AUSTRALIAN COMPLETE PATENT SPECIFICATION Title: A PUMP PRIMING ASSEMBLY Applicant: Weir Minerals Australia Ltd The invention is described in the following statement which includes the best method known to us: 2 A PUMP PRIMING ASSEMBLY Technical Field 5 The present disclosure relates to pump priming assembly and particularly relates to priming assemblies for use with centrifugal pumps. The disclosure has particular application to centrifugal pumps used in remote locations such as in mining applications. 10 Background Art Most centrifugal pumps are not self priming. This means that the pump casing must be filled with liquid before the pump is started. If the casing becomes filled with vapours or gases, then the impeller is said to be "gas-bound" and is incapable of 15 pumping. To ensure that centrifugal pumps remain primed, they are typically installed at a location below the level of the source from which the pump is to take its suction. In some applications, it is not possible to locate a pump below the level of the source, for instance, in the case of a mine dewatering pump, the pump may be mounted on a floating platform that floats on top of, or is positioned on ground alongside of, the 20 body of water that is to be pumped. In such applications a pump priming arrangement is used. One known pump priming arrangement includes a priming vessel that is in fluid communication with the inlet side of a centrifugal pump. A vacuum pump is in turn connected to the priming vessel. By drawing air from the priming vessel with the 25 vacuum pump, the inlet side of the pump becomes filled with a head of fluid. The level of fluid in the priming vessel must be carefully controlled so that the head of fluid in the priming vessel is of a sufficient height to adequately prime the pump. Further, the level must not be raised too far, as this brings the risk that fluid will be drawn from the priming vessel by the vacuum pump which can cause significant 30 damage to the vacuum pump. In one known arrangement, electronic fluid level sensors have been provided in association with a pump priming tank, and the vacuum pump has been provided with a magnetic clutch. The output of the electronic sensors is used to engage or disengage the vacuum pump by switching of the magnetic clutch. However, this arrangement can be 35 problematic to fix or maintain as a skilled electrician is needed to service and repair the electrical components of the priming system. Further, the use of electrical components and magnetic clutch incurs significant cost.
3 In other known arrangements, it has been tried to control the level in the priming vessel by a mechanical valve arrangement actuated by a float. However, in the case of pumping fluids such as mud or sludge, then these mechanical arrangements can become fouled and operate incorrectly. 5 There remains a need for an improved pump priming arrangement. Summary of the Disclosure In a first aspect, embodiments are disclosed of a pump priming assembly including: 10 - a priming vessel for holding a head of fluid for pump priming, the priming vessel including a removable lid assembly; - the lid assembly including a lid, a boom mounted at the underside of the lid, and a flotation device mounted to the boom to move the boom in response to changes in the level of fluid in the priming vessel; 15 - the lid assembly further including an air valve arrangement which is mounted to the boom and including a vacuum supply valve and an atmospheric air valve; - the vacuum supply valve being openable to put the priming vessel in fluid communication with a vacuum source to remove air from the priming vessel; - the atmospheric air valve openable to put the priming vessel in fluid 20 communication with the atmosphere to allow air to enter the priming vessel; and wherein movement of the boom operates the air valve arrangement, to thereby control the level of fluid in the priming vessel. By providing a mechanical fluid level arrangement, the sophistication and expense of an electronic arrangement is avoided. Further, by providing the air valve 25 arrangement and boom on the underside of a removable lid, the lid can be removed to facilitate cleaning. Should the pump priming assembly become fouled by mud or sludge or the like, then the lid can be removed, thus exposing all moving parts of the pump priming arrangement mounted on the underside of the lid for easy cleaning, adjustment or replacement. 30 In one embodiment, the air valve arrangement may be operable to open both of the vacuum supply valve and the atmospheric air valve simultaneously. In one embodiment, the boom can be pivotably mounted to the lid. In a second aspect, embodiments are disclosed of a method of retrofitting a priming vessel including the steps of: 35 - providing a removable lid assembly according to claim 1; and - retrofitting the lid assembly to the priming vessel.
