GB2458825A - Bending stress monitoring system for piston rod - Google Patents

Abstract

A piston rod assembly 12 for coupling between a power end 18 and a fluid end 20 of a reciprocating pump consists of a pair of clamping members 22, 24 and a tensioning device. The clamping members 22, 24 have a first end adapted to be coupled to the power 18 end component of the pump and a second end for coupling to the fluid end 20 component of the pump. The tensioning device 34a, b generates a force to secure the power and fluid ends 18, 20 against release. Preferably the tensioning device is in the form of a piston 34a,b. Preferably a monitoring system is provided for indicating that the piston rod is experiencing bending stress. The monitoring system may include a number of sensors 52a, b coupled to the piston rod assembly 12, for providing an output indicative that the piston rod assembly 12 is experiencing bending stress, which occurs in the event that the piston rod assembly becomes misaligned, in use of the pump. The sensors may be load sensing washers 52a, b.

Description

1 MONITORING SYSTEM 3 This invention relates to reciprocating pumps such as 4 those used to pump drilling mud in the oil and gas exploration and production industry, including those 6 pumps commonly referred to in the industry as mud and 7 slush pumps. In particular, the present invention 8 relates to a monitoring system to determine misalignment 9 in the piston rod assembly and in the cross-head mechanism of such pumps.

12 Within a typical reciprocating pump there is arranged a.

13 piston rod assembly which provides a connecting piston 14 rod between the primary dynamic component of the pump's fluid end, the piston, and the dynamic components of the 16 pump's power end. The assembly comprises a power end 17 component, a fluid end component and a connector which is 18 coupled to both end components. Due to the abrasive 19 nature of the slurries which pumps utilised in the oil and gas exploration and production industry must handle 21 and the high reciprocating pressure of such pumps, the 22 piston requires regular replacement and as such the 1 piston rod assembly must be accessible and be easily 2 uncoupled.

4 This arrangement therefore provides a link over a distance between the cross-heads of the fluid end and the 6 power end of the pump. Accordingly, the pump must be 7 correctly set-up so that no bending force will be induced 8 in the piston rod assembly or in the cross-heads that 9 produce axial motion from rotary movement in the power end of the pump.

12 Figure 1 illustrates the link and cross-heads in a 13 typical high pressure (H.P.) reciprocating pump. In 14 Figure 1(a), the cross-heads A,B and the linking piston rod assembly C all lie on a central axis D and are thus 16 aligned. This is the correct set-up. As will be 17 apparent from Figure 1(b), when a misalignment E occurs 18 in the cross-head assembly A, large bending moments and 19 side-thrust are induced in the piston rod assembly C and in the cross-head mechanism B. In turn, the high side 21 loadings are transmitted back into the gear train that 22 drives the cross-heads A,B. All of the afore-mentioned 23 high stresses will typically result in high wear and, not 24 infrequently, failure of the entire drive mechanism, causing the pump to be shut down for a lengthy re-build 26 to be carried out. A misaligned cross-head will also 27 result in premature wear in pistons and cylinder liners.

28 This can result in the abrasive drilling fluid migrating 29 past piston seals and causing damage to components of the pump.

32 It is therefore amongst the objects of at least one 33 embodiment of the present invention to provide a 1 monitoring system for a reciprocating pump to detect 2 bending stresses.

4 It is also amongst the objects of at least one embodiment of the present invention to provide a piston rod assembly 6 for a reciprocating pump which includes stress detection.

8 According to a first aspect of the present invention, 9 there is provided a monitoring system for a reciprocating pump of a type comprising a fluid end component, a power 11 end component, and a piston rod assembly extending 12 between the fluid and power end components, the 13 monitoring system comprising at least one sensor adapted 14 to be coupled to the piston rod assembly, for providing an output indicative that the piston rod assembly is 16 experiencing bending stress.

18 Preferably, the monitoring system comprises an indicator 19 or indicator means coupled to or otherwise operatively associated with the at least one sensor, for signalling 21 that the piston rod assembly is experiencing bending 22 stress.

