CA1044952A - Method and apparatus for flushing the plunger of a positive displacement pump - Google Patents
Method and apparatus for flushing the plunger of a positive displacement pumpInfo
- Publication number
- CA1044952A CA1044952A CA296,022A CA296022A CA1044952A CA 1044952 A CA1044952 A CA 1044952A CA 296022 A CA296022 A CA 296022A CA 1044952 A CA1044952 A CA 1044952A
- Authority
- CA
- Canada
- Prior art keywords
- packing rings
- plunger
- location
- pressure
- pump
- 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.)
- Expired
Links
Landscapes
- Details Of Reciprocating Pumps (AREA)
Abstract
METHOD AND APPARATUS FOR FLUSHING
THE PLUNGER OF A POSITIVE DISPLACEMENT PUMP
ABSTRACT OF THE DISCLOSURE
A method and apparatus for flushing the plunger of a positive displacement pump which handles a suspension of abrasive particles. Plush liquid is introduced at two or more locations to the packing surrounding the pump plunger. The larger volume of flush liquid is introduced in front of the packing to wash abrasive particles from the plunger in the usual manner.
smaller volume is introduced intermediate front and back sets of packing rings. Initially the back packing rings provide the seal for the plunger, but when they wear, flush liquid from between the two sets of packing rings leaks past the back packing rings to furnish an indication of the wear. The front packing rings now provide the seal, and it is known that the back packing rings should be replaced.
THE PLUNGER OF A POSITIVE DISPLACEMENT PUMP
ABSTRACT OF THE DISCLOSURE
A method and apparatus for flushing the plunger of a positive displacement pump which handles a suspension of abrasive particles. Plush liquid is introduced at two or more locations to the packing surrounding the pump plunger. The larger volume of flush liquid is introduced in front of the packing to wash abrasive particles from the plunger in the usual manner.
smaller volume is introduced intermediate front and back sets of packing rings. Initially the back packing rings provide the seal for the plunger, but when they wear, flush liquid from between the two sets of packing rings leaks past the back packing rings to furnish an indication of the wear. The front packing rings now provide the seal, and it is known that the back packing rings should be replaced.
Description
s~
This invention relates to an improved me~hod and apparatus for flushing the plunger of a posi~ive displacement pump.
Although the invention is not thus limited, our flushing method and apparatus are particularly useful as ~pplied to slurry pumps which handle water suspensions of abrasive particles. A conventional positive displacement slurry pump includes a plurality of cylinders, xespec~ive plungers in each cyli~der, and packing rings surr~unding ~he plungers where they enter~the cylinders. In operating such pumps, it is conventional to flush the plungers with ~lean water or other flush liquid applied immediately in front of the packing rings to wash away abrasive particles and prevent such particles from being drawn into the packing during suction ~trokes of the plungers.
Several types of flush systems have been used heretofore, among which are:
~ a) Low pressure flush, in which a small quantity of clean flush liquid flows around the plunger through a narrow annular passage in the cylinder wall only during suction strokes of the plunger. A check valve in the flush liquid supply line prevents back flow during discharge strokes.
(b) Synchronized flush, in which a small flush pump is synchronized to discharge flush liquid into the annular ~rea ahead of the packing during suction strokes of the slurry pump.
tc) High pressure flush, in which clean flush liquid is introduced to an annular passage around the plunger at a pressure slightly higher than the pump discharge pr~ssure. This system enables a large portion of the flush liquid to flow around the plunger during suction strokes when the pressure differential is greatest and the flush liquid is needed to exclude abrasive
This invention relates to an improved me~hod and apparatus for flushing the plunger of a posi~ive displacement pump.
Although the invention is not thus limited, our flushing method and apparatus are particularly useful as ~pplied to slurry pumps which handle water suspensions of abrasive particles. A conventional positive displacement slurry pump includes a plurality of cylinders, xespec~ive plungers in each cyli~der, and packing rings surr~unding ~he plungers where they enter~the cylinders. In operating such pumps, it is conventional to flush the plungers with ~lean water or other flush liquid applied immediately in front of the packing rings to wash away abrasive particles and prevent such particles from being drawn into the packing during suction ~trokes of the plungers.
