thermal insulation

The invention provides a method for producing a pipe section for thermal, acoustic and/or fire insulation having a body made of mineral wool and provided with a longitudinal axis and a circular cross section, an outer surface and an inner opening being arranged centrically in the body and extending through the whole body. Furthermore the invention provides a device for producing a pipe section for thermal, acoustic and/or fire insulation having a body made of mineral wool and provided with a longitudinal axis and a circular cross section, an outer surface and an inner opening being arranged centrically in the body and extending through the whole body, said device comprising a support for carrying the pipe section.

Insulation elements having a body made of fibers, especially mineral fibers, preferably stone wool and provided with a longitudinal axis and a circular cross section, an outer surface and an inner opening being arranged centrically in the body and extending through the whole body are well known as fibrous tubular pipe insulation members made from mats of fibers and are used for the insulation of tubes for liquids or gases. Such tubular pipe insulation is usually made by wrapping a length of mat around a forming mandrel whose external diameter corresponds to that of the pipe to be insulated. The mat may be either pre-treated with a settable binder, which is caused to set after wrapping on the mandrel, or the material may be treated with a binder after wrapping, which is then caused to set. For many applications, a thermo setting resin binder is commonly used, and often additives are added as well. Such length of fibrous tubular pipe insulation are known as pipe sections. For convenience, one wall of the thus formed pipe section is slit through axially to enable it to be fitted over an existing pipe. For ease of handling a partial slit may also be made in the opposite wall, from the inside. Alternatively, the tube may be slit into two halves.

An apparatus for producing pipe sections on a semi-automatic basis is known. It comprises a wrapping station where binder-impregnated length of mat are cut from a roll and wrapped around individual forming mandrels. These mandrels and pipe sections are then forwarded by a conveyer through an oven, wherein the binder is caused to set. After setting the . binder, the pipe section still on their forming mandrels are forwarded by the same or another conveyor to a station at which the mandrels are removed for return to the wrapping station.

Whilst the mandrel itself accurately defines the bore of the pipe section, its external diameter and indeed its external surface appearance and distance to the centre may be difficult to control because of the somewhat ragged, fibrous nature of the starting material. The external surface of a pipe section can be shaped by using an external sleeve, preferably foraminous to facilitate setting of the binder by means of hot air streams, but this approach demands not only a large stock of mandrels, but also an even larger stock of external sleeves, since the pipe section thickness may have to be changed to meet different insulation requirements. Furthermore, the mandrel and sleeve must be kept sensibly concentric, which may present considerable handling problems in a production line process. It is also possible to smooth the outer surface of a pipe section whilst setting the binder. For example, the pipe section can be rotated on its mandrel whilst presenting its outer surface to a concaved curved stational surface which smoothes and compresses the surface of the fibrous mat. Unfortunately, fibrous mats can be of variable density and this smoothing technique may give a pipe section of non-uniform wall thickness.

According to US 4,085,548 an apparatus for manufacturing pipe sections is well known comprising an abrasive treatment apparatus with conveyor means operable to receive pipe sections mounted on their respective forming mandrels after setting the binder and to forward said pipe sections on said mandrels to an abrasive treatment station, abrading means at said station to abrade the outer surface of said pipe sections and means to rotate a pipe section, on its mandrel, in contact with said abrading means whilst maintaining a control spacing between the mandrel and the abrading means. A preferred abrading means is a grinding roller. Alternatively a finishing belt may also be used. The abrasive treatment is applied to the pipe section whilst it is still mounted on the mandrel on which it was formed and in a conventional section manufacturing apparatus, a plurality of such forming mandrels is employed, a conveyor being used to advance these mandrels through the various stages of the manufacturing process.

