MX2012011512A

MX2012011512A - Phase shift controller for a reciprocating pump system.

Info

Publication number: MX2012011512A
Application number: MX2012011512A
Authority: MX
Inventors: Rudolfus Johannes Adeleida Van Rijswick; Felix Johannes Jacobus Van Osch
Original assignee: Weir Minerals Netherlands Bv
Priority date: 2010-04-07
Filing date: 2011-04-05
Publication date: 2012-11-29
Also published as: AR080839A1; US20130078114A1; CA2795538A1; DE112011101269T5; WO2011126367A2; AU2011239051A1; PE20130791A1; TW201207236A; CA2795538C; WO2011126367A3; DE112011101269B4; CN102893028B; CN102893028A; AU2011239051B2; RU2012147256A

Abstract

The present invention discloses a pump system using multiple reciprocating positive displacement pumps which phase shift is controlled by a phase shift controller. The phase shift controller uses a virtual master pump inside the phase shift controller which is used as a phase reference against which the phase shifts of the individual pumps is calculated. The phase shift controller adjusts the speed reference set-point for the variable speed drives of the individual pumps such that a desired phase shift is obtained and maintained. The operation op multiple reciprocating pumps using phase shift control can significantly reduce the pressure pulsation levels in the pump system. The use of a virtual master pump eliminates master slave scheduling and increases system reliability and availability as is the operating of the phase control is not depending on the reliability of a real master pump as is the case in prior art phase shift controllers.

Description

PHASE DISPLACEMENT CONTROLLER FOR A SYSTEM OF ALTERNATIVE PUMPS This description refers to pumps in general and, more particularly, to multiple alternative positive displacement pumps for the handling of mineral pulps.

Alternative positive displacement pumps are used to pump liquid against a relatively high pressure, for example, compared to single-phase centrifugal pumps. Other characteristics of these positive displacement pumps include their high efficiency and accuracy in the flow rate, although when compared to centrifugal pumps, they have a relatively low flow capacity. When the flow requirements of a typical application with a single pump can not be met, more positive displacement pumps can be arranged in parallel, so that their suction and / or discharge connections are connected to a single line of suction and / or discharge. This means that the summed flow of the individual pumps can satisfy the total flow requirements of the application. The combination of the individual pumps and the interconnected suction and discharge lines forms a pump system.

In the alternative pumps, an element of displacement -as for example, a piston or piston- performs an reciprocating or reciprocating motion inside the cylinder inner jacket, allowing the positive displacement of the fluid to be pumped. In a particular embodiment of the alternative pump, the reciprocating movement of the displacement element is generated by a mechanism that converts the rotary movement of the pump control to a reciprocating movement of the displacement element. Particular embodiments of this mechanism may include a crankshaft, an eccentric shaft, a camshaft or cam disc mechanisms.

In the following description, only the embodiment of the crankshaft type will be detailed, which will henceforth be referred to as a positive displacement pump driven by a crankshaft. In Figure 1, a schematic cross section of a positive displacement pump, driven by a crankshaft, 3-cylinder or triplex individual action is presented. The displacement element can directly displace the pumped fluid or displace an intermediate fluid, which displaces a flexible displacement element, which displaces the pumped fluid, such as, for example, an abrasive pulp. The description applies to one embodiment of a positive displacement pump, but since the improvement is of particular interest for the slurry positive pumps described below, the embodiment using an intermediate fluid displacement is also mentioned. and flexible, as shown specifically in figure 1.

A typical characteristic of the positive displacement pump driven by a crankshaft is the non-constant reciprocal velocity of the displacement element. Therefore, positive displacement pumps driven by a crankshaft inherently generate a flow or a non-constant flow pulsation with each revolution of the crankshaft. In Figure 2, a typical pulsation of flow generated during a revolution of the crankshaft or cycle of the pump, of a positive displacement pump in triplex of individual action is shown. According to the hydraulic response of the connected system, these pulsations of flow can derive in pulsations of pressure in the pumped fluid, which in turn can result in the vibration of the pipe and its supporting structure, through which the fluid flows. fluid, and pressure pulsations can create an unbalanced load on the pipe system.