Several types of flush systems have been used heretofore, among which are:
~ a) Low pressure flush, in which a small quantity of clean flush liquid flows around the plunger through a narrow annular passage in the cylinder wall only during suction strokes of the plunger. A check valve in the flush liquid supply line prevents back flow during discharge strokes.
(b) Synchronized flush, in which a small flush pump is synchronized to discharge flush liquid into the annular ~rea ahead of the packing during suction strokes of the slurry pump.
tc) High pressure flush, in which clean flush liquid is introduced to an annular passage around the plunger at a pressure slightly higher than the pump discharge pr~ssure. This system enables a large portion of the flush liquid to flow around the plunger during suction strokes when the pressure differential is greatest and the flush liquid is needed to exclude abrasive
- 2 - ~
particles from the packing. A small flow is maintained during discharge strokes, thus eliminating need :fDr check valves or synchronizing means and assuring ~lean packing at all times.
An object of ~he present invent:ion is to p~ovide an improved flushing methc~ and apparatus of th~ high pressure type in which we effectively wash particles fro~ a pump pl~r.aer and exclude them from the packing and at the same time obtain a ready indication of ~he condition of the packing.
According to the present invention, there is provided, in a pumping operation in which a suspension of particles is handled in a positive displacement pump, the plunger of which passes through front and back sets of packing rings, a method of flushing particles from said plunger, said method comprising introducing flush liquid to said plunger at a location in front of said front set of packing rings, introducing a smaller volume of flush liquid at a location between said front and back sets of packing rings, and initially maintaining the liquid introduced at the two locations at approximately the same pressure and relying on said back set of packing rings to provide a seal for said Plun~er, wherebv when the ~ackinq rinqs of said back set wear and commence to leak a differential in the pressure of the flus~
liquid introduced at the two locations is created and said front set of packing rings provides the seal.
The invention also provides a positive displacement pump for handling a suspension of particles, comprising at least one cylinder, a plunger reciprocable in said cylinder, a stuffing box carried by said cylinder, front and back sets of packing rings within said stuffing box surrounding said plunger, and a flushing apparatus comprising means for introducing flush liquid to said stuffing box at a first location in front of said front set of packing rings to wash particles from said plunger and prevent ~4~
the particles from being drawn into said packing rings, and means for introducing a smaller volume of ~lush liquid to said stuffing box at a second location between said front and back sets of packing rings initially at substantially the same pressure as the liquid introduced at the first location, whereby said back set of packing rings initially provides a seal for said plunger, and said front set of packing rings provides a seal for said plunger after the packing rings of said back set wear and commence to leak and thereby create a differential in the pressure of the flushing liquid introduced at the two locations.
The invention is further described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a vertical sectional view through onecylinder of a positive displacement pump equipped with our flushing apparatus; and Figure 2 is a diagrammatic view of a modified arrangement for supplying flush liquid to the pump.
Figure 1 shows one cylinder 10 of a positive displacement pump, such as may be used for pumpin~ slurries of abrasive particles suspended in water. The pump includes a plunger 12 arranged for reciprocable movement within the cylinder, suction and discharge manifolds 13 and 14, and suction and discharge valves 15 and 16. A ~tuffing box 17 surrounds the plunger, and contains front and back sets of packing rings 18 and 19/ an intermediate lantern ring 20 between the two sets of packing rings, a front lantern ring 21, and spreader rings 22 in front of the lantern ring 21. A suitable drive (not shown) is connected to the plunger 12 to reciprocate i~ out of and into the cylinder 10 through suction and disch~rge strokes. The pump illustrated is conventional, apart from ~he flushing apparatu~ and some of the packing details, and hence ~s not described in detail.
i2 The flushing apparatus of the present invention includes a flush manifold 26 from which extends a pipe 27 preferably containing a check valve 28. ~wo branch pipes 29 and 30 extend from pipe 27 beyond the check valve. The larger branch 29 is c~nnected int~ the stuffing box 17 in line with the front lantern ring 21, and contains a relatively large orifice 31 and a check valve 32. The smaller branch 30 is connected in~o the ~tuffing box in line with the intermediate lantern ring 20 and contains a relatively small orifice 33. Preferably we connect a pressure measuring device 34, illustrated as a gauge, to the stuffing box 17 also in line with the intermediate lantern ring. The flush manifold 26 is connected to a suitable source of flush liquid at a pressure higher than the discharge pressure of the pump.
