GB2531873A

GB2531873A - Quick priming pumps

Info

Publication number: GB2531873A
Application number: GB1514283.9A
Authority: GB
Inventors: James Beer William; Heslop Jonathan; Randall Jack; Peter Walker Samuel
Original assignee: Gilbert Gilkes & Gordon Ltd
Current assignee: Gilbert Gilkes & Gordon Ltd
Priority date: 2014-11-01
Filing date: 2015-08-12
Publication date: 2016-05-04
Also published as: GB201419526D0; GB201514283D0

Abstract

A quick prime pump with two reservoirs 5, 14, one communicating with the inlet pipework 2A, 2B, and the other communicating with both the outlet pipework 18 and a part of the pump body 17. These two reservoirs supplement the held water in the inlet pipework so that the pump body can remain largely full of water and so operate at, or near, full efficiency, thus priming the pump quickly and maintaining a permanent flow of coolant to the engine. Once primed the reservoirs fill naturally from the water in the system. Preferably the pumping system is used in a ships engines cooling system.

Description

QUICK PRIMING PUMPS

This specification relates to pumps which are used intermittently and where the liquid being pumped drains out of a part of the system during periods of non-use so that the pump has to re-prime itself when restarted. One particular application relates to the pumps providing cooling water to the engines on ships, such as ferries, where the engines are always being used on a stop / start basis.

Pumps have thousands of uses in domestic and industrial applications. One common usage is to provide the cooling for internal combustion engines. In many cases, these are closed systems, e.g. as in cars, where the heat removed from the engines is discharged to the ambient air via the radiator, i.e. the same water is continuously recirculated. On ships, open cooling systems are preferred, where water from the sea, lake or river in which the ship is floating, is drawn in, used to cool the engine and discharged back to the sea, lake or river, i.e. the water is used once in a single pass. Though engines are mounted low in ships' hulls, they are usually above the waterline and, while the water intakes are well submerged, it is normal for the water to drain out of part of the cooling system, through the intakes, when the engine is not in use.

Fig. 1 shows a typical marine installation in which cooling water is drawn in through inlet pipework 2 from an intake 2C (not shown), via a riser 2A, over an inverted U-bend 2B via downcomer 3 and axial inlet pipe 4 to inlet manifold 8A of a pump 8. Pump 8, and its associated system, provides cooling water via pipes 12 and 18 to a ship's engine (not shown). In such an installation, it is normal for the engine, though mounted low in the ship for stability requirements, to be above the water line. As pump B is normally driven 11 via a power take-off 10 from the engine via seal 13, this too will be above the water line typically about 1m (39-40 inches) above.

The result of this arrangement is that, when the engine is switched off, pump 8 also stops and, after a while, some of the water drains out of the cooling system, in particular out of inlet pipe 2A. The presence of inverted U-bend 2B stops all the water draining out and, in a traditional system shown, only pipes 3, 4, pump 8 and outlet pipe 12 will remain essentially full up to the level of the bottom of inverted U-bend 2B. When the engine (not shown) is restarted, impeller 9 of pump 8 will rotate 11 and the water in pipes 3 and 4 will be pumped into outlet pipes 12 and 18. This will generate a reduction in pressure in pipes 2, 3 and 4, drawing fresh water in via intake 2C (not shown).

Unfortunately, as the water is pumped into pipe 12, impeller 9 starts to churn a mixture of air and water. Under these conditions pump 8 operates inefficiently, generating a much smaller reduction of pressure in pipes 2, 3 and 4 but also retaining some of the water in pipe 12. This situation persists for a period of time until, eventually, water 2C rises up pipe 2A over bend 2B and floods pipes 3 and 4, thus priming pump 8. While pump 8 is priming itself, an air-water mixture, is churning around in pump body 17. Often there is so much air in the pump body that the water can barely act as a seal and the suction head is well down, prolonging the priming period. Other problems of the air-water mixture churning around in pump 8 is that it could possibly cause cavitation damage to the pump internals, and the engine (not shown) is running without adequate cooling, particularly if it is still warm.

Clearly, neither of these is desirable and, on a stop / start vessel such as a ferry, damage can occur on a cumulative basis.

A ship's engine, and any system which could lead to it failing, e.g. the cooling system, are Level 1 Systems' (failure of which could cause loss of the ship and of life) that must be designed to the highest engineering standards. Thus, there is an urgent need for pumps which can prime themselves extremely rapidly to minimise the damage that might otherwise occur to both engine and pump.

