SHOWER PIPES

Abstract: A shower pipe (9) for use in the papermaking industry has a series of nozzles (13) through which jets of water are directed at a surface to be treated (for example, a filter screen or a paper­ maker's felt). To prevent the nozzles becoming blocked by par­ ticles separating out of the water (particularly when the water has been recycled), a partition (24) or insert (33) is located within the shower pipe to define a passageway of reduced cross-sectional area through which water flows to the nozzles, with a preferred minimum velocity of 8 ft/sec.

Description: The present invention relates to shower pipes and, more especially, to shower pipes for use in the papermaking industry. Showers are used at various stages in the papermaking process, for example to clean and/or recondition conveying surfaces and to clean filters that are used for treating waste water. A shower fitting commonly used in the papermaking industry comprises a hollow shower pipe which is closed or restricted at one end and connected, at the other end, to a source of cleaning/reconditioning fluid (usually water). The pipe has apertures along its length through which the cleaning/reconditioning fluid is discharged in jets, and the apertures contain nozzles to produce jets of various sizes and shapes (eg, needle-or fan-shaped). The shower can be stationary or it can move relative to the surface to be treated. For example, if the shower pipe is used to clean/recondition a papermaker's felt, it can extend across the felt and be reciprocated lengthwise. If, on the other hand, the shower pipe is used to clean a circular screen, it can extend radially outwards from the centre of the screen and rotate over the screen about an axis at the centre. Various arrangements of shower pipes of the structural type described above and arranged lengthwise across the width of a fabric belt of a papermaking machine for guiding or cleaning the belt, are, for example, described in British Patent Specification No. 1,484,681. A problem that is often encountered in shower pipes, especially those used in the papermaking industry, is blockage of the nozzle apertures. The problem occurs frequently when the fluid supplied to the shower is filtered, or otherwise recycled, water (even though individual particles remaining in the water after recycling are small enough to pass easily through the nozzle orifices) and is likely to increase with the increasing tendency, in the papermaking industry, to use recycled water and thereby reduce consumption of fresh water. The problem can be overcome by installing brushes within a shower pipe for cleaning the nozzle orifices and also the interior of the pipe, or by using so-called purgable nozzles (that is, nozzles through which a purging fluid can be passed, at intervals, to clean the nozzle orifices). These solutions are, however, comparatively complex. European Patent Application Specification No. 0174758 discloses a method for solving the problem of the blocking of spray apertures in the wash arm of a dishwater by solid particles suspended in the wash fluid. The method comprises forming the apertures or openings of a particular shape, by, inter alia , inwardly depressing a section of pipe around each opening, so as to prevent the apertures clogging. It is an object of the present invention to enable blockage of the nozzles in the apertures of a shower pipe to be avoided in a comparatively simple manner. The present invention provides shower apparatus including at least one shower pipe formed from a hollow member the interior of which has a preselected cross-sectional area, the pipe being closed or restricted at one end, the other end being for connection to a liquid supply, a liquid supply passageway extending, within the pipe, from the said other end to the said one end, a plurality of apertures being disposed along the length of the pipe, and a plurality of liquid discharge nozzles each being fitted in a respective aperture and providing communication only between the liquid supply passageway and the exterior of the pipe for discharging liquid flowing along the passageway, characterized in that, over part at least of the length of the pipe, the liquid supply passageway has a cross-sectional area less than the preselected cross-sectional area of the interior of the said member for increasing the liquid velocity, in operation, to a level sufficient to prevent the separation of solids from the liquid. Preferably, the cross-sectional area of the passageway is such that, in operation, the minimum fluid velocity in the passageway, at least at the first nozzle, is 8ft/sec (2.6m/sec). The cross-sectional area of the passageway need not be constant along its length: it may, for example, decrease towards the said one end of the pipe. The fluid passageway may be defined by at least one member located within the pipe. In one embodiment of the invention, the fluid passageway is defined by at least one partition within the pipe. In other embodiments, an insert is located in the pipe such that the remaining space within the pipe constitutes the fluid passageway. Alternatively, the pre-selected pipe may be deformed to reduce the cross-sectional area of the interior of the pipe. In the shower apparatus at least that length of the pipe in which the said discharge nozzles are provided may be unsupported. The present invention also provides a method of