Figure ~ shows a modification in which we locate the large orifice 31 in pipe 27 upstream of the branch pipes 29 and 30. This modification assures that the flow through the small orifice 32 is relatively low without need for the small orifice to be so small that it readily clogs.
According to our flushing method, the larger branch pipe 29 and orifice 31 carry a relatively large volume of flush liquid from the manifold 26 to the stuffing box ~7. This liquid serves to wash particles from the plunger 12 during its suction strokes and thus acts in the usual manner to prevent the particles from being drawn ints the front set of packing rings 18. The smaller branch pipe 30 and orifice 33 carry a relatively small volume of flush liquid to the intermediate lantern ring ~0.
The pressure measuring device 34 indica~es the pressure at this ring. The check ~alves 28 and 32 prevent flush liquid from backing up during discharge stro~es ~ thc plunger. The check valve 32 also prevent~ ~lurry from entering the back section o~
the flush ~ystem if the pac~ing fail~ or if there i5 a ~alfunction in ~he flu~h ~y~te~.
~L~4~
Initially there is approximately equal pressure at ~pposite si~es ~f the fr~nt set of packing rings 18, while there is a pressure differential at opposite sides of the back set of packing rings 19, since the latter are subject only to atmospheric pressure at their back end. Under these conditions the back packing rings provide the seal around the plunger. Hence they are the first t~ wear and eventually begin t~ leak.
Nevertheless they continue t~ provide the seal until they leak at a greater rate than flush liquid is delivered t~ the intermediate lantern ring 20. At this stage the pressure at the intermediate lantern ring drops a~d there i5 a pressure differential at opposite sides of the front set of packing rings la, The fr~nt packing rings now provide a seal for the plunger 12.
We can detect the point at which the back packing rings 19 cease to pr~ide a seal in several ways. We may detect it by observing an increase in flow through the branch pipe 30 supplying flush liquid to the intermediate lantern ring 20. We may detect it by observing a pressure drop at the intermediate ring, as indicated by the pressure gauge 34. We may also detect it by observing the volume of liquid leaking past the back packing rings. By observing the deterioration of the back packing rings, we can schedule packing replacement while the front packing rings are providing a seal before they wear out.
~ rom the foregoing description it is seen that our inventi~n provides a flushing method and apparatus which effectively wash particles from the plunger of a p~si~ive displacement pump and at the same time facilitate ~etermining the ~tate ~f wear of the plunger paclcing. The invention enables the packing t~ be replaced ~nly when necessary with~ut waiting for a total failure to take place.
particles from the packing. A small flow is maintained during discharge strokes, thus eliminating need :fDr check valves or synchronizing means and assuring ~lean packing at all times.
An object of ~he present invent:ion is to p~ovide an improved flushing methc~ and apparatus of th~ high pressure type in which we effectively wash particles fro~ a pump pl~r.aer and exclude them from the packing and at the same time obtain a ready indication of ~he condition of the packing.
According to the present invention, there is provided, in a pumping operation in which a suspension of particles is handled in a positive displacement pump, the plunger of which passes through front and back sets of packing rings, a method of flushing particles from said plunger, said method comprising introducing flush liquid to said plunger at a location in front of said front set of packing rings, introducing a smaller volume of flush liquid at a location between said front and back sets of packing rings, and initially maintaining the liquid introduced at the two locations at approximately the same pressure and relying on said back set of packing rings to provide a seal for said Plun~er, wherebv when the ~ackinq rinqs of said back set wear and commence to leak a differential in the pressure of the flus~
liquid introduced at the two locations is created and said front set of packing rings provides the seal.
