding head, and which was the subject of a patent application FR 1501661 established by our company. However, at the source of the pulsed air, no device or process made it possible to guarantee a reduced humidity level, whereas the international standard contains this requirement. The known device attempts to free itself from this constraint by the hypothesis that hot air reduces the humidity level. But this hypothesis is called into question by thermal laws in that hot air can also be humid. This creates a risk of re-wetting the flux, whereas the operating principle of the "Cerf"® in a nuclear environment is to guarantee a dry solder flux.

[0003] It is for the purpose of removing the uncertainties arising from this state of affairs that the invention is intended.

[0004] State of knowledge: Before addressing the principle of a “Cerf”®, it seems useful to recall the scientific and technological environment in terms of solder flux treatment:

[0005] Relating to the welding flux: These have a physical behavior (temperature supported, temperature variable within the same mass due to their composition and in particular their granulometry, abrasion, more or less fragile transport capacity, etc.) which is very different depending on their compositions, which constrains the design of the equipment which processes them. However, and in order to ensure the quality of welding, they must be composed of a set of small granulometric elements added to fines. Arc welding fluxes are classified into several categories according to standard NF EN 760.

[0006] There is, however, a constant of behavior observed, on three points: - The soldering fluxes are all moisture-hungry, and more particularly the agglomerated fluxes which are those most used. It is therefore important that the devices which support them during treatment - conservation - or transport do not allow any recovery of moisture load, - They also have a thermal insulation property which considerably constrains the homogeneity of the temperature treatment, in that this property prevents the diffusion of temperature in the mass of flow to be treated, - They slope at 45 degrees, which also constrains the design of the equipment, both in their thermal design (locations and temperature load, dimensions of mechanical equipment), and for a perfect flow without residual flow remaining in the equipment.

[0007] In a field of application in a nuclear environment, it is possible to mix new soldering flux with reprocessed flux provided that: - The new flow represents at least 50% of the total mixed flow, - The reprocessed flux is free from slag larger than 2mm and has undergone systematic heat treatment according to a standard in force which requires the soldering flux to be maintained at a constant baking temperature for a minimum period. agreed, which forces the flow reprocessing equipment to respect the indicated cycle, - The steamed flow is maintained at a storage temperature to avoid moisture re-absorption.

[0008] These requirements constrain solder flux reprocessing equipment in that significant delays due to processing conditions mean that large volumes of solder flux have to be processed together, volumes which are incompatible with: - a principle of continuous release at the welding head, - a second principle of compact and mobile device.

[0009] In terms of solder flux reprocessing devices, there are several solder flux reprocessing devices:

[0010] - A first technology commonly called "flow recycler" consists of Place a tank above the welding head which feeds the welding head. On this tank a vacuum device allows the excess flux to be sucked up and returned to the tank. This first device therefore does not allow for continuous sorting of the recovered flux, mixing of new flux and recovered flux and heat treatment of the latter.

[0011] - Based on the principles of this first technology, another technology consists of supplementing the feed tank of the welding head with new flux by a pressure device (see US patent 4,221,957). In this case as in the previous one, which do not indicate any slag treatment system that it would be intellectually possible to add by a sieve at the inlet of the tank, it would also be a question of periodically evacuating this slag, which would require stopping the suction, so that the device cannot act continuously,

[0012] - Still according to a technological variant of the first device, the JP patent H06 83170 U refers to two separate tanks, one receiving the recovered flow according to the first technology listed, while the other is intended to receive the new flow. Below these two tanks, which have evacuation systems, is placed a receptacle which randomly receives the flows released by the phenomenon of depression, so that the ratio of new flow to recovered flow cannot be managed.

[0013] In such a way that these technologies are not compatible: - with the standards in force in the field of welding intended for nuclear applications, - and cannot claim continuous processing of welding fluxes.

