WO1994027106A1

WO1994027106A1 - Apparatus for countering deposition on a conduit

Info

Publication number: WO1994027106A1
Application number: PCT/IE1994/000024
Authority: WO
Inventors: Robert John Spencer; John Glynn
Original assignee: Envirecon Services Limited
Priority date: 1993-05-07
Filing date: 1994-05-06
Publication date: 1994-11-24
Also published as: EP0707702A1; AU6687594A; IN184672B

Abstract

The invention concerns an elongate rod (10) for countering deposition on a conduit (12), the rod (10) being adapted for insertion and location in the conduit (12) and having a substantially helical, longitudinally extending groove (34). When the rod (10) is non-hollow, the groove (34) is on an external surface of the rod (10). Alternatively, when the rod is hollow, the groove is located on an internal surface of the rod and the rod is optionally provided with an additional groove on the external surface of the rod.

Description

APPARATUS FOR COUNTERING DEPOSITION ON A CONDUIT

The problem of deposition of, for example, scale caused by hard water in fluid conduits associated with fluid flow systems such as water wells, heat exchangers, injection moulding machines, air conditioning systems, vacuum pumps, compressor cooling systems, condensors, refrigeration systems, general and sea water cooling circuits and steam boilers is well known. In severe cases, substantial deposition in fluid conduits, pumps and other equipment associated with the fluid flow system may occur and this can eventually cause operational problems.

Bothersome mineral materials found in fluids would include calcium bicarbonate, calcium carbonate, calcium sulphate, magnesium sulphate, sodium salts, silica, alumina, iron and manganese salts and free sulphur.

Our Irish Patent Specification No. 39035 describes a solution to the deposition problem, by providing an elongate rod for countering deposition on and wear of a conduit by flow of fluid therethrough, the rod being adapted for insertion into the conduit and having a substantially triangular cross-section, each side thereof having a longitudinally extending outwardly concave arcuate surface, and wherein a plurality of projections are provided which extend outwardly from each surface, said projections being disposed perpendicularly in the direction of fluid flow along each said surface in use. However, one problem with this apparatus is that the elongate rod itself becomes covered with deposited materials during use, so that its effectiveness diminishes over a period of time and eventually stops.

It is an object of the invention to provide an apparatus for countering deposition on a conduit, which apparatus is more resistant to deposition on itself.

According to the invention there is provided an elongate rod for countering deposition on a conduit, the rod being adapted for insertion and location in the conduit, characterised in that the rod has a substantially helical, longitudinally extending groove.

Preferably, the rod is non-hollow and the groove is on an external surface of the rod.

Alternatively, the rod is hollow and the groove is on an internal surface of the rod.

Preferably, the rod is provided with a longitudinally extending passageway therethrough, the groove being located about the passageway.

More preferably, the rod is additionally provided with a groove on the external surface of the rod.

Even more preferably, the rod is provided with end regions which serve to locate, in use, the rod in the conduit.

Advantageously, the end regions are substantially triangular in cross-section, the apices of the end regions serving to locate, in use, the rod in the conduit.

Advantageously, the rod comprises an alloy of copper, zinc, nickel and tin, and incidental impurities.

More advantageously, the rod comprises, by weight, 40-50% copper, 20-30% zinc, 15-25% nickel and 9-15% tin, and incidental impurities.

The invention also provides a combination of an elongate rod as hereinabove defined and a conduit adapted to receive the rod.

Preferably, a washer is provided, which washer is located, or is adapted to be located, within the conduit to secure the rod in the conduit.

Two embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a first embodiment of an elongate rod according to the invention in a partially cut-away conduit section;

Figure 2 is a transverse section along line II-II of Figure 1 ; and

Figure 3 is a transverse section of a second embodiment of an elongate rod according to the invention.

In the drawings, similar numerals have been used to indicate like parts.

Referring now to Figures 1 and 2 of the accompanying drawings, there is illustrated a first embodiment of an elongate rod 10 according to the invention for countering deposition on a conduit 12. The rod 10 is tapered at one end to form a head 14 to offer as little resistance as possible to fluid flow over the head 14 by promoting a smooth fluid pressure transition. The other end or tail 16 of the rod 10 is flat, thereby promoting a high local fluid pressure drop, which in turn aids in releasing acid-forming gases.

Adjacent the head 14 and the tail 16, the rod 10 is provided with end regions 18, 20 which are substantially triangular in cross-section, with sides 22, 24, 26. The end regions 18, 20 include longitudinally extending apices 28, 30, 32 at the intersections of sides 22 and 24, 24 and 26, and 26 and 22. The apices 28, 30, 32 serve to locate, in use, the rod 10 in the conduit 12. Lugs (not shown) may extend outwardly from, for example, apex 28 to accommodate variations in the inner diameter of the conduit 12 in which the rod 10 is to be inserted.

