BACKGROUND

[0001] The present invention relates to an injection system and control for injecting high pressure fluid. More specifically, the invention relates to an injection system and control for injecting high pressure fluid that includes multiple intensifiers.

[0002] Prior injection systems provided two intensifiers or topworks to provide the necessary high pressure fluid. Each topworks typically included a plunger that reciprocated within a cylinder to provide the desired high pressure fluid at the desired pressure. To provide redundancy, some systems add one additional topworks that is maintained in a "standby" mode until it is needed. Only two of the three topworks operate at any given time to deliver the desired high pressure fluid to a downstream system

[0003] Historically, 'phase flow" pumps (ie., pumps with more man one topworks operating at other than 180 degrees out of phase, sometimes referred to as 'puke fiee") have been sold without any operating redundancy of high pressure components. In order to provide redundancy to reduce or eliminate downtime due to a pump failure, users oflen employed entire pump assemblies that were idle unless needed.

SUMMARY

[0004] In one construction, the invention provides a control strategy that offers the capability to run three topworks in sequence or to remove any one topworks from the stroke sequence for maintenance without affecting the discharge flow rate. The control strategy also provides for limited independent operation of a topworks that has been removed from the stroke sequence for maintenance activities.

[0005] The system or pump skid features three side-by-side iotensifier assemblies that operate with the same control strategy. However, the system includes a service mode feature for use when service of high pressure components is required on any one of the three topworks. With this feature, the field operator can indefinitely idle and lock out the topworks needing service without interrupting flow of high pressure fluid from the pump skid.

Furthermore, while service mode is enabled, the software allows simultaneous control of both production and service topworks. This allows the technician to control the topworks which is in service mode to purge the system and/or to draw in fresh high pressure fluid in preparation of returning the redundant topworks back into prediction Service mode is enabled from the local control paneL

[0006] In one construction, a fluid pressurizing system includes a group of three intensifiers each including a reciprocating piston operable through, a cycle at a frequency to discharge a flow of ultra high pressure fluid. The group of three intensifiers is operable in a normal mode and a service mode. In the normal mode, during each operating cycle each intensifier performs each of a discharge phase, a suction phase, an idle phase, and a precharge phase, and no two intensifiers of the group of three intensifiers performs the same phase at the same time. In the service mode, during each operating cycle one of the intensifiers operates in the idle phase and the remaining two intensifiers of the group of three intensifiers operates in one of the suction phase, the discharge phase, and the precharge phase and neither of the remaining two intensifiers performs the same phase at the same time. A controller is operable to transition the group of three intensifiers between the normal mode and the service mode and to control the phase of each intensifier.

[0007] In another construction, a method of operating a fluid pressurizing system includes arranging a group of three intensifiers to operate at a frequency to discharge ultra high pressure fluid to a common outlet during each cycle of operation The method also includes operating the group of three intensifiers in a normal mode in which each of the three intensifiers operates in one of a discharge phase, a suction phase, an idle phase, and a precharge phase and wherein no two intensifiers of the group of three intensifiers operates in the same phase at the same time. The method former includes transitioning the group of three intensifiers into a service mode in which one of the intensifiers is out of service and is continuously in the idle phase, and operating the remaiiing two ntensifiers in the service mode such that each intensifier operates in one of the suction phase, the discharge phase, and the precharge phase and neither of the remaining two intensifiers operates in the same phase at the same time. [0008] Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is a perspective view of a pump skid including three intensifiers each having an independent topworks embodying the present invention;

[0010] Fig. 2 is an enlarged perspective view of one of the intensifiers of Fig. 1;

[0011] Fig. 3 is a partially broken away perspective view of a prior art intensifiers;

[0012] Fig. 4 is a schematic flow diagram for the pump skid of Fig. 1;

[0013] Fig. 5 is a schematic illustration of the intensifiers of Fig. 1 during normal operation;

[0014] Fig. 6 is a chart illustrating the relative position of each of the intensifiers during normal operation; and

[0015] Fig. 7 is a series of charts illustrating the relative position of each of the intensifiers during operation in service mode when one of the three intensifiers is out of service.

DETAILED DESCRIPTION

[0016] Before any embodiments of the invention are explained in detail, i is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other ernbodiments and of being practiced or of being carried out in various ways.