[0014] To enable continuous treatment of the solder flux according to the requirements mentioned above, the present inventor designed a solder flux treatment device in a compact and easy-to-handle block (patent application No. 1800706), called "cerf"® to be moved into a boilermaking workshop for the purpose of providing a flow of powders to the welding head of 60 liters per hour over 72 continuous hours according to the prerogatives of welding in a nuclear environment: - integrating the combined functions of: = recovery of excess solder flux, = screening of the latter, = mixing of these fluxes with new flux, = baking and preservation, = and release of the reprocessed flux to the welding head, - receiving other devices patented by the same applicant: = No. 1200997 of April 4, 2012 relating to a continuous flux baking module with unlimited capacity intended for drying powdered products, = No. 1400960 relating to a solder flux baking and preservation module intended for installations meeting the standards for processing solder flux in a nuclear environment, = No. 1402232 of October 2014 relating to a module for coupling accelerated treatment ovens and solder flux preservation ovens, = No. 1501661 of October 2015 relating to a module for transporting new / and / or recycled welding flux to the head hopper of the welding torch, based on a principle of supply by several steaming and conservation modules, = No. 1600710 of April 26, 2016 relating to a solder flux recovery module, = No. 1700193 of February 27, 2017 relating to a pneumatic suction recycling device mixing new solder flux and recovered flux.

[0015] This “Cerf” ® device has been the subject of several developments concerning certain modules:

[0016] The limitation of the treatment and preservation module (patent No. 1400960) is that it receives solder flux, which depending on whether it is placed near the heating elements, will be at a temperature more or less 30% away from the setpoint. This problem is notably due to the mechanical design which is constrained due to the slope of the flux at 45° (physical property of the solder flux) which requires the design of a conical sole with a spherical base to completely release the flux after treatment and without residue, and which in fact prevents the heating elements from being placed in a perfectly distributed manner. Consequently, the location and distance between the heating elements does not allow for perfect temperature homogeneity despite the introduction of continuous and precise thermal regulation. This is why the device allowed high temperatures above 450°C, within the limit of the maximum admissible temperature for each welding flux, in order to diffuse the calories. It seems useful to recall the temperature constraints to be observed in the field of welding in a nuclear environment, in that the temperature setpoint in the treatment and storage phases is provided by the flux manufacturer, and supports a difference of plus or minus 25 °C at each point of the volume of powder treated for the most sensitive fluxes.

[0017] A first development consisted of a patent filed under number FR190370, by the present applicant, which aimed to free itself from the constraints of temperature difference in each treatment phase: steaming, then conservation. The problem posed by this device remained linked to the release of the product. Let us recall that in the steaming phase, the flow rose to significant temperatures (up to 425°C), while in the conservation phase this flow is maintained at around 150°C. However, the flow contained inside the oven will (due to its nature) between these two phases, descend slowly in a non-homogeneous manner, in that the flow placed at the periphery of the oven will lower its temperature more quickly than the flow placed in the center of the oven.This posed a problem, in that the regulatory guidelines in the nuclear sector present new requirements for temperature control at all points and at all times of the treatment so that the flow only has a temperature difference of plus or minus 25°C. If this patent application No. FR190370 made it possible to obtain a temperature maintained at plus or minus 25°C in each phase of treatment, it had the disadvantage of being disturbed as soon as one passes from one phase to another. On the other hand, if this patent FR1910370 made it possible to obtain an adequate temperature as soon as the oven was at full load, as soon as it was not, this produced a heterogeneity of temperature of the flow, because electrical resistances not surrounded by flux produced a temperature disturbance.The complex control system partially solved the problem, as the primary purpose of this segmented control was to ensure uniform treatment of the flux, which was disturbed by the shape and dimensions of the oven. However, this technology was conditioned by the need for the oven to be full during its baking phase. However, depending on user needs, it is not always useful for the oven to be used at its maximum capacity (at the end of the welding cycle, or on small construction sites, for example).

