CA2466434C - Mechanism for sealing a rotating shaft from load end leakage - Google Patents
Mechanism for sealing a rotating shaft from load end leakage Download PDFInfo
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- CA2466434C CA2466434C CA 2466434 CA2466434A CA2466434C CA 2466434 C CA2466434 C CA 2466434C CA 2466434 CA2466434 CA 2466434 CA 2466434 A CA2466434 A CA 2466434A CA 2466434 C CA2466434 C CA 2466434C
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Abstract
A sealing mechanism to prevent leakage out of a pump along the shaft to the motor, has the shaft running through an adaptor housing which connects the motor to the pump; a primary shaft seal at the pump end of the adaptor housing and a secondary seal at the motor end; the secondary seal has an energization source for seal pressure that is radially displaced from the seal faces; a seal leakage outlet at the lowest point in the adaptor hauling provides gravity drainage of leaking material; the outlet has a large cross section area relative to the cross section area of the leaf; path annulus of the primary seal so the secondary seal has a pressure rating less than primary seal pressure; the bearing assembly, adaptor housing, shaft, seals and pump in combination have a shaft overhang L3/D4 ratio of less than 50.
Description
159flP08CA01 MEC ISM FOR SEALI~1G A ROTATING S FROM LOAD END
LEAKAGE
Field of Invention This invention relates to a sealing methodology for rotating machinery. More particularly, this invention relates to a sealing mechanism far sealing a rotating shaft against passage of a fluid along a central axis defined by the shaft.
Background of the Invention Environmentally hazardous media such as acids, oils, and toxins, in both liquid and gaseous form, that can cause serious harm to the environme~~t, often need to be processed within systems consisting of pipes and vessels. These systems often utilize rotating shaft driven equipment such as compressors, blowers, pumps and mixers to transfer or agitate the fluid or gaseous media within the process system. When handling such dangerous media, it is important that the media does not escape to the atmosphere.
Heretofore, conventional mechanical seals were developed to overcome rotating shaft sealing problems. When functioning properly these prior art mechanical seals can be configured to allow for a fairly secure seal against the fluids and gaseous media so as to limit leakage along the shaft to detection levels that are compliant with current federal and state environmental guidelines. Mechanical seals are available in numerous configurations, usually involving a combination of staging of flat seal faces and various ports that allow for flushing, draining, or venting. A number of these priar art configurations are shown by reference herein. Regardless of the configuration the objective is to prevent leakage of hazardous media to the atmosphere.
Predicting the amount of staging or the complexity required can only be broadly approximated based on the type of media being handled. The more hazardous the liquid or gas, the more secure the seal construction need be.
_1_ One problem with the aforesaid conventional mechanical seals is that gasses by themselves, or gases produced by liquids that are being sealed against, often escape.
Conventional mechanical seals are often permeated by these vapors. One solution to this problem was the creation of a seal configuration known as a double seal 'with a barner fluid, or gas, protection. In this arrangement, two seals form a cavity that is filled with a clean or environmentally safe fluid, or inert gas, referred to herein as the barrier, at a higher pressure than the liquid or gasses being sealed against. Because of this higher pressure, flow is from the barrier side of the seal to the hazardous process side, preventing any atmospheric contamination.
A drawback associated with conventional double seal systems is that any failure by the first seal can defeat the entire double seal arrangement. If the first of the two seals breaks down, the barrier is permitted to escape from the cavity, in effect allowing the harmful liquid or gases to reach the second seal at a higher than atmospheric pressure. 'The hazardous liquid or gas then penetrates the second seal due to its higher pressure thus creating harmful leakage that can injure people and pollute tl~e surrounding environment.
Therefore there exists a need for a reliable seal system that will not leak to the outside environment in the event of failure of a conventional mechanical seal.
The breaking of the aforesaid conventional double seals is a problem of longstanding concern due to the sometimes high differential pressures that they operate under. These high pressures often result in a break or Leak in one of the two seals. Often conventional double seals share common internal parts. When one seal fails, damage to the 1 st seal can often adversely affect shared components failing the second seal. Therefore, there exists a need for a seal arrangement that would be relatively unaffected by the failure, or leakage, of an adjacent seal.
Another problem with conventional mechanical seals of this type is that they utilize springs, bellows, or other forms of mechanical means to energize sealing surfaces and assist them in maintaining a close proximity with each other for proper seal operation.
LEAKAGE
Field of Invention This invention relates to a sealing methodology for rotating machinery. More particularly, this invention relates to a sealing mechanism far sealing a rotating shaft against passage of a fluid along a central axis defined by the shaft.
Background of the Invention Environmentally hazardous media such as acids, oils, and toxins, in both liquid and gaseous form, that can cause serious harm to the environme~~t, often need to be processed within systems consisting of pipes and vessels. These systems often utilize rotating shaft driven equipment such as compressors, blowers, pumps and mixers to transfer or agitate the fluid or gaseous media within the process system. When handling such dangerous media, it is important that the media does not escape to the atmosphere.
Heretofore, conventional mechanical seals were developed to overcome rotating shaft sealing problems. When functioning properly these prior art mechanical seals can be configured to allow for a fairly secure seal against the fluids and gaseous media so as to limit leakage along the shaft to detection levels that are compliant with current federal and state environmental guidelines. Mechanical seals are available in numerous configurations, usually involving a combination of staging of flat seal faces and various ports that allow for flushing, draining, or venting. A number of these priar art configurations are shown by reference herein. Regardless of the configuration the objective is to prevent leakage of hazardous media to the atmosphere.
Predicting the amount of staging or the complexity required can only be broadly approximated based on the type of media being handled. The more hazardous the liquid or gas, the more secure the seal construction need be.
_1_ One problem with the aforesaid conventional mechanical seals is that gasses by themselves, or gases produced by liquids that are being sealed against, often escape.
Conventional mechanical seals are often permeated by these vapors. One solution to this problem was the creation of a seal configuration known as a double seal 'with a barner fluid, or gas, protection. In this arrangement, two seals form a cavity that is filled with a clean or environmentally safe fluid, or inert gas, referred to herein as the barrier, at a higher pressure than the liquid or gasses being sealed against. Because of this higher pressure, flow is from the barrier side of the seal to the hazardous process side, preventing any atmospheric contamination.
A drawback associated with conventional double seal systems is that any failure by the first seal can defeat the entire double seal arrangement. If the first of the two seals breaks down, the barrier is permitted to escape from the cavity, in effect allowing the harmful liquid or gases to reach the second seal at a higher than atmospheric pressure. 'The hazardous liquid or gas then penetrates the second seal due to its higher pressure thus creating harmful leakage that can injure people and pollute tl~e surrounding environment.
Therefore there exists a need for a reliable seal system that will not leak to the outside environment in the event of failure of a conventional mechanical seal.
The breaking of the aforesaid conventional double seals is a problem of longstanding concern due to the sometimes high differential pressures that they operate under. These high pressures often result in a break or Leak in one of the two seals. Often conventional double seals share common internal parts. When one seal fails, damage to the 1 st seal can often adversely affect shared components failing the second seal. Therefore, there exists a need for a seal arrangement that would be relatively unaffected by the failure, or leakage, of an adjacent seal.
Another problem with conventional mechanical seals of this type is that they utilize springs, bellows, or other forms of mechanical means to energize sealing surfaces and assist them in maintaining a close proximity with each other for proper seal operation.