24 The at least one sensor may be arranged in parallel to a central axis of the piston rod assembly.

27 The at least one sensor may be a stress-measurement 28 sensor.

The pump may be a high pressure reciprocating pump.

32 According to a second aspect of the present invention, 33 there is provided a monitoring system for a high pressure 1 reciprocating pump, the system comprising one or more 2 stress-measurement sensors, the one or more sensors being 3 arranged in parallel to a central axis through a piston 4 rod assembly located between a fluid end component and a power end component, and indicator means for signalling 6 to a user that the assembly is under bending stress.

8 Preferably the one or more sensors are strain gauges.

9 When the piston rod assembly experiences a bending load (due to misalignment) and thus a bending stress, this may 1]. cause consequent strains to be generated within the 12 piston rod assembly. Accordingly, by providing a sensor 13 in the form of a strain gauge, a detected strain may 14 indicate that the piston rod assembly is experiencing a bending load/stress, and is thus out of alignment. It 16 will be understood that, during normal operation of the 17 pump (when the piston rod assembly is in correct 18 alignment), there may be negligible detectable strain in 19 the piston rod assembly. In particular preferred embodiments, the at least one sensor may comprise or take 21 the form of a semiconductor strain gauge, such as those 22 commercially available from Kyowa Electronics Instrument 23 Company of Japan. Sensors of this type provide outputs 24 up to 500 tunes greater than other types of strain gauges, such as resistance strain gauges, and are of 26 particular utility in the present invention, where the 27 strains induced in a piston rod assembly through 28 misalignment are relatively small.

Alternatively, the one or more sensors may be load 31 sensing washers or any other suitable sensors. If 32 desired, a combination of types of sensors may be 33 provided.

1 Preferably the one or more sensors are located at points 2 distal to and thus spaced from a central axis of the 3 piston rod assembly. In this way the earliest warning of 4 stress can be given. For example, strains and bending stresses in the rod assembly increase away from the 6 central axis of the piston rod assembly. Accordingly, by 7 spacing the sensor as far as possible from the central 8 axis, the output of the sensor may be optimised.

9 Additionally, access to the sensor for maintenance/ replacement may be facilitated.

12 Preferably the system includes a power supply. The power 13 supply may be remote to the pump. In this way, all parts 14 of the system except the sensors can be remote from the pump and one or more cables for connection can be run 16 between them. Alternatively the system includes a signal 17 amplifier, the amplifier being mounted with the power 18 supply at or near the pump, such that sensor signals are 19 transmitted to a remote data processing unit.

21 The indicator/indicator means may comprise an audible 22 warning system which provides an audible signal when a 23 sensor records a stress measurement over a pre-deterinined 24 level. Optionally the indicator includes a visual display. The indicator may be local or remote from the 26 piston rod assembly.

28 The system may comprise a connector for coupling the at 29 least one sensor to a remote location, in particular to the indicator. The connector may be a cable, wire or the 31 like. The at least one sensor may be coupled to the 32 indicator, which may take the form of a personal computer 33 (PC) or the like, for data storage, review and/or 1 analysis. In an alternative, the system may comprise a 2 data transmission device for transmitting data from the 3 sensor to a remote location. For example, the data 4 transmission device may be adapted to transmit data to the indicator, which may be a PC, to facilitate 6 generation of a signal indicative that the piston rod 7 assembly is experiencing bending stress. The data 8 transmission device may comprise a transmitter for 9 transmitting an electromagnetic signal (such as a radio frequency or microwave signal) and a suitable remote 11 receiver. This may avoid a requirement to provide a hard 12 connection between the sensor and the remote location.

14 The system may additionally comprise a data recordal device for recording data from the at least one sensor.

16 This may facilitate monitoring of data output from the 17 sensor over a period of time, which may indicate that the 18 piston rod assembly is approaching a condition where it 19 is out of alignment. The data recordal device may comprise a chart recorder or plotter.