operating shower apparatus comprising at least one shower pipe which is closed or restricted at one end, the other end being connected to a liquid supply, and a liquid supply passageway extending, within the pipe, from the said other end to a plurality of liquid discharge nozzles along the length of the pipe; the method comprising causing liquid to flow in the passageway and being characterized by the step of restricting the cross-sectional area of the passageway to increase the liquid velocity to a level sufficient to prevent separation of solids from the liquid. The shower apparatus may include at least one shower pipe formed from a hollow member the interior of which has a preselected cross-sectional area, a plurality of apertures being disposed along the length of the pipe, and a plurality of liquid discharge nozzles each being fitted in a respective aperture and providing communication only between the liquid supply passageway and the exterior of the pipe for discharging liquid flowing along the passageway, and the method may involve arranging for the cross-sectional area of that passageway, over part at least of the length of the pipe, to be less than the preselected cross-sectional area of the interior of the hollow member by an amount such that the minimum liquid velocity in the passageway is sufficient substantially to prevent separation of solids from the liquid. By way of example, shower pipes constructed in accordance with the invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a diagrammatic illustration, partly broken away, of a filtering device incorporating several shower pipes, each being in accordance with the invention; Fig. 2 is a longitudinal cross-section through one of the shower pipes of the device of Fig. 1; Fig. 3 is a view on the line III-III of Fig. 2; Figs 4 to 6 are longitudinal cross-sections through other forms of shower pipes; Fig. 7 is a view on the line VII-VII of Fig. 6, and Fig. 8 is an end view of another form of shower pipe. The filtering device shown in Fig. 1 has a circular filter screen 1 which extends across the top of a cylindrical container 2. Liquid to be filtered flows onto the screen 1 at its periphery from a cylindrical tank 3 which surrounds the container 2. The liquid being filtered, together with any very fine solids, passes through the screen 1 and collects in the dish-shaped floor 4 of the container 2 from where it runs out through an outlet pipe 5. Solids remain on the screen 1 and are directed, by a spray of water from a rotating shower 6, towards an outlet opening 7 at the centre of the screen. The solids pass through the opening 7 and into an outlet pipe 8 for subsequent collection. The shower 6 comprises three horizontal shower pipes 9 which extend radially outwards, over the screen 1, from a shaft 10 located on the vertical axis of the container 2. The shaft 10 extends downwards from a support beam 11 located diametrically across the tank 3 and is rotated by a motor 12 mounted on the support beam. Each shower pipe 9 has a series of nozzles 13 and, in use, is supplied with water via the shaft 10 from a conduit 14. The nozzles 13 are directed inwardly towards the centre of screen 1, so that the jets of water from the nozzles will urge solids on the screen towards the outlet opening 7. Filtering devices of the type shown in Fig. 1 are known and are used in, for example, the papermaking industry for treating waste water. To reduce consumption of fresh water, the shower 6 is often supplied with filtered or otherwise recycled water. The construction of a shower pipe 9 is shown in greater detail in Figs. 2 and 3. The inner end 20 of the pipe is open and, in the device shown in Fig. 1, is connected to the rotatable shaft 10 by an angled pipe 21. The outer end 22 of the pipe is closed. The nozzles 13 are located in apertures in the pipe and, as already mentioned, are inclined so that the spray of water from the nozzle orifices 23 is directed inwards towards the centre of the screen 1. The nozzles 13 shown in Figs. 2 and 3 are of a basic form and would normally be of more complex construction selected to produce spray jets of a required shape and size. The cross-sectional diameter D of the pipe 9 is determined mainly by structural and manufacturing considerations. Thus, the requirement that the pipe should not bend under the weight of water that it carries, despite being unsupported at its outer end, together with the requirement that installation of the nozzles 13 should not present undue difficulty, generally imposes a predetermined minimum value on the cross-sectional diameter D . Typically, if the pipe length is 450 mm the minimum internal diameter would be 26.5 mm. The shower pipe 9 as so far described is generally effective but it is found that the nozzle orifices 23 can become blocked during use, despite the fact that the water supplied to the shower pipe has been filtered and that any particles remaining in the water are small enough to pass through the nozzle orifices. Investigation shows that the problem can very largely be overcome by decreasing the effective cross-sectional area of the flow path within the pipe 9, thereby increasing the velocity of the water within the pipe. The pipe 9 itself, however, remains of the predetermined minimum size selected to meet the structural and manufacturing requirements described above. The effective cross-sectional area of the pipe 