-2-This adds to the complexity, cost, and the overall shaft length required to accommodate the seal arrangement. Increased seal length increases the a:~ial distance between the supporting bearings and the driven load. Those familiar with the art of rotating equipment design recognize that this in turn causes an increase in bending or deflection of the shaft that in itself is a known contributing factor to failure of mechanical seals.
Therefore there exits a need for a seal system of simple design that shortens the shaft overhang required for a multiple stage sealing arrangement.
Some equipment, such as that described by Rockwood U.S. Pat. No. 5,261,676, attempt to eliminate the possibility of sealing leakage to atmosphere; by enclosing the bearing frame and the sealed media within a common housing sealed from the external environment. Rockwood teaches the use of multiple barrier sealing devices including an expeller, multiple stage seal arrangement, and piston seal arrangement, al.l arranged axially between the motor and pump assembly adding complexity and cost to that assembly.
Another common alternative is to use what is known as a close coupled motor. A
close couple motor eliminates a bearing housing, driving the load directly with an extended shaft supported by the motor bearings. Close coupled motors either rely on conventional mechanical seals, with all of the size, complexity, and cost associated therewith, such as described by Gogwer U.S. Patent 566012, or they rely on elastomeric seals such as Ramthum U.S. Patent 6008556 that rub on the rotating shaft, expellers such as Thompson U.S. patent 633453 that use a pumping device, either attached to, or integral with the rotating shaft, various labyrinth designs such as Orlowski U.S.
Patent 6311984 that use a torturous path with a combination vents and drains. Elastomeric Seals, expellers, and labyrinth designs are effective at keeping grease or oil in a bearing, and are somewhat effective in dealing with incidental weepage from an adjacent mechanical seal.
However none of these designs can seal completely against a positive pressure, such as from a failed mechanical seal, on a continuous basis, both when the machine is idle and when it is in operation.
Therefore there exits a need for a seal system of simple design that shortens the shaft overhang required for a multiple stage sealing arrangement.
Some equipment, such as that described by Rockwood U.S. Pat. No. 5,261,676, attempt to eliminate the possibility of sealing leakage to atmosphere; by enclosing the bearing frame and the sealed media within a common housing sealed from the external environment. Rockwood teaches the use of multiple barrier sealing devices including an expeller, multiple stage seal arrangement, and piston seal arrangement, al.l arranged axially between the motor and pump assembly adding complexity and cost to that assembly.
Another common alternative is to use what is known as a close coupled motor. A
close couple motor eliminates a bearing housing, driving the load directly with an extended shaft supported by the motor bearings. Close coupled motors either rely on conventional mechanical seals, with all of the size, complexity, and cost associated therewith, such as described by Gogwer U.S. Patent 566012, or they rely on elastomeric seals such as Ramthum U.S. Patent 6008556 that rub on the rotating shaft, expellers such as Thompson U.S. patent 633453 that use a pumping device, either attached to, or integral with the rotating shaft, various labyrinth designs such as Orlowski U.S.
Patent 6311984 that use a torturous path with a combination vents and drains. Elastomeric Seals, expellers, and labyrinth designs are effective at keeping grease or oil in a bearing, and are somewhat effective in dealing with incidental weepage from an adjacent mechanical seal.
However none of these designs can seal completely against a positive pressure, such as from a failed mechanical seal, on a continuous basis, both when the machine is idle and when it is in operation.
-3-All rotating equipment that incorporate shaft seals in conjunction with an overhung shaft use a certain amount axial distance between the driven load and the closest bearing to accommodate housings, covers, and the sealing arrangement. Paul E. Griggs' pending U.S. application ser. no. 10/093,99, incorporated herein by reference, teaches that applying L3/D4 of less than 50 to a canned motor seal design greatly improves the shaft stiffness and thus the operating environment for the mechanical seal. The L3/D4 ratio is defined as the overhung shaft length (L) measured between the axial centerline of the bearing closest to the impeller (inboard bearing) and the axial centerline of impeller cubed (L3) divided by the shaft diameter (D), defined as the diameter of the smallest cross section within length L, exclusive of the impeller mounting surface, raised to the fourth power (Da) A larger the L3/D4 ratio results in more shaft deflection. Such shaft deflection may be generated by any unexpected operating conditions such as pump cavitations, closed suction or discharge valves, or improper operating conditions i.e. improper equipment selection. Greater shaft deflection results in greater wear on seals and bearings in the system. Close coupled motors are particularly susceptible to deflection problems because the shaft extension is usually applied by the motor manufacturer without changing the motor frame or bearing design. This results in close coupled motors having a poor reputation for maintaining seal reliability. It would be desirable to reduce;
the L3/D4 to less than 50 on new designs and to reduce it on retrofits where the existing bearing frame or close coupled motor is used in a conversion to this innovative sealing system thereby increasing the seal reliability. It would further be desirable to achieve the improved decreased L31D4 while at the same time lowering the manufacturing cost.
Canned motors are an excellent choice for handling hazardous media. The problem with canned motors is that they are expensive to build due to the extra containment housings (or cans) and they typically rely on a liquid filled cavity for lubrication.
The extra drag associated with rotating the cans through a viscous fluid decreases the motor efficiency and increases the cost of operation due to the increased power draw. Therefore it would be desirous to have a design that will not leak process liquids or gasses to atmosphere and _q._ that eliminates the additional costs associated with containment cans and that does not rewire a liquid filled housing for bearing lubrication.
Summary of the Invention The principle object of this invention is to provide a sealing arrangement which enables the user to efficiently and safely handle fluids and gasses.
Another object of this invention is to provide a sealing arrangement that will not leak to the outside environment in the event of failure of a conventional mechanical seal.
Another object of the invention is to provide a sealing arrangement with .at least one sealing member that is relatively unaffected by the failure of adjacent seals.
1 S It is still a further object of this invention to provide a simple seal design that shortens the shaft overhang required of a multiple stage sealing arrangement.
It is still a further object of this invention to provide a close-couple motor arrangement that can effectively seal against positive pressure, such as from a failed mechanical seal, on a continuous basis, both when the machine is idle, and when it is in operation, without the use of mechanically energized seal faces.
It is still a further object of this invention to provide and enable the use of a L3/D4 of less than 50 at a reduced cost relative to similar machines using mechanically energized seal faces to achieve the same Ievel of sealing protection.
It is still a further object of this invention to enable the reduction of L3/Dø on retrofit units thereby increasing their seal reliability while simultaneously providing a design that prevents leakage of harmful liquids or gasses to the environment.
It is still a further object of this invention to provide a close-coupled configuration whereby the motor is protected from cantamination from the process media.
It is still a further object of this invention to provide protection against leakage of hazardous liquids and gasses to the environment, without utilizing mechanically energized seal faces to seal bearing frames or motor housings, and to do so without the cost associated with motor cans, or the viscous drag associated with liquid filled housings.
According to the invention, the arrangement of construction, preferably, has a shaft driven load rnernber such as an impeller, mixer, or fan, mounted on rotatable drive shaft cantilevered some axial distance from a supporting bearing such that the load member is exposed to a process liquid or gas that is desirable to seal from the external environment.