22 The system may include attachment means so that the 23 system can be retro-fitted to existing piston/power rod 24 assemblies. The attachment means may be adhesive.

Alternatively the attachment means may be a mechanical 26 connection.

28 According to a third aspect of the present invention, 29 there is provided a piston rod assembly for coupling between a power end and a fluid end of a reciprocating 31 pump, the piston rod assembly comprising: 32 a power end component; a fluid end component; 1 at least one clamping member having a first end adapted 2 to be coupled to the power end component and a second end 3 adapted to be coupled to the fluid end component, for 4 coupling the power and fluid end components together; and a tensioning device for generating a force to secure the 6 power and fluid end components against release.

8 The piston rod assembly may comprise a monitoring system 9 for indicating that the piston rod assembly is experiencing bending stress. In preferred embodiments, 11 the monitoring system may comprise a monitoring system 12 according to the first or second aspect of the present 13 invention.

The at least one clamping member may be arranged relative 16 to a rod axis between the power and fluid ends. The 17 tensioning device may be a tensioning means and may 18 comprise a piston adapted to provide a load orthogonal to 19 an axis of the piston rod assembly to thereby secure the power and fluid end components against release.

22 According to a fourth aspect of the present invention 23 there is provided a piston rod assembly for coupling 24 between a power end and a fluid end of a high pressure reciprocating pump, the assembly comprising one or more 26 clamping members arranged relative to a rod axis between 27 the power end and the fluid end, each member having a.

28 first end adapted to grip a power end component and a 29 second end adapted to grip a fluid end component, at least one member including one or more tensioning means, 31 a monitoring system, wherein said tensioning means 32 comprise a piston to provide a load in said tensioning 1 means orthogonal to said first rod axis and thereby 2 secure said components against release.

4 Preferably the monitoring system is according to the first or second aspect.

7 Preferably the clamping members are part cylindrical 8 bodies which when coupled together or arranged on the rod 9 axis provide a substantially cylindrical body.

Preferably there are two clamping members, an upper 11 clamping member and a lower clamping member. However, 12 any suitable number of clamping members may be provided.

14 Preferably the first and second clamping member ends each include a contact face which, in use, is disposed 16 parallel to an axis of the piston rod assembly on an 17 inner surface thereof. The face may provide a recess on 18 the inner surface in which a portion of the power end 19 component or fluid end component may be located such that the component is gripped and held when the clamping 21 member is coupled to the power and fluid ends. Where the 22 assembly comprises two clamping members, the clamping 23 members may be adapted to be brought together by the 24 tensioning device/means, for gripping the power and fluid end components. Advantageously each component end and the 26 first/second end provide a knuckle joint. Alternatively, 27 they may provide a ball and socket.

29 Where the tensioning device/tensioning means comprises a piston adapted to provide a load orthogonal to an axis of 31 the piston rod assembly to thereby secure the power and 32 fluid end components against release, each piston may be 33 slideable within an hydraulic cylinder. Each piston may 1 include a stem adapted to receive a nut or a lock. Said 2 stems may extend from one clamping member through an 3 aperture in an adjacent clamping member. The nut may 4 then engage the stem to couple the clamping members together. Also, a spring may be arranged within the 6 hydraulic cylinder to tension the said stem.

7 Advantageously, the assembly includes non-rotational 8 means for preventing rotation of said stem. The non- 9 rotational means may be a pin locating in a matching recess arranged parallel to the stem.

12 A space may be defined between a base of the cylinder and 13 a base of the piston for accommodating hydraulic fluid.

14 The assembly may include a fluid inlet port to permit the input of hydraulic fluid to the cylinder. Advantageously 16 a chamber may be included in each member to provide a 17 common feed for hydraulic fluid to all cylinders within 18 the member.

According to a fifth aspect of the present invention, 21 there is provided a pump comprising a monitoring system 22 according to one of the first and second aspects of the 23 invention.