[0018] To overcome this drawback, the present applicant has carried out a second technological development (see patent FR3106994) consisting of the design of a device for steaming and preserving solder flux in a nuclear environment using hot air stirring technology, already integrated in other fields of application. This patent is a steaming and preservation module device equipped with a particularly innovative air stirring technology. This new principle to the subject of the treatment of the solder flux, allows to satisfy a treatment of the solder flux at any place where it is placed in the oven, in that the circulation of hot air arrives equally at any point inside the oven. If this technology was new in our field of application, the evolution of the state of knowledge was established on the technological level due to the specific dimensions which were studied in relation to the physical characteristics of the different solder fluxes used in the nuclear sector. These latter having different characteristics between them, we had succeeded in developing a device allowing a universal treatment.The inventive nature is established by the following characterizations: a) a technology for mixing hot air for the purpose of extracting the moisture contained in the powder by means of two separate circuits: a first which transports the hot air through the volume of the oven, the other receiving the powder stored to undergo the treatment, these two circuits being adjacent to ensure an exchange perfectly distributing the thermal load in the direction of the powder without the air contained in the air circuit coming into contact with the circuit of the powders, these circuits also being intermingled with each other by repeated alternating partitioning in the volume of the oven; . b) the following components: - a thermally insulated envelope constituting the volume of the steaming chamber, - a silo fixed inside the steaming chamber according to a principle that the air contained in said chamber can circulate in the volume of the silo, this silo being composed: = in its lower perimeter by a funnel-shaped base which receives uprights, the whole constituting the walls of the silo and delimiting its volume, = this silo receiving a drain valve at the bottom of the funnel-shaped base while it is open at the top to receive the powder, = this same silo is crossed by tubes spaced apart from each other, which are placed in parallel over the entire volume of the silo following the axis of the air mixing turbine, these tubes crossing the walls of the silo form with the volume of the steaming chamber the hot air circuit, while the remaining volume of the silo forms the circuit of powder stored to undergo treatment, - a hot air mixing module consisting of a motor equipped with an air mixing turbine surrounded by heating resistors, other heating resistors being able to be placed at any other location in the steaming chamber, - a dedicated control system for maintaining the temperature inside the chamber and which manages the different cycles of drying, conservation and release of powders.

[0019] Thus by this device, the control managing the temperature of the air contained in the hot air circuit, this hot air circuit passing through the tubes in numerous places the silo and its walls, steaming takes place in the heart of the silo at uniform temperatures throughout the silo and throughout all treatment cycles.

[0020] To date, and with regard to the subject of the "Cerf" ®, relating to the transport of the welding flux to the welding head in a nuclear environment, no solution has yet been found to reduce the humidity level of the flux during the transport phase to the welding head. Indeed, if the reprocessed flux was protected from any humidity when it is placed in the conservation modules, as soon as it is released from these modules, it is subject to the hygrometric influence of its environment.

[0021] More particularly in the transfer of the welding flux from the oven to the welding head, as introduced in the “Cerf” device (patent No. FR1501661), this was characterized by: - guillotine valves (a and c) which ensure the opening of the steaming and preservation modules in a precise order towards the transfer box, - A network of tubes (b) which connects the guillotine valves (a and c) and supplies the transfer box (j), - A transfer box (j) inclined at 45°C to prevent the flux from remaining in the box, - A PLC (m) with special programming collecting information from both the welding head and the steaming and preservation modules, synchronizing the opening and closing actions of the hatches and the air intake from the turbine, regulating the opening times of the valves (a and c) and the blower according to the length of the flux supply pipes to the welding head, the difference in level and the flux flow rate at the welding head.

[0022] Furthermore, each guillotine valve (a and c) of the transport module was composed of: a feed tube (h) in the upper part, a support plate (d) of the casing fixed to the feed tube (h), the pouring funnel (o) which distributes the released solder flux, a second connecting tube (f) placed between the feed tube (h) and the guillotine (i) to manage thermal expansion and contribute to the air and dust tightness of the valve, a compression seal (e) positioned between the support plate (d) and the connecting tube (f) in order to ensure a perfect seal, and a guillotine (i).

[0023] It should be noted that this technology does not solve the problem of moisture absorption, in that patent FR1501661 transports the heated solder flux in the storage oven to the welding head, without the issue of moisture absorption being able to be managed during this transport. Note that this patent does not mention any technology for heating the air used to transport the flux, apart from the air sucked into the welding head, which can be heated by the welding operation but without any certainty or temperature control. However, as we As we have indicated in the subject of the present invention, it is not because the air is hot that it is no longer humid.

