EP3510287A1 - Pressure relief device for centrifugal pump - Google Patents

Pressure relief device for centrifugal pump

Info

Publication number
EP3510287A1
EP3510287A1 EP17777964.2A EP17777964A EP3510287A1 EP 3510287 A1 EP3510287 A1 EP 3510287A1 EP 17777964 A EP17777964 A EP 17777964A EP 3510287 A1 EP3510287 A1 EP 3510287A1
Authority
EP
European Patent Office
Prior art keywords
piston
pressure
seal chamber
relief device
pressure relief
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP17777964.2A
Other languages
German (de)
French (fr)
Inventor
Luis Fernando Echeverri
Klayton KIDD
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
FLSmidth AS
Original Assignee
FLSmidth AS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by FLSmidth AS filed Critical FLSmidth AS
Publication of EP3510287A1 publication Critical patent/EP3510287A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D7/00—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts
    • F04D7/02—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type
    • F04D7/04—Pumps adapted for handling specific fluids, e.g. by selection of specific materials for pumps or pump parts of centrifugal type the fluids being viscous or non-homogenous
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
    • F04D15/0077—Safety measures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D15/00—Control, e.g. regulation, of pumps, pumping installations or systems
    • F04D15/0077—Safety measures
    • F04D15/0083—Protection against sudden pressure change, e.g. check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
    • F16K17/02—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side
    • F16K17/14—Safety valves; Equalising valves, e.g. pressure relief valves opening on surplus pressure on one side; closing on insufficient pressure on one side with fracturing member
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K17/00—Safety valves; Equalising valves, e.g. pressure relief valves
    • F16K17/40—Safety valves; Equalising valves, e.g. pressure relief valves with a fracturing member, e.g. fracturing diaphragm, glass, fusible joint
    • F16K17/406—Safety valves; Equalising valves, e.g. pressure relief valves with a fracturing member, e.g. fracturing diaphragm, glass, fusible joint the fracturing member being a generally elongated member, e.g. rod or wire, which is directly connected to a movable valve member, the breaking or buckling of the elongated member allowing the valve member to move to a closed or open position