4 Brief Description of the Drawings Notwithstanding any other forms which may fall within the scope of the apparatus as set forth in the Summary, specific embodiments will now be described, by 5 way of example, and with reference to the accompanying drawings in which: Figure 1 is a side view of a mine dewatering apparatus including a pump priming assembly in accordance with one embodiment; Figure 2 is a side view of the lid of the pump priming apparatus of Figure 1; and 10 Figure 3 is an end view of the lid of Figure 2. Detailed Description of Specific Embodiments Referring to Figure 1, a mine dewatering apparatus 10 is shown which includes 15 a diesel engine 14 to which is mounted a centrifugal pump 12 so that the engine 14 drives the pump 12. The diesel engine and pump combination are mounted to skid 16. In use, the pump 12 draws fluid in through inlet 18, which is connected to a large bore suction pipe (not shown). In one application, the skid 16 is mounted onto a floating platform and the suction pipe hangs down from inlet 18 into the body of water upon 20 which the skid is floating. The outlet of pump 12 is connected to an outlet pipe (not shown) which is laid out to end at the location where the fluid is to be pumped to, such as away from the mine area, or into a holding tank or outflow. A pump priming assembly 20 is mounted to the inlet 18 and includes a pump priming vessel in the form of priming tank 22 and a lid assembly 24. An opening in the 25 base of priming tank 22 corresponds with an opening in the inlet pipe 18 (not visible) to allow fluid in the inlet pipe 18 to be drawn up into the priming tank 22. A vacuum pump 15 is mounted to the diesel engine 14 and is continuously run during operation of the engine 14 by way of a drive belt that passes around both the shaft of the engine 14 and the shaft of the vacuum pump 15. A vacuum line 17 joins the vacuum pump 15 to 30 the lid assembly 24. The vacuum generated by the vacuum pump 15 provides a region of low air pressure in the top of priming tank which serves to suck water from the source, up through the inlet pipe 18 and into the priming vessel 22. Referring to Figures 2 and 3, the lid assembly 24 of Figure 1 is shown removed from the pump priming assembly 20 and includes a lid 26 which in use is mounted to 35 the pump priming tank 22 in an air tight manner by fastening bolts through apertures 23. An opening is provided in the form of vacuum connection 28 which connects to the vacuum line 17 seen in Figure 1. An air valve arrangement is provided in the form of 5 vacuum valve 36 and vacuum valve seat 38 and atmosphere valve 40 and atmosphere valve seat 42. A fluid level detection device is provided in the form of a spherical ball float 32 attached to a boom arm 34. The boom arm 34 is pivotally mounted to the lid 5 assembly 24 by way of bush 35. In use the fluid level detection device detects changes in the level of the fluid in the priming tank 22 by way of the angle of the boom arm 34. As the fluid level rises and falls, the buoyancy of the float 32 causes the angle of boom arm 34 to change. This movement operates the air valve arrangement to control the level of fluid in the tank by maintaining the fluid at a predetermined optimum level. 10 Each of the vacuum valve 36 and the atmospheric valve 40 are mounted on threaded rods and fixed to the boom arm 34 by way of threaded fasteners. This allows fine adjustment of the height of the valves 36, 40. In Figure 2, the assembly is shown as it would appear with no fluid in the priming tank 22. The weight of the float 32 and boom arm 34 acts to force the atmosphere valve 40 closed against valve seat 42. The 15 height of valve 40 has been adjusted by way of the screw threaded arrangement so that the boom arm is horizontal when the atmosphere valve 40 is closed. In this position, it is to be noted that vacuum valve 36 is open. The height of the vacuum valve has been adjusted so that there is a clearance of approximately 3mm (1/8 inch) between the vacuum valve 36 and its corresponding valve seat 38. 20 It is undesirable to allow fluid to enter the vacuum pump 15 as this can cause damage to the vacuum pump. In this regard a condensation baffle 30 is provided to block water droplets that may form as condensation inside the vacuum connection. Further, a splash guard 31 is provided about the vacuum valve seat 38. As explained above, the vacuum pump 15 is permanently engaged with the 25 output shaft of the diesel engine 14 and operates continuously along with the diesel engine 14. When the dewatering apparatus 10 is delivered and installed on-site, the inlet 18 and priming tank 22 are empty of fluid. When the diesel engine 14 is turned on, the pump 12 rotates but is gas-bound and so does not draw fluid into inlet 18. The vacuum pump 15 operates along with engine 14 and applies a vacuum to the vacuum 30 