FR2672344A1 - Pump with magnetic drive equipped with a monobloc separation component made of composite material - Google Patents

Abstract

Centrifugal pump with magnetic drive for corrosive liquids comprising a monobloc composite component (21) of slight thickness over its cylindrical annular part, which can be joined to the pump body (1) allowing leaktight containment of the liquid to be pumped and positioning of the rotor (5) so as to increase the torque of the rotor, limit the risk of leaks, and facilitate assembly/dismantling of the pump. The monobloc composite component (21) is obtained by the inter-crossing of local and radial fibrous reinforcements, preferably made of carbon fibres.

Description

MAGNETICALLY DRIVEN PUMP EQUIPPED WITH A PIECE OF
MONOBLOCK SEPARATION IN COMPOSITE MATERIAL
FIELD OF THE INVENTION
The invention relates to the field of centrifugal pumps with magnetic drive and more particularly the means used to ensure the separation between the motor unit and the rotor ensuring the setting in motion of the fluid to be pumped.

PRIOR ART
Centrifugal pumps with magnetic drive (PCEM for short) are already widely developed and marketed.

Their main interest lies in the fact that there is not, as in other centrifugal pumps, a direct mechanical connection, generally by a drive shaft, between the engine block and the rotor, so that, as it does there's more on these
CDR of seals or seals between the moving part and the fixed part, there is therefore, at least in theory, no leakage of the fluid to be pumped out.

A CDR typically consists of the essential elements shown diagrammatically in FIG. 1 and which are as follows (listed in the order of assembly of the pump) - a pump body (1) comprising a bearing with blind hole (2), an orifice suction (3) and a discharge orifice (4) provided with flanges, - a rotor (5) provided with magnets (6), - a means of confining the liquid to be pumped and holding the rotor, constituted in the case of FIG. 1 by a flange (7) fixed to the pump body (1), and a separation piece (8) in the form of a box provided with a flange (10) allowing it to be secured to the flange (7) , and provided with a blind hole (9) forming a bearing and allowing, with the blind hole bearing (2), to position the rotor (5) in the axis of the motor shaft (14), with alignment along the 'axis (13), - a driving crown (11) furnished with magnets (12) mounted at the end of a motor shaft (14) and centered along the axis (13) of the rotor using a level so that you can turn without friction or contact with the separation piece (8) and thus drive the rotor (5), thanks to the magnets (6) and (12) located on either side of the separation piece (-8).

Separation pieces of metal, plastic and even composite material are known, as in German patent No. 3 818 832 which describes the manufacture of a separation piece by assembly-bonding of a cylindrical piece and of a carbon composite base.

POSITION OF THE PROBLEM
In order to meet an unmet demand from the chemical industry in particular, the applicant has sought to develop a magnetic drive pump of easy mounting, with a high torque rotor, and intended for industrial use in particular in highly corrosive conditions and at relatively high temperatures.

Under these relatively harsh conditions, the problem of sealing is crucial because it essentially conditions the safe operation of the pump.

Indeed, the prior art does not make it possible to manufacture CDRs which have both a high torque rotor and which meet the aforementioned requirements.

OBJECT OF THE INVENTION
The object of the invention is a PCEM which satisfies the following conditions required by the chemical industry a) ease of assembly / disassembly and great tightness, which the present invention obtains by reducing the number of parts and by manufacturing one-piece sealed parts , b) high torque rotor, which the present invention obtains by increasing the electromagnetic coupling, which can therefore be provided with a large diameter turbine, c) corrosion resistance and temperature resistance, which the present invention obtains by a appropriate choice of materials known per se for their properties.

d) high mechanical strength to resist pressure, which the present invention obtains both by a choice of materials and by the particular design of the parts.