9 can be decreased in a number of ways, one of which is illustrated in Figs. 2 and 3. An elongated partition 24 is inserted into the pipe to divide the bore of the pipe, lengthwise, into two spaces 25, 26 one of which (26) contains the nozzles 13. Bolts 27 inserted through the wall of the pipe 9 into the second space 25 and in a direction perpendicular to the partition 24, contact the partition 24 and urge it into contact, along each side, with the internal surface of the pipe. The end of the space 25 adjacent the inlet end 20 of the shower pipe is closed by an end piece 28. Water entering the shower pipe 9 is now confined to the space 26 and flows to the nozzles 13 with increased velocity. It is thought that the increase in velocity discourages any particles in the water from separating out and subsequently collecting together to block the nozzle orifices 23. Preferably, the cross-sectional area of the passageway formed by space 26 is such that the water has a minimum velocity of approximately 8 ft/sec (2.6 m/sec), at least at the first nozzle 13 a , and the location of the partition 24 is selected accordingly. In the arrangement illustrated in Figs. 2 and 3, the passageway 26 is of constant cross-section along its length. In some circumstances, however, it may be advantageous to vary the cross-sectional area of the passageway 26 and, in particular, to decrease the area towards the outer end of the pipe, where the flow of water is reduced. Preferably, the decrease in cross-sectional area of the passageway 26 is such that a minimum flow velocity of 8ft/sec (2.6m/sec) is maintained along its length. This can be achieved by, for example, using two partitions 29, as shown in Fig. 4, the combined length of the partitions being comparable to the length of the single partition 24 of Figs. 2 and 3. One partition 29 is narrower than the other so that it will sit lower down in the pipe 9 (as seen in the drawings): this partition is located at the outer end of the pipe and that part of the space 25 defined by this partition is closed by an end piece 31. The second partition 30 is then inserted in the pipe with one end adjacent the end piece 31 and that part of the space 25 defined by this partition is closed by an end piece 32. The flow passageway 26 of this arrangement is of reduced cross-sectional area towards the outer end of the pipe 9, the reduction occurring abruptly at the junction between the partitions 29, 30. It will be appreciated that a similar arrangement having more than two partitions could be employed if required. It may, for example, be desirable to have a reduction in the cross-sectional area of the passageway 26 in the region of each of the nozzles 13. Another arrangement, in which the cross-sectional area of the flow passage 26 reduces continuously along the length of the pipe, is shown in Fig. 5. In this case the pipe 9 contains a solid insert 33 the cross-section of which increases continuously towards the outer end of the pipe. The insert 33 can be formed by, for example, pouring a suitable material into the pipe and allowing the material to harden while the pipe is held at an angle to produce the required taper. Bolts 34 inserted through the wall of the pipe, in this case into the flow passage 26, contact the insert 33 and hold it in position. It will be appreciated that the insert 33 need not be tapered but could have a constant cross-section along the length of the pipe. Figs. 6 and 7 show another arrangement in which the pipe 9 contains a solid insert but, in this case, the insert is formed before it is located in the pipe. The insert comprises a rod 35 having a circular cross-section which substantially fills the pipe. Part of the rod is machined away to form a channel 36 through which water flows to the nozzles. The channel 36 is shown as having a constant cross-section along the length of the rod 35 but it could have a decreasing cross-sectional area towards the outer end of the pipe 9. Instead of using an insert to reduce the effective cross-sectional area of the pipe 9 the pipe itself can be deformed, for example as illustrated in Fig. 8. Such a shower pipe is only suitable for use at low pressures because of the weakening effect of the deformation. The degree of deformation can vary along the length of the pipe so that the effective cross-sectional area of the pipe reduces towards its outer end. Although the shower pipes described above are all intended for use with a circular filter in a device of the type shown in Fig. 1, similar shower pipes could be used to clean/recondition other filters or conveying surfaces. For example, a shower pipe similar to any one of those shown in the drawings could be mounted to extend across a papermaker's felt, the shower being brought into operation as required to direct a spray of liquid at the felt and restore the permeability of the felt to a required value. A shower of this type is described, for example, in European Patent Specification No 0 009 399. Moreover, although the shower pipes 9 are described as being of particular use in showers for the papermaking industry they are also of use in any similar shower apparatus utilizing filtered water. Finally, it will be understood that, although each of the shower pipes described above has a circular cross-section (at least initially), this is not essential and cylindrical pipes of non-circular cross-section could be used.