The process is sealed by a first mechanical shaft seal of a conventional type whereby flat seating faces are held in extremely close proximity each other by a combination of mechanical energization means, such as bellows and springs, and any pressure differential that exists between the upstream (process) side, and the downstream (non-process) side of the seal. This seal can be in a single or mufti-stage configuration and can be designed to seal either gas or liquid. This seal will herein. be referred to as the primary seal. For the purpose of clarification herein the side of any component that is closest in the axial direction to the driven load will be referred to as the inboard side and the side of any component that is located axially furthest away from the driven load will be referred to as the outboard side. A second seal activated by a radially displaced source of sealing force, such as by a radially adjacent magnetic force applied between the sealing surfaces, and capable of withstanding a sufficient differential pressure from either liquid or gas without leakage, while either running or idle, is positioned indeper.~dently, in that it has no shared components with the first seal, axially along the shaft on the outboard side of the primary seal. This second seal, referred to herein as the secondary seal, is mounted in an adapter housing that mates to either a motor or bearing frame such that the secondary seal is positioned between the primary seal and the most inboard bearing within the bearing ar motor housing. The axial space required by the secondary seal is i 590P08CA01 less than the axial length of an equivalent conventional mechanically energized face seal.
The adapter housing axially separates the bearing or motor housing from the process housing forming a chamber between the fist mechanical seal and the second mechanical seal. The adapter housing's purpose is to rigidly connect and axisymetrically align the S bearing frame or motor housing, the primary seal and the secondary seal, to serve as a leak free adapter between the bearing frame, or motor housing, and the process containing housing such that a single bearing frame or motor housing could be adapted to multiple process housings without re-machining the process housing, or the bearing frame or motor housing, and to house a connection means for a conduit to redirect any leakage from the first mechanical seal away from the bearing frame in such a way that the pressure in the adapter housing separating the primary seal and the secondary seal does not pressurize beyond the sealable limits of the secondary mechanical seal.
The adapter housing can also serve as a location for instruments that might monitor for leakage from the first mechanical seal and activate an appropriate alarm.
An outlet connection in the wall of the adapter housing, with a cross sectional area of some magnitude greater than the cross sectional area of the largest a.nnulu~s that could serve as a leak path in the event of failure of the primary seal, leads to a safe location such as a environmental containment vessel, or scrubber system which is at or near atmospheric pressure. Those skilled in the art know that the differential area between the outlet connection and the largest annulus that could serve as a leak path, serves to breakdown pressure leaking by the primary seal, such that should the leakage fill the chamber, the maximum pressure in the chamber would be equal to the inverse of the ratio between the area of the larger outlet connection and the smaller seal leak path. ~y way of example an outlet connection of ten tines the cross sectional area of the annulus formed by the largest leak path at the primary seal would limit the accumulation of pressure in the chamber to 1/l0th the process pressure. This would mean that a 200 psi process could be reliably contained by a secondary seal that would only see 20 psi pressure, which is within the capabilities of current non-mechanical face seals such as those of magnetic type.
Brief Description of the Drawings Fig. 1 is a cross section view of a rotating shaft with load end process fl~zid sealed from leakage along the shaft by a primary mechanical seat and a secondary magnetic seal devided by a chamber having a leak path to a containment vessel.
Detailed Description of the Preferred Embodiment While the invention is susceptible to various modifications and alternative forms, certain specific embodiments thereof have been shown by way of .example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular forms described. Dn the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
l2efernng now to Fig. I, there is shown a preferred embodiment with the following parts:
A load member, such as an impeller, mixer, or fan, 1, coaxially mounted on a drive shaft 2, such that the load member 1 extends into a process containment housing 3, such as a pump casing or vessel. A cover 4 facilitates the removal of the load member 1 from the process containment housing 3. Primary seal 5, is sealingly mounted to cover
the L3/D4 to less than 50 on new designs and to reduce it on retrofits where the existing bearing frame or close coupled motor is used in a conversion to this innovative sealing system thereby increasing the seal reliability. It would further be desirable to achieve the improved decreased L31D4 while at the same time lowering the manufacturing cost.
Canned motors are an excellent choice for handling hazardous media. The problem with canned motors is that they are expensive to build due to the extra containment housings (or cans) and they typically rely on a liquid filled cavity for lubrication.
The extra drag associated with rotating the cans through a viscous fluid decreases the motor efficiency and increases the cost of operation due to the increased power draw. Therefore it would be desirous to have a design that will not leak process liquids or gasses to atmosphere and _q._ that eliminates the additional costs associated with containment cans and that does not rewire a liquid filled housing for bearing lubrication.
Summary of the Invention The principle object of this invention is to provide a sealing arrangement which enables the user to efficiently and safely handle fluids and gasses.
Another object of this invention is to provide a sealing arrangement that will not leak to the outside environment in the event of failure of a conventional mechanical seal.
Another object of the invention is to provide a sealing arrangement with .at least one sealing member that is relatively unaffected by the failure of adjacent seals.
1 S It is still a further object of this invention to provide a simple seal design that shortens the shaft overhang required of a multiple stage sealing arrangement.
It is still a further object of this invention to provide a close-couple motor arrangement that can effectively seal against positive pressure, such as from a failed mechanical seal, on a continuous basis, both when the machine is idle, and when it is in operation, without the use of mechanically energized seal faces.
It is still a further object of this invention to provide and enable the use of a L3/D4 of less than 50 at a reduced cost relative to similar machines using mechanically energized seal faces to achieve the same Ievel of sealing protection.
It is still a further object of this invention to enable the reduction of L3/Dø on retrofit units thereby increasing their seal reliability while simultaneously providing a design that prevents leakage of harmful liquids or gasses to the environment.
It is still a further object of this invention to provide a close-coupled configuration whereby the motor is protected from cantamination from the process media.
It is still a further object of this invention to provide protection against leakage of hazardous liquids and gasses to the environment, without utilizing mechanically energized seal faces to seal bearing frames or motor housings, and to do so without the cost associated with motor cans, or the viscous drag associated with liquid filled housings.
According to the invention, the arrangement of construction, preferably, has a shaft driven load rnernber such as an impeller, mixer, or fan, mounted on rotatable drive shaft cantilevered some axial distance from a supporting bearing such that the load member is exposed to a process liquid or gas that is desirable to seal from the external environment.
The process is sealed by a first mechanical shaft seal of a conventional type whereby flat seating faces are held in extremely close proximity each other by a combination of mechanical energization means, such as bellows and springs, and any pressure differential that exists between the upstream (process) side, and the downstream (non-process) side of the seal. This seal can be in a single or mufti-stage configuration and can be designed to seal either gas or liquid. This seal will herein. be referred to as the primary seal. For the purpose of clarification herein the side of any component that is closest in the axial direction to the driven load will be referred to as the inboard side and the side of any component that is located axially furthest away from the driven load will be referred to as the outboard side. A second seal activated by a radially displaced source of sealing force, such as by a radially adjacent magnetic force applied between the sealing surfaces, and capable of withstanding a sufficient differential pressure from either liquid or gas without leakage, while either running or idle, is positioned indeper.~dently, in that it has no shared components with the first seal, axially along the shaft on the outboard side of the primary seal. This second seal, referred to herein as the secondary seal, is mounted in an adapter housing that mates to either a motor or bearing frame such that the secondary seal is positioned between the primary seal and the most inboard bearing within the bearing ar motor housing. The axial space required by the secondary seal is i 590P08CA01 less than the axial length of an equivalent conventional mechanically energized face seal.
