Description:
FIELD OF THE INVENTION
This invention relates to mechanical seals which are employed in various industry sectors from food and chemical to pharmaceutical and oil and gas, and specifically mechanical seals which are intended to fit in traditional rotating equipment which was originally designed for gland packing sealing, where the radial distance between the rotational and stationary components is very small and physically restricted by the available cross-sectional sizes of said gland packing. Such rotational equipment includes Pumps such as Centrifugal Pumps, Rotary Lobe Pumps and Submersible Pumps.

BACKGROUND TO THE INVENTION
Mechanical seals are employed across all industry sectors on rotating equipment such as pumps. They are designed to seal the counter-rotational interface between stationary components (such as the pump housing) and the rotating components (such as the pump shaft) of said equipment.
Mechanical seals can also be employed on equipment where the opposite is true, where the housing is rotating and shaft is stationary.
Along with a series of static elastomer components or O-rings, the seal faces of the mechanical seal are primarily designed to prevent the process fluid escaping the process equipment.
They create a seal, the counter-rotational seal faces of the mechanical seal are typically spring biased together and hence they generate frictional heat as they interact. To help keep the seal faces cool, mechanical seals can be hydraulically balanced in that, by design, a fluid film is formed between the two counter rotational seal faces. This fluid film is very small, often only microns (tens of thousands of an inch) thick, but it helps to cool and lubricate the seal faces allowing them operate in a leak free nature. However, if the fluid film gets too hot, the fluid between the seal faces will vaporize and it will seize to act in a cooling and lubricating manner.
For this reason, the condition of the fluid film is therefore vitally important to the success of the mechanical seal in service. A poor fluid film, in terms of thickness and temperature, will ultimately damage the seal faces and cause the mechanical seal to leak.
Needless to state, a leaking mechanical seal is not only an environmental hazard, it is a health and safety hazard and it can have a huge commercial impact to the processing plant in lost process fluid costs, clean-up costs and failed equipment costs.
Mechanical seal failure is a primary reason why process equipment fails in an unplanned manner across all industry sectors.
For these reasons, removing heat at the counter-rotational seal faces and specifically at the seal face fluid film, is highly desirable for a successful mechanical seal installation.
The reader will note that traditional rotating equipment employed gland packing to seal the rotating and stationary interface, hence traditionally the term ‘stuffing box bore’ is used, as the gland packing was stuffed into the radial gap between the process equipment’s shaft and housing. The radial gap of a stuffing box bore is typically 8mm on small pumps and 10mm on larger pumps, largely designed to suit the available sizes of gland packing cross sections.
Increasingly tighter environmental pressures have moved many process plant engineers towards the replacement of gland packing with mechanical seals, however typically this ‘sealing upgrade’ must be implemented using the existing process equipment installed.
So, preferably, mechanical seals are designed to fit traditional process equipment that previously employed gland packing. Unfortunately, this does not create the ideal sealing environment for the mechanical seal and its fluid film, as there is little physical space available for seal face cooling. This means traditional mechanical seal faces, installed on traditional process equipment, which was originally designed to suit gland packing, are prone to run hot, deteriorate and prematurely leak.
Furthermore, certain process fluids can contain particles, debris and/or have a slurry nature. Particles and debris can chip and damage mechanical seal faces as they get in-between the counter-rotational seal faces and into the fluid film causing the faces to open and leak.
It is therefore further advantageous that the mechanical seal discourages particles and debris entering the seal face area.
STATEMENTS OF THE INVENTION
First embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, characterised in that said rotary seal face member has one or more radially extending grooves with an inclined surface which runs radially outwardly in the direction of the longitudinal axis of the rotating equipment shaft, towards the counter-rotational sealing interface and fluid film.
Preferably, said rotary seal face comprises of a seal face insert member and a seal face holder member forming a seal face assembly, wherein said seal face holder is of a metallic nature and contains a series of radially extending grooves with inclined surfaces which runs radially outwardly in the direction of the longitudinal axis of the rotating equipment shaft, towards the counter-rotational sealing interface and fluid film.
Second embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, wherein the stationary seal face is mounted in a stationary gland member that is connected to the stationary housing of the process equipment in an anti-rotational manner, characterised in that said seal gland member contains one or more longitudinally extending cavities which act to maximise the surface area of the seal gland member facilitating heat dispersal from the seal face area.
Preferably, the gland member contains at least one longitudinal extending cavity at the atmospheric side of the mechanical seal and at least one longitudinal extending cavity at the process side of the mechanical seal.
Preferably, the gland member contains a number of said cavities disposed around the periphery of the gland between the slots/holes that facilitate connection of the gland member to the equipment housing.
Third embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, wherein the stationary seal face is mounted in a stationary gland member that is connected to the stationary housing of the process equipment in an anti-rotational manner, characterised in that said seal gland member contains at least two longitudinally extending and inter-connected cavities which permits bi-directional airflow around the glands outermost surfaces to facilitate effective heat removal from said gland and connected members.