When more than one positive displacement pump driven by a crankshaft is connected to a single suction and / or discharge inlet or outlet, an interaction may occur between the flow pulsations generated by the individual pumps. This interaction can cancel or increase the total level of pressure and flow pulsations in the pump system, once again, according to the hydraulic response of the connected system. Also, the hydraulic resonances present in the pump system can be excited by the pulsations of flow generated by each individual pump. An important parameter that determines the total pressure and flow pulsation in a given pump system is the phase shift between the crankshafts of the individual pumps. Therefore, controlling this phase shift can help control the pulsation of flow and pressure in a given pump system, using positive displacement pumps driven by a crankshaft.

This phase shift control, also called pump synchronization, is described below and is shown in Figure 3. The phase shift control requires pumps equipped with variable speed drives (VSD), which may be Use to adjust and maintain the phase shift between the pumps, by adjusting the speed of the individual controls. On the other hand, the individual pump and / or its controls are equipped with a phase sensor, which indicates the position of the pump cycle of the individual pump, which will henceforth be referred to as the individual pump phase. This information about the phase is then used by the phase shift calculator, to calculate the phase shifts between the individual pumps, which are then used by the phase shift controller to adjust the speed of the individual pumps, so that that the phase shift is adjusted to the phase shift or is maintained in this displacement.

In the prior art known, a pump included in the pump system is designated as the master pump. This master pump follows the reference point of the pump system reference speed, without any adjustment for the phase shift control. The other pumps are designated as slaves, which must follow the master pump. The phase shift controller calculates the phase difference between the master pump and each slave pump and generates a speed set point for each individual slave pump, which is based on the phase shift between the master pump and the slave pump individual, in such a way that the constant and desired phase displacement between the master pump and the slave pump is obtained and maintained.

This approach has several disadvantages: 1. The system operator has to decide which pump will operate as the master pump before starting the pump system, after which the phase shift of the slave pumps with respect to the selected master pump is determined. This can result in complex programming procedures for master / slave pumps and phase shift, which may also depend on the particular system. 2. The phase shift control is lost when the master pump is disconnected or has to be stopped. Depending on the specific embodiment of the phase shift control, it may be necessary to have to stop the entire pump system, because both the master and the slaves may have to start from the start. The reliability of the phase shift control for the complete pump system then depends on the reliability of a single pump that is designated as a master pump. 3. When the operation of the master pump is unstable - for example, due to a malfunction of the suction and / or discharge valves - oscillation of the master pump may occur. The unstable operation resulting from the master pump leads to the creation of an unstable operation in all other pumps included in the pump system and, therefore, to an unstable operation of the complete pump system.

These disadvantages constitute a particular concern with the positive displacement pumps driven by a crankshaft used in the mining and mineral processing industry, in which highly abrasive pulps are pumped. Applications in the mining and mineral processing industry require continuous operation of the pump system without unexpected stops. In addition, the disadvantages of the known arrangements make them even more of a concern in applications with high flow velocity, which are also typical for the mining and mineral processing industry.

Embodiments known and used in the prior art are normally limited to three or four pumps per pump system, for which the master / slave programming procedures are relatively simple. In addition, the total flow rate of prior art pump systems with phase shift control is limited such that the system can still operate reliably, because the unbalanced loads generated by the pulsations of pressure are relatively low and may still be acceptable in certain applications.

However, in applications that employ high volumes of pulp in the mining and mineral processing industry, it is possible to use considerably more pumps in a single pump system. Known examples typically use up to 10 pumps in a single pump system, which makes master / slave programming very complex. The larger size of the pump systems used in the mining and mineral processing industry can result in unbalanced loads, generated by pressure pulsations in the pump system in the connected pipe, reaching a magnitude such that the control of the Phase shifting is a prerequisite for reliable operation of the pump system.

In addition, it should be noted that as a result of the abrasive characteristics of the pumped pulp, which results in higher wear rates of the pump components, the period between one maintenance and the next of the positive displacement pumps for pulps can be relatively short , compared to applications where there are no pulps involved. Whenever maintenance is required on the master pump, a new pump should be designated as a master, which could require shutting down the pump system, which in turn greatly influences the availability of the entire pump system in the that a continuous operation is preferred.

