Patent Application
20140064923
The present invention relates generally to a slurry pump, and, more particularly, to centrifugal slurry pump for dredging.
Centrifugal pumps are commonplace in industry and are used in a variety of pumping applications. Referring to
Of particular interest herein are pump applications involving slurries or other materials which tend to be abrasive to the pump. Such applications include, for example, dredging and mining in which soil/mud/sand in one location is mixed with water and pumped through a pipeline to a different location. In such applications, the pumps are fitted with protective liners, which are disposed between the pump impeller and the front head or cover of the pump. The pump 600 shown in
The efficiency of a centrifugal slurry pump is dependent upon the gap 610 between the impeller and the front liner 104a. This gap is set typically at the factory. As the pump is operated this gap widens due to wear. The front liner typically wears about twice as fast as the back liner. The more abrasive the material is being pumped, the more rapidly the liner wears. As the gap becomes wider, the efficiency of the pump diminished as a result of the reduction in total dynamic head (TDH). Therefore, to maintain the efficiency of the pump, the front liner must be periodically adjusted with respect to the impeller to provide an optimum gap.
There are three popular methods to adjust the gap 610 in the slurry pump back to factory specifications. The first involves moving the bearing box of the pump. Specifically, the bolts that hold down the entire bearing block of the pump assembly are loosened and the bearing block is moved towards the front liner. Then the bolts are retightened. This method takes time and it is difficult to set the gap to original factory specification. Ordinarily, maintenance personnel must remove the suction clean-out cover and reach inside the pump cavity with a feeler gauge to check the gap. Another drawback of this approach is that moving the entire bearing block can cause axial mis-alignment that can result in bearing wear and/or overheating.
Another approach to adjust the gap between the liner and the impeller is to move the front liner toward the impeller. This is accomplished by adjusting inward jacking bolts 620 which are installed through the front head 603 as shown in
Yet another approach for adjusting the gap is to disassemble the wet end of the pump. This is the least desirable method, but necessary if the pump is not configured to be adjusted by moving the bearing housing or liner as described above. This method requires removing the suction clean-out cover, and measuring the impeller/front liner gap with feeler gauges. Once the gap is determined, the entire wet end of the pump, including the impeller, is removed. Next, copper gaskets are placed behind the impeller to narrow the gap to the desired measurement, and the pump is reassembled. This is a very time consuming procedure.
Applicant has determined that the time spent in adjusting the gap between the impeller and the liner is significant and detrimental to productivity. For example, in a typical mining application, the slurry pump might have to be adjusted every 40-50 hours. The adjustment itself might take about 20-30 minutes if the bearing or liner can be adjusted. (If the pump must be taken apart, as in the last approach described above, then the adjustment may take even longer.) In addition, emptying the pipeline, shutting down the dredge, raising the ladder and then restarting the dredge, lowering the ladder, and filling the pipeline to start dredging, takes an additional 30 minutes at a minimum. If such an operation typically has two 10-hour shifts (common), the pump must be adjusted two times a week. Therefore, in one year, these pump adjustments can account for more than 100 hours in lost production. Additionally, just before an adjustment is made, the pump tends to be particularly inefficient because the gap is relatively wide.
Therefore, Applicant has identified that liner pump adjustments have a significant impact on productively and that a need exists to minimize this impact. The present invention fulfills this need among others.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later.
The present invention provides an approach for adjusting the gap between the liner and the impeller of a pump without dismantling, or even touching, the pump. Specifically, the approach relies on one or more actuators operatively connected between the front head and the liner to move the liner relative to the impeller. Not only does the use of the actuators facilitate quick adjustment of the gap, but also the actuation system to which the actuators are operatively connected provides feedback on the position of the actuators (and thus the position of liner relative to the impeller) such that the gap can be optimized for efficiency. Furthermore, in one embodiment, the actuation system is synergistically integrated with components of the machine to which the pump is connected such that few additional components are needed to control the actuators in the pump.