The invention also provides a positive displacement pump for handling a suspension of particles, comprising at least one cylinder, a plunger reciprocable in said cylinder, a stuffing box carried by said cylinder, front and back sets of packing rings within said stuffing box surrounding said plunger, and a flushing apparatus comprising means for introducing flush liquid to said stuffing box at a first location in front of said front set of packing rings to wash particles from said plunger and prevent ~4~
the particles from being drawn into said packing rings, and means for introducing a smaller volume of ~lush liquid to said stuffing box at a second location between said front and back sets of packing rings initially at substantially the same pressure as the liquid introduced at the first location, whereby said back set of packing rings initially provides a seal for said plunger, and said front set of packing rings provides a seal for said plunger after the packing rings of said back set wear and commence to leak and thereby create a differential in the pressure of the flushing liquid introduced at the two locations.
The invention is further described, by way of example, with reference to the accompanying drawings, in which:-Figure 1 is a vertical sectional view through onecylinder of a positive displacement pump equipped with our flushing apparatus; and Figure 2 is a diagrammatic view of a modified arrangement for supplying flush liquid to the pump.
Figure 1 shows one cylinder 10 of a positive displacement pump, such as may be used for pumpin~ slurries of abrasive particles suspended in water. The pump includes a plunger 12 arranged for reciprocable movement within the cylinder, suction and discharge manifolds 13 and 14, and suction and discharge valves 15 and 16. A ~tuffing box 17 surrounds the plunger, and contains front and back sets of packing rings 18 and 19/ an intermediate lantern ring 20 between the two sets of packing rings, a front lantern ring 21, and spreader rings 22 in front of the lantern ring 21. A suitable drive (not shown) is connected to the plunger 12 to reciprocate i~ out of and into the cylinder 10 through suction and disch~rge strokes. The pump illustrated is conventional, apart from ~he flushing apparatu~ and some of the packing details, and hence ~s not described in detail.
i2 The flushing apparatus of the present invention includes a flush manifold 26 from which extends a pipe 27 preferably containing a check valve 28. ~wo branch pipes 29 and 30 extend from pipe 27 beyond the check valve. The larger branch 29 is c~nnected int~ the stuffing box 17 in line with the front lantern ring 21, and contains a relatively large orifice 31 and a check valve 32. The smaller branch 30 is connected in~o the ~tuffing box in line with the intermediate lantern ring 20 and contains a relatively small orifice 33. Preferably we connect a pressure measuring device 34, illustrated as a gauge, to the stuffing box 17 also in line with the intermediate lantern ring. The flush manifold 26 is connected to a suitable source of flush liquid at a pressure higher than the discharge pressure of the pump.
Figure ~ shows a modification in which we locate the large orifice 31 in pipe 27 upstream of the branch pipes 29 and 30. This modification assures that the flow through the small orifice 32 is relatively low without need for the small orifice to be so small that it readily clogs.
According to our flushing method, the larger branch pipe 29 and orifice 31 carry a relatively large volume of flush liquid from the manifold 26 to the stuffing box ~7. This liquid serves to wash particles from the plunger 12 during its suction strokes and thus acts in the usual manner to prevent the particles from being drawn ints the front set of packing rings 18. The smaller branch pipe 30 and orifice 33 carry a relatively small volume of flush liquid to the intermediate lantern ring ~0.
The pressure measuring device 34 indica~es the pressure at this ring. The check ~alves 28 and 32 prevent flush liquid from backing up during discharge stro~es ~ thc plunger. The check valve 32 also prevent~ ~lurry from entering the back section o~
the flush ~ystem if the pac~ing fail~ or if there i5 a ~alfunction in ~he flu~h ~y~te~.
~L~4~
Initially there is approximately equal pressure at ~pposite si~es ~f the fr~nt set of packing rings 18, while there is a pressure differential at opposite sides of the back set of packing rings 19, since the latter are subject only to atmospheric pressure at their back end. Under these conditions the back packing rings provide the seal around the plunger. Hence they are the first t~ wear and eventually begin t~ leak.
Nevertheless they continue t~ provide the seal until they leak at a greater rate than flush liquid is delivered t~ the intermediate lantern ring 20. At this stage the pressure at the intermediate lantern ring drops a~d there i5 a pressure differential at opposite sides of the front set of packing rings la, The fr~nt packing rings now provide a seal for the plunger 12.