The present description focuses on a solution for the described disadvantages of phase shift control systems of positive displacement pumps driven by a prior art crankshaft. In the prior art systems, an actual pump is used as a master in a master / slave control scheme, to control the phase shift between the master pump and the slave pump. The disadvantages included complex programming procedures of the master / slave pumps, lower reliability of the pump system, since it depends on the reliability of a single master pump and lower performance of the entire pump system, in case the operation of the Master pump is unstable.

The present description relates to a pump system, in which multiple positive displacement pumps are employed, where the phase shift is controlled by a phase shift controller. The phase shift controller employs a virtual master pump within the phase shift controller, which is used as a reference of the phase against which the phase shifts of the individual pumps are calculated. The phase shift controller regulates the reference speed set point for the variable speed drives of the individual pumps, so that a desired phase shift is obtained and maintained. The operation of multiple alternative pumps through the use of phase shift control can significantly reduce pressure pulsation levels in the pump system. The use of a virtual master pump eliminates the programming of master and slave pumps and optimizes system reliability and availability since the operation of the control phase does not depend on the reliability of a real master pump, as is the case in the phase shift controller of the prior art.

The virtual master pump creates a reference phase signal within the phase shift controller based on a single reference point of the pump system reference speed, in the same way as it would with a real master pump. All actual pumps in the pump system act as slaves in the phase shift controller. The phase of each individual pump is compared to the phase of the virtual master pump that is inside the controller, which is then used as an input to control the phase shift. In Figure 4, a control flow diagram for the virtual controller of the phase shift of the master pump is shown.

The use of a virtual master pump can provide certain operational improvements with respect to positive displacement phase shift control systems, driven by crankshafts. Slave pumps are always checked against the same virtual master pump, so no programming is required. The virtual master pump is considered available at all times, as it requires no maintenance and has a reliability much greater than a real mechanical pump. On the other hand, the speed of the master pump is stable at all times, since it does not affect the performance of a single master pump, which is especially useful when using a positive displacement pump to pump abrasive pulps in the industry mining and processing of minerals.

The description is not limited to single action triplex positive displacement pumps, but applies to all positive displacement, single or dual acting, single cylinder or multi cylinder cylinders.

Independently of any other form that can fit within the scope of the apparatus that is detailed in the summary, the following will describe the specific embodiments, by way of example, and with reference to the attached drawings in which: Figure 1 illustrates a schematic cross section of a single action triplex positive displacement pump of the prior art, which also shows an embodiment which employs an intermediate fluid and an additional flexible displacement element.

Figure 2 illustrates the flow pulsation of a triplex positive displacement pump, single action, of the prior art.

Figure 3 illustrates a control flow diagram of the phase control of an alternative pump of the prior art, with a master-slave control scheme employing a real pump as a master pump.

Figure 4 illustrates a control flow diagram of the phase control of an alternative pump employing a virtual master pump, in accordance with the present disclosure.

The present disclosure includes various embodiments for the individual parts of the phase shift controller. To complete, a list of some forms of realization is offered: Variable speed control The description is not limited to a particular embodiment of the variable speed control used; however, the following particular embodiments are mentioned: 1. Electropropulsores of alternating current. 2. Direct current electroproducers. 3. Diesel thrusters. 4. Hydraulic thrusters.

Phase sensor of the pump cycle The description is not limited to a particular embodiment of the phase sensor used; however, the following particular embodiments are mentioned: 1. The sensor embodiment can generate absolute phase information about the pump cycle. 2. The sensor embodiment can generate relative phase information about the pump cycle, which is combined with a reference of the zero point of the pump cycle phase. 3. The sensor embodiment can generate phase information about the pump cycle, based on the angular position of the main rotating component of the pump, which transfers the rotary control movement of the pump. to a reciprocating movement of the displacement elements, such as a crankshaft. 4. The embodiment of the sensor can generate phase information about the pump cycle, based on the linear position of one or more displacement elements present in the pump. 5. The sensor embodiment can generate phase information on the pump cycle, based on the angular position of the variable speed control, which can be directly coupled or can be coupled by means of a speed reducer, with a known reduction ratio , to the main rotating component of the pump. 6. The embodiment of the sensor can generate phase information about the pump cycle, based on a single pulse generated at a predetermined position of the pump cycle. 7. The sensor embodiment can generate phase information about the pump cycle, based on multiple pulses generated at predetermined pump cycle positions 8. The sensor embodiment can generate phase information about the pump cycle, based on multiple pulses generated at predetermined pump cycle positions, such that the number of pulses per pump cycle is equal to the number of pulses per cycle of the pump. displacement elements included in the pump 9. The embodiment of the sensor can be composed of any combination of the sensor embodiments described above.