This well known technique has on the one hand the disadvantage that abrading the outer surface of said pipe sections results in very fine dust particles made of parts of the fibers and binder so that for example a dust extraction hood is necessary. On the other hand depending on the bulk density of the pipe sections abrading the outer surface can have the effect that bigger parts of fibers and binder can be extracted from the outer surface which gives the pipe section an outer appearance with a lot of small apertures and which in worst case reduce the thermal insulation characteristics of the pipe section. One main aspect of producing round pipe sections is the improvement of the quality of the products, in particular to improve the concentricity, i.e. the alignment of the inner surface with the outer surface. Round pipe sections often have some unalignment between the inner surface and the outer surface meaning that they are not completely parallel. This means that the central hole is not always located at the exact center of the pipe section. For the single pipe section the variation may not be important, but when more pipe sections are arranged after each other along the pipe the un-alignment becomes clearly visible, since the pipe sections show a step from one pipe section to the other. As there is no outer cladding or the outer cladding is a pre-applied alloy foil or a flexible outer cladding is applied on site such step is clearly visible and there is also the risk of technical failure in this area. Furthermore, this appearance can be qualified as low quality.

Therefore, it is one object of the invention to provide a method and a device for producing a pipe section avoiding the before mentioned disadvantages. Another object is to provide such a method and such a device with which insulation pipe sections can be produced fast and without high costs.

With respect to the method according to the invention it is proposed to bring the outer surface of the body made of fibers into contact with a cutting device having a length being at least equal to the length of the body and being arranged parallel to the longitudinal axis and to rotate the pipe section for at least 360° relative to the cutting device thereby removing any mineral wool being arranged outside a predetermined radial distance from the longitudinal axis.

The advantage of the method according to the invention is that any mineral wool being arranged outside a predetermined radial distance from the longitudinal axis can be removed very easily by cutting off the mineral wool, which can be made of mineral fibers and of binder with the cutting device which can be done in one or more consecutive cutting steps avoiding a big amount of dust. According to a further embodiment of the invention the pipe section made of mineral wool contains a binder whereby the binder is cured before any mineral wool is removed by the cutting device. Furthermore the method according to the invention can be realized in that the pipe section is moved towards a stationary cutting device, while the pipe section is rotating or in that the cutting device is moved towards the pipe section, while the pipe section is rotating. It is preferred to move the cutting device towards the pipe section which has the advantage that the cutting device can be adjusted in a predetermined distance to the longitudinal axis so that several insulation pipe sections can be treated according to the method in consecutive steps. The quality of these pipe sections is increased hereby.

The removed fibers may be returned to a recycling process for the production of fibers. The removed fibers containing a binder can be returned directly to a melting device, but it is preferred to use the removed fibers for the production of artificial stones, so-called briquettes, which are moulded from these removed fibers and used in the melting device. Alternatively, the removed mineral wool material is scattered evenly on top of a new web of uncured mineral wool that is about to be wound into a pipe section.

According to a further embodiment of the invention a cladding is applied to the outer surface of the pipe section after removing the fibers. Such a cladding can be used to realize a highly even surface of the insulation pipe section. On the other hand such a cladding can be used as a basis for a further cladding being applied to a pipe insulated with several pipe sections which covers several pipe sections and therefore the joints between two neighbored insulation pipe sections, too.

It has been of advantage to remove the mineral wool in at least two consecutive thin layers of less than 5 mm of thickness which means that the body has to be rotated for 360° for each consecutive layer which has to be removed. Removing the mineral wool in thin layers has the advantage that a resistance against the cutting device which may be a blade is decreased compared to only one cutting step within which a thicker layer has to be removed from the body of the pipe section. Furthermore it has to be highlighted that the cutting of the mineral wool takes only part in areas of the body where mineral wool is arranged outside a predetermined radial distance between the outer surface and the longitudinal axis of the insulation pipe section. As cutting device a blade, especially tightly stretched between two supports is used. Preferably the blade is movable between the two supports to endorse the cutting procedure. Furthermore it is of advantage to use a revolving blade which on the one hand cuts the mineral wool from the body and on the other hand passes through a device to sharpen the blade for the next cutting step.

With respect to the device according to the invention the before-mentioned object is solved by a cutting device with a blade for removing mineral wool from the outer surface of the body, whereby the cutting device has a length being at least equal to the length of the body, whereby the cutting device is arranged parallel to the longitudinal axis of the body, whereby the support for the cutting device is provided with a first drive for a movement of the outer surface of the body relatively and rotationally preferably for at least 360° to the cutting device and whereby the support or the cutting device is provided with a second drive for a movement of the cutting device relatively to the outer surface of the body.

Preferably the support is provided with a mandrel onto which the pipe section is placed.