The adapter housing axially separates the bearing or motor housing from the process housing forming a chamber between the fist mechanical seal and the second mechanical seal. The adapter housing's purpose is to rigidly connect and axisymetrically align the S bearing frame or motor housing, the primary seal and the secondary seal, to serve as a leak free adapter between the bearing frame, or motor housing, and the process containing housing such that a single bearing frame or motor housing could be adapted to multiple process housings without re-machining the process housing, or the bearing frame or motor housing, and to house a connection means for a conduit to redirect any leakage from the first mechanical seal away from the bearing frame in such a way that the pressure in the adapter housing separating the primary seal and the secondary seal does not pressurize beyond the sealable limits of the secondary mechanical seal.
The adapter housing can also serve as a location for instruments that might monitor for leakage from the first mechanical seal and activate an appropriate alarm.
An outlet connection in the wall of the adapter housing, with a cross sectional area of some magnitude greater than the cross sectional area of the largest a.nnulu~s that could serve as a leak path in the event of failure of the primary seal, leads to a safe location such as a environmental containment vessel, or scrubber system which is at or near atmospheric pressure. Those skilled in the art know that the differential area between the outlet connection and the largest annulus that could serve as a leak path, serves to breakdown pressure leaking by the primary seal, such that should the leakage fill the chamber, the maximum pressure in the chamber would be equal to the inverse of the ratio between the area of the larger outlet connection and the smaller seal leak path. ~y way of example an outlet connection of ten tines the cross sectional area of the annulus formed by the largest leak path at the primary seal would limit the accumulation of pressure in the chamber to 1/l0th the process pressure. This would mean that a 200 psi process could be reliably contained by a secondary seal that would only see 20 psi pressure, which is within the capabilities of current non-mechanical face seals such as those of magnetic type.
Brief Description of the Drawings Fig. 1 is a cross section view of a rotating shaft with load end process fl~zid sealed from leakage along the shaft by a primary mechanical seat and a secondary magnetic seal devided by a chamber having a leak path to a containment vessel.
Detailed Description of the Preferred Embodiment While the invention is susceptible to various modifications and alternative forms, certain specific embodiments thereof have been shown by way of .example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular forms described. Dn the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
l2efernng now to Fig. I, there is shown a preferred embodiment with the following parts:
A load member, such as an impeller, mixer, or fan, 1, coaxially mounted on a drive shaft 2, such that the load member 1 extends into a process containment housing 3, such as a pump casing or vessel. A cover 4 facilitates the removal of the load member 1 from the process containment housing 3. Primary seal 5, is sealingly mounted to cover
4. Adapter housing 6 is seallably mounted to bearing frame or motor housing '7 and to cover 4.
Primary seal 5 consists of a rotating portion 8 that is driven by shaft 2 through lCey, o-rings, setscrews, or other suitable means, and a stationary portion 9, both installed in accordance with the manufacturer's instructions. Conventional mechanically energized mechanical seals are available in many configurations, but in practice use an axially stacked mechanism of springs or bellows to energize one closely toleranced flat sealing surface or face against another, with one seal face rotating and the other stationary. The energization mechanism can be on either the rotating or the stationary member, but is preferred to be on the pressure side of the seal so that the process pressure is additive to the sealing force of the energization mechanism. The configuration shown in Fig. 1 one _g_ is by way of illustration only. tether seal configurations could be applied without detracting from the invention described and claimed herein.
Secondary seal IO is positioned inboard of bearing 11, with rotating portion 12 mounted on shaft 2 , and stationary portion 13 mounted onto adapter housing 6. Magnet 17, radially adjacent to rotating seal face component 19, attracts target 18 which is likewise radially adjacent to stationary seal face component 20 in st<~tionary portion 13, thereby providing sealing pressure to secondary seal 10, irrespective of shaft rotation.
The operation of the secondary seal is fully independent of the operation of the primary seal; in particular it is not operationally affected by any failure mode of the primary seal.
The two seals are preferrabiy distinctly separate assemblies, sharing only a common fixed mechancial reference in the form of the common housing, frame or structure to which their stationary components are attached. However, a common assembly incorporating the primary and secondary seals is within the scope ofthe claimed invention, so long as the seals operate independently, and a failure of the primary seal does not adversely affect the operation of the secondary seal.
The axial length of primary seal S is denoted by the letter A. The axial length of secondary seal 10 is denoted by the letter C. Length C is less than length A.
Length B
represents the gap between primary seal 5 and secondary face seal 10.
Connection 14 penetrates the outer wall of adapter housing 6 in a plane normal to the shaft axis. The cross sectional area of connection 14 is greater than the cross sectional area of the annulus formed by the rotating portion 8 and stationary portion 9 of mechanical seal 5 at the largest radial cross sectional area that could forms a leak path to adapter housing 6 denoted by t6 in the typical arrangement shown in Fig. 1.
The inside diameter of connection 14 is approximately tangent to wall of adapter housing 6 at its lowest elevation, and approximately tangent to cover 4, such that any leakage from primary seal 5 will drain from adapter housing 6 regardless of whether the assembly is oriented horizontally or vertically with the load end downward. A sealed conduit such as _9_ piping leads from connection 14 is connected to a hazardous waste atmospheric collection tank or to the plant's sub-atmospheric processing system such as a flare or scrubber that collects and processes hazardous vapor from various plant-site areas.
In operation, fluid or gas from the process 3 which is at a higher pressure than the environment within adapter housing 6 will try to pass between the rotating portion 8 and the stationary portion 9 of primary seal 5. Due to the extremely close proximity of these parts only minute amounts of liquid or gas normally cross the seal faces into adapter housing 6. The pressure within adapter housing ~ is at atmospheric, or sub atmospheric pressure depending on the configuration of the waste collection system. .Any liquid or vapor passing into the adapter housing from primary seal 5 leaves adapter housing 6 through connection 14 to the atmospheric or sub-atmospheric collection system.
Adapter housing 6 does not pressurize and no gas or liquid passes secondary seal 10 to the bearing housing or motor frame 7.
In the event of a failure of primary seal 5, the fluid or gas from the process 3 which is at a higher pressure than the environment within adapter housing 6 will try to pass through the largest opening available to it which is a annulus ~6 formed by rotating portion 8 and stationary portion 9 at the point where the two parts enter adapter housing 6.
The differential area between the outlet connection 14 and the largest annulus that could serve as a leak path 16, serves to break down or relieve the pressure caused by fluid or gas leaking by the conventional first mechanical face seal 5 such that should the leakage fill the adapter housing 6, the maximum pressure in the adapter housing 6 would be no more than equal to the inverse of the ratio between the area of the larger outlet connection 14 and the smaller seal leak path 16. By way of example an outlet connection of ten times the cross sectional area of the annulus formed by the smallest leak path at the first mechanical seal would limit the pressure build up on the adapter housing to lJlOth the process pressure. This example demonstrates that a 200 psi process with a failed primary seal could be reliably contained by a secondary seal that would only see a maximum of 20 psi pressure, which is within the capabilities of current non-mechanical face seals such as those of magnetic type.
10_ Because secondary seal 10 would not leak into bearing frame or motor housing 7 under these circumstances, it would have zero leakage to the environment, and sealing would be accomplished without the extra expense and loss of efficiency associated with liquid filled motors or complex bearing frame seal arrangements.