Claims: Shower apparatus including: at least one shower pipe formed from a hollow member the interior of which has a preselected cross-sectional area, the pipe being closed or restricted at one end, the other end being for connection to a liquid supply, a liquid supply passageway (26) extending, within the pipe, from the said other end to the said one end, a plurality of apertures being disposed along the length of the pipe, and a plurality of liquid discharge nozzles (13) each being fitted in a respective aperture and providing communication only between the liquid supply passageway and the exterior of the pipe for discharging liquid flowing along the passageway, characterized in that, over part at least of the length of the pipe, the liquid supply passageway (26) has a cross-sectional area less than the preselected cross-sectional area of the interior of the said member for increasing the liquid velocity, in operation, to a level sufficient to prevent the separation of solids from the liquid. Shower apparatus as claimed in claim 1, in which the cross-sectional area of the passageway (26) is such that, in operation, the minimum liquid velocity in the passageway, at least at the first nozzle, is 8ft/sec (2.6m/sec). Shower apparatus as claimed in claim 1 or claim 2, in which the cross-sectional area of the passageway (26) is not constant along its length. Shower apparatus as claimed in claim 3, in which the cross-sectional area of the passageway (26) varies along its length in such a manner that, in operation, the minimum liquid velocity in the passageway is 8ft/sec (2.6m/sec). Shower apparatus as claimed in claim 3 or claim 4, in which the cross-sectional area of the passageway (26) decreases towards the said one end of the pipe. Shower apparatus as claimed in claim 5, in which the cross-sectional area of the passageway (26) decreases continuously towards the said one end of the pipe. Shower apparatus as claimed in any one of the preceding claims, in which the liquid passageway (26) is defined by at least one member (24) located within the pipe. Shower apparatus as claimed in claim 7, in which the liquid passageway (26) is defined by at least one partition (24) within the pipe. Shower apparatus as claimed in claim 8, in which the liquid passageway (26) is defined by two or more partitions (29,30) within the pipe, each partition defining a length of the passageway having a respective cross-sectional area. Shower apparatus as claimed in claim 7, in which the liquid passageway (26) is defined by an insert (33) so located in the pipe that the remaining space within the pipe constitutes the liquid passageway. Shower apparatus as claimed in claim 10, when appendant to any one of claims 3 to 6, in which the cross-sectional area of the insert (33) varies along its length. Shower apparatus as claimed in any one of claims 1 to 6, in which the said hollow member is deformed to reduce the cross-sectional area of the interior of the member, and in which the interior of the deformed member (Fig. 8) constitutes the liquid supply passageway. Shower apparatus as claimed in any one of the preceding claims, in which at least that length of the pipe in which the said discharge nozzles are provided is unsupported. A method of operating shower apparatus comprising at least one shower pipe which is closed or restricted at one end, the other end being connected to a liquid supply, and a liquid supply passageway extending, within the pipe, from the said other end to a plurality of liquid discharge nozzles along the length of the pipe; the method comprising causing liquid to flow in the passageway and being characterized by the step of restricting the cross-sectional area of the passageway to increase the liquid velocity to a level sufficient to prevent separation of solids from the liquid. A method as claimed in claim 14 of operating shower apparatus including at least one shower pipe formed from a hollow member the interior of which has a preselected cross-sectional area, a plurality of apertures being disposed along the length of the pipe, and a plurality of liquid discharge nozzles each being fitted in a respective aperture and providing communication only between the liquid supply passageway and the exterior of the pipe for discharging liquid flowing along the passageway, the method involving arranging for the cross-sectional area of that passageway, over part at least of the length of the pipe, to be less than the preselected cross-sectional area of the interior of the hollow member by an amount such that the minimum liquid velocity in the passageway is sufficient substantially to prevent separation of solids from the liquid. A method as claimed in claim 15 in which the minimum liquid velocity in the passageway, at least at the first nozzle, is 8 ft/sec (2.6 m/sec).

Inventors: BLOYCE, LIONEL TERRENCE, HUDON, JAMES DENIS
Applicants: ALBANY INTERNATIONAL CORP.
Application year: 1987
Main classification: D21F1
IPC codes: D21F1