According to the invention, there is provided a quick-priming pump comprising:-i) a water intake; ii) inlet pipework connecting the intake to the pump; iii) a first reservoir communicating with the inlet pipework; iv) a manifold fast with the inlet pipework through which water is fed to the pump inlet; v) a pump adapted to create a reduced pressure in its inlet and able to draw in water and / or air-water mixtures from the inlet pipework into the pump body and pump the water or air-water mixtures out through the pump outlet and into the outlet pipework; vi) means to provide a rotary drive to the pump; vii) a second reservoir communicating both with the pump outlet pipework or adjacent pipework and the pump body; and viii) a tangential outlet from the pump connecting the pump to the outlet pipework and thence to the means of using the water thus pumped; characterised in that: a) when the pump is started the impeller turns in water held within the pump body and a part of the inlet pipework and, being full of water, generates its maximum reduction of pressure in the inlet pipework, drawing in fresh water through the intake and pumping the held water into the outlet pipework; and b) when all the held water in the inlet pipework has been drawn into the pump and passed through it, the pump progressively draws in air from the inlet pipework and water from the first and second reservoirs thus maintaining the body of the pump largely full of water so that it continues to generate close to its maximum reduction in inlet pressure and continues to draw in fresh water through the intake until the inlet pipework is full and fresh water is being drawn directly into the pump while also maintaining a continuous flow of water into the outlet pipework; and c) when the inlet pipework is fully primed, the air in the first reservoir is progressively replaced by water and the replaced air is passed via the pump into the outlet pipework while the pump continues to supply water to the outlet pipework; and further characterised in that the slow downward motion of the water in the second reservoir allows air bubbles in the air-water mixture which entered the second reservoir 15 from the outlet pipework to rise upwards and be discharged back into the outlet pipework without being recirculated through the pump; and further characterised in that during and after the priming process, the pump is full or largely full of water so that the air drawn into the pump from the inlet pipework and first reservoir enters as a stream of bubbles, as opposed to in large slugs, thus enabling the pump to operate essentially at / near its design rating throughout the whole priming process and at its full rating thereafter; and further characterised in that the second reservoir is a chamber, separate from the outlet pipework, and communicating with the outlet pipework via only a minor aperture so that the presence of the second chamber and minor aperture do not materially cause any reduction in the output head generated by the pump.

According to a first variation of the apparatus of the invention, the water intake is located below the pump inlet.

According to a second variation of the apparatus of the invention, the inlet pipework includes an inverted U-shaped part, the apex of which is above the pump inlet.

According to a third variation of the apparatus of the invention, the first reservoir communicates with the inlet pipework via a first connection at the top of the first reservoir and also via a second connection at the bottom of the first reservoir.

According to a fourth variation of the apparatus of the invention, the manifold feeds water axially into the pump.

According to a fifth variation of the apparatus of the invention, the pump drive means is a 5 power take off from an engine.

According to a sixth variation of the apparatus of the invention, the pump outlet and outlet pipework are essentially tangential to a radius from the pump axis.

According to a seventh variation of the apparatus of the invention, the second reservoir is wholly or mostly located above the axis of the pump.

According to an eighth variation of the apparatus of the invention, the second reservoir communicates with the outlet pipework via a connection at the top of the second reservoir.

According to a ninth variation of the apparatus of the invention, the second reservoir also communicates via an orifice with a part of the pump manifold where, while priming, the pressure in that part of the manifold is lower than that inside the second reservoir adjacent to said orifice According to a tenth variation of the apparatus of the invention, water from the second reservoir is drawn into the pump manifold during the priming process.

According to an eleventh variation of the apparatus of the invention, the orifice between the second reservoir and the pump manifold is replaced by a non-return valve to prohibit back flow from the manifold into the second reservoir.

According to a twelfth variation of the apparatus of the invention, air bubbles in the second reservoir rise and are discharged into the outlet pipework via the connection to said outlet 30 pipework.

According to a thirteenth variation of the apparatus of the invention, air is separated from the water in the second reservoir by virtue of its lower density.

According to a fourteenth variation of the apparatus of the invention, air-water mixtures are discharged via the outlet pipework during priming and immediately after priming and water alone is discharged thereafter.

According to a fifteenth variation of the apparatus of the invention, the first and second reservoirs refill themselves automatically as the priming process becomes complete and remain essentially full when water drains out of the inlet pipe.