Definitions

  • the present invention relates to pressure relief devices for centrifugal pumps used in the mining and mineral processing industries to transport mixtures of liquids and solids such as slurries.
  • centrifugal pumps are typically transported using centrifugal pumps. Because of the nature of the slurry, pipelines can be susceptible to blockages or "sanding" or the formation of scale deposits or “caking” in some cases, which results in low or zero flow of the slurry through the centrifugal pump.
  • a centrifugal pump operating at a low or zero flow results in progressive heating of the slurry within the pump, which if left unattended results in steam generation and rapid increases in pressure within the pump that can exceed the mechanical limits of the pump and can produce a pump explosion resulting in e.g. catastrophic damage to the centrifugal pump, damage to adjacent equipment or harm to nearby personnel.
  • the shear tabs and shear ring are not directly exposed to the slurry and it is the seal chamber which is released in case of an overpressure event, permitting some displacement that is expected to break the seal around the seal chamber and allow the slurry to escape relieving internal pressure.
  • this arrangement requires that the pump be disassembled for maintenance or replacement of the pressure relief device after an overpressure incident since the shear ring is an internal component with no easy access, and in order to inspect and or replace this element it is required to disassemble the pump resulting in a laborious and time-consuming replacement process and down-time.
  • a pressure relief device for a centrifugal pump having a drive shaft and a seal chamber for sealing a slurry within the inside of the centrifugal pump, the seal chamber positioned on a rear side of the centrifugal pump containing the drive shaft is provided.
  • the pressure relief device may comprise a shear pin, a piston and a rod.
  • the rod may have a first end and a second end and the piston may have a top face and a bottom face.
  • the second end of the rod may be connected to the top face of the piston, the shear pin may be disposed through the rod and the shear pin may be connected to the piston via the rod.
  • the piston may be disposed on the seal chamber such that the bottom face of the piston is directly exposed to the slurry located inside the seal chamber and the top face of the piston is located outside the seal chamber.
  • the piston may be configured to apply a pressure proportional shear force to the shear pin and the shear pin may be configured to break or shear when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure such that the piston can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump.
  • the pressure relief device may further comprise a cylinder, the cylinder for housing the shear pin and the piston. The piston may be positioned within the cylinder and the piston may assume a retracted position within a cavity in the cylinder when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure.
  • the pressure relief device may further comprise a bracket positioned above the piston.
  • the shear pin may be disposed through the bracket and the piston may assume a retracted position below or against the bracket when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure.
  • the pressure relief device may further comprise one or more seals disposed on or around the piston.
  • the seal may be disposed on the piston such that the piston can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump.
  • the sealing chamber may be a stuffing box.
  • the pressure relief device may further comprise a cylinder, the cylinder for housing the shear pin, the piston and the seal; wherein the piston and the seal are positioned within the cylinder and wherein the piston and the seal may assume a retracted position within a cavity in the cylinder when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure.
  • Figure 1 shows an overview of a first exemplary embodiment of the centrifugal pump and pressure relief device.
  • Figure 2 shows a close-up view of a first exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 3 shows an overview of a first exemplary embodiment of the seal chamber and pressure relief device with cut lines A- A and B-B.
  • Figure 4 shows a B-B cross sectional view of a first exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 5 shows a A-A cross sectional view of a first exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 6 shows an overview of a second exemplary embodiment of the centrifugal pump and pressure relief device.
  • Figure 7 shows a close-up view of a second exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 8 shows an overview of a second exemplary embodiment of the seal chamber and pressure relief device with cut lines A-A and B-B.
  • Figure 9 shows a B-B cross sectional view of a second exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 10 shows a A-A cross sectional view of a second exemplary embodiment of the seal chamber and pressure relief device.
  • Figure 1 1 shows a close-up view of section C from Figure 10.
  • FIG. 1 depicts a first exemplary embodiment of the pressure relief device 1 mounted to a seal chamber 1 1, e.g. a stuffing box as shown and further described herein, on a drive side or rear of a centrifugal pump 50.
  • a seal chamber 1 e.g. a stuffing box as shown and further described herein
  • Most centrifugal pumps have a pump casing for containing slurry with an impeller rotating inside of the pump casing.
  • the impeller is typically attached to one end of a cantilevered shaft.
  • the shaft rotates supported in bearings and enters the drive side of the pump casing through a seal chamber 1 1, e.g. through a cylindrical cavity 32, that typically houses a sealing device of some form.
  • the seal chamber 1 1 is normally a separate component that is positioned at the rear of the pump casing and can take a number of forms.
  • One form, as shown in e.g. Figure 2 is a stuffing box.
  • FLSmidth utilizes such a stuffing box on its KREBS millMAX slurry pumps.