Accordingly, one aspect of the invention is a pump comprising a liner connected to at least one actuator to move the liner relative to the impeller. In one embodiment, the pump comprises: (a) a housing; (b) an impeller within the housing defining an axis; (c) a front head connected to the housing; (d) a liner disposed between the front head and the impeller; and (e) at least one actuator operatively connected between the front head and the liner to move the liner axially with respect to the impeller, the actuator being adapted for connection to an actuation system.
Another aspect of the invention is a method setting the gap between the liner and the impeller using the actuated pump described above. In one embodiment, the method comprises: (a) before starting the pump, actuating the actuator in a first direction such that the liner contacts the impeller; (b) actuating the actuator in a second direction a certain distance to a position to define a gap between the liner and the impeller; and (c) maintaining the actuator in the position.
a-6c depict a prior art centrifugal pump.
Referring to
Generally speaking the housing 101, impeller 102, front head 103 and liner 104 are essentially standard components, which have well known configurations and functions. The front liner 104 in the pump 100, however, is modified slightly. Instead of attaching the liner with bolts, it is attached via a plurality (for example, three or four) of actuators 105. In the embodiment, shown in
The actuators 105 may be any known mechanism for translating force (e.g. hydraulic, pneumatic, or torsional force) into lateral movement. Such mechanisms include, for example, a hydraulic piston 105a (see
The actuation system may have a variety of configurations. For example, referring to
Referring to
Referring to
The pump and acturation system combine to provide a simple and efficient approach for adjusting the gap between the liner and the impeller. In one embodiment, the pump and actuation system function to set the gap by actuating the actuator until the liner contacts the impeller. To avoid damage to the liner and impeller, this step should be conducted while the pump is idle. An indication that the liner is contacting the impeller can be provided in different ways. In one embodiment, the indication is provided by noting the change in force required to advance the actuator. This change may be noted, for example, by a sudden increase in current draw by the motor as described above, or by an increase in hydraulic pressure.
After the liner is in contact with the impeller the controller backs up each actuator the distance necessary to establish the optimum gap. Backing the actuator up a certain distance can be achieved in different ways. For example, in one embodiment, the controller notes the position of the actuator when the liner is in contact with the impeller, and then backs the actuator to a different predetermined position. Alternatively, the controller may be programmed to calculate the distance the actuator moves for a given period it is actuated. Still other approaches for setting the gap with the actuator will be known by others in light of this disclosure.
Gap adjustment can be accomplished at various times. For example, in one embodiment, the gap is adjusted by the user before dredging. For example, after starting the dredge, but prior to dredging, the operator presses a button on a control panel or joy stick. The pump is automatically adjusted to the factory setting in seconds using the process described above. In another embodiment, if the dredge is equipped with a PLC (Programmable Logic Control) the pump adjustment can be programmed to be performed as part of the normal dredge start-up sequence.
In another embodiment, the gap between the impeller and liner is adjusted dynamically by monitoring the efficiency of the pump. Specifically, in one embodiment, the power to the pump is monitored along with the pump's output. A PLC is used to continuously optimize the gap to maximize the pump's efficiency. Still other approaches for adjusting the gap between the liner and the impeller will be obvious in light of this disclose.
In yet another embodiment, the gap is adjusted using a measuring device to measure the distance between the liner and the impeller. Suitable measuring devices include, for example, lasers, acoustical, infrared, etc. Such an approach may be performed while the pump is operating or when it is idle. For example, in one embodiment, a bore hole is added to front head 103 and the front liner, thereby providing an “eye” into the pump itself. A laser measurement device is disposed on the back of the head such that it is pointed through the borehole. Once calibrated, the laser is used to measure the gap between the impeller and the liner. Although the measurement may be taken while the pump is in operation, preferably it is taken when only water is being pumped and not material which can interfere with the laser beam. To keep the measurement device from being worn or destroyed by the abrasive material, another borehole may be added diagonally through the head and connect to the bore hole through which the measurement device is pointed. An air compressor would pump air into this cavity with enough positive pressure to keep water/debris from entering.
It should be understood the pump 100 shown in
It should be understood that the foregoing is illustrative and not limiting and that obvious modifications may be made by those skilled in the art without departing from the spirit of the invention. Accordingly, the specification is intended to cover such alternatives, modifications, and equivalence as may be included within the spirit and scope of the invention as defined in the following claims.