connection 28. This vacuum sucks air from the priming tank 22 and causes fluid to be drawn slowly up into inlet 18 and to fill the casing of the centrifugal pump 12. After a certain amount of filling, the pump 12 becomes primed to a sufficient extent to effectively pump the fluid and a normal pumping operation can be commenced. At this stage, fluid continues to be drawn into priming tank 22 until it reaches 35 its predetermined optimum height. It is to be noted that the priming tank extends above the height of centrifugal pump. This allows a head of water to be maintained inside the priming tank 22 which is at a level above the casing of the centrifugal pump 12 to 6 ensure that the pump 12 is adequately primed for subsequent pump starts. As the fluid level rises towards the top of the priming tank 22 , the float is moved upwards by the fluid, and the boom arm 34 is caused to rotate in an anticlockwise direction as shown in Figure 2. This causes the atmospheric valve 40 to 5 move away from atmospheric valve seat 42. This puts the inside of the priming vessel 22 into fluid communication with the atmosphere outside. Air can now enter tank 22 by way of the aperture in the valve seat 42. At this stage, the vacuum pump 15 draws air from the tank through vacuum valve seat 38 at the same time that air is allowed to enter at atmospheric valve seat 42. 10 Should the water level rise still further in tank 22, then boom arm 34 rotates further in an anti-clockwise direction and thus causes the vacuum valve 36 to close against the vacuum valve seat 38. The vacuum supply is thus isolated from the priming tank. Air enters through atmospheric valve seat 42 to permit the water level in tank 22 to fall. 15 As the fluid level falls in the priming vessel, the float 32 drops downwards and causes the boom arm 34 to rotate in a clockwise direction as seen in Figure 2. This causes the vacuum valve 36 to move away from the vacuum valve seat 38 thus putting the priming vessel into fluid communication with the vacuum pump. At this stage, both valves 36, 40 are open again. 20 Should the level of fluid in the tank 22 fall still further, then the boom arm 34 rotates further in a clockwise direction to close the atmospheric valve 40 against valve seat 42. The tank is again put under vacuum pressure and fluid is drawn into the tank 22. In this manner, the combination of float 32, boom arm 34, and valve 25 arrangement 36, 40 operate to maintain an optimum head of fluid in tank 22. The use of two valves, one controlling the vacuum supply, and one controlling the admission of atmospheric air, which operate either alone or together provides a smooth transition of pressures in the tank 22 ranging from vacuum pressure to atmospheric pressure. This in turn provides for well controlled fluid level in the tank. 30 Fine adjustments to the levels at which the valves cut in and out can be effected by way of adjusting the height of the valves with respect to the boom arm 34 by way of their screw threaded mountings. Should the pumping arrangement remove water from the source faster than it enters the source, then the pump 12 will suck air in through inlet 18 and the pump 12 35 will run dry. Thus the pump 12 will lose its prime. However, the diesel engine continues to run with a dry pump 12. In this mode, the vacuum pump 15 will again act to draw water slowly into inlet 18 and when a sufficient level is reached, pumping will 7 commence again. The apparatus 10 may thus be left unattended and will automatically re-prime itself as and when more fluid becomes available at the source to pump. As part of a regular maintenance schedule, the lid 23 is removed to gain access to the level detector and valves and these can be cleaned and adjusted appropriately as 5 required. In further embodiments the boom arm and float can be of any particular shape and configuration which can achieve the cyclical level control operation described hereinabove. The apparatus is not confined to applications involving diesel engines or pumps mounted to a skid, but can be used in a range of pump priming situations. 10 In one arrangement, the lid assembly 24 can be provided and sold separately for fitting (or retrofitting) to a pump priming tank 22, perhaps in situations where a pre existing electronic control system is being replaced. It can be seen that embodiments disclosed have at least the following advantages: 15 e No electrical components are utilised in the priming arrangement, thus avoiding the need for maintenance staff with electrical qualifications and avoiding the need to maintain an inventory of spare electrical components for servicing. 0 Simplified construction is cheaper to fabricate than prior art arrangements using electrical sensing techniques. 20 Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated. Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention. 25