According to a sixth aspect of the present invention, 26 there is provided a pump comprising a piston rod assembly 27 according to one of the third and fourth aspects of the 28 present invention.

The features of one or more of the above aspects of the 31 present invention may optionally be provided together or 32 in combination. Thus one or more features of the 33 first/second aspect of the invention may be provided in 1 combination with one or more features of the third/fourth 2 aspect of the invention.

4 Further features of the invention are defined in the appended claims.

7 Embodiments of the present invention will now be 8 described, by way of example only, with reference to the 9 accompanying drawings, in which: 11 Figure 1 is a schematic view of a portion of a high 12 pressure reciprocating pump including a piston rod 13 assembly and cross-heads, shown in an. (a) aligned and (b) 14 misaligned configuration; 16 Figure 2(a) is a schematic view of a portion of a high 17 pressure reciprocating pump including a piston rod 18 assembly, Figures 2(b) and 2(c), according to a first 19 embodiment of the present invention; 21 Figure 3(a) is a schematic view of a portion of a high 22 pressure reciprocating pump including a piston rod 23 assembly, Figure 3(b), according to a second embodiment 24 of the present invention; and 26 Figure 4(a) is a schematic view of a portion of a high 27 pressure reciprocating pump including a piston rod 28 assembly, Figure 4(b), according to a third embodiment of 29 the present invention.

31 Referring initially to Figure 2 of the drawings there is 32 illustrated a portion of a high pressure reciprocating 33 pump, generally indicated by reference numeral 10, 1 including a piston rod assembly 12, according to a first 2 embodiment of the present invention, located between a 3 power end 14 and a fluid end 16 of the pump 10.

Referring now to Figures 2(b) and (c), the piston rod 6 assembly 12 may be considered as a clamping link by 7 virtue of its purpose i.e. to provide a releasable 8 coupling between the power end component 18 and the fluid 9 end component 20 which is secure during the high reciprocating force applied by the pump. Assembly 12 is 11 based on the assembly presented in Applicant's 12 International Patent Application No. PCT/GB2004/004260 13 (published as W02005/035986) Assembly 12 comprises two clamping members in the form of 16 half-cylindrical clamps 22,24. Each clamp 22,24 has an 17 inner planar surface 26,28 respectively. The surfaces 18 26,28 are arranged on and lie parallel to the rod axis 19 30. The rod axis is a central line located between the end components 18,20.

22 The piston rod assembly 12 includes two tensioning 23 modules 32a,b to connect the clamps 22,24. Each 24 tensioning module includes a piston 34a,b, a piston stem 36a,b, and a disc spring stack 38a,b arranged within a 26 cylindrical housing 40a,b within the lower clamp 24.

27 These elements 34,36,38 are all disposed orthogonally to 28 the rod axis 30 of the assembly 12. Covers 42a,b, held in 29 place by screws 44a-d, close the housings 40a,b retaining the spring force. The upper clamp 22 includes apertures 31 46a,b through which extend the stems 36a,b from the lower 32 clamp 24. Each aperture 46 widens to provide a lip 48a,b 33 parallel to the rod axis 30. A nut 50a,b is screwed to 1 the stem 36a,b and may be tightened against the lip 2 48a,b.

4 Below each piston 34a,b in a space defined by the base of the piston 34a,b and the base of the housing 40a,b is a 6 fluid chamber 50a,b. Hydraulic fluid 52 may enter this 7 chamber 50 and exert a force upon the piston 34a,b. The 8 chambers are connected to a fluid line 54 located along 9 the length of the assembly 12. The fluid line 54 is sealed, but includes an inlet port 56 illustrated in 11 Figure 2(c). Also shown in Figure 2(c) is a pin 58 which 12 prevents the piston 34 from turning in the housing 40.