  • the pressure relief device 1 may be used with other forms of sealing chambers 1 1, e.g. with centrifugal expeller chambers or mechanical seals which are well known in the art.
  • Figure 2 depicts a first exemplary embodiment of the pressure relief device 1 disposed on a seal chamber 11, e.g. a stuffing box.
  • the stuffing box shown in Figure 2 is comprised of a flat plate 30, a lip 3 1 and a cylindrical cavity 32 for receiving the cantilevered shaft.
  • the stuffing box has bosses 33 (as shown in e.g. Figure 3) disposed on the flat plate 30 or ribs 34, e.g. stiffening ribs, disposed on the flat plate 30 projecting radially outwardly from the cylindrical bore 32 where the pressure relief device 1 is anchored.
  • the seal chamber 1 1, e.g.
  • the stuffing box may be disposed directly on the rear of the pump casing such that the back side of the seal chamber (e.g. the flat plate 30) abuts the casing or the back side of the seal chamber 1 1 may directly contact the slurry within the pump casing.
  • the back side of the seal chamber e.g. the flat plate 30
  • Figures 3-5 depict a first exemplary embodiment of the pressure relief device 1 mounted to the seal chamber 1 1.
  • the pressure relief device 1 has a shear pin 3 and a piston 4, with a top face 4a and a bottom face 4b, and may include a rod 6, with a first top end 6a and a second bottom end 6b, to connect the shear pin 3 to the piston 4.
  • the shear pin 3 may be disposed laterally through the first top end 6a of the rod 6.
  • the second end 6b of the rod 6 can be disposed on the top face 4a of the piston 4.
  • the second end 6b of the rod 6 is integrally connected to the top face 4a of the piston 4.
  • the piston 4 is disposed through the seal chamber 1 1 such that the bottom face 4b of the piston 4 is directly exposed to pressurized slurry which is contained inside the centrifugal pump, i.e. - inside the seal chamber 1 1.
  • the bottom face 4b of the piston 4 may be flush with the inner flat surface of the seal chamber 11.
  • the bottom face 4b of the piston 4 may project past the inner flat surface or back side of the seal chamber 1 1 or outer edge of the pump casing such that the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 11 inside the centrifugal pump casing.
  • the bottom face 4b of the piston 4 When the bottom face 4b of the piston is flush with the inner flat surface of the seal chamber 1 1 or when the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing, the bottom face 4b of the piston 4 is in contact with the slurry.
  • the top face 4a of the piston 4 is located outside of the seal chamber 1 1 and pump casing such that it is not in contact with the slurry and is exposed just to atmospheric pressure.
  • the bottom face 4b of the piston 4 may be comprised of a wear resistant material, e.g. rubber, hard metal, urethane, neoprene or the like, which can eliminate or minimize the impact of erosive wear on the performance of the pressure relief device 1.
  • MTP Maximum Working Pressure
  • An effective relief pressure PI for the pressure relief device will be defined here, whose value can be chosen at any required limit that does not exceed the testing pressure with safety margin 1.5.
  • the effective relief pressure PI is preferably chosen within the range between Maximum Working Pressure and the testing pressure, i.e. within 1.0 - 1.5 times the Maximum Working Pressure.
  • the piston face 4b is exposed to the inner fluid pressure producing a proportional force equal to this pressure by the cross sectional area of the piston, and this load is transferred through rod 6 to the shear pin 3 - such force can be defined as the "pressure proportional shear force" Fl .
  • a shear pin 3 can be selected and configured such that it will shear or break when the pressure proportional shear force Fl exceeds the maximum limit corresponding to the desired effective relief pressure P 1. In operation when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position allowing at least a portion of the slurry to exit from the inside of the centrifugal pump casing which can relieve the internal pressure within the pump.
  • the piston 4 can move upwards such that the bottom face 4b is above the outer edge of the seal chamber 1 1 or pump casing creating an opening for venting of the slurry.
  • there are one or more seals 60 e.g. - O-rings, gaskets, or equivalent seals disposed on and/or around the circumference of the piston 4 for preventing slurry from leaking out of the seal chamber 1 1 / pump casing.
  • seals 60 e.g. - O-rings, gaskets, or equivalent seals
  • the pressure relief device 1 can further comprise a housing, in the form of e.g. a cylinder 2.
  • the cylinder 2 can contain the shear pin 3, the rod 6 and the piston 4.
  • the cylinder 2 has a first longitudinal arm 21, a second longitudinal arm 22 and a connection portion 23 there between.
  • the connection portion 23 connects the upper end of the first longitudinal arm 21 to the upper end of the second longitudinal arm 22.
  • a portion of the lower ends of the first and second longitudinal arms 21, 22 may be disposed on the surface of the seal chamber 1 1, e.g. on the flat plate 30.
  • the first longitudinal arm 21, the second longitudinal arm 22 and the connection portion 23 define a cavity 5.
  • the piston 4 may be disposed at the lower end of the cavity 5.
  • the rod 6 may proj ect from a bore in the upper end of the cavity 5.
  • the cavity 5 may be tapered so that, for example, when the shear pin 3 shears or breaks the piston 4 retracts within the cavity 5 such that the bottom face 4b of the piston is above the tapered section such that the slurry can exit the inside of the centrifugal pump 50 through for example an opening 7.
  • the cylinder 2 also contains shoulder portions 24 projecting laterally from one or more of the longitudinal arms 21, 22.
  • the shoulder portions 24 may be disposed directly on the seal chamber 1 1 or may be disposed on bosses 33 or ribs 34 which project from the cylindrical cavity 32 portion of the seal chamber 1 1.
