US 3914752 A
An alarm system for a high pressure reciprocating pump includes a detector member positioned adjacent the pump packing for detecting leakage of fluid therepast, and an alarm indicator responsive to movement of the detector member for operating an audible or visual alarm device or for stopping the pump.
Description (OCR text may contain errors)
United States Patent Howard et a1.
[4 1 Oct. 21, 1975' PUMP ALARM SYSTEM Inventors: Willis W. Howard; William C.
Maurer; Everett H. Lock, all of Houston, Tex.
Exxon Production Research Company, Houston, Tex.
Filed: June 4, 1973 Appl. No.: 367,021
Published under the Trial Voluntary Protest Program on January 28, 1975 as document no. B 367,021.
US. Cl 340/242; 95/5 R; 277/2; 340/240 Int. Cl. G08B 21/00; FOlB 25/26 Field of Search 340/240, 241, 242; 417/9; 92/5, 86; 73/46, 47, 49.4, 49.7, 49.8, 228; 277/2  References Cited UNITED STATES PATENTS 2,801,409 7/1957 Sperling 340/242 3,180,134 4/1965 Wadlingtom 417/9 X 3,209,830 10/1965 Orr et a1. i 277/2 X 3,276,246 10/1966 Truman et a1. 277/2 X Primary ExaminerJohn W. Caldwell Assistant ExaminerDaniel Myer Attorney, Agent, or FirmRobert L. Graham  ABSTRACT An alarm system for a high pressure reciprocating pump includes a detector member positioned adjacent the pump packing for detecting leakage of fluid therepast, and an alarm indicator responsive to movement of the detector member for operating an audible or visual alarm device or for stopping the pump.
13 Claims, 3 Drawing Figures US. Patent Oct. 21, 1975 Sheet 1 of 2 U.S. Patent Oct. 21, 1975 Sheet2of2 3,914,752
PUMP VISUAL AUDIBLE CONTROL SIGNAL SIGNAL RELAY 5| 53 FIG. 3 LIMIT SWITCH 52 PUMP ALARM SYSTEM BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for the detection of leakage past packing employed in a reciprocating pump. In one aspect it relates to an alarm system for a high pressure plunger pump.
2. Description of the Prior Art A major problem associated with high pressure reciprocating pumps is in providing a satisfactory seal between the pump housing and the pump plunger. The seal is normally provided by soft packing mounted in an enlargement in the pump housing and adapted to engage both the housing and the plunger in fluid tight relationship. In high pressure pumps, the packing frequently fails repeatedly during the operating life of a pump. For this reason the packing is normally an expendable member designed to permit rapid replacement.
When operating at high pressures, it is extremely important that packing failure be detected as soon as possible to avoid damaging the pump or injuring personnel. The packing usually fails as a result of seal rings deteriorating from heat, friction, fatigue, or abrasion. Small flow passages develop through the packed interval with the result that fluid pressure is no longer confined. At high differential pressures, fluid discharges through the passage at extremely high velocities. If permitted to continue even for a short period of time the high velocity jets will wash out or erode a portion of the pump housing causing serious damage to the pump. The erosive nature of the fluid is particularly severe when the fluid being pumped is a drilling fluid which typically contains abrasive material. Tests have shown that the drilling fluid discharging as a high velocity jet through packing which has failed can severely damage the pump housing and/or plunger within five minutes. If the pump housing and/or plunger become damaged, the pump cannot be repaired simply by replacing the pump packing. The damaged parts must be reworked or replaced at substantial cost to the operator. Moreover, the pump which has been damaged cannot be returned immediately to operation. If a standby pump is not available, this means that the process or operation in which the pump is employed must be discontinued.
SUMMARY OF THE INVENTION The purpose of the present invention is to provide an apparatus that is capable of detecting incipient leakage of fluid past pump packing. The effectiveness of the invention relies to a large extent on the fact that the onset of packing failure can be detected several minutes prior to complete failure of the packing.
The operating characteristics of a reciprocating pump are such that the pressure differential across the pump packing fluctuates from a minimum value on the suction stroke of the plunger to a maximum value on the power stroke (pumping stroke) of the plunger. It has been discovered that the initial evidence of packing failure occurs as a high velocity jet or spurt through the packing. The high velocity jet is of short duration and frequently occurs on a single pumping stroke of the plunger.