14 Returning to Figure 2(b), the inner surfaces 26,28 at the ends of the clamps 22,24 are shaped such that, when the 16 clamps 22 and 24 are brought together, recesses 60a,b are 17 defined between the clamps at each end thereof. These 18 recesses 60a,b take the form of circumferential grooves 19 which extend around the inner surfaces 26,28 equidistantly from the rod axis 30. Each component end 21 18,20 includes a protrusion 62,64 (shown in part-section) 22 which may be likened to a knob or knuckle in profile, and 23 these protrusions 62,64 fit into the recesses 60a,60b and 24 are effectively gripped by the.clamps 22,24. In this way, when the clamps 22, 24 are coupled together, the power 26 end component 18 is secured relative to the fluid end 27 component 20. To aid the fitting of each protrusion 28 62,64 into each recess 60a,b, bearing pads 66,68 are 29 located at the distal ends of the protrusions 62,64. The bearing pads 66,68 may be formed of a material which 31 provides some give and has a relatively high elastic 32 modulus. The bearing pads 66, 68 are typically of a 33 plastics material such as Acetyl, with a low moisture 1 absorption rate (around 1%). Minor swelling of the pads 2 66, 68 provides an interference fit which eases assembly 3 of the piston rod assembly 10 by a single operator.

This assembly 12 advantageously applies a force 6 orthogonal to the rod axis 30 so that a greater force is 7 applied to grip the fluid and power end components 18,20.

9 Located between each nut 50a,b and the corresponding lip 48a,b, is a load sensing washer 52a,b. Each washer 52 is 11 connected to a power supply 70 including a signal 12 amplifier. In turn a computer 72 displays the measurement 13 of the load upon each of the washers 52. Additional 14 strain gauges 74a,b are mounted on an outer surface 76 of the upper clamp 22. The gauges 74a,b are also connected 16 to power supply 70 and their measurements displayed on 17 the monitor of the computer 72 and the gauges 74 and 18 washer 52 are coupled to the computer 72 by appropriate 19 cable or wires. The computer 72 typically includes an analogue/digital converter, for converting analogue 21 signals output by the sensors 52,74 into digital signals 22 for processing by the computer 72. Alternatively, the 23 signals output by the sensors 52,74 may be converted by 24 known means to current signals, for example for transmission over a 4-2OmA current loop. The strain 26 gauges 74a,b take the form of semiconductor strain 27 gauges, such as those available from Kyowa Electronics 28 Instrument Company of 3apan, which provide strong signal 29 outputs in response to small applied strains on the piston rod assembly 12 due to misalignment bending 31 stresses. The strain gauges 74 will detect any strain 32 indicative of bending stresses applied to the piston rod 33 assembly 12 or experienced by the power train of the pump 1 10, shown in Figure 2(a). The position at which the 2 strain gauges 74 are mounted is selected on the basis of 3 the highest likely bending stress in the assembly 12.

Alternatively, the signals output by the sensors may be 6 converted by known means to current signals e.g. for 7 transmission over a 4.2OrnA loop.

9 The power supply 70 and the signal amplifier provide a signal that will be used to calibrate the system and 1]. provide a continuous visual display -locally and 12 remotely -of bending stress. Signal alarm sensors will 13 provide warning of an excessive increase in bending 14 stress and thus allow remedial action to be taken to remedy any misalignment in the power train.

17 The sensors 52,74 can be easily fitted to the rod 18 assembly 12 without requiring any alteration to the rod 19 design. This allows the monitoring system to be retrofitted and easily removed and mounted on another 21 pump if required. Additionally, the sensors can be 22 replaced in event of damage.

24 In a variation, the piston rod assembly 12 includes a data transmission device 76 such as a radio frequency or 26 microwave transmitter, which transmits data from the 27 sensors 52,74 to a remotely located receiver 77. Thus 28 data from the sensors 52,74 indicative that the piston 29 rod assembly 12 is experiencing bending stress may be transmitted to the receiver for suitable output.