  • Attachment means 26 such as hex bolts or locking washers can be disposed through the shoulder portions 24 to attach the housing 2 to the seal chamber 1 1.
  • Figure 6 depicts a second exemplary embodiment of the pressure relief device 1 mounted to a seal chamber 1 1, e.g. a stuffing box as shown and further described herein, on the drive side or rear of the centrifugal pump 50.
  • Figure 7 depicts a second exemplary embodiment of the pressure relief device 1 disposed on a seal chamber 1 1, e.g. a stuffing box.
  • the seal chamber 1 1 shown in Figure 7 is identical to the seal chamber 1 1 shown in Figure 2 and described above.
  • Figures 8-1 1 depict a second exemplary embodiment of the pressure relief device 1 mounted to the seal chamber 1 1.
  • the pressure relief device 1 has a shear pin 3and a piston 4, with a top face 4a and a bottom face 4b, and may include a rod 6, with a first top end 6a and a second bottom end 6b, to connect the shear pin 3 to the piston 4.
  • the shear pin 3 may be disposed laterally through the first top end 6a of the rod 6.
  • the second end 6b of the rod 6 can be disposed on the top face 4a of the piston 4.
  • the second end 6b of the rod 6 is integrally connected to the top face 4a of the piston 4.
  • the second end 6b of the rod 6 can be threaded into the piston 4.
  • the piston 4 is disposed through the seal chamber 1 1 such that the bottom face 4b of the piston 4 is directly exposed to pressurized slurry which is contained inside the centrifugal pump, i.e. - inside the seal chamber 1 1.
  • the bottom face 4b of the piston 4 may be flush with the inner flat surface of the seal chamber 1 1.
  • the bottom face 4b of the piston 4 may project past the inner flat surface or back side of the seal chamber 1 1 or outer edge of the pump casing such that the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing.
  • the bottom face 4b of the piston 4 When the bottom face 4b of the piston is flush with the back side of the seal chamber 1 1 or when the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing, the bottom face 4b of the piston 4 is in contact with the slurry.
  • the top face 4a of the piston 4 is located outside of the seal chamber 1 1 and pump casing such that it is not in contact with the slurry and is exposed just to atmospheric pressure.
  • the bottom face 4b of the piston 4 may be comprised of a wear resistant material, e.g.
  • the piston face 4b is exposed to the inner fluid pressure producing a proportional force equal to pressure by the area of the piston, which is applied through rod 6 to the shear pin 3 - such force can be defined as the "pressure proportional shear force" F l .
  • a shear pin 3 can be selected and configured such that it will shear or break when the pressure proportional shear force Fl exceeds the maximum limit corresponding to the desired effective relief pressure PI .
  • the piston 4 When the shear pin 3 shears or breaks due to pump overpressure the piston 4 is able to assume a retracted position allowing at least a portion of the slurry to exit from the inside of the centrifugal pump casing which can relieve the internal pressure within the pump.
  • the piston 4 can move upwards such that the bottom face 4b is above the outer edge of the seal chamber 1 1 or pump casing.
  • there at least one seal 60 e.g. - O-rings, gaskets or equivalent seals
  • the piston 4 In operation, when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position creating an opening for allowing at least a portion of the slurry to exit from the inside of the centrifugal pump.
  • the pressure relief device 1 can further comprise a bar mechanism or bracket 20 where the shear pin 3 is mounted.
  • the shear pin 3 can be disposed laterally through the first top end 6a of the rod 6 and through the bracket 20.
  • the bracket 20 is disposed above the piston 4 and the rod 6 can be disposed through a bore in e.g. the central portion of the bracket 20 such that there is a cavity 5 formed between the piston 4 and the bracket 20.
  • the bracket 20 is connected to the surface of the seal chamber 1 1, e.g. on the flat plate 30.
  • attachment means 26 such as hex bolts or locking washers can be disposed through the bracket 20 to attach the bracket 20 to the seal chamber 1 1, e.g. onto bosses 33 or ribs 34 which project from the cylindrical cavity 32 portion of the seal chamber 1 1.
  • the bracket 20 and the attachment means 26 define a cavity 5.
  • the piston 4 may be disposed at the lower end of the cavity 5.
  • the rod 6 may project from a bore through the bracket 20 in the upper end of the cavity 5.
  • the stem guard 28 may also assist in guaranteeing that enough room is available for the travel of the piston 4 and rod 6.
  • the stem guard 28 may also assist in guaranteeing that enough room is available for the travel of the piston 4 and rod 6.
  • the stem guard 28 may also assist in guaranteeing that enough room is available for the travel of the piston 4 and rod 6.
  • the stem guard 28 may also assist in guaranteeing that enough room is available for the travel of the piston 4 and rod 6.
  • a pressure relief device 1 is simple in design and construction, and is user friendly as the design permits external access resulting in easiness for inspections, shear pin replacement, and fast maintenance in the case of an overpressure shear pin breakage event.
  • This solution can be conveniently retrofitted in existing centrifugal pumps simply by replacing seal chamber 1 1 with a new one that includes the pressure relief device 1.
  • the shear pin 3 or entire pressure relief device 1 can be replaced without the need to disturb pipe connections or disassemble the pump 50. Additionally, by positioning the bottom face 4b of the piston 4 such that it is flush with the inner flat face of the seal chamber 1 1 or stuffing box and directly in contact with the moving slurry, scaling and wear problems associated with standard pressure relief devices when used with slurry pumps can be significantly reduced or eliminated.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