Phase shift controller The description is not limited to a particular embodiment of the phase shift controller; however, the following particular embodiments are mentioned: 1. Analog electronic control circuit. 2. Digital electronic control circuit, based on solid state electronics. 3. Programmable controller, using microprocessor technology. 4. Programmable logic controller. 5. Inlaid microcontroller.

In the foregoing description of the preferred embodiments, specific information has been used to preserve the clarity of the concepts. However, the description is not limited to the specific terms selected in this way, and it should be understood that each specific term includes all technical equivalents that operate in a similar manner to achieve a similar technical purpose. Certain terms are used as convenient words to provide reference points and are not to be construed as limiting terminology.

The reference in this specification to any prior publication (or information derived therefrom) or to any issue that is known is not an acknowledgment or admission, nor a form of suggestion that said prior publication (or information derived therefrom) or The known subject is part of the general knowledge common in the field of interest to which this descriptive report refers and should not be taken as such.

Finally, it should be understood that it is possible to incorporate various alterations, modifications and / or additives to the various constructions and provisions of the parts, without departing from the spirit or scope of the invention.

Claims

1. A phase shift control device that is used to control the individual speed of multiple positive displacement alternative pumps, in order to obtain and maintain a desired phase shift, between the pump cycle of the individual pumps, which includes embodiments of the phase sensor for generating phase information about the pump cycles of the individual pumps, characterized in that the phase information of the individual pump cycles is compared to a virtual reference phase, which is generated within the device of phase shift control, this being a phase difference which is used to regulate the speed set points for the individual variable speed drives of the individual pumps.

2. A phase shift control device according to claim 1, characterized in that the pump contains some form of mechanism for converting the rotary movement of the pump control to a reciprocating movement of the displacement elements included in the pump, such as for example, although in non-exhaustive form, a crankshaft, an eccentric shaft, a camshaft or a cam disk.

3. A phase shift control device according to claim 1, characterized in that the variable speed control can be of the type mentioned in any of the embodiments, such as, but not limited to, AC electroproducers or continuous, diesel propellers and hydraulic thrusters.

4. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates absolute phase information about the pump cycle.

5. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates relative phase information about the pump cycle, which is combined with the reference of the zero point of the cycle phase of the pump. the bomb.

6. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on the angular position of the main rotating component included in the pump, which converts the rotary movement of the pump control in a reciprocating movement of the displacement elements, such as a crankshaft.

7. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on the linear position of one or more displacement elements included in the pump .

8. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on the angular position of the variable speed control, which can be coupled directly or by means of a speed reducer, to the main rotating component of the pump.

9. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on a single pulse generated at a predetermined position of the pump cycle.

10. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on multiple pulses generated at predetermined pump cycle positions.

11. A phase shift control device according to claim 1, characterized in that the sensor embodiment generates phase information about the pump cycle, based on multiple pulses generated at predetermined pump cycle positions, so such that the number of pulses per pump cycle equals the number of displacement elements included in the pump.

12. A phase shift control device according to claim 1, characterized in that the embodiment of the sensor is composed of any combination of embodiments of the sensor, as described in claims 4, 5, 6, 7, 8 , 9, 10 and 11.

13. A pump system employing multiple positive displacement alternative pumps, incorporating a phase shift control device according to any one of the preceding claims.

14. A method for controlling the individual speed of multiple alternative positive displacement pumps, in order to obtain and maintain a desired phase shift, between the pump cycle of the individual pumps, which comprises the following steps: generate phase information about pump cycles, individual pumps; generate a virtual reference phase within a phase shift control device; comparing said phase information of the pump cycles with said virtual reference phase; determine the phase difference between the phase information and the virtual reference phase and regulate the speed adjustment points for the individual variable speed controls of the individual pumps, based on said phase difference.