DESCRIPTION OF THE INVENTION
The centrifugal magnetic drive pump (PCEM) according to the invention comprises as essential elements a) a pump body (1) provided with a suction port (3), a discharge port (4) and a bearing (2) or equivalent means intended to receive one end (16) of the axis of a rotor (5), b) a rotor (5) comprising a turbine (18) integral with a cylinder (20) furnished with magnets (6), mounted on an axis and ensuring the displacement of the fluid to be pumped, c) a driving crown (11) furnished with magnets (12) rotating along the axis (13) of the rotor thanks to a motor associated, the cylinder (20) furnished with rotor magnets being inside the cylindrical ring (11), d) means for confining the fluid to be pumped and for separating the rotor (5) and the driving ring ( 11), comprising a cylindrical tube (23), closed at one end by a bottom (24) provided with a blind hole (9) serving as a bearing for the other end (17) of the axis of the rotor, and is characterized n that, said means of containment and separation consist of a single piece (21) of composite material comprising an annular disc (22) connecting at its inner edge with the other end of said cylindrical tube (23) , and of outer diameter greater than that of said turbine (18) so that it can be assembled directly to the pump body (1).

According to the invention, the thickness of the annular disc (22) and that of the cylindrical tube (23) are close and relatively small. This thickness is between 0.3 and 3 mm. It is important to note that according to the invention the connection of the annular disc (22) and the cylindrical tube (23) is at right angles and does not include any additional thickness.

Indeed, on the one hand, a cylindrical tube (23) of small thickness is desirable, as is known, to reduce the air gap, that is to say the distance between the magnets (12) carried by the driving crown ( 11) and the magnets (6) carried by the cylinder (20) of the rotor (5).

On the other hand, the invention makes it possible, thanks to a small thickness of the one-piece part, in particular in the connection area between the annular disc (22) and the cylindrical tube (23), to increase the magnetic surface of the - driving crown, that is to say, with equal dimensions, the rate of recovery of the cylinder (20) by the driving crown (11) and therefore the power of the pump (rotor torque). Indeed, the electromagnetic forces which allow the driving crown (11) to drive the cylinder (20) of the rotor are, all other things being equal, substantially proportional to the magnetized surfaces facing each side of the monobloc part. (21).

If these magnetized surfaces are insufficient, or if the magnetic field emitted by the magnets is too weak, then, for an operation of the pump with a given load, the cylindrical crown risks turning without being able to drive the cylinder of the rotor, it is the phenomenon of "slippage", which must be avoided at all costs in installations or industrial processes which require high reliability and operational safety.

The one-piece part according to the invention can be adapted to any pump of the PCEM type, whatever its size and the power of the pump. However, the invention applies especially to compact pumps, which have a rotor (5), having a high torque, the turbine (18) of which has a large diameter relative to the cylinder (20). Likewise, the single piece itself must have a geometry adapted to that of the rotor. According to the invention, the outside diameter of the annular disc (22) of the single piece (21) is between 1.2 and 4 times its inside diameter or, which is equivalent, the diameter of the cylindrical tube (23).

According to the invention, the annular disc (22), which is preferably planar, can comprise at its periphery a zone forming a relief / recess relative to the plane of the annular disc, so as to promote the tight assembly of the disc with the pump body (1). Typically, the relief zone is used to position a seal or any other means intended to seal the assembly of the one-piece part and the pump body.

According to the invention, the one-piece piece (21) is made of an electrically non-conductive composite material comprising a fibrous reinforcement, the tests carried out by the applicant having led to the exclusion of other materials, such as metals, graphite or the usual thermoplastic materials. , which do not simultaneously meet all the constraints, thermal, mechanical or corrosion resistance, already mentioned or others related to the presence of rotating magnetic field.

Thus, metal is not recommended, if not excluded, because of the eddy current losses which are generated in a monobloc piece (21) of metal.

To make the one-piece piece (21) from a thin, very rigid composite material, the applicant had to carry out numerous tests. In fact, the rigidity of the monobloc part is essential since the monobloc part (21), and in particular the part constituted by the cylindrical tube (23), must not deform under the influence of a variation in fluid pressure. to be pumped, with the risk of touching the moving parts that are the cylinder (20) of the rotor (5) or the driving crown (11), a risk which is all the greater when the air gap is relatively small.