32 The piston rod assembly 12 also optionally includes a 33 data recordal device in the form of a chart recorder or 1 plotter 78 for recording output sensor data. This 2 facilitates monitoring of data output from the sensors 3 74a,b over a period of time, which may indicate that the 4 piston rod assembly 12 is approaching a condition where it is out of alignment.

7 Reference is now made to Figure 3 (a) of the drawings 8 which illustrates a portion of a high pressure 9 reciprocating pump, generally indicated by reference numeral 100, including a piston rod assembly 102, 11 according to a second embodiment of the present 12 invention, located between a power end 104 and a fluid 13 end 106 of the pump 100. The rod assembly 102 is as 14 described in UK Patent Application GB 2190170, the disclosure of which is incorporated herein by way of 16 reference.

18 Referring now to Figure 3(b), the H.P. reciprocating pump 19 100 has a composite piston rod comprising a power end component 104, a fluid end component 106 and a connector 21 120 releasably connected to said end components. The 22 connector 120 has a pair of tensioned links 150 extending 23 therefrom and apertures 120 in the components and 24 respective links co-operate for location of a locking pin therein. Pressure means 160,170,180,190 within the 26 connector causes movement of the links against tension to 27 permit coupling or uncoupling and for returning the links 28 under tension to secure the components when coupled 29 against release. The coupling means comprises a valve 122 provided in the body 113 of the connector 120 to 31 inject or release pressure fluid into or out of a space 32 170 between two pistons 180 which form the links. In 33 use, fluid supplied under pressure into the space 170 1 acts on rear faces of the pistons 180, to translate the 2 pistons in axially opposite directions. This movement 3 aligns apertures 121 in the pistons 180 with 4 corresponding apertures (not shown) in the power and fluid end components 104, 106. The connector 120 may 6 then be securely coupled to the power and fluid end 7 components 104, 106 by pins (not shown) located within 8 the aligned apertures. Subsequent bleeding of fluid from 9 the space 170 causes springs 190 to act upon the pistons 180, thereby generating retaining tension forces on the 11 power and fluid end components 104, 106 to securely 12 couple the components together.

14 Returning to figure 3(a), a strain gauge 125 is located on connector 126, in which the rod assembly 102 is 16 mounted. Although only one gauge is shown, it will be 17 appreciated that gauges may be placed over the outer 18 surface 128 at any location over the power train shown in 19 Figure 3 (a). Advantageously the gauge 125 is located on the outer surface 128, distal to the rod axis 130, as any 21 bending stress applied to the train will be amplified at 22 distances furthest from the axis 130. The gauges 125 23 will be linked to a power supply and monitor as shown in 24 Figure 2(b).

26 In this arrangement no modification is required to the 27 rod assembly 102. The monitoring system may be 28 retrofitted by mounting the gauges on the outer surface 29 128. A groove may be machined on the outer surface so that the gauges and other components can be located in a 31 recess with an optional protective covering for safety.

32 It will be appreciated that the gauges may be mounted by 1 any means such as adhesive or they may be screwed/bolted 2 to the surface 128.

4 Reference is now made to Figure 4(a) of the drawings which illustrates a portion of a high pressure 6 reciprocating pump, generally indicated by reference 7 numeral 200, including a piston rod assembly 202, 8 according to a third embodiment of the present invention, 9 located between a power end 204 and a fluid end 206 of the pump 200. The rod assembly 202 is as described in US

11 Patent No. 5,904,071 the disclosure of which is

12 incorporated herein by way of reference. Rod assembly 202 13 is an improvement over the assembly of the second 14 embodiment, Figure 3.

16 Referring to Figure 4(b), assembly 202 has a cylindrical 17 body 213 and two spring retainers 214. A male tension 18 link 215 projects axially from one end of the assembly 19 202. The male link 215 is the rotatable outer portion of a piston 216 and is connected to the piston 216 by means 21 of a shoulder 217, a swivel link 218 and adjustment shims 22 219. A female tension link 220 is contained axially 23 within the body 213 at the opposite end to that 24 containing the male link 215. The female link 220 is the outer portion of a non rotating piston 221. Pistons 216 26 and 221 are located within the body 213 in back-to-back 27 relation such that a chamber 222 is provided between the 28 two pistons 216 and 221. Spring means, such as disc 29 springs 223 between the respective pistons 216 and 221 and spring retainers 214 resist outward movement of the 31 pistons 216, 221. Thus, the pistons 216, 221 are normally 32 in their withdrawn position with the links 215 and 220 33 being pushed by the springs 223 into the body 213.