A pressure relief device (1) for a centrifugal pump (50) comprising a shear pin(3), a piston (4) and a rod (6), the rod (6) having a first end (6a) and a second end (6b) and the piston (4) having a top face (4a) and a bottom face (4b), the second end (6b) of the rod (6) connected to the top face (4a) of the piston (4), the shear pin (3) disposed through the rod (6) and connected to the piston (4) via the rod (6). The piston (4) is disposed on the seal chamber (11) such that the bottom face (4b) of the piston (4) is directly exposed to the slurry located inside the seal chamber (11) and the top face (4a) of the piston (4) is located outside the seal chamber (11). The piston (4) is configured to apply a pressure proportional shear force to the shear pin (3). The shear pin (3) is configured to break or shear when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure such that the piston (4) can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump (50).

Description

PRESSURE RELIEF DEVICE FOR CENTRIFUGAL PUMP
FIELD OF THE INVENTION The present invention relates to pressure relief devices for centrifugal pumps used in the mining and mineral processing industries to transport mixtures of liquids and solids such as slurries.
BACKGROUND OF THE INVENTION
Mixtures of liquids and solids, such as slurries in mining and mineral processing operations, are typically transported using centrifugal pumps. Because of the nature of the slurry, pipelines can be susceptible to blockages or "sanding" or the formation of scale deposits or "caking" in some cases, which results in low or zero flow of the slurry through the centrifugal pump. A centrifugal pump operating at a low or zero flow results in progressive heating of the slurry within the pump, which if left unattended results in steam generation and rapid increases in pressure within the pump that can exceed the mechanical limits of the pump and can produce a pump explosion resulting in e.g. catastrophic damage to the centrifugal pump, damage to adjacent equipment or harm to nearby personnel. There have been numerous accidents, particularly in Alumina processing due to the relatively high temperature and high caking tendency of the slurry, and they have been discussed at length in the art. Conventional pressure relief devices tend to be inadequate and unreliable when dealing with slurry pipe blockages, or vulnerable to wear when in contact with the slurry. For example, with conventional pressure relief devices installed in slurry pipelines downstream from the pumps, during a pipe blockage event the pipe connections become obstructed by settling solids or caking, isolating the pump from the relief device and leaving it unprotected. A pressure relief device is provided in US Patent No. 8,287,231 which has several shear tabs arranged around a shear ring that break in the case of over pressurization. In this design, the shear tabs and shear ring are not directly exposed to the slurry and it is the seal chamber which is released in case of an overpressure event, permitting some displacement that is expected to break the seal around the seal chamber and allow the slurry to escape relieving internal pressure. However, this arrangement requires that the pump be disassembled for maintenance or replacement of the pressure relief device after an overpressure incident since the shear ring is an internal component with no easy access, and in order to inspect and or replace this element it is required to disassemble the pump resulting in a laborious and time-consuming replacement process and down-time.
OBJECT OF THE INVENTION
It is an object of the invention to overcome or at least alleviate one or more of the above problems. It is a further object of the invention to provide a pressure relief device for centrifugal pumps that can reduce the risk of human and /or material losses while providing the consumer with a useful or commercial choice that is user friendly to install or retrofit in existing installations, and easier to inspect and maintain.
SUMMARY OF THE INVENTION
A pressure relief device for a centrifugal pump having a drive shaft and a seal chamber for sealing a slurry within the inside of the centrifugal pump, the seal chamber positioned on a rear side of the centrifugal pump containing the drive shaft is provided. The pressure relief device may comprise a shear pin, a piston and a rod. The rod may have a first end and a second end and the piston may have a top face and a bottom face. The second end of the rod may be connected to the top face of the piston, the shear pin may be disposed through the rod and the shear pin may be connected to the piston via the rod. The piston may be disposed on the seal chamber such that the bottom face of the piston is directly exposed to the slurry located inside the seal chamber and the top face of the piston is located outside the seal chamber. The piston may be configured to apply a pressure proportional shear force to the shear pin and the shear pin may be configured to break or shear when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure such that the piston can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump. In an exemplary embodiment, the pressure relief device may further comprise a cylinder, the cylinder for housing the shear pin and the piston. The piston may be positioned within the cylinder and the piston may assume a retracted position within a cavity in the cylinder when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure.
In an exemplary embodiment, the pressure relief device may further comprise a bracket positioned above the piston. The shear pin may be disposed through the bracket and the piston may assume a retracted position below or against the bracket when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure.
In an exemplary embodiment, the pressure relief device may further comprise one or more seals disposed on or around the piston. The seal may be disposed on the piston such that the piston can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump.
In an exemplary embodiment the sealing chamber may be a stuffing box.
In an exemplary embodiment, the pressure relief device may further comprise a cylinder, the cylinder for housing the shear pin, the piston and the seal; wherein the piston and the seal are positioned within the cylinder and wherein the piston and the seal may assume a retracted position within a cavity in the cylinder when the pressure proportional shear force exceeds a limit corresponding to the effective relief pressure. Other details, objects, and advantages of the invention will become apparent as the following description of certain present exemplary embodiments thereof and certain present exemplary methods of practicing the same proceeds.
BRIEF DESCRIPTION OF THE FIGURES
Embodiments of the invention, by way of example only, will be described with reference to the accompanying drawings in which: Figure 1 shows an overview of a first exemplary embodiment of the centrifugal pump and pressure relief device.
Figure 2 shows a close-up view of a first exemplary embodiment of the seal chamber and pressure relief device.
Figure 3 shows an overview of a first exemplary embodiment of the seal chamber and pressure relief device with cut lines A- A and B-B.
Figure 4 shows a B-B cross sectional view of a first exemplary embodiment of the seal chamber and pressure relief device.
Figure 5 shows a A-A cross sectional view of a first exemplary embodiment of the seal chamber and pressure relief device.
Figure 6 shows an overview of a second exemplary embodiment of the centrifugal pump and pressure relief device.
Figure 7 shows a close-up view of a second exemplary embodiment of the seal chamber and pressure relief device.
Figure 8 shows an overview of a second exemplary embodiment of the seal chamber and pressure relief device with cut lines A-A and B-B.
Figure 9 shows a B-B cross sectional view of a second exemplary embodiment of the seal chamber and pressure relief device.
Figure 10 shows a A-A cross sectional view of a second exemplary embodiment of the seal chamber and pressure relief device.
