FR3101003A1 - Solder flux curing and conservation device intended for the nuclear sector for a flow rate of 60 liters / hour over 72 uninterrupted hours, in order to guarantee uniformity of temperature of the flux treated at all points of the oven - Google Patents

Abstract

Cylindrical and conical solder flux curing and conservation device intended for the welding sector of equipment in a nuclear environment, capable of producing a constant temperature up to 420°C in a homogeneous manner over the entire capacity of the oven , at plus or minus 25°C at any point in the volume of the oven receiving the solder flux, characterized in that: - The electrical heating resistors (a) are made up of several groups, at least a first series (b) in the lower part of the oven, at least one part (c) placed in the upper part of the oven, and possibly series placed between these heights (d), according to a principle of maximum spacing (i) of 150 mm between the resistors (a) at any point of their position, - Each group of resistors is equipped with a separate thermal regulation servo system (h).

Description

Solder flux curing and conservation device for the nuclear sector

The invention relates to a welding flux curing and conservation device according to the regulations in force in the nuclear sector, capable of supplying a flow rate of powders to the welding head of 60 liters per hour over 72 continuous hours, according to the principle of guaranteeing a uniform treatment temperature inside the oven with a tolerance of plus or minus 25°C at all positioning points of the flow in the device and at all times during the treatment.

State of knowledge: Before approaching the principle of a curing module, it seems useful to recall the scientific and technological environment in terms of solder flux processing.

Related to x solder flux: These have a physical behavior (supported temperature, variable temperature inside the same mass due to their composition and in particular their grain size, abrasion, more or less fragile transport capacity, etc.) that are very different depending on their compositions. , which constrains the design of the equipment that processes them. There is, however, a behavioral constant observed, on three points:
- Solder fluxes are all moisture-hungry, and more particularly agglomerated fluxes which are the most used. It is therefore important that the devices that support them during treatment - storage - or transport do not allow any moisture load recovery,
- They also have a thermal insulation property which considerably constrains the homogeneity of the temperature treatment, in that this property prevents the diffusion of the 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 the mechanical equipment), and for perfect flow without residual flow remaining in the equipment.

In the field of soldering intended for equipment subject to the nuclear environment, it is possible to mix new soldering flux with reprocessed flux when:
- The new flow represents at least 50% of the totality of the mixed flow,
- The reprocessed flux is free of 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 an agreed minimum duration , which forces the flow reprocessing equipment to respect the indicated cycle,
- The parboiled flux is maintained at a storage temperature avoiding the resumption of humidity.

These requirements constrain solder flux reprocessing equipment in that significant delays due to processing conditions involve jointly processing large volumes of solder flux, volumes incompatible with:
- a principle of continuous release at the welding head,
- a second principle of compact and mobile device.

In terms of devices , there are several solder flux reprocessing devices:
- A first technology commonly called “flux recycler” consists in placing above the welding head a tank which feeds the welding head. On this tank, a vacuum device makes it possible to suck up the excess flow and put it back in the tank. This first device therefore does not make it possible both to continuously sort the recovered flow, to mix new flow and recovered flow and to heat treat the latter,
- Based on the principles of this first technology, another technology consists in supplementing the supply tank of the welding head with new flux by means of a pressure device (cf. 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 through a sieve at the inlet of the tank, it would also be a question of periodically evacuating this slag , which would make it necessary to stop the suction, so that the device cannot act continuously,
- Still according to a technological variant of the first device, patent JP H06 83170 U mentions two separate tanks, one receiving the flow recovered 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 flows and recovered flows cannot be managed.

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 solder fluxes.