1 When chamber 222 is pressurised by fluid 240 the pistons 2 216 and 221 are forced outwards for a short distance lust 3 sufficient to bring a pin aperture 224 in each link into 4 register with a similar opening in the two end components 210, 211 after which a pin 225 is inserted into each of 6 the through apertures 224.

8 When pressure in the chamber 222 is released by bleeding 9 fluid 240 from the chamber, the pistons 216, 221 are pushed inwards by the springs 223 thus placing in shear 11 the pins 225 and retaining the end components 210, 211 12 securely attached to the connector 212. The operation of 13 coupling the end components 210, 211 to the release link 14 connector 212 takes approximately thirty seconds. To uncouple, the chamber 222 is again pressurised to release 16 the shear force on the locking pins 225 which can then be 17 easily removed out of the apertures 224. The couplings 18 can be removed, the piston changed, and the rod re- 19 assembled in less than five minutes.

21 Mounted centrally on the assembly are a pair of strain 22 sensors 242a,b. Sensors 242 are oppositely arranged and 23 orthogonal to the port 227. They are kept away from the 24 port 227 to prevent any stress induced by fluid flow having an effect on the bending stress measurement to the 26 power train. Any bending stress experienced by the power 27 train shown in Figure 4(a) will be detected 28 preferentially on one of the sensors 242a,b due to their 29 arrangement. The signal from the strain sensor can be sent to a remote site 244 by any communication system 31 known in the art. In this way the monitoring of bending 32 stress in the pump 200, can be integrated with other 33 monitoring systems used on an oil rig/platform. An 1 acceptable limit of bending stress can be set so that a 2 warning signal is provided if the pump is operating over 3 this limit. This allows maintenance to be undertaken to 4 correct the alignment of the power train.

6 In use, the sensors are located on the piston rod 7 assembly, as described hereinbefore. This may be a 8 retrofit or they may be put in place during manufacture.

9 The sensors are mounted so as not to interfere with the operation of. the piston rod assembly. In this way, the 11 pump can operate with or without monitoring being 12 undertaken. When monitoring is required, a signal is 13 either detected from the sensors remotely, or cables can 14 be connected to the sensors and data read from them. If cables are used, it is preferable to stop the pump and 16 adjust the piston rod manually to obtain the stress 17 signals. This signal monitoring over short periods with 18 the pump off, will provide stress measurements at 19 predetermined times. A chart recorder or computer may be used to display the measured data and thus indicate the 21 stress measured. This method provides a cheap and simple 22 monitoring system if desired.

24 Alternatively, the sensors can be run continuously on the piston rod assembly with the pump on. This will provide 26 continuous data collection and offers the opportunity of 27 immediate warning of a stress level being reached.

28 However it has been found that regular monitoring at set 29 time periods provides effective determination of stress.

31 The principal advantage of the present invention is that 32 it provides a monitoring system to a pump rod assembly 33 for safe use of the assembly.

2 Further advantages of the present invention are that an 3 alarm can be used to give a warning of excessive stress 4 before direct or secondary failure has occurred; continuous monitoring of stresses is possible even while 6 the pump is in operation; and monitoring extends the pump 7 and liner life.

9 Yet further in the first embodiment, an advantage is found in that the system can be used to ensure correct 11 tensioning of the clamping arrangement.

13 Modifications may be made to the invention 14 hereindescribed without departing from the scope thereof.

For example, the number and type of sensors may be varied 16 depending on the environment of the pump and space 17 available for mounting.