Referring again to fig. 1, the axial length C of secondary seal 10 is less than the axial length A of primary seal S. Distance B is some minimum distance required solely to prevent contact between primary seal 5 arid secondary seal 10 that is a insignificant percentage of the total axial length of the sealing system described by the sum of lengths A, ~, and C. ~f primary importance is the fact that due to its radially displaced energization mechanism for providing sealing pressure rather than an axially stacked mechanical means of energizing the sealing surfaces in order to maintain the close operating proximity with each other necessary for sealing, secondary seal 10 will always have an overall length less than that required by a similar sized seal that employs an axially stacked means to energize the sealing surfaces. Therefore the overhung shaft length (L) measured between the axial centerline of the bearing closest to the load member (inboard bearing) and the axial centerline of load member will be shorter for this sealing arrangement than for any machinery using two axially stacked mechanically energized seals to provide an emissions free system that seals bearing frame or motor housing 7. For any give diameter shaft a lower L3/D4 will be obtainable as a result of this lower L value, providing an environment that facilitates a greater reliability for the seals.
The benefits of a small shaft overhang ratio are readily apparent. A new piece of machinery can be provided with a L3IDø ratio of less than 50 with a smaller diameter shaft, and thus a lower cost due to the shorter axial length L. Existing pieces of machinery can be retrofitted with this design by machining adapter Housing 6 to mate with exiting cover 4 and existing bearing frame or motor Housing 7. Adapter housing 7 can be designed to minimize distance B, allowing the existing shaft 2 to be shortened, again decreasing the L3/D~ ratio while, simultaneously, eliminating the risk if environmental contamination due to the release of hazardous liquids or gasses.
Among the many examples within the scope of the invention as claimed, there is a sealing mechanism for sealing a rotary shaft from leakage along the shaf from a high pressure zone through a bulkhead to a low pressure zone, consisting of a sealing chamber incorporated with the bulkhead such that the chamber is disposed between the high pressure zone and the low pressure zone with the shaft extending theretlwough.
A
primary seal around the shaft is sealingly engaged with the high pressure end of the chamber/bulkhead structure, with the primary seal haring a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between the seal face components. A secondary seal around the shaft is sealingly engaged with the low pressure end of the chambe:r/bulkhead structure, with the secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source that is radially displaced from the seal face components for applying sealing pressure between said seal face components.
The sealing chamber is configured with an outlet for conducting leakage away from the chamber. The outlet has a low pressure connection to a suii:able leakage material disposal system which might simply contain or otherwise process tlve leakage material.
The outlet has a cross sectional area greater than the cross sectional area of the leak:
path annulus of the primary seal. The secondary seal has a pressure rating at Least equal to the maximum working pressure of the primary seal multiplied by the ratio of the cross section areas of the annulus to the outlet.
'The low pressure zone and the low pressure connection may be substantially at or less than ambient or atmospheric pressure. The secondary seal rnay ha s a maximum working pressure rating of at least 5 psi.
There may be a rotatable load mounted to the shaft external to the chamber proximate the primary seal, with a shaft bearing assembly configured external of the chamber proximate the secondary seal so as to be supporting the shaft; and a duive motor incorporated with the shaft proximate or just outboard of the shaft bearing assembly. The load may be ~12~
confined within a housing, where the housing is incorporated with or forms the bulkhead structure.
The chamber incorporated with the bulkhead may be in the form of an adaptor housing which sealingly connects a motor frame to a pump housing with the intent that there be no leakage from the pump housing through the adaptor housing into the motor.
The energization source of the primary seal may be a spring or bellows assembly axially stacked with one of the sealing face components in the usual manner such that the axial length of the primary seal is extended by about the axial length of the spring or bellows assembly. Other axially stacked mechanisms would likewi se be additive in length to the sealing face components.
The outlet is preferrably tangential to at least one of a sidewall and an end of the chamber or adaptor housing such that any leakage into the chamber drains by gravity from the chamber through the outlet when the shaft and chamber are oriented so as to have the outlet at the lowest point within the chamber.
The drive motor may be a close coupled motor. 'The drive xnator, shaft, load, and sealing mechanism in combination may have a shaft overhang L3/~4 ratio of les;> than 50.
The invention is inclusive of methods as well. For example, there is according to the invention a method for sealing a rotary shaft from leakage along the shaft from a higher pressure zone through a bulkhead to a lower pressure zone consisting of several steps:
incorporating with the bulkhead a sealing chamber through which the shaft extends such that the chamber is exposed to the higher pressure zone at one end and the lower pressure zone at the other end; sealingly engaging a primary seal around the shaft with the higher pressure end of the chamber, where the primary seal has a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between the seal face components; sealingly engaging a secondary seal around the shaft with the lower pressure end of the chamber, where the secondary seal has a rotating seal face component co~atacting a stationary seal face component and an energization source radially displaced from the seal face components for applying sealing pressure between the seal face components; configuring the sealing chamber with an outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of the primary seal; and connecting the outlet at or below the pressure of the lower pressure zone to a leakage matez~ials disposal system.
The pressure at this connection to the leakage materials disposal system may controlled by the same source as the lower pressure zone, such as atmospheric or ambient pressure, or have a separate control device maintaining the pressure at or even slightly lower than the lower pressure zone. Also, the secondary seal may have a pressure rating at least equal to the maximum working pressure of the primary seal times the ratio of the cross section areas of said annulus to said outlet, providing redundant sealing protection to the motor and/or lower pressure zone. Alternatively, secondary seals having .a maximum working pressure rating of at least S psi (pounds per square inch) may be employed for use in systems requiring Spsi or lower secondary seal pressures.
According to this method, there may also be a rotatable load mounted to the shaft external to the chamber proximate the primary seal. There may be a shaft bearing assembly configured external of the chamber proximate the secondary seal supporting the shaft. There may also be a drive motor incorporated with the shaft proximate the shaft bearing assembly. Also, the load may be confined within a housing, and the housing incorporated with the bulkhead. Turthermore, the sizing and spacing of the shaft, bearing assembly, seals, and load may be such that the shaft overhand L3JD4 ratio is less than 50.
In both apparatus and method aspects of the invention, there is a secondary seal on the shaft sealingly engaged on one end of the chamber or housing. 'The secondary seal has a rotating seal face component contacting a stationary seal face component and an energization source, such as a magnet or electromagnetic device, displaced radially outward somewhat from one of the seal face components so as to apply a magnetic force on a correspondingly configured magnetic or EIvIIF (electromagnetic force) responsive target relating to the other sealing face component for applying sealing pressure between the seal face components. The length of such a seal is able t:o be less than the sum of the lengths of the seal face components and the energization sources due to the radial displacement of the energization mechanism from the sealing faces.
In another aspect, while the invention contemplates the more typical case where the load end of the shaft extends into a higher pressure environment from which leakage may be expected; the invention is equally applicable to the case where the load end is intended to be at sub-ambient or relatively lower pressure than the drive end, and leakage into the dividing chamber is more likely to occur at the drive end or motor end of the shaft. The primary seal in this case is understood to be on the motor or drive end of the shaft, and the secondary seal on the load or driven end, with the adaptor housing or central chamber outlet functioning in the same manner, being held normally at or near the lower of the two pressures so as to transport material leaked through the primary seal away from the zone between the two seals while limiting the maximum pressure to which the secondary seal might be subjected in the event of total primary seal failure.