According to a sixteenth variation of the apparatus of the invention, the cutwater in the pumping volute is located below the horizontal plane through the axis of the impeller.

According to a seventeenth variation of the apparatus of the invention, the cutwater is located at an angle of 30° below the horizontal plane through the axis of the impeller.

A preferred application of the apparatus of the invention is to a ship's engine cooling system, part of which will drain when the engine is switched off. A first reservoir is provided communicating with the inlet pipework and a second reservoir communication both with the outlet system and also, via an orifice, with a part of the pump inlet manifold. The first reservoir has a volume essentially equivalent to that of the pipework which has drained so that, before the first reservoir has emptied completely, fresh water will be coming over the U-bend and flooding into the pump inlet. Not only do the reservoirs provide more water for use during the priming process but the location and connections to the inlet and outlet pipework maintain the pump body largely full of water during the priming process so that the pump essentially generates nearly its full suction head throughout the whole priming process. This greatly shortens the time to prime the pump minimising the risk of damage to either pump or engine.

Because the pump is essentially full of water during the whole priming process, the air from the inlet pipework passes through the primed pump as a stream of bubbles rather than as large slugs. Thus, as the stream of bubbles enters the volute, it is spun around violently by the impeller to give the equivalent of an essentially uniform emulsion of small bubbles in water. This enables the pump to generate close to its maximum suction head throughout the whole priming process and so minimise the time required for the operation.

Optionally the orifice is replaced by a non-return-valve.

For a clearer understanding of the invention and to show how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawing in which:-Figure 1 is a diagrammatic representation of a typical example of a ship's engine cooling

system (Prior Art);

Figure 2 is a diagrammatic representation of one example of the apparatus of the invention.

Figure 3 is a diagrammatic sectional representation of a conventional pump volute showing the position of the cutwater (Prior Art); and Figure 4 is a diagrammatic sectional representation of an example of the pump volute of the apparatus of the invention showing the changed position of the cutwater.

In the following description, the same reference numeral is used for the same component in different Figures and / or for different components fulfilling identical functions.

Referring to Fig. 2, assume that quick priming system 1 is shut down and all water above the level of the bottom of U-bend 2B and from pipe 2A has drained out. Additionally, two reservoirs 5 and 14 have been added to the traditional system shown in Fig. 1. Reservoir 1 has a volume approximately equivalent to that of pipe 2A. Water will be held in the pipework below the bottom of U-bend 2B and in reservoirs 5 and 14. When pump 8 is started 11, it will be full of water and generate its maximum reduction in pressure in manifold 8A, pipes 4, 3, U-bend 2B and pipe 2A, so that water is drawn in via intake 2C (not shown). The water held in pump 8 and pipes 3, 4 is pumped into outlet pipes 12, 18 and on to cool the engine (not shown). As soon as the last held water leaves pipe 4, it is replaced by water from reservoir 5 via pipe 7 and from reservoir 14 via orifice 16.

Thus, because the body of pump 8, pipe 4 and manifold 8A remain largely full of water, the pump operates at near its maximum efficiency drawing in fresh water via intake 2C, up pipe 2A and over U-bend 2B and down into manifold 8A essentially before reservoir 5 has emptied. Additional water is supplied by reservoir 14, via orifice 16. Thus, pump 8 remains largely full of water until it is fully primed. After this, the residual air in pipe 3 and reservoir 5 is progressively drawn in as a stream of bubbles into volute 30 rather than as large slugs. The violent rotation 11 of impeller 9 breaks up the stream of air bubbles into microbubbles in the water so that the mixture is essentially homogeneous. While it is incorrect to describe this air microbubble-water mixture as a 'single phase', it does act as essentially a single phase (compared to conventional priming (Fig. 1) with slugs of air in the water) so that the suction head produced by pump 8 will be only slightly reduced and hence water will continue to be drawn in, via intake 2C (not shown), at a high rate.

It is important to compare this with what happens in the traditional system (Fig. 1). As all the held water passes through pump 8, large slugs of air are ingested 8A and impeller 9 will be churning around in an air-water mixture containing, perhaps, as little as 50% water. The action of impeller 9 pumps water and air slugs upwards 23 into pipe 12, emptying much of the water in volute 30. As pump 8 cannot work when largely full of air, this results in a reduced output pressure from pump 8 so that some of the water falls back down pipe 12 10 into volute 30. This enables impeller 9 to generate more output pressure, pump the water back up pipe 12 and so the process is repeated. Thus, volute 30 is full of a two phase mixture, e.g. 50% water, 50% air, with which it works inefficiently, creating a greatly reduced suction head to draw in fresh water via the intake 2C (not shown).