To allow continuous processing of the solder flux according to the requirements mentioned above, the present inventor has designed a device for processing solder flux in a compact and manageable block (patent application No. 1800706) to be moved in a workshop of boilermaking to provide 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 fluxes,
= sifting of these,
= mixture of these fluxes with new flux,
= steaming and conservation,
= and release of the reprocessed flux towards the welding head,
- receiving other devices patented by the same applicant:
= No. 1200997 of April 4, 2012 relating to a continuous flow steaming module with unlimited capacity intended for the drying of powdery products,
= No. 1400960 relating to a solder flux curing and conservation module intended for installations meeting the standards for the treatment of solder flux in a nuclear environment,
= No. 1402232 of October 2014 relating to a coupling module for accelerated treatment ovens and welding flux conservation ovens,
= No. 1501661 of October 2015 relating to a new/and or recycled welding flux transport module at the head hopper of the welding torch, based on a principle of supply by several stoving 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.

The object of the present invention is to remedy the drawbacks of device No. 1400960 published under No. 302045, and intended to be installed in the solder flux processing device which is the subject of patent No. 1800706. Said patent No. 1400960 is characterized in that it is composed of:
- A thermally insulated cover with a central opening,
- An outer body serving as a structure containing thermal insulation and a hopper in the inner part,
- Heating elements installed in the hopper, and arranged over the entire volume of the latter,
- A series of safety temperature sensors,
- Flow temperature measurement sensors,
- Temperature regulation,
- A locking and release hatch blocked by a solenoid valve,
- A level sensor.

The limit of the treatment and conservation module as defined in patent No. 1400960, is that it receives solder flux, which depending on whether or not it is placed near the heating elements, will undergo variations in temperatures more or less than 30% compared to the setpoint. This problem is due in particular to the mechanical design of the device, which is constrained due to:
- the sloping of the flux at 45° (physical property of the welding flux) within it, which makes it necessary to design 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 in the volume of the oven. Consequently, the location and the distance between the heating elements does not make it possible to obtain perfect temperature homogeneity despite the introduction of continuous and precise thermal regulation. This is why, and in order to compensate for these temperature disparities, the device allows a rise to significant temperatures beyond 450°C, according to a principle that by forcing it the temperature diffuses, this in the maximum allowable temperature limit for each solder flux.

To clarify these different constraints, it seems useful to indicate:
- With respect to the disturbance of the homogeneity of the treatment temperature at all points of the oven, this is mainly caused by the physical characteristic of the solder flux which has great thermal insulation capacities.
- In addition and due to the circulation of the flow when the steaming device is placed in invention No. 1800706, this flow moves by gravity from one tank to another, which constrains the shape and the sizing of the tanks, in that they receive the flow in the upper part, and require a conical device in the lower part to facilitate total emptying. As a result, a phenomenon of natural sloping of the flow in the oven is observed, which forms as the oven is filled, which indicates that its top varies, and that the heat requirements vary. also on this same area depending on the filling level.

With regard to heating equipment installed for drying purposes, these are therefore thermally disturbed by the presence or absence of products in their spatial environment. For this purpose:
- at the top of the embankment, the hot air circulates and is evacuated, which generates heat losses, and after a certain time in this same zone, a diffusion of heat generated by the mass of powder which compensates for the thermal losses caused by areas without product, so that the temperature observed in this area varies considerably from a low point to a high point,
- in the lower conical zone of the oven (which represents the heart of the volume) which is characterized by the proximity of the mechanical elements (due to the mechanical stresses generated by the need for displacement by gravity), this zone is always supplied in flux Welding. At this location, it is found that the presence of heating elements causes a rapid rise in temperature, while the presence of mechanical elements degrades the temperature obtained inside the zone,
- so that different but interdependent thermal phenomena (because the solder flux must observe a consistency of treatment) occur in the receptacle of the oven which disturbs the homogeneity of the treatment.

It is also appropriate to indicate recent recommendations from solder flux manufacturers which until then did not stipulate any temperature constraints in the treatment of the flux, since the melting point was not reached: an oven value was indicated, with very high tolerances which allowed the equipment to meet the requirements. This setpoint was modified very recently with the introduction of lower temperatures specific to each solder flux reference, allowing a difference of plus or minus 25°C at each point of the storage volume of the treated powder. This change in the professional field of application disrupts automatic flow processing equipment, especially for those whose purpose is to supply large volumes and reduce processing times. To date, no known device makes it possible to satisfy these new recommendations.