Other and various examples within the scope of the claims that follow will be apparent to those skilled in the art, from the specification and drawings provided.
_ l~ _
Primary seal 5 consists of a rotating portion 8 that is driven by shaft 2 through lCey, o-rings, setscrews, or other suitable means, and a stationary portion 9, both installed in accordance with the manufacturer's instructions. Conventional mechanically energized mechanical seals are available in many configurations, but in practice use an axially stacked mechanism of springs or bellows to energize one closely toleranced flat sealing surface or face against another, with one seal face rotating and the other stationary. The energization mechanism can be on either the rotating or the stationary member, but is preferred to be on the pressure side of the seal so that the process pressure is additive to the sealing force of the energization mechanism. The configuration shown in Fig. 1 one _g_ is by way of illustration only. tether seal configurations could be applied without detracting from the invention described and claimed herein.
Secondary seal IO is positioned inboard of bearing 11, with rotating portion 12 mounted on shaft 2 , and stationary portion 13 mounted onto adapter housing 6. Magnet 17, radially adjacent to rotating seal face component 19, attracts target 18 which is likewise radially adjacent to stationary seal face component 20 in st<~tionary portion 13, thereby providing sealing pressure to secondary seal 10, irrespective of shaft rotation.
The operation of the secondary seal is fully independent of the operation of the primary seal; in particular it is not operationally affected by any failure mode of the primary seal.
The two seals are preferrabiy distinctly separate assemblies, sharing only a common fixed mechancial reference in the form of the common housing, frame or structure to which their stationary components are attached. However, a common assembly incorporating the primary and secondary seals is within the scope ofthe claimed invention, so long as the seals operate independently, and a failure of the primary seal does not adversely affect the operation of the secondary seal.
The axial length of primary seal S is denoted by the letter A. The axial length of secondary seal 10 is denoted by the letter C. Length C is less than length A.
Length B
represents the gap between primary seal 5 and secondary face seal 10.
Connection 14 penetrates the outer wall of adapter housing 6 in a plane normal to the shaft axis. The cross sectional area of connection 14 is greater than the cross sectional area of the annulus formed by the rotating portion 8 and stationary portion 9 of mechanical seal 5 at the largest radial cross sectional area that could forms a leak path to adapter housing 6 denoted by t6 in the typical arrangement shown in Fig. 1.
The inside diameter of connection 14 is approximately tangent to wall of adapter housing 6 at its lowest elevation, and approximately tangent to cover 4, such that any leakage from primary seal 5 will drain from adapter housing 6 regardless of whether the assembly is oriented horizontally or vertically with the load end downward. A sealed conduit such as _9_ piping leads from connection 14 is connected to a hazardous waste atmospheric collection tank or to the plant's sub-atmospheric processing system such as a flare or scrubber that collects and processes hazardous vapor from various plant-site areas.
In operation, fluid or gas from the process 3 which is at a higher pressure than the environment within adapter housing 6 will try to pass between the rotating portion 8 and the stationary portion 9 of primary seal 5. Due to the extremely close proximity of these parts only minute amounts of liquid or gas normally cross the seal faces into adapter housing 6. The pressure within adapter housing ~ is at atmospheric, or sub atmospheric pressure depending on the configuration of the waste collection system. .Any liquid or vapor passing into the adapter housing from primary seal 5 leaves adapter housing 6 through connection 14 to the atmospheric or sub-atmospheric collection system.
Adapter housing 6 does not pressurize and no gas or liquid passes secondary seal 10 to the bearing housing or motor frame 7.
In the event of a failure of primary seal 5, the fluid or gas from the process 3 which is at a higher pressure than the environment within adapter housing 6 will try to pass through the largest opening available to it which is a annulus ~6 formed by rotating portion 8 and stationary portion 9 at the point where the two parts enter adapter housing 6.
The differential area between the outlet connection 14 and the largest annulus that could serve as a leak path 16, serves to break down or relieve the pressure caused by fluid or gas leaking by the conventional first mechanical face seal 5 such that should the leakage fill the adapter housing 6, the maximum pressure in the adapter housing 6 would be no more than equal to the inverse of the ratio between the area of the larger outlet connection 14 and the smaller seal leak path 16. By way of example an outlet connection of ten times the cross sectional area of the annulus formed by the smallest leak path at the first mechanical seal would limit the pressure build up on the adapter housing to lJlOth the process pressure. This example demonstrates that a 200 psi process with a failed primary seal could be reliably contained by a secondary seal that would only see a maximum of 20 psi pressure, which is within the capabilities of current non-mechanical face seals such as those of magnetic type.
10_ Because secondary seal 10 would not leak into bearing frame or motor housing 7 under these circumstances, it would have zero leakage to the environment, and sealing would be accomplished without the extra expense and loss of efficiency associated with liquid filled motors or complex bearing frame seal arrangements.
Referring again to fig. 1, the axial length C of secondary seal 10 is less than the axial length A of primary seal S. Distance B is some minimum distance required solely to prevent contact between primary seal 5 arid secondary seal 10 that is a insignificant percentage of the total axial length of the sealing system described by the sum of lengths A, ~, and C. ~f primary importance is the fact that due to its radially displaced energization mechanism for providing sealing pressure rather than an axially stacked mechanical means of energizing the sealing surfaces in order to maintain the close operating proximity with each other necessary for sealing, secondary seal 10 will always have an overall length less than that required by a similar sized seal that employs an axially stacked means to energize the sealing surfaces. Therefore the overhung shaft length (L) measured between the axial centerline of the bearing closest to the load member (inboard bearing) and the axial centerline of load member will be shorter for this sealing arrangement than for any machinery using two axially stacked mechanically energized seals to provide an emissions free system that seals bearing frame or motor housing 7. For any give diameter shaft a lower L3/D4 will be obtainable as a result of this lower L value, providing an environment that facilitates a greater reliability for the seals.
The benefits of a small shaft overhang ratio are readily apparent. A new piece of machinery can be provided with a L3IDø ratio of less than 50 with a smaller diameter shaft, and thus a lower cost due to the shorter axial length L. Existing pieces of machinery can be retrofitted with this design by machining adapter Housing 6 to mate with exiting cover 4 and existing bearing frame or motor Housing 7. Adapter housing 7 can be designed to minimize distance B, allowing the existing shaft 2 to be shortened, again decreasing the L3/D~ ratio while, simultaneously, eliminating the risk if environmental contamination due to the release of hazardous liquids or gasses.
Among the many examples within the scope of the invention as claimed, there is a sealing mechanism for sealing a rotary shaft from leakage along the shaf from a high pressure zone through a bulkhead to a low pressure zone, consisting of a sealing chamber incorporated with the bulkhead such that the chamber is disposed between the high pressure zone and the low pressure zone with the shaft extending theretlwough.
A
primary seal around the shaft is sealingly engaged with the high pressure end of the chamber/bulkhead structure, with the primary seal haring a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between the seal face components. A secondary seal around the shaft is sealingly engaged with the low pressure end of the chambe:r/bulkhead structure, with the secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source that is radially displaced from the seal face components for applying sealing pressure between said seal face components.
The sealing chamber is configured with an outlet for conducting leakage away from the chamber. The outlet has a low pressure connection to a suii:able leakage material disposal system which might simply contain or otherwise process tlve leakage material.