Tests have shown that for a short period of time fol lowing the initial high velocity spurt, no additional packing leakage occurs. Evidently, the reduced differential pressure across the packing on the suction stroke permits the soft packing to temporarily reestablish the plunger seal for subsequent power strokes. The packing, however, normally fails completely within about 5 minutes following the initial leakage spurt. These tests have also shown that by the time the packing has completely failed, the pump housing or plunger frequently is damaged to the extent as to require replacement or repair.
The apparatus of the present invention permits the early detection of packing failure thereby enabling replacement of the packing before any of the pump parts have become damaged.
Briefly, the apparatus includes a detector member positioned adjacent the pump packing for detecting the leakage of fluid therepast, and an alarm indicator responsive to actuation of the detector member for operating an audible or visual alarm device or stopping the pump.
In the preferred embodiment of the invention, the alarm system of the present invention is used in conjunction with a tandem packing arrangement wherein the plunger packing is provided with two packings separated by a vent port. During the initial pumping stage, the inner packing provides the plunger seal and the outer packing remains in reserve. The outer packing is actuated after failure of the inner packing by merely closing the vent port permitting the pump to be operated through a second stage. The detector member in such an arrangement is positioned opposite the vent port. Packing leakage discharges as a high velocity jet from the vent port striking the detector member and actuating the alarm system. This notifies the operator that the initial packing has failed. The reserve packing can then be actuated by closing the vent port. Alternatively, the alarm system may include a control for automatically closing the vent port upon actuation of the detector member.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a portion of a reciprocating pump provided with a leak detecting member of the alarm system of the present invention. Portions of the pump are schematically illustrated.
FIG. 2 is a transverse sectional view of the apparatus shown in FIG. 1 with the cutting plane taken through line 22 .thereof.
FIG. 3 is a wiring diagram of the alarm system capable of use in the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS The alarm system of the present invention may be used in any of the high pressure reciprocating pumps including symplex or multiplex, single acting or double acting pumps. Its preferred application, as described in this preferred embodiment, however, is in connection with high pressure, multiplex plunger pumps.
As shown in FIG. 1, the fluid end of a plunger pump comprises separate steel forgings which include fluid end housing 10 mounted on a pump frame 11 and a crossbore body, shown partially as 12 coupled to the housing 10. The crossbore body 12 can be similar in structure as that disclosed in U.S. Pat. No. 3,801,234, entitled Fluid End for Plunger Pump", dated Apr. 2, 1974. Other structures including a monoblock structure may also be employed. The housing has formed therein a cylindrical bore 13 which is in fluid communication with the flow passages with the crossbore body 12. A plunger 14 is mounted for reciprocation in the bore 13. The plunger 14 extends beyond the rear extremity of the housing 10 and is connected to the power end of the pump (not shown) by a drive rod 15. Coupling 16 attaches the forward end of the drive rod to the rear end of plunger 14. The power end of the pump which may be provided by hydraulic power or crankshaft drive moves the plunger 14 through a suction stroke and a power stroke. On the suction stroke fluid is drawn into the crossbore body and bore 13 and on the power stroke fluid is discharged at a high pressure from the crossbore body. For a high pressure plunger pump, the fluid is normally received at a pressure between about 50 to 100 psi and discharged at pressures up to 20,000 psi. It is thus seen that the pres sure within the fluid end housing 10 fluctuates within wide limits.
In order to seal the annular space between the moving plunger 14 and the stationary housing 10, a packing indicated generally as 17 is provided near the rear end of housing 10. The packing 17 in this preferred embodiment is shown in FIG. 1 as being a cartridge 18. The alarm system of the present invention, however, may also be employed in pumps equipped with conventional stuffing box assemblies.
The cartridge 18 which may take the form of a ho]- low cylindrical sleeve 20 is detachably mounted in a complementary shaped recessed end portion of a housing 10. The forward transverse surface 21 of the cartridge 18 abuts internal shoulder 22 of the housing 10 and an O-ring 23 provides a pressure seal at this joint.
As illustrated in FIG. 1, a peripheral portion of sleeve 20 is threaded for mating with internal threads formed in the mouth of the housing recess. Other fasteners in lieu of the threaded connection may be employed for attaching the sleeve to the rear end of housing 10. These include clamping collars, flange connections, and the like. The sleeve 20 is machined to provide a central annular support member 24 flanked by enlarged sections sized to receive the packing assemblies described below. The opening 25 through support 24 permits free movement of plunger 14.