[0017] Fig. 3 illustrates an intensifier 10 that is suitable for use with a pump skid 15 of Fig. 1. The iutensifier 10 includes a hydraulic section 20 and a high pressure unit 25 or topworks arranged along a reciprocation axis 30. The hydraulic section 20 includes a double acting piston 35 disposed within a cylinder 40 such that the piston 35 divides the cylinder 40 into two high pressure chambers 45, 50. High pressure oil is directed to one of the high pressure chambers 45, 50, while the other of the high pressure chambers 45, 50 is connected to a drain to move the piston 35 in the desired direction, at a desired rate as is known in the art. The piston 35 supports a shaft 55 that extends torn the cylinder 40 and is connected to the topworks 25 to allow the movement of the piston 35 to do the desired work.

[0018] The topworks 25 includes a plunger 60 that is disposed within a cylinder 65 and that is coupled to the shaft 55 such that movement of the piston 35 produces a corresponding movement of the plunger 60. A cylinder head 70 is positioned at one end of the cylinder 65 to seal the opening and to provide a fluid inlet and a fluid outlet As the plunger 60 is moved away from the cylinder head 70, relatively low pressure fluid is drawn into the cylinder 65. As the plunger 60 moves toward the cylinder head 70, the pressure of the fluid within the cylinder 65 is increased until the fluid is discharged through the fluid outlet

[0019] During operation of the intensifier 10 of Fig 3, a booster pump 75 provides a supply of pressurized fluid to the inlet of the topworks 25. A check valve 80 is typically positioned to inhibit entry of the pressurized fluid into the cylinder 65 until the plunger 60 begins to retract or move away from the cylinder head 70. High pressure hydraulic fluid is directed to the first of the high pressure chambers 45 to move the piston 35 and the pkmger 60 to fill the cylinder 65. Ibis is the suction portion of the stroke. High pressure hydrauhc fluid is then directed to the second of the high pressure chambers 50, with the first high pressure chamber 45 connected to the drain to reverse the direction of the piston 35. As the piston 35 and pkmger 60 move, the fluid within the cylinder 65 is compressed and discharged from the cylinder 65. This is the discharge stroke. During the discharge stroke, a discharge check valve 85 opens and the now highly compressed fluid is discharged from the topworks 25.

[0020] A single intensifier 10, such as the one illustrated in Fig. 3 is capable of delivering a desired flow at a desired pressure. However, the flow is delivered in a series of spikes or pulses rather man an even or continuous flow pattern To overcome these deficiencies, the system of Fig. 1 provides a phased flow system The phased flow system includes two or more intensifiers 10 similar to the one illustrated in Fig. 3 and arranged to operate in an out- of-sync manner to reduce the pulsing effect produced when a single intensifier 10 is employed. Typically, with two intensifiers 10, one is on a discharge stroke while the other is on an intake stroke. However, phase flow arrangements that include only two intensiilers 10 do not provide for any redundancy.

[0021] As illustrated in Fig. 1, the present invention provides a system that includes three intensifiers 10 (and in some constructions more than three) arranged in a side-by-side relationship on a single base 90. Fig. 2 illustrates one of the intensifiers 10 in greater detail Each intensifier 10 is sinilar to the intensifier 10 of Fig. 3 and includes the hydraulic section 20 and the topworks 25.

[0022] As illustrated schematically in Fig. 4, the system includes a hydraulic unit 95 that provides pressurized hydraulic fluid. Three hydraulic control valves 100 are arranged to control the flow of hydraulic fluid to and from the hydraulic section 20 of each of the intensifiers 10. Each of the control valves 100 is electronically connected to an electric control system 105. Each of the topworks 25 includes an inlet 110 that is connected to the supply of pressurized fluid and an outlet 115 that is connected to a high pressure connection that leads to a point of use 120.

[0023] In operation, the three intensifiers 10 of Fig. 1 are operated sequentially during normal operation to provide a further reduction in the pulsations when compared to a two intensifier design. In addition, because three intensifiers 10 are being utilized, the operating speed and more importantly the number of cycles per second mat the plunger 60 reciprocates within the cylinder 65 can be reduced when compared to the two intensifier design. This reduced individual duty cycle, when compared to two topworks designs, increases mean time between failures (MTBF) of the high pressure components. This results in an increase in the time between scheduled maintenance cycles, thereby reducing the cost of operation of the system

[0024] In addition, the electric control system 105 can transition the system, and specifically any one of the three intensifiers 10 into a service mode. The electric control software automatically deterrnines the precise time to remove the intensifier 10 needing service from the stroke sequence and simultaneously increase the duty cycle of the remaining two intensifiers 10. This strategy provides a seamless transition that is invisible to the downstream process. Specifically, the control software transitions the intensifiers 10 requiring maintenance to the service mode when the piston 35 is in the idle position as illustrated in Fig. 5.