According to the invention, a solid piece (21) of good rigidity was obtained by combining a) local fibrous reinforcements located in one of the four parts of the solid piece, namely the annular disc (22), the cylindrical tube (23 ), the bottom (24), and the area of its blind hole (9), with radial fibrous reinforcements connecting and joining these four parts together, so that each of the four parts of the part is substantially thick homogeneous.

As local fibrous reinforcements, use is made of fibrous reinforcement washers, pierced or not and of outside / inside diameter suitable as reinforcement of the annular disc (22), of the bottom (24) with its blind hole (9). A winding of a fibrous reinforcement strip is used for the cylindrical tube (23).

As radial fibrous reinforcements, use is made either of cross-shaped pieces, pierced in their center (hole having the diameter of the blind hole (9)) or not, or of narrow width ribbons connecting all the parts of the monoblock piece (21 ), so as to make the various parts of the one-piece part (21) completely integral. These radial fibrous reinforcements extend symmetrically with respect to the axis (13), this axis also being an axis of axial symmetry for the one-piece part (21).

The choice of fibrous reinforcement partly depends on the matrix chosen for the composite material constituting the one-piece part.

When the single piece (21) must meet the most stringent requirements, it is preferably made of carbon-based composite material. For this, we start with carbon fabrics, pre-impregnated with thermosetting liquid resin, which we cut into local and radial fibrous reinforcements, stack on a punch and compress between punch and matrix, so as to obtain by thermoforming a piece with dimensions of the single piece to be obtained. After polymerization of the prepreg resin and its carbonization, the part is densified and sealed by resin impregnation, preferably the resin used to prepreg the fibrous reinforcements, so as to obtain a one-piece waterproof piece (21).

Under less severe conditions of use, in particular with regard to corrosion, it is possible to choose other plastic or thermoplastic matrices (epoxy resins, polyester, polyimide, etc.) and / or other fibrous reinforcements chosen from fibers and fabrics known for their high mechanical characteristics (glass fibers, Kevlar @ OR, ...).

It is also possible to produce, from non-prepreg fabrics, cuttings and stacks of fibrous reinforcements similar to the preceding ones, place them in a mold substantially to the dimensions of the finished one-piece part and inject into the mold a plastic or thermoplastic resin.

EXAMPLES
A one-piece composite part (carbon fiber reinforcement and thermosetting resin matrix) was prepared, as shown diagrammatically in FIGS. 3a (in cross section along the axis 13) and 3b (perspective view).

Dimensions of the different parts of the monobloc part - annular disc (22): outside diameter = 385 mm
inner diameter = 145 mm
thickness = 3 mm - cylindrical tube (23): inside diameter = 145 mm
length = 126 mm
thickness = 3 mm - bottom (24): diameter = 145 mm
thickness = 25 mm - blind hole (9): inside diameter = 30 mm
thickness = 15 mm
For this, we cut in a carbon fabric, satin type, at 320 g / m2, local and radial reinforcements
Local reinforcements - 2 washers (item 41, see figure 4a) 385 mm in outside diameter and 145 mm in inside diameter for the annular disc (22).

- 18 washers (item 43, see Figure 4c) of 145 mm outside diameter and 30 mm inside diameter, for the bottom (24), excluding the blind hole (9).

- 37 full washers (item 42, see Figure 4b) 145 mm in diameter for the bottom (24), blind hole (9) included.

- 1 ribbon (item 44, see Figure 4d) 80 mm wide and 1400 mm long, for winding forming reinforcement of the cylindrical tube (23).

Radial reinforcements - 3 crosses (item 45, see Figure 4c), one with a central hole 30 mm in diameter and an outside diameter of 145 mm, two without central hole, one of which with branches longer than 20 mm - 4 ribbons (item 46, see Figure 4f) 80 mm wide and 710 mm long.