Figure 1 1 shows a close-up view of section C from Figure 10.
DETAILED DESCRIPTION OF THE INVENTION Figure 1 depicts a first exemplary embodiment of the pressure relief device 1 mounted to a seal chamber 1 1, e.g. a stuffing box as shown and further described herein, on a drive side or rear of a centrifugal pump 50. Most centrifugal pumps have a pump casing for containing slurry with an impeller rotating inside of the pump casing. The impeller is typically attached to one end of a cantilevered shaft. The shaft rotates supported in bearings and enters the drive side of the pump casing through a seal chamber 1 1, e.g. through a cylindrical cavity 32, that typically houses a sealing device of some form. The seal chamber 1 1 is normally a separate component that is positioned at the rear of the pump casing and can take a number of forms. One form, as shown in e.g. Figure 2 is a stuffing box. For example, FLSmidth utilizes such a stuffing box on its KREBS millMAX slurry pumps. It is also envisaged herein that the pressure relief device 1 may be used with other forms of sealing chambers 1 1, e.g. with centrifugal expeller chambers or mechanical seals which are well known in the art.
Figure 2 depicts a first exemplary embodiment of the pressure relief device 1 disposed on a seal chamber 11, e.g. a stuffing box. The stuffing box shown in Figure 2 is comprised of a flat plate 30, a lip 3 1 and a cylindrical cavity 32 for receiving the cantilevered shaft. In some embodiments the stuffing box has bosses 33 (as shown in e.g. Figure 3) disposed on the flat plate 30 or ribs 34, e.g. stiffening ribs, disposed on the flat plate 30 projecting radially outwardly from the cylindrical bore 32 where the pressure relief device 1 is anchored. In one embodiment, there are four ribs 34. The seal chamber 1 1, e.g. the stuffing box, may be disposed directly on the rear of the pump casing such that the back side of the seal chamber (e.g. the flat plate 30) abuts the casing or the back side of the seal chamber 1 1 may directly contact the slurry within the pump casing.
Figures 3-5 depict a first exemplary embodiment of the pressure relief device 1 mounted to the seal chamber 1 1. As shown, in an exemplary embodiment, the pressure relief device 1 has a shear pin 3 and a piston 4, with a top face 4a and a bottom face 4b, and may include a rod 6, with a first top end 6a and a second bottom end 6b, to connect the shear pin 3 to the piston 4. The shear pin 3 may be disposed laterally through the first top end 6a of the rod 6. The second end 6b of the rod 6 can be disposed on the top face 4a of the piston 4. In some embodiments the second end 6b of the rod 6 is integrally connected to the top face 4a of the piston 4. As shown, the piston 4 is disposed through the seal chamber 1 1 such that the bottom face 4b of the piston 4 is directly exposed to pressurized slurry which is contained inside the centrifugal pump, i.e. - inside the seal chamber 1 1. In some embodiments, the bottom face 4b of the piston 4 may be flush with the inner flat surface of the seal chamber 11. In other embodiments, the bottom face 4b of the piston 4 may project past the inner flat surface or back side of the seal chamber 1 1 or outer edge of the pump casing such that the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 11 inside the centrifugal pump casing. When the bottom face 4b of the piston is flush with the inner flat surface of the seal chamber 1 1 or when the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing, the bottom face 4b of the piston 4 is in contact with the slurry. By positioning the bottom face 4b of the piston 4 such that it is directly in contact with the slurry scaling problems associated with standard pressure relief devices when protecting slurry pumps can be significantly reduced or eliminated. The top face 4a of the piston 4 is located outside of the seal chamber 1 1 and pump casing such that it is not in contact with the slurry and is exposed just to atmospheric pressure. In some embodiments, the bottom face 4b of the piston 4 may be comprised of a wear resistant material, e.g. rubber, hard metal, urethane, neoprene or the like, which can eliminate or minimize the impact of erosive wear on the performance of the pressure relief device 1.
Slurry inside of an operating centrifugal pump exerts an internal pressure on all the pump walls in contact, including the seal chamber 1 1, and this pressure must remain at all times below a maximum pressure limit specified by the pump manufacturer and typically referred to as the Maximum Working Pressure (MWP) of the pump, which normally will incorporates a safety margin of 1.5. An effective relief pressure PI for the pressure relief device will be defined here, whose value can be chosen at any required limit that does not exceed the testing pressure with safety margin 1.5. The effective relief pressure PI is preferably chosen within the range between Maximum Working Pressure and the testing pressure, i.e. within 1.0 - 1.5 times the Maximum Working Pressure. In operation of the pressure relief device 1, the piston face 4b is exposed to the inner fluid pressure producing a proportional force equal to this pressure by the cross sectional area of the piston, and this load is transferred through rod 6 to the shear pin 3 - such force can be defined as the "pressure proportional shear force" Fl . A shear pin 3 can be selected and configured such that it will shear or break when the pressure proportional shear force Fl exceeds the maximum limit corresponding to the desired effective relief pressure P 1. In operation when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position allowing at least a portion of the slurry to exit from the inside of the centrifugal pump casing which can relieve the internal pressure within the pump. For example, the piston 4 can move upwards such that the bottom face 4b is above the outer edge of the seal chamber 1 1 or pump casing creating an opening for venting of the slurry. In some embodiments, and as shown in e.g. Figure 4, there are one or more seals 60 (e.g. - O-rings, gaskets, or equivalent seals) disposed on and/or around the circumference of the piston 4 for preventing slurry from leaking out of the seal chamber 1 1 / pump casing. In operation, when the shear pin 3 shears or breaks the piston 4 with the seal 60 is able to assume a retracted position allowing at least a portion of the slurry to exit from the inside of the centrifugal pump.
As further shown in e.g. Figure 4, in some embodiments the pressure relief device 1 can further comprise a housing, in the form of e.g. a cylinder 2. The cylinder 2 can contain the shear pin 3, the rod 6 and the piston 4. In some embodiments, the cylinder 2 has a first longitudinal arm 21, a second longitudinal arm 22 and a connection portion 23 there between. The connection portion 23 connects the upper end of the first longitudinal arm 21 to the upper end of the second longitudinal arm 22. A portion of the lower ends of the first and second longitudinal arms 21, 22 may be disposed on the surface of the seal chamber 1 1, e.g. on the flat plate 30. The first longitudinal arm 21, the second longitudinal arm 22 and the connection portion 23 define a cavity 5. The piston 4 may be disposed at the lower end of the cavity 5. The rod 6 may proj ect from a bore in the upper end of the cavity 5. During operation when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position within the cavity 5 which e.g. can fully open the entire piston area for venting of the pressurized slurry to the atmosphere, which can be directed preferably downwards, for example via opening 7 which can be in the form of e.g. slots or grooves, for added safety. The cavity 5 may be tapered so that, for example, when the shear pin 3 shears or breaks the piston 4 retracts within the cavity 5 such that the bottom face 4b of the piston is above the tapered section such that the slurry can exit the inside of the centrifugal pump 50 through for example an opening 7. In some embodiments the cylinder 2 also contains shoulder portions 24 projecting laterally from one or more of the longitudinal arms 21, 22. The shoulder portions 24 may be disposed directly on the seal chamber 1 1 or may be disposed on bosses 33 or ribs 34 which project from the cylindrical cavity 32 portion of the seal chamber 1 1. Attachment means 26 such as hex bolts or locking washers can be disposed through the shoulder portions 24 to attach the housing 2 to the seal chamber 1 1.