The outlet has a cross sectional area greater than the cross sectional area of the leak:
path annulus of the primary seal. The secondary seal has a pressure rating at Least equal to the maximum working pressure of the primary seal multiplied by the ratio of the cross section areas of the annulus to the outlet.
'The low pressure zone and the low pressure connection may be substantially at or less than ambient or atmospheric pressure. The secondary seal rnay ha s a maximum working pressure rating of at least 5 psi.
There may be a rotatable load mounted to the shaft external to the chamber proximate the primary seal, with a shaft bearing assembly configured external of the chamber proximate the secondary seal so as to be supporting the shaft; and a duive motor incorporated with the shaft proximate or just outboard of the shaft bearing assembly. The load may be ~12~
confined within a housing, where the housing is incorporated with or forms the bulkhead structure.
The chamber incorporated with the bulkhead may be in the form of an adaptor housing which sealingly connects a motor frame to a pump housing with the intent that there be no leakage from the pump housing through the adaptor housing into the motor.
The energization source of the primary seal may be a spring or bellows assembly axially stacked with one of the sealing face components in the usual manner such that the axial length of the primary seal is extended by about the axial length of the spring or bellows assembly. Other axially stacked mechanisms would likewi se be additive in length to the sealing face components.
The outlet is preferrably tangential to at least one of a sidewall and an end of the chamber or adaptor housing such that any leakage into the chamber drains by gravity from the chamber through the outlet when the shaft and chamber are oriented so as to have the outlet at the lowest point within the chamber.
The drive motor may be a close coupled motor. 'The drive xnator, shaft, load, and sealing mechanism in combination may have a shaft overhang L3/~4 ratio of les;> than 50.
The invention is inclusive of methods as well. For example, there is according to the invention a method for sealing a rotary shaft from leakage along the shaft from a higher pressure zone through a bulkhead to a lower pressure zone consisting of several steps:
incorporating with the bulkhead a sealing chamber through which the shaft extends such that the chamber is exposed to the higher pressure zone at one end and the lower pressure zone at the other end; sealingly engaging a primary seal around the shaft with the higher pressure end of the chamber, where the primary seal has a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between the seal face components; sealingly engaging a secondary seal around the shaft with the lower pressure end of the chamber, where the secondary seal has a rotating seal face component co~atacting a stationary seal face component and an energization source radially displaced from the seal face components for applying sealing pressure between the seal face components; configuring the sealing chamber with an outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of the primary seal; and connecting the outlet at or below the pressure of the lower pressure zone to a leakage matez~ials disposal system.
The pressure at this connection to the leakage materials disposal system may controlled by the same source as the lower pressure zone, such as atmospheric or ambient pressure, or have a separate control device maintaining the pressure at or even slightly lower than the lower pressure zone. Also, the secondary seal may have a pressure rating at least equal to the maximum working pressure of the primary seal times the ratio of the cross section areas of said annulus to said outlet, providing redundant sealing protection to the motor and/or lower pressure zone. Alternatively, secondary seals having .a maximum working pressure rating of at least S psi (pounds per square inch) may be employed for use in systems requiring Spsi or lower secondary seal pressures.
According to this method, there may also be a rotatable load mounted to the shaft external to the chamber proximate the primary seal. There may be a shaft bearing assembly configured external of the chamber proximate the secondary seal supporting the shaft. There may also be a drive motor incorporated with the shaft proximate the shaft bearing assembly. Also, the load may be confined within a housing, and the housing incorporated with the bulkhead. Turthermore, the sizing and spacing of the shaft, bearing assembly, seals, and load may be such that the shaft overhand L3JD4 ratio is less than 50.
In both apparatus and method aspects of the invention, there is a secondary seal on the shaft sealingly engaged on one end of the chamber or housing. 'The secondary seal has a rotating seal face component contacting a stationary seal face component and an energization source, such as a magnet or electromagnetic device, displaced radially outward somewhat from one of the seal face components so as to apply a magnetic force on a correspondingly configured magnetic or EIvIIF (electromagnetic force) responsive target relating to the other sealing face component for applying sealing pressure between the seal face components. The length of such a seal is able t:o be less than the sum of the lengths of the seal face components and the energization sources due to the radial displacement of the energization mechanism from the sealing faces.
In another aspect, while the invention contemplates the more typical case where the load end of the shaft extends into a higher pressure environment from which leakage may be expected; the invention is equally applicable to the case where the load end is intended to be at sub-ambient or relatively lower pressure than the drive end, and leakage into the dividing chamber is more likely to occur at the drive end or motor end of the shaft. The primary seal in this case is understood to be on the motor or drive end of the shaft, and the secondary seal on the load or driven end, with the adaptor housing or central chamber outlet functioning in the same manner, being held normally at or near the lower of the two pressures so as to transport material leaked through the primary seal away from the zone between the two seals while limiting the maximum pressure to which the secondary seal might be subjected in the event of total primary seal failure.
Other and various examples within the scope of the claims that follow will be apparent to those skilled in the art, from the specification and drawings provided.
_ l~ _
Claims (21)
What is claimed is:
1. A sealing mechanism for sealing a rotary shaft from leakage along the shaft from a high pressure zone through a bulkhead to a low pressure zone comprising:
a sealing chamber incorporated with said bulkhead such that said chamber is disposed between said high pressure zone and said low pressure zone with said shaft extending therethrough;
a primary seal around said shaft sealingly engaged with the high pressure end of said chamber, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying scaling pressure between said seal face components; and a secondary seal around said shaft sealingly engaged with the low pressure end of said chamber, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal face components;
said sealing chamber configured with an outlet for conducting leakage away from said chamber, said outlet having a low pressure connection to a leakage material disposal system, said outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal multiplied by the ratio of the cross section areas of said annulus to said outlet.
a sealing chamber incorporated with said bulkhead such that said chamber is disposed between said high pressure zone and said low pressure zone with said shaft extending therethrough;
a primary seal around said shaft sealingly engaged with the high pressure end of said chamber, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying scaling pressure between said seal face components; and a secondary seal around said shaft sealingly engaged with the low pressure end of said chamber, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal face components;
said sealing chamber configured with an outlet for conducting leakage away from said chamber, said outlet having a low pressure connection to a leakage material disposal system, said outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal multiplied by the ratio of the cross section areas of said annulus to said outlet.
2. A sealing mechanism for sealing a rotary shaft according to claim 1, said low pressure zone and said low pressure connection being substantially at or less than atmospheric pressure.
3. A sealing mechanism for sealing a rotary shaft according to claim 1, said secondary seal having a maximum working pressure rating of at least 5 psi.
4. A sealing mechanism for sealing a rotary shaft according to claim 1, wherein a rotatable load is mounted to said shaft external to said chamber proximate said primary seal; a shaft bearing assembly is configured external of said chamber proximate said secondary seal supporting said shaft; and a drive motor is incorporated with said shaft proximate said shaft bearing assembly.
5. A sealing mechanism for sealing a rotary shaft according to claim 4, said load confined within a housing, said housing incorporating said bulkhead.
6. A sealing mechanism for sealing a rotary shaft according to claim 1, said chamber incorporated with said bulkhead comprising an adaptor housing sealingly connecting a motor frame to a pump housing.