Then, after having impregnated the local and radial reinforcements with a phenolic resin with 72% of dry extract and soluble in water, they are stacked and they are mounted on the male part (47) of a mold as shown in the Figure 4, so that local reinforcements are always taken in sandwhich between two radial reinforcements.

When stacking is complete, place a sheet of
Mylar OR (49) on the impregnated carbon fabric.

The female part (48) of the mold is put in place and the stack is compressed so as to have a thickness of 3 mm (annular disc and cylindrical tube). Then the mold is brought to 1200C for 6 hours to polymerize the resin.

After demolding, the part obtained is impregnated with the phenolic resin used for shaping. This impregnation is done with an initial vacuum of 133 Pa, then impregnation of resin under pressure of 1 MPa at 1200C for 9 h. The part is then stabilized at 1800C for 10 h.

There was thus obtained a single piece for a CDR intended to be used in concentrated HCl medium at 80 "C.

ANOTHER EXAMPLE
Figure 5 illustrates another example of a one-piece part of a
PCEM, which has a tuck-in bottom to increase the compactness of the pump. Impregnated graphite was used to manufacture the pump body (1) and to manufacture the rotor (5) and in particular its cylinder (20) furnished with magnets (6). The latter was obtained by providing cavities in the graphite cylinder, a depth slightly greater than the thickness of the magnets, by filling these cavities with resin, typically the resin used for impregnating graphite, and by "drowning "the magnets in the cavities so that they are covered by a weak layer of resin (0.5 to 3 mm) so that, after polymerization of the resin, they are held in place and protected from corrosive action of the liquid to be pumped.

The resin used is a thermosetting resin (phenolic resin, epoxy, etc.), but preferably a phenolic resin with a high dry extract (> 70%) is used, containing a fine solid filler (graphite with particle size less than 70 rm) and a catalyst (paratoluene sulfonic acid), which overcomes each magnet with a thin layer of resin (0.5 to 3 mm) and thus reduces the air gap while ensuring effective protection of rotor magnets.

ADVANTAGES OF THE INVENTION
The Applicant has succeeded in manufacturing a CDR presenting numerous advantages by being able to manufacture, as a means of confinement and separation of the fluid to be pumped, a large monobloc composite part, rigid while being thin, and resistant to corrosion. which makes it possible - to reduce the air gap, to increase the torque of the rotor and therefore to limit the risks of "slipping". Note that the protection of the magnets according to the invention with a small thickness of polymerized resin contributes to achieving this goal.

- Increase the length of the magnets and therefore increase the torque of the rotor with identical dimensions or reduce the dimensions with identical torque.

- to be able to use large turbines and therefore to have high flow rates.

- to reduce the number of parts of a CDR and therefore to reduce both the assembly / disassembly costs and the risks of leaking corrosive fluid.

- Obtain a CDR whose parts in contact with the fluid to be pumped are of a chemical nature and have similar thermomechanical (expansion) properties, which is favorable for the life of the CDR.

DESCRIPTION OF THE FIGURES
Figure 1 is a cross-sectional view of a CDR according to the prior art which presents, in this case where the turbine is of large diameter, a flange (7) and a separation piece (8) as a means of confining the liquid to be pumped and as a means for separating the magnets (6) of the rotor (5) and the magnets (12) of the driving crown (11).

Figure 2 is an enlargement of the section of Figure 1 so as to facilitate the positioning of all the pins.

The white line (19) symbolizes the glue joint ensuring the connection of the bottom and the cylindrical wall of the separation piece (8).

Figures 3a and 3b show a single piece (21) according to the invention. Figure 3a is a cross-sectional view along the axis (13) and Figure 3b is a perspective view of the same part.

FIG. 4 illustrates the manufacture of a single piece with the stack of different local (41, 42, 43, 44) and radial (45, 46) fibrous reinforcements, covered by a film of Mylar OR (49), placed on the male part (47) of a mold and compressed by bringing together the male (47) and female (48) parts.