According to a further embodiment of the invention the blade is provided, especially tightly stretched between two supports of the cutting device. Preferably, the blade is arranged at the supports of the cutting device in that the blade can be moved in length-wise direction of the supports from and to the pipe section. In this way the cutting device can be adjusted in a position relatively to the insulation pipe section which allows to remove any mineral wool being arranged outside a predetermined radial distance from the longitudinal axis. Furthermore, the cutting device is provided with at least one distance holder being adjustable with respect to the distance of the blade to the outer surface of the pipe section. Such a distance holder has the advantage that the distance can be pre-adjusted before several insulation pipe sections are worked on in the device resulting in several insulation pipe sections of high quality because of their exact identical dimensions.

Finally it is of advantage to provide a grinding device at the cutting device with which the blade can be sharpened.

Further features and advantages of the invention are described in the following description of the drawings. The drawings show in Fig. 1a fibrous tubular pipe section in a cut side elevation;

Fig. 1b the fibrous tubular pipe section according to fig. 1a in a view on a first face side;

Fig. 1c the fibrous tubular pipe section according to figures 1a and 1b in view on a second face side;

Fig. 2a the fibrous tubular pipe section according to figures 1a to 1c in a device for producing a pioe section in a cut side view and

Fig. 2b the device and the fibrous tubular pipe section according to figure 2a in a view on the face side.

Figures 1a to 1c show a fibrous tubular pipe section 1 having a body 2 made of mineral wool, especially of mineral fibers connected by a binding agent. The body 2 has an outer surface 3 and an inner opening 4 is arranged centrically in the body 2 and extends through the whole body 2. The pipe section 1 is used for thermal insulation of pipes.

The pipe section 1 is produced by wrapping a fibrous mat around a mandrel 5 (compare fig. 2a/2b) and it can be seen from Fig. 1a to 1c that the opening 4 is partly not arranged exactly centrically in the body 2. Figure 1a shows thicknesses S ₍ ¾, S ₃ and S ₄ of the body 2 which differ from each other. These thicknesses can also be seen in figures 1b and 1c.

As it is preferable to have a constant thickness of the body 2 over the overall length of the pipe section 1 a part of the mineral wool of the pipe section 1 has to be removed.

For this purpose the pipe section 1 is provided into a device 6 according to Figs. 2a and 2b together with the mandrel 5 which runs through the opening 4 of the pipe section 1. The mandrel 5 is connected to two supports 7 being arranged at distant ends of the mandrel 5 so that the pipe section 1 is provided between the two supports 7. The pipe section 1 is rotated by a first drive (not shown) in a direction according to arrows 8 in Fig. 2b. The device 6 can a separate device or it could be the pipe section production machine itself. Furthermore a blade 9 for removing mineral fibers from the outer surface 3 of the body is arranged between the two supports 7 whereby the blade 9 is movable to and from the pipe section 1.

With the help of two distance holders 10 the distance between the blade 9 and the pipe section 1 can be preadjusted so that the blade 9 can only be moved in the direction to the pipe section 1 until the blade 9 reaches the distance holders 10. The distance holders 10 achieve that the blade 9 is arranged exactly parallel to the longitudinal axis of the mandrel 5 and therefore with respect to the pipe section 1.

By cutting the pipe section 1 and thereby removing any mineral wool being arranged outside a predetermined radial distance S _s from the longitudinal axis a pipe section 1 with a consistent thickness of the body 2 with respect to the overall length of the pipe section 1 is achieved. It can be seen from Fig. 2a that the cutting procedure takes only part in areas where mineral wool is present outside the predetermined radial distance Ss from the longitudinal axis of the mandrel 5 and therefore of the pipe section 1.

The movement of the blade 9 to and from the outer surface 3 of the pipe section 1 is achieved by using a second drive (not shown). Furthermore the blade 9 can be operated in an endless loop (not shown). In this embodiment the blade 9 can run through a not shown grinding device which covers a part of the loop through which the blade 9 is running. In this embodiment the blade 9 can be moved constantly through the loop or in intervals.

Finally, it has to be pointed out that the supports 7 and the blade 9 form a cutting device 11. Reference list

1 pipe section

2 body

3 outer surface

4 inner opening

5 mandrel

6 device

7 supports

8 arrow

9 blade

10 distance holder

11 cutting device