7. A sealing mechanism for sealing a rotary shaft according to claim 1, said energization source of said primary seal being a spring assembly axially stacked with one of said sealing face components such that the axial length of said primary seal is extended by about the axial length of said spring assembly.
8. A sealing mechanism for sealing a rotary shaft according to claim 1, said outlet being tangential to at least one of a sidewall and an end of said chamber such that any said leakage into said chamber drains by gravity from said chamber through said outlet when said shaft and chamber are oriented accordingly.
9. A sealing mechanism for sealing a rotary shaft according to claim 4, sand drive motor comprising a close coupled motor.
10. A sealing mechanism for sealing a rotary shaft according to claim 4, said drive motor, shaft, load, and sealing mechanism in combination having a shaft overhang L3/D4 ratio of less than 50.
11. A motorized shaft driven pump with protection from leakage out of t!he high pressure pump along the shaft to the motor, comprising:
an adaptor housing with a motor end and a pump end through which a drive shaft extends, said adaptor housing sealingly connecting a motor to a pump, said motor comprising a main motor bearing assembly proximate said adaptor housing supporting said shaft;
a primary seal around said shaft sealingly engaged with the pump end of said adaptor housing, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between said seal face components; and a second stage seal around said shaft sealingly engaged with the motor end of said adaptor housing, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal face components;
said adaptor housing configured with an outlet for conducting leakage away from said adaptor housing; said outlet being tangential to at least one of a sidewall and a said end of said adaptor housing such that any said leakage through said primary seal drains by gravity from said adaptor housing through said outlet when said motorized shaft driven pump is oriented accordingly; said outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; said outlet having a connection at or below atmospheric pressure to a leakage materials disposal system; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal times the ratio of the cross section areas of said annulus to said outlet; said motor main bearing assembly, adaptor housing, shaft, seals and pump section in combination configured with a shaft overhang L3/D4 ratio of less than 50.
an adaptor housing with a motor end and a pump end through which a drive shaft extends, said adaptor housing sealingly connecting a motor to a pump, said motor comprising a main motor bearing assembly proximate said adaptor housing supporting said shaft;
a primary seal around said shaft sealingly engaged with the pump end of said adaptor housing, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between said seal face components; and a second stage seal around said shaft sealingly engaged with the motor end of said adaptor housing, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal face components;
said adaptor housing configured with an outlet for conducting leakage away from said adaptor housing; said outlet being tangential to at least one of a sidewall and a said end of said adaptor housing such that any said leakage through said primary seal drains by gravity from said adaptor housing through said outlet when said motorized shaft driven pump is oriented accordingly; said outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; said outlet having a connection at or below atmospheric pressure to a leakage materials disposal system; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal times the ratio of the cross section areas of said annulus to said outlet; said motor main bearing assembly, adaptor housing, shaft, seals and pump section in combination configured with a shaft overhang L3/D4 ratio of less than 50.
12. A motorized shaft driven pump according to claim 11, said energization source of said primary seal being axially stacked with one of said sealing face components such that the axial length of said primary seal is extended by about the axial length of said energization source.
13. A method for sealing a rotary shaft from leakage along the shaft from a higher pressure zone through a bulkhead to a lower pressure zone comprising:
incorporating with said bulkhead a sealing chamber through which said shaft extends such that the chamber is exposed to said higher pressure zone at one end and said lower pressure zone at the other end;
sealingly engaging a primary seal around said shaft with the higher pressure end of said chamber, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between said seal face components;
sealingly engaging a secondary seal around said shaft with the lower pressure end of said chamber, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal fact;
components;
configuring said sealing chamber with an outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; and connecting said outlet at or below the pressure of said lower pressure zone to a leakage materials disposal system; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal times the ratio of the cross section areas of said annulus to said outlet.
incorporating with said bulkhead a sealing chamber through which said shaft extends such that the chamber is exposed to said higher pressure zone at one end and said lower pressure zone at the other end;
sealingly engaging a primary seal around said shaft with the higher pressure end of said chamber, said primary seal having a rotating seal face component contacting a stationary seal face component and an energization source for applying sealing pressure between said seal face components;
sealingly engaging a secondary seal around said shaft with the lower pressure end of said chamber, said secondary seal having a rotating seal face component contacting a stationary seal face component and an energization source radially displaced from said seal face components for applying sealing pressure between said seal fact;
components;
configuring said sealing chamber with an outlet having a cross sectional area greater than the cross sectional area of the leak path annulus of said primary seal; and connecting said outlet at or below the pressure of said lower pressure zone to a leakage materials disposal system; said secondary seal having a pressure rating at least equal to the maximum working pressure of said primary seal times the ratio of the cross section areas of said annulus to said outlet.
14. A method for sealing a rotary shaft according to claim 13, the pressure of said lower pressure being substantially atmospheric pressure.
15. A method for sealing a rotary shaft according to claim 13, said secondary seal having a maximum working pressure rating of at least 5 psi.
16. A method for sealing a rotary shaft according to claim 13, wherein a rotatable load is mounted to said shaft external to said chamber proximate said primary seal; a shaft bearing assembly is configured external of said chamber proximate said secondary seal supporting said shaft; and a drive motor is incorporated with said shaft proximate said shaft bearing assembly.
17. A method for sealing a rotary shaft according to claim 16, comprising:
confining said load within a housing, said housing incorporating said bulkhead.
confining said load within a housing, said housing incorporating said bulkhead.
18. A method for sealing a rotary shaft according to claim 13, said chamber comprising an adaptor housing sealingly connecting a motor housing to a pump housing.
19. A method for sealing a rotary shaft according to claim 13, said energization source of said primary seal being a spring assembly axially stacked with one of said sealing face components such that the axial length of said primary seal is extended by about the axial length of said spring assembly.
20. A method for sealing a rotary shaft according to claim 13, comprising:
configuring said outlet as tangential to both a sidewall and an end of said chamber such that any said leakage drains from said chamber through said outlet during either of vertical and horizontal orientation of said rotary shaft.
configuring said outlet as tangential to both a sidewall and an end of said chamber such that any said leakage drains from said chamber through said outlet during either of vertical and horizontal orientation of said rotary shaft.
21. A method for sealing a rotary shaft according to claim 16, comprising:
Sizing and spacing said shaft, bearing assembly, seals, and load such that the shaft overhand L3/D4 ratio is less than 50.
Sizing and spacing said shaft, bearing assembly, seals, and load such that the shaft overhand L3/D4 ratio is less than 50.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US56769404P | 2004-05-03 | 2004-05-03 | |
| US60/567,694 | 2004-05-03 |
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| Publication Number | Publication Date |
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| CA2466434A1 CA2466434A1 (en) | 2005-11-03 |
| CA2466434C true CA2466434C (en) | 2012-05-01 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2466434 Expired - Fee Related CA2466434C (en) | 2004-05-03 | 2004-05-05 | Mechanism for sealing a rotating shaft from load end leakage |
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| CA (1) | CA2466434C (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| DE102019111774A1 (en) * | 2019-03-25 | 2020-10-01 | Liebherr-Components Biberach Gmbh | Drive device for a trench wall cutter |
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2004
- 2004-05-05 CA CA 2466434 patent/CA2466434C/en not_active Expired - Fee Related
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|---|---|
| CA2466434A1 (en) | 2005-11-03 |
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| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20150505 |