A substantially helical groove 34 is provided on an external surface of the rod 10 intermediate the end regions 18, 20. In use, as the fluid flows along the rod 10 in the region of the groove 34, laminar fluid flow is inhibited and helical fluid flow is promoted, thereby increasing fluid turbulence. Increased fluid turbulence and the attendant mixing effect enhances the extent of surface contact between the rod 10 and the fluid, thereby increasing the effective fluid contact area of the rod 10. As the fluid flows along the groove 34, it is thought that the fluid is subjected to localised pressure rises and drops, as well as localised pH rises and drops. The localised pressure drops aid in releasing dissolved acid-forming gases such as carbon dioxide and hydrogen sulphide which, it is thought, decrease scaling tendancies and influence the amount of precipitate formed. Increased turbulence also inhibits deposition on the rod itself. The rod 10 is preferably installed in the conduit 12 and is retained therein by a friction or press fit between the apices 28, 30, 32 and the inner wall 36 of the conduit 12.

Referring now to Figure 3 of the accompanying drawings, there is illustrated a second embodiment of a rod 110 according to the invention. The rod 110 is retained in the conduit 112 by a circumferential washer 38 welded or otherwise secured to the inner wall 136 of the conduit 112 adjacent the end region 118 of the rod 110. When the washer 38 is used as the retaining means, the rod 110 preferably has a shoulder (not shown) on the end region 118, so that the head 114 projects through the washer 38 with the shoulder engaging the inwardly facing surface of the washer 38. The rod 110 may also be provided with a circumferential washer (not shown) welded or otherwise secured to the inner wall 136 of the conduit 112 adjacent the end region 120.

In the alternative embodiment, the rod 110 has a central longitudinally extending passageway 40, which constitutes an additional fluid flow channel. The passageway 40 has a substantially helical groove 42 therein. In use, as fluid flows along the groove 42 of the passageway 40, helical fluid flow is promoted and thus fluid turbulence is increased.

In use, the rod 10, 110 is inserted in the conduit 12, 112 and retained in place by, for example, washers or welding and, thus retained, is installed in a fluid flow system, such as a water well, or a steam boiler, without having to modify the fluid flow system. Generally, the diameter of the conduit 12, 112 corresponds to the diameter of the tubing of the fluid flow system, unless a smaller diameter conduit 12, 112 is necessary to ensure a minimum flow rate over the rod 10, 110. The conduit 12, 112 may have means, such as external threads (not shown), for installing the conduit 12, 112 in the fluid flow system with the rod 10, 110 already positioned in the conduit 12, 112.

Alternatively, the conduit 12, 112 may be welded or otherwise fluid-tightly inserted and secured into the fluid flow system. The fluid is caused to flow over the head 14, 114 of the rod 10, 110, whereupon it divides over the head 14, 114 to flow through three channels 44, 144; 46, 1 6; 48, 148 bounded by the sides 22, 122; 24, 124; 26, 126 and the inner wall 36, 136. Fluid is then caused to flow along the substantially helical groove 34, 134. If a central passageway 40 is present, fluid is also caused to flow along the substantially helical groove 42. Turbulent flow and localised pressure fluid rises and drops occur, causing mixing and extensive contact between the fluid and the rod 10, 110, so that polarisation of the minerals in the fluid occurs. Efficient polarisation is achieved by virtue of the substantially helical configuration of the groove 34, 134 and the groove 42, if present, which grooves promote turbulent flow and afford a large surface area for fluid contact.

It will be appreciated that, although the washer 38 is only shown in connection with the hollow rod 110 shown in Figure 3, it can equally well be employed with the solid rod 10 shown in Figures 1 and 2. Similarly, the rod 10 shown in Figures 1 and 2 may have a longitudinally extending passageway with a groove therein similar to the passageway 40/groove 42 shown in Figure 3. Alternatively, it is envisaged that the rod according to the invention shown in Figure 3 may not necessarily have the groove 134 in the external surface of the rod 110 and the rod is so shaped that fluid flow is primarily directed through the passageway 40. Such a rod could take the form of a hollow tube, having the groove 42 on its inner surface and adapted to engage the conduit 12, 112 at its outer surface.

The rod 10, 110 can be manufactured in lengths of from about 20cm to 1 metre and in widths suitable for insertion in conduits having internal diameters ranging from 0.8cm to 35cm. Generally, the length of the rod increases as the diameter of the rod increases.