Water is incompressible but air is highly compressible so that much of the reduced suction head generated by impeller 9 (Fig. 1) is absorbed by expansion of the air in pump 8 and the reduction in pressure in inlet pipework 2, 3 and 4 is much less than normal leading to drawing in water via intake 2C at only a sluggish rate, i.e. the priming process takes an extended period of time during which time no cooling water is being fed to the engine (not shown). In contrast, each of the microbubbles in the essentially single phase air microbubble-water mixture is relatively much less affected by changes in pressure and each microbubble is likely to retain its own identity so that the mixture remains as essentially a single phase, allowing pump 8 to continue to operate at only a slightly reduced efficiency, i.e. still drawing fresh water into intake 2C at a relatively high rate and passing coolant to the engine (not shown).

A further feature of the invention is the position of the cutwater in the pump volute. Fig. 3 shows the standard prior art arrangement in which cutwater 31 is aligned essentially horizontally 34 with the impeller axis (i.e. the axis of shaft 10). Tests have shown that moving the position of cutwater 32 to a position below the horizontal axis 34 (Fig. 4) improves the suction that is generated during the priming period. An angle 33 of about 30° has been found empirically to be near the optimum. The precise hydrodynamics of how the changed location of cutwater 32 generates greater suction heads during priming is not known but may be related to the essentially single phase air microbubble-water mixture.

The volumes of reservoirs 5 and 14 are more than adequate to supply pump 8 during the whole of the priming process.

The air-water mixture 23 pumped up outlet pipe 12 passes round bend 19, where some of it goes upward 25, 27 in pipe 18 and some goes down 26, via inlet 15 into second reservoir 14. Inlet 15 is a small aperture in outlet pipe 12, 18 so that it allows water or air / water 26 into reservoir 14 but does not materially affect the outlet flow 25 or 27. As shown (Fig.2), inlet 15 is in the bottom of outlet pipe 12, 18 and does not materially affect the geometry of the right-left double bend in pipe 12, 18.

At the bottom of reservoir 14 is a small orifice 16 communicating with part 17 of inlet manifold 8A. When the pressure at 17 is less that that at the bottom of reservoir 2 (shown by height 30), there will be a small flow from reservoir 14 into part 17 of manifold 8A. This flow is indicated by short arrow downward 28. However, any air bubbles carried 26 into reservoir 14 from circulation 23, 24 will rise rapidly (long arrow 29) through slow moving flow 28 and pass out through aperture 15 into flow 27. Thus, no air will be recirculated through pump 8A, so that the pumping efficiency will remain high during the whole priming process.

After priming, there could be a flow through orifice 16 into reservoir 14, when pump 8 had built up its full head. As this would reduce the overall efficiency of pump 8, a non-return valve (not shown) is preferably substituted for orifice 16. This would allow full, or partial, 20 flow during the priming process but stop the flow once it was complete.

The apparatus of the invention should allow the priming to be completed in less than 60 seconds compared to typical times of around 2 minutes or more for the traditional (Fig. 1) design. This is a very significant improvement and will contribute greatly to the reliability 25 and longevity of both pump and engine.

It is a feature of the invention that inlet 15 into reservoir 14 is a small aperture, faired into the wall of outlet pipe 12, 18, i.e. not much bigger that orifice 16. During priming, there will be a small flow 26 through inlet 15 to replace that which is passes through orifice (or non-return valve) 16. Immediately after priming, residual bubbles in reservoir 14 will rise 28 and exit inlet 15 into flow 27 and, once this process is complete, there will be no flow through inlet 15 so that outflow 23, 27 will continue essentially unaffected by the presence on inlet 15, i.e. effectively the full head generated by pump 8 will be available to pass cooling water to the engine (not shown).