We can detect the point at which the back packing rings 19 cease to pr~ide a seal in several ways. We may detect it by observing an increase in flow through the branch pipe 30 supplying flush liquid to the intermediate lantern ring 20. We may detect it by observing a pressure drop at the intermediate ring, as indicated by the pressure gauge 34. We may also detect it by observing the volume of liquid leaking past the back packing rings. By observing the deterioration of the back packing rings, we can schedule packing replacement while the front packing rings are providing a seal before they wear out.
~ rom the foregoing description it is seen that our inventi~n provides a flushing method and apparatus which effectively wash particles from the plunger of a p~si~ive displacement pump and at the same time facilitate ~etermining the ~tate ~f wear of the plunger paclcing. The invention enables the packing t~ be replaced ~nly when necessary with~ut waiting for a total failure to take place.
Claims (9)
INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED
ARE AS FOLLOWS:
1. In a pumping operation in which a suspension of particles is handled in a positive displacement pump, the plunger of which passes through front and back sets of packing rings, a method of flushing particles from said plunger, said method comprising introducing flush liquid to said plunger at a location in front of said front set of packing rings, introducing a smaller volume of flush liquid at a location between said front and back sets of packing rings, and initially maintaining the liquid introduced at the two locations at approximately the same pressure and relying on said back set of packing rings to pro-vide a seal for said plunger, whereby when the packing rings of said back set wear and commence to leak a differential in the pressure of the flush liquid introduced at the two locations is created and said front set of packing rings provides the seal.
2. A method as claimed in claim 1 in which the pressure of flush liquid introduced at the first location is greater than the discharge pressure of the pump.
3. A method as claimed in claim 1 or claim 2 in which the suspension is a water slurry of abrasive particles and the flush liquid is water.
4. A method as claimed in claim 1 including the step of measuring the pressure of liquid introduced between said sets of packing rings.
5. A positive displacement pump for handling a suspension of particles, comprising at least one cylinder, a plunger recipro-cable in said cylinder, a stuffing box carried by said cylinder, front and back sets of packing rings within said stuffing box surrounding said plunger, and a flushing apparatus comprising means for introducing flush liquid to said stuffing box at a first location in front of said front set of packing rings to wash particles from said plunger and prevent the particles from being drawn into said packing rings, and means for introducing a smaller volume of flush liquid to said stuffing box at a second location between said front and back sets of packing rings initially at substantially the same pressure as the liquid introduced at the first location, whereby said back set of packing rings initially provides a seal for said plunger, and said front set of packing rings provides a seal for said plunger after the packing rings of said back set wear and commence to leak and thereby create a differential in the pressure of the flushing liquid introduced at the two locations.
6. A pump as claimed in claim 5 in which the pressure at which the flush liquid is introduced at the first location is greater than the discharge pressure of the pump.
7. A pump as claimed in claim 5 including a pressure gauge in communication with the interior of said stuffing box be-tween said front and back sets of packing rings.
8. A pump as claimed in claim 5 including, in said stuffing box, a front lantern ring at said first location and an intermediate lantern ring at said second location.
9. A pump as claimed in any one of claims 5 to 7 in which the two means for introducing flushing liquid include a flush manifold, a pipe extending from saicL manifold, a larger branch pipe extending from said pipe to said first location, a smaller branch pipe extending from said pipe to said second location, a check valve and a larger flow orifice in said first-named pipe, a check valve in said larger branch pipe, and a smaller flow orifice in said smaller branch pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,022A CA1044952A (en) | 1978-02-02 | 1978-02-02 | Method and apparatus for flushing the plunger of a positive displacement pump |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA296,022A CA1044952A (en) | 1978-02-02 | 1978-02-02 | Method and apparatus for flushing the plunger of a positive displacement pump |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1044952A true CA1044952A (en) | 1978-12-26 |
Family
ID=4110666
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA296,022A Expired CA1044952A (en) | 1978-02-02 | 1978-02-02 | Method and apparatus for flushing the plunger of a positive displacement pump |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1044952A (en) |
-
1978
- 1978-02-02 CA CA296,022A patent/CA1044952A/en not_active Expired
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