[00014] the invention therefore relates to a soldering flux treatment and conservation oven, capable of being installed in a soldering flux treatment device in a compact and easy to handle block of the patent No. 1800706 type, of in such a way as to satisfy a treatment of 60 liters per hour for 72 continuous hours in a nuclear environment, and capable of complying with the setpoint for stoving and conservation at plus or minus 25°C on all the flows contained in the volume of the oven, a characteristic hitherto impossible to achieve due to the physical nature of the solder flux.

Presentation of the invention:the invention relates to a soldering flux curing and conservation device, intended for the soldering sector of equipment in a nuclear environment according to patent No. 1400960, and placed in a soldering flux treatment device such as patent No. 1800706, this Cylindrical and conical proofing module featuring:
-A thermally insulated cover with a central opening,
-An outer body serving as a structure containing thermal insulation and a hopper on the inside,
-Heating elements installed in the hopper, and arranged over the entire volume of the latter,
-A series of safety temperature sensors,
-Flow temperature measurement sensors,
-A temperature control,
-A locking and release flap blocked by a solenoid valve,
-A level sensor,
capable of producing a temperature of 420°C evenly over the entire capacity of the oven, at plus or minus 25°C at any point in the volume of the oven receiving the solder flux, characterized in that that :
-The resistances (a) are composed of several groups positioned on - at least two series on the height, at least a first series (b) in the lower part of the oven, at least a part (c) placed in the upper part of the oven, and possibly of the series placed between these heights (d), according to a principle of maximum spacing (i) of 150 mm between the resistors (a) at any point of their position, on the basis of:
= At least two central groups (e, e'') placed one on top of the other,
=At least two peripheral groups (f, f'') also placed one above the other, based on plate resistor technology,
=As many intermediate groups (g, g'') placed between the central and peripheral groups,
-Each group of resistors is equipped with a thermal regulation servo system (h).

So that in its minimum configuration in height, the device has two series on the height represented in the figure by the following indices: upper part "c", "e", "f", and possibly "g"; lower part "b", "e''", "f''" and possibly "g''". In a configuration with high series placed between these high and low series, the figure represents its components by the subscripts 'd', 'e', 'f' and possibly 'g'.

so also that in a minimum configuration in height and width, the components will be contained will be: "e" and "f" on the upper part, and "e''" and "f''".
: cross-sectional view of the device

[00018] Glossary :
a) Resistances
b) First series of resistors in the lower part of the oven
c) Series of resistors placed in the upper part of the oven
d) Series of resistors placed between these heights
e) and e’, e’’) Central resistance groups placed on top of each other
f) and f’, f’’) Peripheral resistor groups
g) and g’) , g’’) Intermediate resistance groups
h) Thermal regulation servo system
i) Maximum spacing of 150 mm between resistors at all points of their positions.

Claims (1)

Cylindrical and conical solder flux curing and conservation device, intended for the soldering sector of equipment in nuclear environment, equipped with: a thermally insulated cover with a central opening, an outer body serving as a structure containing a thermal insulation and a hopper in the interior part, heating elements installed in the hopper, and arranged over the entire volume of the latter, a series of safety temperature sensors, flow temperature measurement sensors, temperature regulation, a locking and release hatch blocked by a solenoid valve, a level sensor, capable of producing a temperature of 420°C evenly over the entire capacity of the oven, at plus or minus 25°C at any point in the volume of the oven receiving the solder flux, characterized in that that :
-The electrical heating resistors (a) are composed of several groups positioned on - at least two series on the height, at least a first series (b) in the lower part of the oven, at least a part (c) placed in the upper part of the oven, and possibly series placed between these heights (d), according to a principle of maximum spacing (i) of 150 mm between the resistors (a) at any point of their position, on the basis of:
=At least two central groups (e, e'') placed one on top of the other,
=At least two peripheral groups (f, f'') also placed one above the other, based on plate resistor technology,
=As many intermediate groups (g, g'') placed between the central and peripheral groups,
-Each group of resistors is equipped with a separate thermal regulation servo system (h).