Figures 4a to 4f show schematically the various local (reinforcing fibers) (fig. 4a to 4d) and radial reinforcements (fig. 4e and 4f).

FIG. 5 represents in section a CDR with a monobloc piece (21) (represented by black dots on a white background), with an annular disc having a hollow part for placing a seal, and with a bottom "retracted" so as to reduce the size of the CDR. Such a bottom is obtained according to the invention by stacking local and radial reinforcements with a mold of specific shape.

Claims (12)

1 - Centrifugal pump with magnetic drive which comprises as essential elements a) a pump body (1) provided with a suction port (3), a discharge port (4) and a bearing (2) or equivalent means intended to receive one end (16) of the axis of a rotor (5), b) a rotor (5) comprising a turbine (18) secured to a cylinder (20) furnished with magnets (6), mounted on an axis and ensuring the displacement of the fluid to be pumped, c) a driving crown (11) furnished with magnets (12) rotating along the axis (13) of the rotor thanks to an associated motor, the cylinder (20) furnished with magnets being inside the driving crown (11), d) means for confining the fluid to be pumped and for separating the rotor (5) and the driving crown (11), comprising a tube cylindrical (23), closed at one end by a bottom (24) provided with a blind hole (9) serving as a bearing for the other end (17) of the axis of the rotor, characterized in that, the said means containment and separation consist of a single piece (21) of composite material comprising an annular disc (22) connecting at its inner edge with the other end of said cylindrical tube (23), and of outer diameter greater than that of said turbine (18) so that it can be assembled directly to the pump body (1). 2 - Centrifugal pump according to claim 1 wherein said annular disc (22) and said cylindrical tube (23) of said one-piece piece (21) have a thickness between 0.3 and 3 mm. 3 - Pump according to any one of claims 1 to 2 wherein the inner edge of said annular disc (22) and the end of said cylindrical tube (23) are connected at right angles and without excess thickness so as to be able to increase the magnetic surfaces of the driving crown (11). 4 - Pump according to any one of claims 1 to 3 wherein the outer diameter of said annular disc (22) is 1.2 to 4 times larger than the diameter of said cylindrical tube (23). 5 - Pump according to any one of claims 1 to 4 wherein said annular disc (22) has at its periphery an area forming a link / a hollow relative to the plane of the annular disc so as to promote the tight assembly of said annular disc with the pump body (1). 6 - Pump according to any one of claims 1 to 5 wherein said composite material constituting the material of said one-piece part (21) comprises a stack of local fibrous reinforcements in each of the parts of the one-piece part, and of radial reinforcements joining these different parts , so that each of the parts of the single piece is of substantially uniform thickness. 7 - Pump according to claim 6 wherein said stack comprises alternating local and radial reinforcements so that the local reinforcements are "sandwiched" between radial reinforcements. 8 - Pump according to any one of claims 6 to 7 wherein said fibrous reinforcements consist of fabrics, sheets obtained from fibers with high mechanical characteristics (carbon fibers, glass, Kevlar 9 - Pump according to claim 8 wherein a fibrous carbon fiber reinforcement is preferably chosen. 10 - Pump according to any one of claims 6 to 9 wherein the matrix of said composite material is a thermosetting resin selected from epoxy, polyester, phenolic resins. 11 - Pump according to claim 10 wherein the matrix of said composite material is preferably a phenolic resin obtained by polymerization of a liquid phenolic resin with high dry extract (> 70%) and soluble in water. 12 - Pump according to any one of claims 6 to 9 wherein the matrix of said composite material is a thermoplastic resin chosen from polyimide, polyetherimide, polycarbonate resins. 13 - Pump according to any one of claims 1 to 12, the pump body and the rotor are made of graphite impregnated with a resin and the cylindrical tube (20) of the rotor is provided with magnets embedded in cavities of said cylindrical tube and covered with a thin layer of said resin.