It will be appreciated that the groove(s) may be cut into the rod according to the invention or, alternatively, extend outwardly from the rod according to the invention.

It will also be appreciated that the rod's dimensions are ideally chosen to prevent any significant drop in the flow rate, or pressure, of the fluid flowing through the conduit 12, 112. It will also be appreciated that, as the diameter of the rod increases, the rods become quite massive and may become an impediment or restriction to flow through the conduit. Accordingly, it may be desirable that a longitudinally extending passageway is formed in the rod (as is shown in Figure 3) to provide an additional fluid flow channel and, at the same time, an additional surface area.

The rod 10 or 110 is preferably formed of an alloy of copper, zinc, nickel and tin by melting the alloy at between 1 ,000-1 ,500°C and then sand casting the rods to the desired shape. Preferred rod compositions comprise, by weight, 40-50% copper, 20-30% zinc, 15-25% nickel and 9-15% tin, and incidental impurities. Rods having compositions in the aforementioned ranges have been found to be non-sacrificial or only slowly sacrificial with expected useful lives in normal use of up to about 10 years.

Without wishing to be bound to any particular theory of operation, it is believed that the mechanism of operation is that the alloy has a very high surface activity, due to a reaction between the phases of the alloy, which promotes a rise in pH very close to the rod's surface and attracts mineral ions to the rod's surface, thereby triggering the early formation of, for example, calcium carbonate seed crystals by creating local areas of supersaturation in the fluid. It is believed that the precipitated calcium carbonate is in the form of stable aragonite crystals, which are unlikely to be deposited on conduits or, if deposited, are more easily removed than the calcite crystals which are normally formed.

It will be appreciated that, by using a substantially helical groove(s), it is possible to greatly increase the amount of surface area that is available for reaction between the alloy of the rod and the fluid, specifically, by more than 50%, when compared with an elongate rod of similar dimensions as claimed in our earlier Irish Patent Specification No. 39035.

Despite the substantial increase in reactive surface area of the elongate rod according to the present invention, the volume taken up by the elongate rod according to the present invention is reduced, when compared with the elongate rod as claimed in our earlier Irish Patent Specification No. 39035. This reduces the obstruction and the amount of head loss in the fluid flow system, so that less pump energy is required to pump the fluid around the fluid flow system.

It will further be appreciated that the increased turbulence over the groove(s) causes active fluid mixing which in turn both increases contact between the fluid and the rod 10,110 and reduces the risk of deposition on the rod itself.

Claims

CLAIMS :

1. An elongate rod (10; 110) for countering deposition on a conduit (12;112), the rod (10; 110) being adapted for insertion and location in the conduit (12;112), characterised in that the rod (10; 110) has a substantially helical, longitudinally extending groove (34;134,42).

2. An elongate rod (10) as claimed in Claim 1 , wherein the rod (10) is non-hollow and the groove (34) is on an external surface of the rod (10).

3. An elongate rod (110) as claimed in Claim 1 , wherein the rod (110) is hollow and the groove (42) is on an internal surface of the rod (110).

4. An elongate rod (110) as claimed in Claim 3, wherein the rod (110) is provided with a longitudinally extending passageway (40) therethrough, the groove (42) being located about the passageway (40).

5. An elongate rod (110) as claimed in Claim 4, wherein the rod (110) is additionally provided with a groove (134) on the external surface of the rod (110).

6. An elongate rod (10;110) as claimed in any one of the preceding claims, wherein the rod (10;110) is provided with end regions (18,20; 118, 120) which serve to locate, in use, the rod (10; 110) in the conduit (12; 112) .

7. An elongate rod (10; 110) as claimed in Claim 6, wherein the end regions (18,20;118, 120) are substantially triangular in cross-section, the apices (28,30,32;128,130,132) of the end regions (18,20,-118,120) serving to locate, in use, the rod (10;110) in the conduit (12;112).

8. An elongate rod (10;110) as claimed in any one of the preceding claims, wherein the rod (10;110) comprises an alloy of copper, zinc, nickel and tin, and incidental impurities.

9. An elongate rod (10;110) as claimed in Claim 8, wherein the rod (10;110) comprises, by weight, 40-50% copper, 20-30% zinc, 15-25% nickel and 9-15% tin, and incidental impurities.

10. A combination of an elongate rod (10;110) as claimed in any one of the preceding claims and a conduit

(12;112) adapted to receive the rod (10;110).

11. A combination as claimed in Claim 10, wherein a washer (38) is provided, which washer (38) is located, or is adapted to be located, within the conduit (12;112) to secure the rod (10;110) in the conduit (12;112).