Figure 6 depicts a second exemplary embodiment of the pressure relief device 1 mounted to a seal chamber 1 1, e.g. a stuffing box as shown and further described herein, on the drive side or rear of the centrifugal pump 50. Figure 7 depicts a second exemplary embodiment of the pressure relief device 1 disposed on a seal chamber 1 1, e.g. a stuffing box. The seal chamber 1 1 shown in Figure 7 is identical to the seal chamber 1 1 shown in Figure 2 and described above. Figures 8-1 1 depict a second exemplary embodiment of the pressure relief device 1 mounted to the seal chamber 1 1. As shown, in an exemplary embodiment, the pressure relief device 1 has a shear pin 3and a piston 4, with a top face 4a and a bottom face 4b, and may include a rod 6, with a first top end 6a and a second bottom end 6b, to connect the shear pin 3 to the piston 4. The shear pin 3 may be disposed laterally through the first top end 6a of the rod 6. The second end 6b of the rod 6 can be disposed on the top face 4a of the piston 4. In some embodiments the second end 6b of the rod 6 is integrally connected to the top face 4a of the piston 4. In other embodiments, the second end 6b of the rod 6 can be threaded into the piston 4. As shown, the piston 4 is disposed through the seal chamber 1 1 such that the bottom face 4b of the piston 4 is directly exposed to pressurized slurry which is contained inside the centrifugal pump, i.e. - inside the seal chamber 1 1. In some embodiments, the bottom face 4b of the piston 4 may be flush with the inner flat surface of the seal chamber 1 1. In other embodiments, the bottom face 4b of the piston 4 may project past the inner flat surface or back side of the seal chamber 1 1 or outer edge of the pump casing such that the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing. When the bottom face 4b of the piston is flush with the back side of the seal chamber 1 1 or when the bottom face 4b of the piston 4 is completely past the inside edge of the seal chamber 1 1 inside the centrifugal pump casing, the bottom face 4b of the piston 4 is in contact with the slurry. By positioning the bottom face 4b of the piston 4 such that it is directly in contact with the slurry, scaling problems associated with standard pressure relief devices when protecting slurry pumps can be significantly reduced or eliminated. The top face 4a of the piston 4 is located outside of the seal chamber 1 1 and pump casing such that it is not in contact with the slurry and is exposed just to atmospheric pressure. In some embodiments, the bottom face 4b of the piston 4 may be comprised of a wear resistant material, e.g. rubber, hard metal, urethane, neoprene or the like which can eliminate or minimize the impact of erosive wear on the performance of the pressure relief device 1. In operation of the pressure relief device 1 of e.g. Figures 8-1 1, the piston face 4b is exposed to the inner fluid pressure producing a proportional force equal to pressure by the area of the piston, which is applied through rod 6 to the shear pin 3 - such force can be defined as the "pressure proportional shear force" F l . A shear pin 3 can be selected and configured such that it will shear or break when the pressure proportional shear force Fl exceeds the maximum limit corresponding to the desired effective relief pressure PI . When the shear pin 3 shears or breaks due to pump overpressure the piston 4 is able to assume a retracted position allowing at least a portion of the slurry to exit from the inside of the centrifugal pump casing which can relieve the internal pressure within the pump. For example, the piston 4 can move upwards such that the bottom face 4b is above the outer edge of the seal chamber 1 1 or pump casing. In some embodiments, and as shown in e.g. Figure 9, there at least one seal 60 (e.g. - O-rings, gaskets or equivalent seals) disposed on or around the circumference of the piston 4 for preventing slurry from leaking out of the seal chamber 1 1 / pump casing. In operation, when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position creating an opening for allowing at least a portion of the slurry to exit from the inside of the centrifugal pump.
As further shown in e.g. Figure 9, in some embodiments the pressure relief device 1 can further comprise a bar mechanism or bracket 20 where the shear pin 3 is mounted. The shear pin 3 can be disposed laterally through the first top end 6a of the rod 6 and through the bracket 20. The bracket 20 is disposed above the piston 4 and the rod 6 can be disposed through a bore in e.g. the central portion of the bracket 20 such that there is a cavity 5 formed between the piston 4 and the bracket 20. In some embodiments, the bracket 20 is connected to the surface of the seal chamber 1 1, e.g. on the flat plate 30. In some embodiments, attachment means 26 such as hex bolts or locking washers can be disposed through the bracket 20 to attach the bracket 20 to the seal chamber 1 1, e.g. onto bosses 33 or ribs 34 which project from the cylindrical cavity 32 portion of the seal chamber 1 1. The bracket 20 and the attachment means 26 define a cavity 5. The piston 4 may be disposed at the lower end of the cavity 5. The rod 6 may project from a bore through the bracket 20 in the upper end of the cavity 5. In some embodiments, there may be a stem guard 28 disposed on the bracket 20 for accepting the first end 6a of the rod 6 when it retracts through the bore in the bracket 20, which can prevent objects from interfering in the path of the rod 6 as it retracts through the bore and the bracket 20 after an overpressure event. The stem guard 28 may also assist in guaranteeing that enough room is available for the travel of the piston 4 and rod 6. During operation when the shear pin 3 shears or breaks the piston 4 is able to assume a retracted position within the cavity 5. There are numerous advantages to the pressure relief device 1 described and claimed herein. Such a pressure relief device 1 is simple in design and construction, and is user friendly as the design permits external access resulting in easiness for inspections, shear pin replacement, and fast maintenance in the case of an overpressure shear pin breakage event. This solution can be conveniently retrofitted in existing centrifugal pumps simply by replacing seal chamber 1 1 with a new one that includes the pressure relief device 1. The shear pin 3 or entire pressure relief device 1 can be replaced without the need to disturb pipe connections or disassemble the pump 50. Additionally, by positioning the bottom face 4b of the piston 4 such that it is flush with the inner flat face of the seal chamber 1 1 or stuffing box and directly in contact with the moving slurry, scaling and wear problems associated with standard pressure relief devices when used with slurry pumps can be significantly reduced or eliminated.
It is to be understood that the form of this invention as shown is merely a preferred embodiment. Various changes may be made in the function and arrangement of parts; equivalent means may be substituted for those illustrated and described; and certain features may be used independently from others without departing from the spirit and scope of the invention as defined in the following claims.
LIST OF COMPONENTS
1 pressure relief device
2 cylinder
3 shear pin
4 piston
4a top face piston
4b bottom face piston
5 cavity
6 rod
6a first end rod
6b second end rod
7 opening
1 1 seal chamber / stuffing box 20 bracket
21 first longitudinal arm
22 second longitudinal arm
23 connection portion
24 shoulder portions
26 attachment means
28 stem guard
30 flat plate
31 lip
32 cylindrical cavity
33 bosses
34 ribs
50 centrifugal pump
60 seals
Fl pressure proportional shear force PI effective relief pressure