[0024] To this end, it is appropriate to indicate the state of scientific knowledge characterized by the "Carrier" diagram. This diagram allows us to understand the laws of evolution of air humidity according to temperature. Let us note in this diagram the notion of relative humidity (indicated in % of the volume), while the notion of absolute humidity is expressed in grams of water per kg of dry air:

[0025] - Absolute humidity: The absolute humidity of an air mass represents the quantity in grams of water vapor [g vapor / kg dry air] present in a given volume of dry air (lm3) and its value remains constant even if the air temperature varies while remaining above the dew point temperature*. The vapor contained in an air mass is invisible, but if we saturate dry air with humidity beyond a certain limit, we see fog and condensation appear, the water then forms droplets suspended in the air, we then say that the air is saturated. The dew point temperature is the temperature where the water vapor contained in the air begins to condense in the air,

[0026] - Relative humidity: Relative humidity (RH) is expressed as a percentage (%) and corresponds to the ratio between the quantity of water contained in the air (absolute humidity) and the maximum quantity it can contain for a given temperature and this before condensing.

[0027] Temperature variations directly influence relative humidity, so that relative humidity decreases when the temperature rises and increases when the temperature falls.

[0028] According to this diagram, in order to reduce the quantity of water held in the material (here the welding flux), it is appropriate to: - cool the air to a temperature below its dew point, - then condense the water vapor present in the air, - which is then separated from the air.

[0029] Under these conditions the cold dried air must be reheated in order to return to its initial temperature.

[0030] In the state of known technologies relating to the transport of the solder flux, no device or method was known to satisfy this treatment. Indeed, there are air drying devices which use refrigeration technologies. The problem posed by these installations is that they considerably complicate the installations and that they are very energy-intensive. Furthermore, these air dryers are limited in temperature, whereas the air used in patent No. FR150661 uses recovered hot air estimated at approximately 80°C, without it being possible to control or be exact.

[0031] Presentation of the invention: the invention relates to a device for transporting recycled solder flux from the storage oven to the welding head hopper, making it possible to guarantee the standard requirements for soldering in a nuclear environment, in particular to prevent moisture from returning during transport from the oven to the welding head. This device is governed by the principle of maintaining a flux temperature of at least 100°C during said transport, in order to prevent moisture from returning to the flux.

[0032] The device developed in 2022 is strictly similar in mechanical terms to that described in patent FR 1501661. But this new device differs from the environment of patent FR 1501661 in that it is characterized by: - an air heater (a) placed upstream of the transfer box (index J of patent FR1501661), heater equipped with a servo-control (b) and a temperature sensor (c) at the inlet of the flow distribution box, - a second sub-assembly provided with insulation (g) and a heating cord (h) over the entire length of the piping between the flow distribution box and the head hopper (e), a temperature sensor (d) at the inlet of the head hopper (e), and a servo-control (f) controlled by the temperature sensor (d), - a third sub-assembly consisting of a motorized fresh air intake valve (k) at the inlet of the filter (j) associated with a servo-control (1) controlled by a temperature probe (i) at the inlet of the filter (j). [Fig.l] [Fig.l] is a general presentation of the device.

[0033] Glossary: a) an air heater b) air heater control c) Temperature probe at the inlet of the flow distribution box d) Temperature probe at the inlet of the head hopper e) head hopper f) control of the heating cord placed on the piping between the flow distribution box and the head hopper g) insulation of the piping between the flow distribution box and the head hopper h) heating cord on the piping between the flow distribution box and the head hopper i) temperature sensor at the filter inlet j) air purification filter at the head hopper outlet k) motorized fresh air intake valve at the filter inlet 1) control of the fresh air intake valve

Claims

[Claim 1] Claims Device for transporting recycled solder flux from the storage oven to the welding head hopper, for the purpose of preventing moisture from returning, characterized in that: - an air heater (a) placed upstream of the transfer box, heater equipped with a servo (b) and a temperature sensor (c) at the inlet of the flow distribution box, - a second sub-assembly provided with insulation (g) and a heating cord (h) over the entire length of the piping between the flow distribution box and the head hopper (e), a temperature sensor (d) at the inlet of the head hopper (e), and a servo (f) controlled by the temperature sensor (d), - a third sub-assembly consisting of a motorized fresh air intake valve (k) at the inlet of the filter (j) associated with a servo (1) controlled by a temperature sensor (i) at the inlet of the filter (j).

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