The plunger packing contained within sleeve 20 is a tandem packing arrangement which comprises inner and outer packings 17a and 17b, respectively, adapted to operate in staged sequence. The inner packing assembly 17a includes a plurality of seal rings 26 which, as illustrated, may be nested V-rings 26 or similar liptype rings, ring adapter 27, lantern ring 28, spring 29, and spring adapters 30 and 31. Similarly the outer packing assembly 17b may include nested V-rings 32, ring adapter 33, a lantern ring 34, a spring 35, and spring adapter 36.
As shown in FIG. 1, the lantern rings 28 and 34 of assemblies 17a and 17b each fits between two of the V- rings and is positioned within its respective chamber to communicate with a passage for delivering lubricant to the interior of sleeve 20. Passage 36 extends from an outer exposed portion of sleeve 20 to the interior of the packing in fluid communication with lantern ring 28 of packing assembly 17a. Similarly, passage 37 extends from an exposed portion of the sleeve 20 and is in fluid communication with lantern ring 34 of packing assembly 17b. Passages 36 and 37 are schematically illustrated in FIG. 1.
Under pumping conditions, packing 17a is urged against the support 24 and thus prevents hydraulic loading from being transmitted to the reserve packing 17b. Spring 29 maintains the rings of assembly 17a tightly packed together.
The reserve packing 17b is also retained within sleeve 20 but spaced longitudinally to the rear of packing 17a. Bushing 38 which is threadedly connected to the outer end of sleeve 20 closes the rear extremity of the annular space between the sleeve 20 and plunger 14 and serves to maintain the reserve packing 17b in place. The spring 35 interposed between support 24 and retainer 36 urges the packing rings against the bushing 38 thereby maintaining the rings in tightly packed relationship.
A third passage formed in the sleeve 20 and designated by reference numeral 39 extends from an exposed portion of the sleeve 20 to the interior thereof at a point between packings 17a and 17b. Passage 39 which serves as the vent port is initially opened so that there is no differential pressure across the reserve packing 17b. Under this condition, the inner packing 17a provides the plunger seal during the initial stage of operation. The reserve packing 17b is not subjected to severe wear because the hydraulic loading is borne by the support member 24. The differential pressure across the inner packing is substantially equal to the pumping pressure.
When the inner packing 17a fails as will be evidenced by the jetting of a fluid from the outlet of passage 39, this passage can be closed by the use of a valve, shown as 40, or by a plug (not shown). Closing of passage 39 activates the reserve packing 17b since the hydraulic pressure in the space separating the packings will be substantially equal to the pumping pressure. The pump then can be operated through a second stage wherein the reserve packing 17b provides the plunger seal.
During the initial stage of operation, lubricant will be delivered under pressure to the inner packing 17a through passage 36. Lubricant enters the interior sleeve 20, passes through radial openings in the lantern ring 28, and into contact with plunger 14. The seal rings to the rear of the lantern ring 28 insures that the lubricant flows forwardly which usually occurs on the suction stroke of the plunger 14. If external lubrication is provided on the plunger 14, the lantern ring 34 of the reserve packing assembly 24 need not be provided in that assembly.
As mentioned previously, the apparatus of the present invention which is employed to detect the incipient failure of the packing 17, may be used with any type of plunger packing but is particularly suited for use in connection with the tandem packing arrangement described in this preferred embodiment.
The alarm system of the present invention includes a detector member 42 disposed in the immediate vicinity of packing 17 and actuably responsive to movement of the detector member for indicating packing failure. The detector member 42 should be positioned in confronting relation to any point of possible packing failure. For example, in a pump which employs a tandem packing arrangement as described above, the detector member 42 should be positioned opposite the mouth of passage 39. Thus, initial failure of the inner packing 17a will be detected as soon as a high velocity jet pictorially illustrated at 67 in FIG. 1 discharges from passage 39. Failure of the reserve packing 17b (or a single packing) will be evidenced by a high velocity jet illustrated at 68 discharging through the rear extremity of sleeve 20 between bushing 38 and plunger 14. In order to detect this failure, member 42 should be positioned in surrounding relation to the plunger 14 and a short distance to the rear of bushing 38. In order to detect the failure of the O-ring seal 23 or other seal employed at the joint between sleeve 20 and housing 10, a fourth passage 43 is formed in the sleeve 20 and discharges rearwardly. Passage 43 communicates with a circumferentially extending space 44 between housing and the outer periphery of sleeve 20. Thus, if the O-ring 23 fails, fluid will pass into annular space 44 and from there through passage 43. Fluid jet illustrated at 69 discharging from passage 43 will strike detector member 42 and actuate the alarm system.