Claims

1. A pressure relief device (1) for a centrifugal pump (50) having a drive shaft and a seal chamber (1 1) for sealing a slurry within the inside of the centrifugal pump (50), the seal chamber (1 1) positioned on a rear side of the centrifugal pump (50) containing the drive shaft, the pressure relief device (1) comprising:
a shear pin (3), a piston (4) and a rod (6), the rod (6) having a first end (6a) and a second end (6b) and the piston (4) having a top face (4a) and a bottom face (4b), the second end (6b) of the rod (6) connected to the top face (4a) of the piston (4), the shear pin (3) disposed through the rod (6) and the shear pin (3) connected to the piston (4) via the rod
(6);
wherein the piston (4) is disposed on the seal chamber (1 1) such that the bottom face (4b) of the piston (4) is directly exposed to the slurry located inside the seal chamber (1 1) and the top face (4a) of the piston (4) is located outside the seal chamber (1 1);
wherein the piston (4) is configured to apply a pressure proportional shear force
(Fl) to the shear pin (3); and
wherein the shear pin (3) is configured to break or shear when the pressure proportional shear force (Fl) exceeds a limit corresponding to an effective relief pressure (PI) such that the piston (4) can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump (50).
2. The pressure relief device of claim 1, further comprising:
a cylinder (2), the cylinder (2) for housing the shear pin (3) and the piston (4); wherein the piston (4) is positioned within the cylinder (2) and wherein the piston (4) can assume a retracted position within a cavity (5) in the cylinder (2) when the pressure proportional shear force (Fl) exceeds the limit corresponding to the effective relief pressure (PI).
3. The pressure relief device of claim 1, further comprising:
a bracket (20) positioned above the piston (4);
wherein the shear pin (3) is disposed through the bracket (20) and wherein the piston (4) can assume a retracted position below or against the bracket (20) when the pressure proportional shear force (F 1) exceeds the limit corresponding to the effective relief pressure (PI).
4. The pressure relief device (1) of claim 1, further comprising one or more seals (60) disposed on or around the piston (4).
5. The pressure relief device of claim 1, wherein the sealing chamber (11) is a stuffing box.
6. The pressure relief device of claim 4, wherein the seal (60) disposed on the piston (4) can assume a retracted position and at least a portion of the slurry can exit the inside of the centrifugal pump (50).
7. The pressure relief device of claim 6, further comprising:
a cylinder (2), the cylinder (2) for housing the shear pin (3), the piston (4) and the seal (60); wherein the piston (4) and the seal (60) are positioned within the cylinder (2) and wherein the piston (4) and the seal (60) can assume a retracted position within a cavity (5) in the cylinder (2) when the pressure proportional shear force (Fl) exceeds the limit corresponding to the effective relief pressure (PI).
EP17777964.2A 2016-09-06 2017-09-06 Pressure relief device for centrifugal pump Withdrawn EP3510287A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201662384055P 2016-09-06 2016-09-06
PCT/IB2017/055361 WO2018047072A1 (en) 2016-09-06 2017-09-06 Pressure relief device for centrifugal pump

Publications (1)

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EP3510287A1 true EP3510287A1 (en) 2019-07-17

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WO (1) WO2018047072A1 (en)

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CN111677927B (en) * 2020-06-16 2022-03-18 中国船舶工业集团公司第七0八研究所 Overpressure relief device with controllable opening mode
WO2025082960A1 (en) 2023-10-18 2025-04-24 F. Hoffmann-La Roche Ag Dpo4 polymerase variants with improved properties

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US8287231B2 (en) 2003-05-23 2012-10-16 Weir Minerals Australia Ltd. Pressure relief arrangement for a pump
WO2010039858A1 (en) * 2008-09-30 2010-04-08 The Gorman-Rupp Company Chopper pump
TWI577911B (en) * 2011-09-02 2017-04-11 Aurotec Gmbh Pipeline with pressure relief valve
CA2890325C (en) * 2012-12-03 2018-10-30 Douglas Paddock Pump with pressure relief system

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