Claims

Claims:- 1. According to the invention, there is provided a quick-priming pump comprising:-i) a water intake; ii) inlet pipework connecting the intake to the pump; iii) a first reservoir communicating with the inlet pipework; iv) a manifold fast with the inlet pipework through which water is fed to the pump inlet; v) a pump adapted to create a reduced pressure in its inlet and able to draw in water and / or air-water mixtures from the inlet pipework into the pump body and pump the water or air-water mixtures out through the pump outlet and into the outlet pipework; vi) means to provide a rotary drive to the pump; vii) a second reservoir communicating both with the pump outlet or adjacent pipework and the pump body; and viii) a tangential outlet from the pump connecting the pump to the outlet pipework and thence to the means of using the water thus pumped; characterised in that: a) when the pump is started the impeller turns in water held within the pump body and a part of the inlet pipework and, being full of water, generates its maximum reduction of pressure in the inlet pipework, drawing in fresh water through the intake and pumping the held water into the outlet pipework; and b) when all the held water in the inlet pipework has been drawn into the pump and passed through it, the pump progressively draws in air from the inlet pipework and water from the first and second reservoirs thus maintaining the body of the pump largely full of water so that it continues to generate close to its maximum reduction in inlet pressure and continues to draw in fresh water through the intake until the inlet pipework is full and fresh water is being drawn directly into the pump while also maintaining a continuous flow of water into the outlet pipework; and c) when the inlet pipework is fully primed the air in the first reservoir is progressively replaced by water and the replaced air is passed via the pump into the outlet pipework while the pump continues to supply water to the outlet pipework; and further characterised in that the slow downward motion of the water in the second reservoir allows air bubbles in the air-water mixture which entered the second reservoir from the outlet pipework to rise upwards and be discharged back to rise upwards and be discharged into the outlet pipework without being recirculated through the pump; and further characterised in that during and after the priming process, the pump is full or largely full of water so that the air drawn into the pump from the inlet pipework and first reservoir enters as a stream of bubbles, as opposed to in large slugs, thus enabling the pump to operate essentially at / near its design rating throughout the whole priming process and at its full rating thereafter; and further characterised in that the second reservoir is a chamber, separate from the outlet pipework, and communicating with the outlet pipework via only a minor aperture so that the presence of the second chamber and minor aperture do not materially cause any reduction in the output head generated by the pump.
2. A quick priming pump, as claimed in claim 1, wherein the water intake is located below the pump inlet.
3. A quick priming pump, as claimed in claim 1, wherein the inlet pipework includes an inverted U-shaped part, the apex of which is above the pump inlet.
4. A quick priming pump, as claimed in claims 2 and / or 3, wherein the first reservoir communicates with the inlet pipework via a first connection at the top of the first reservoir and also via a second connection at the bottom of the first reservoir.
5. A quick priming pump, as claimed in any preceding claim, wherein the manifold feeds water axially into the pump.
6. A quick priming pump, as claimed in any preceding claim, wherein the pump drive 25 means is a power take off from an engine.
7. A quick priming pump, as claimed in any preceding claim, wherein the pump outlet and outlet pipework are essentially tangential to a radius from the pump axis.
8. A quick priming pump, as claimed in any preceding claim, wherein the second reservoir is wholly or mostly located above the axis of the pump.
9. A quick priming pump, as claimed in claim 8, wherein the second reservoir communicates with the outlet pipework via a connection at the top of the second reservoir.
10. A quick priming pump, as claimed in claim 9, wherein the second reservoir also communicates via an orifice with a part of the pump manifold where, while priming, the pressure in that part of the manifold is lower than that inside the second reservoir adjacent to said orifice.
11. A quick priming pump, as claimed in claim 10, wherein water from the second reservoir is drawn into the pump manifold during the priming process.
12. A quick priming pump, as claimed in claim 10, wherein the orifice between the second reservoir and the pump manifold is replaced by a non-return valve to prohibit back flow from the manifold into the second reservoir.
13. A quick priming pump, as claimed in claims 8-12, wherein air bubbles in the second reservoir rise and are discharged into the outlet pipework via the connection to said outlet pipework.
14. A quick priming pump, as claimed in claim 13, wherein air is separated from the water in the second reservoir by virtue of its lower density.
15. A quick priming pump, as claimed in claim 1, wherein air-water mixtures are discharged via the outlet pipework during priming and immediately after priming and water alone is discharged thereafter
16. A quick priming pump, as claimed in any preceding claim, wherein the first and second reservoirs refill themselves automatically as the priming process becomes complete and remain essentially full when water drains out of the inlet pipe.
17. A quick priming pump, as claimed in any preceding claim, wherein the cutwater in the pumping volute is located below the horizontal plane through the axis of the impeller
18. A quick priming pump, as claimed in claim 17, wherein the cutwater is located at an angle of 30° below the horizontal plane through the axis of the impeller.
19. A quick priming pump, as described in and by the above statement with reference to the accompanying Figures 2 and 4.