The detector member 42 moves in response to the high velocity fluid jet striking it rearwardly and actuates a switch in an alarm system circuit. The closing of this circuit operates an audible indicator such as a siren and/or a visual indicator such as a light. In addition or alternatively, the alarm circuit may be connected through a suitable relay to the pump motor to stop the pump upon packing failure.
As shown in FIG. 3, the alarm circuit in this embodiment is an open loop control circuit comprising a battery 51, a limit switch 52 actuable by the movement of the detector member 42, relays 53 and 54, and visual and audible indicators 55 and 56. The system may also include relay 57 which can be electrically connected to the pump motor controls. Power to relay 57 which will result from actuation of the alarm system can be employed to open the circuit to the pump motor and thus stop the pump before excessive damage occurs.
From the foregoing, it is evident that the detector member 42 can take a variety of forms and shapes and can be actuated by impact, temperature, pressure, or contact of fluid. It can be incorporated in a pneumatic, mechanical or electrical system or combinations of these. In the preferred embodiment disclosed herein, the detector member is provided by a flat-faced member adapted to move in response to a fluid jet striking it. Movement of the member 42 actuates a limit switch to close an electric circuit to the alarm indicator.
Specifically, the member 42 comprises a flat-faced U-shaped member 58 made of thin sheet metal and a closure member pivotally mounted to the outer end of one leg of the U-member 58. In order to impart strength to the sheet metal structure, reinforcement rib 60 provided by steel tubing extend around the inner edge of the U-member 58 and is tack welded to the back side thereof. The lower edge of the closure member is provided with a flange 62 which is urged into engagement with one leg of the U-member by spring 61. The upper edge of the closure member 59 is curved to conform generally to the curvature of the plunger 14. The inner curvature of the U-member 58 and the curved portion of the closure member 59 define generally a circle which is slightly larger in diameter than the plunger 14.
The clearance between the detector member 42 and the plunger 14 should be sufficient to permit free movement of the latter but should be close enough to detect the initial spurt of fluid jet from any one of the points of failure. For a 4-inch plunger, a clearance of about one-fourth inch is satisfactory. The detector member 42 includes a rod 63, the lower end of which is connected to the upper extreme end of a reinforcing rib 60. The upper end of rod 63 is fastened to a shaft of a rotary type limit switch 52 by clamp 65. As best seen in FIG. 2, the switch 52 is attached to the pump frame 1 1 by a clamp 66 or other device such as a magnet. It is thus seen that the actuator 42 is suspended from the switch 52 and maintained in the deactivated (free) position when no external force is applied to the detector 42. The detector 42 may be adjusted relative to the plunger 14 by first placing the detector around plunger 14 (this requires opening closure member 59 to broken line position of FIG. 2), sliding the rod 63 through collar 65 until the detector 42 and plunger 14 are concentric and tightening the set screw on-collar 65. This assembly then can be adjusted relative to packing 17 by loosening clamp 66, moving it and the assembly supported thereon along the wall of frame 11 until actuator 42 is located about one inch to the rear of packing 17, then tightening clamp 66.
The following example illustrates the reliability of the alarm system constructed according to the present invention. A triplex pump containing 3 /2 inch plungers operating at 10,000 psi and 142 strokes per minute had experienced several packing failures. Packing failures were detected in many instances only after the pump plunger, sleeve, or pump housing had been damaged by the complete failure of the packing. Because of high operating pressures, safety precautions precluded operators from visually inspecting the packing with pump operating at normal pressures (about 10,000 psi). Moreover, the high noise area in which the pump was operating made it extremely difficult to detect early packing failure. As a result of these conditions, packing failure was frequently detected only after the pump or pump parts were damaged by high velocity leakage escaping past the plunger packing.
An alarm system constructed according to the present invention was mounted around each of the three plungers of the triplex pump. Each detector had the following dimensions:
U-shaped member (58) height, inches 6 width (overall), inches 6% width of legs (w), inches W4 Closure Member (59) height (h), inches 1% length, inches 6% Rod (63) length, inches 8% Radial clearance between detector and plunger, inches V4 12 volt Type LS sold by Micro Switch, a
division of Honeywell Battery (5 l) Limit Switch (52) Relay (53) Type KHS sold by Potter 8:. Brumfield,
a division of American Machine & Foundry Relay (54) Type DC. Power Relay sold by RBM Controls, a division of Essex lntl.