5 [0025] Once transitioned to the service mode, the intensifier 10 is stroked between the suction and the discharge positions at limited speed to purge the topworks 25 of fluid before transitioning to the idle position in preparation for disassembly.

[0026] After maintenance is complete any physical lockouts are removed, and the intensifier 10 is again jogged or moved between the suction and discharge positions at limited speed to pre-charge the topworks 25 with fluid to prepare the intensifier 10 for reintroduction into the stroke sequence.

[0027] The ntensifier 10 is then moved to the idle position as illustrated in Fig. 5 and is reintroduced into the cycle at the appropriate time by the electric control 105. The duty cycle of the two intensiners 10 that were operating during maintenance is reduced to the normal duty cycle and the system begins normal three intensifier operation without affecting the downstream system.

[0028] In preferred constructions, a microprocessor-based electric control 105 is employed. However other controls such as PLCs and the like may be employed. In addition, a preferred system provides a control panel that allows the user to easily select which intensifier 10 requires maintenance and transitions that intensifier 10 to the service mode without requiring the user to open and cbse a number of valves or switches. The system automatically adjusts the duty cycle of the operating intensifiers 10 so that the system operates without any change in the pressure or quantity of high pressure fluid being produced.

[0029] Dining normal operation, each intensifier 10 operates in an out-of-sync mode to assure reduced spikes in the pressure and quantity of fluid being discharged by the system Fig. 6 illustrates the position of each of the hydraulic pistons 35 during a predetermined time period that includes two complete system cycles. Fig. 6 is not to scale but rather illustrates the relative positions of the different intensifiers. In a preferred system, each piston 35 spends about one third of its cycle in the discharge process, 25 to 40 percent of the cycle in the suction process, 20 to 40 percent of the cycle in the idle condition, and the remaining time (0 to 15 percent) in a precharge process. No two pistons 35 within the system perform the discharge process in unison such that one intensifier 10 is always discharging fluid. Actual suction, discharge, and precharge timing is calibrateable or adjustable by the user. Figures 6 and 7 show schematic stroke timing intervals to illustrate the synchronization theory. The basic phase flow strategy requites that the precharge portion of the stroke vary with discharge pressure. As the discharge pressure increases the pre- charge stroke distance increases.

[0030] Before proceeding, it should be noted that variation of the pre-charge portion of the stroke directly aflects the magnitude of the other portions of the stroke (discharge, suction and idle). Figs. 6 and 7 are schematic illustrations and do not necessarily illustrate the length of each portion of the sequence in scale. The particular process being run or the pressure the system is operating at can affect the operation such mat slightly adjusted times produce a smoother or more desirable output However, during a predetermined time period or time segment, the system, when operating in a normal mode completes two full cycles. Thus, each intensifier completes two discharge cycles and the system completes six discharge cycles in the predetermined time period.

[0031] The following table illustrates the preferred ranges of each of the operating cycles. The term "about" or "approximately" or any other tike term, when referring to these cycle portions should be interpreted as including the range described in the fo flowing table with a tolerance of 15 percent

[0032] Fig. 7 illustrates the same system with one of the intensifiers 10 in the service mode. The intensifier 10 in me service mode is identified as being idle. As can be seen, the two operating intensifiers 10 still spend about the same amount of time during the discharge, suction and precharge steps as they did in the normal mode. However, the idle portion of each cycle is eliminated, thereby allowing each topworks 25 to complete three cycles in the same predetermined time period in which two cycles are completed during normal operation. From a downstream standpoint, the system operation appears unchanged during maintenance. As with the normal operating cycle, the durations of each portion of the service mode cycles are adjustable and variable. [0033] For purposes of Ibis application, the term "high pressure" when used in conjunction with the output of the intensifiers should be considered fluid having a pressure in excess of 15,000 psi (1035 bar). Devices operating at these pressures often do not react as expected when compared to similar devices operating at lower pressures.

[0034] Thus, the invention provides, among other things, an injection system and control for irjecting high pressure fluid that includes multiple intensifiers 10. Various features and advantages of the invention are set forth in the following claims.