Claims (19)

1 CLAIMS 3 1. A piston rod assembly for coupling between a power 4 end and a fluid end of a reciprocating pump, the piston rod assembly comprising: 6 a power end component; a fluid end component; 7 at least one clamping member having a first end 8 adapted to be coupled to the power end component 9 and a second end adapted to be coupled to the fluid end component, for coupling the power and fluid end 11 components together; and 12 a tensioning device for generating a force to 13 secure the power and fluid end components against 14 release.

16

2. An assembly as claimed in claim 1, comprising a 17 monitoring system for indicating that the piston 18 rod assembly is experiencing bending stress.

3. An assembly as claimed in any preceding claim, 21 wherein the at least one clamping member is 22 arranged relative to a rod axis between the power 23 and fluid ends.

4. An assembly as claimed in any preceding claim, 26 wherein the tensioning device comprises a piston 27 adapted to provide a load orthogonal to an axis of 28 the piston rod assembly to thereby secure the power 29 and fluid end components against release.31

5. An assembly as claimed in any preceding claim, 32 comprising a plurality of clamping members, wherein 33 the clamping members are part cylindrical bodies 1 which when coupled together provide a substantially 2 cylindrical body.4

6. An assembly as claimed in any preceding claim, comprising two clamping members, an upper clamping 6 member and a lower clamping member.8

7. An assembly as claimed in any preceding claim, 9 comprising first and second clamping members, the ends of each clamping member including a contact 11 face on an inner surface thereof which, in use, is 12 disposed parallel to an axis of the piston rod 13 assembly.

8. An assembly as claimed in claim 7, wherein the 16 faces include recesses on the inner surface in 17 which a portion of the power end component and 18 fluid end components are located such that the 19 components are gripped and held when the clamping member is coupled to the power and fluid ends.22

9. An assembly as claimed in any preceding claim, 23 comprising two clamping members, the clamping 24 members adapted to be brought together by the tensioning device for gripping the power and fluid 26 end components.28

10. An assembly as claimed in any preceding claim, 29 wherein each of the power end and fluid end components and the first and second ends of the 31 clamping member provide a knuckle joint.1

11. An assembly as claimed in any one of claims 1 to 9, 2 wherein each of the power end and fluid end 3 components and the first and second ends of the 4 clamping member provide a ball and socket joint.6

12. An assembly as claimed in any preceding claim, 7 wherein the tensioning device comprises a piston 8 adapted to provide a load orthogonal to an axis of 9 the piston rod assembly to thereby secure the power and fluid end components against release, and 1]. wherein the piston is slideable within an hydraulic 12 cylinder.14

13. An assembly as claimed in claim 12, wherein the piston includes a stem adapted to receive a locking 16 element.18

14. An assembly as claimed in claim 13, wherein the 19 stem extends from one clamping member through an aperture in an adjacent clamping member.22

15. An assembly as claimed in either of claims 13 or 23 14, wherein a spring is arranged within the 24 hydraulic cylinder to tension the stem.26

16. An assembly as claimed in any one of claims 13 to 27 15, including non-rotational means for preventing 28 rotation of the stem.

17. An assembly as claimed in any one of claims 12 to 31 16, wherein a space is defined between a base of 32 the cylinder and a base of the piston for 33 accommodating hydraulic fluid.2

18. A piston rod assembly for coupling between a power 3 end and a fluid end of a high pressure 4 reciprocating pump, the assembly comprising one or more clamping members arranged relative to a rod 6 axis between the power end and the fluid end, each 7 member having a first end adapted to grip a power 8 end component and a second end adapted to grip a 9 fluid end component, at least one member including one or more tensioning means, a monitoring system, 11 wherein said tensioning means comprise a piston to 12 provide a load in said tensioning means orthogonal 13 to said first rod axis and thereby secure said 14 components against release.16

19. An assembly according to claim 18, in which the at 17 least one clamping member comprises an intermediate 18 component coupling the first end to the second end.