Each detector 42 was positioned about 1 /2 inches to the rear of its associated packing 17. The limit switch required 6 from the free position to close its contacts. This required only l-inch movement of the detector 42 to close switch 52.
The alarm system described above was designed to operate as follows. The impact of fluid jetting through a point of packing failure moves detector 42 rearwardly.closing switch 52 which energizes the coil of relay 53. This closes contacts of the relay S3 energizing the coil of relay 54. The contacts of relay 54 are closed operating the siren and the light. Following the initial spurt, detector 42 may return to its home position opening switch 52. The contacts of relay 54 however remain closed. The alarm can be shut off by opening manual switch 70.
During the first few tests of the alarm system, the alarm was actuated indicating packing failure. However, visual inspection of the packing indicated that the packing was in good repair and therefore was believed not to require replacement. Without exception, however, the packing completely failed within five minutes from the first alarm indication. The initial spurt failure characteristic was discovered from these early tests. Following the early tests, it was found prudent both from a safety point of view and for equipment maintenance to replace the packing immediately following the initial alarm.
In summary, the present invention broadly contemplates the combination of a detector for detecting the discharge of fluid past the pump packing, and an indicator responsive to the detector. Although the preferred embodiment of the invention is described with reference to a movable detector and an electric indicator, the invention is sufficiently broad in scope to include other types of detectors and indicator systems.
1. In a reciprocating pump having a packing for sealing the annular space between the pump housing and shaft, rod or plunger, an apparatus for detecting the initial failure of said packing which comprises a detector member positioned adjacent to a point of packing failure and being actuated by impact of fluid discharging from said point of packing failure; and alarm indicator; and means for operating said alarm indicator upon actuation of said detector member.
2. Apparatus as defined in claim 1 wherein said detector member is positioned in confronting relation to said point of packing failure in a first position and is movable by the impact of fluid discharging at such point of packing failure to a second position and wherein said means for operating an alarm indicator is actuated by the movement of said member to said second position.
3. An apparatus as defined in claim 2 wherein said alarm indicator is an electrically operated device, said means for actuating said alarm indicator includes an open loop electric circuit including said alarm indicator and an electric switch for closing said electric circuit, said switch being closed by movement of said member to said second position.
4. An apparatus as defined in claim 3 wherein said alarm indicator includes an audible device.
5. An apparatus as defined in claim 3 wherein said alarm indicator includes a visual device.
6. An apparatus as defined in claim 3 wherein said alarm indicator includes means for stopping the operation of said pump.
7. In a reciprocating pump having a packing for sealing the annular space between the pump housing and the pump plunger an alarm system for detecting failure of said packing which comprises: a detector member substantially surrounding said plunger at a location to the rear of and externally of said packing, said detector member being sufficiently close to said packing to be movable by the discharge of fluid therepast; an alarm indicator; and means responsive to movement of said detector member for actuating said alarm indicator.
8. An apparatus as defined in claim 7 wherein the alarm indicator includes means for stopping the operation of said pump. 7 9. In a plunger pump having an inner and outer packing for sealing the annular space between the pump housing and the pump plunger at axially spaced intervals along said plunger and a vent passage in fluid communication with said annular space at a point intermediate said inner and outer packings, an apparatus for detecting the initial failure of said inner packing which comprises a detector member for detecting flow of fluid through said vent passage, said detector being actuable by impingement of fluid flowing through said vent passage; an alarm indicator; and means responsive to actuation of said detector member for operating said alarm indicator.
10. An apparatus as defined in claim 10 wherein the alarm indicator includes means for stopping the operation of said pump.
11. An alarm system for detecting incipient leakage of fluid past the plunger packing of a plunger pump which comprises: a detector member adapted to be positioned substantially around the pump plunger and to the rear of the plunger packing, said detector member being movable by high velocity fluid leakage through the plunger packing; and an alarm circuit including an indicator and a switch for actuating said indicator, said switch being movable to an activated position in response to movement of said detector member.
12. An alarm system as recited in claim 11 wherein said circuit includes means for stopping said pump in response to movement of said detector member.
13. An alarm system for detecting and indicating failure of plunger packing for a plunger pump which comprises: a detector member for detecting high velocity leakage of fluid past said packing; said member being movable by the impact of said high velocity leakage past said packing; means for indicating packing failure; and means responsive to movement of said detector member by impact of said high velocity leakage for actuating said indicating means.