Fourth embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, characterised in that connected to the mechanical seal rotary member is one or more air-fan blades that facilitate atmospheric air movement.
Preferably, the mechanical seal is a cartridge design comprising of a cartridge sleeve assembly connected to the rotary seal face assembly, characterised in that the air-fan member is connected to the cartridge sleeve assembly.
Preferably, the air-fan member is substantially adjacent to the axial surface of the gland member.
Preferably, the rotary air-fan member is substantially shielded by a fan-guard member, which is, connected to the stationary member, such as the gland member or housing of the rotating equipment.
DESCRIPTION OF DRAWINGS
The accompanying drawings are as follows:
Figure 1 shows a longitudinal section of a prior art single cartridge mechanical seal.
Figure 2 corresponds to Figure 1 and shows longitudinal section through a single cartridge mechanical seal of the current invention
Figure 3 corresponds to Figure 2 and shows longitudinal section through the first embodiment of the current invention.
Figure 4 corresponds to Figure 3 and shows debris and particles adjacent to the seal faces in the seal chamber when the equipment is not rotating.
Figure 5 corresponds to Figure 4 and shows the debris and particles being radially displaced by the first embodiment of the current invention when the equipment is rotating.
Figure 6 corresponds to Figure 3 and shows an alternate design of the first embodiment of the current invention.
Figure 7 corresponds to Figure 3 and shows a further alternate design of the first embodiment of the current invention.
Figure 8 corresponds to Figure 1 and shows a partial longitudinal cross section of a conventional prior art mechanical seal installed in a stuffing box bore of an item of rotating equipment.
Figure 9 corresponds to Figure 6 and shows a partial longitudinal cross section of the first embodiment of the current invention, showing a mechanical seal installed in a stuffing box bore of an item of rotating equipment.
Figure 10 shows an isometric view, front and back, of the second embodiment of the current invention, a mechanical seal gland.
Figure 11 corresponds to Figure 10 and shows a partial longitudinal section through a mechanical seal of the second embodiment of the current invention, together with an end-view of the mechanical seal gland adjacent to the housing of the item of rotating equipment.
Figure 12 shows a longitudinal section through a mechanical seal of the third embodiment of the current invention; a seal gland with bi-directional airflow circulation cavities.
Figure 13 corresponds to Figure 12 and shows an end view of the seal gland of the third embodiment.
Figure 14 corresponds to Figure 13, Section B-B and shows a longitudinal section through a mechanical seal of the third embodiment of the current invention with bi-directional airflow circulation cavities.
Figure 15 shows a longitudinal section through a mechanical seal of the fourth embodiment of the current invention; a mechanical seal with an integral air-fan.
Figure 16 corresponds to Figure 15 and shows an end view of the mechanical seal air-fan member.
DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described, by way of examples only, with reference to the accompanying drawings.
Figure 1 shows a longitudinal section of a prior art single cartridge mechanical seal (10) installed on an item of rotating equipment (11) such as a centrifugal pump. Said rotating equipment (11) comprises of a pump housing (12) and a pump shaft (13) which in operation create a counter-rotational interface area (14) which requires sealing to prevent the process media (15) contained in the pump housing (12) from escaping into the atmosphere (16)
From Figure 1, the mechanical seal (10) has a rotary seal face (17) which is substantially connected to the rotating pump shaft (13) by cartridge seal sleeve (18) and clamp ring (19) assembly. The mechanical seal (10) also has a stationary seal face (20) which is substantially connected to the stationary pump housing (12) by seal gland (21) and bolt (22).
The rotary seal face (17) is biased to the stationary seal face (20) by one or more spring members (23). The counter-rotational surface where the rotary seal face (17) and stationary seal face (20) meets is the primary sealing interface containing the fluid film (24).
The fluid film (24) helps to lubricate and cool the set of mechanical seal faces (17 & 20) in operation. In certain conditions of process media type, process fluid pressure and rotational shaft velocity, the fluid film (24) breaks down and overheats/vaporizes. This causes the mechanical seal faces (17 & 20) to deteriorate and leak.
To help reduce seal face (17 & 20) heat, a second fluid can be injected into the seal gland flush orifice (25). Firstly this second fluid enters the process media and therefore must be compatible with the process fluid. Secondly, it is often very expensive to flush fluid into the seal chamber. Thirdly this system is often environmentally harmful.
For these reasons, it is preferred not to employ the aforementioned flushed system to cool the seal faces.
Figure 2 corresponds to Figure 1 and shows longitudinal section through a single cartridge mechanical seal (30) of the current invention.
From Figure 2, rotary seal face (31) is connected to the cartridge sleeve (32) by at least one drive pin (33) and said cartridge sleeve (32) is connected to the clamp ring (33) by at least one screw (34). The clamp ring (33) also contains at least one setscrew (35) which connects the clamp ring (33) to the shaft (36) of the item of rotating equipment (37).
The experienced reader will therefore understand that as the shaft (36) rotates, so does the rotary seal face (31).
The rotary seal face (31) is biased towards the stationary seal face (38) by at least one spring member (39). The stationary seal face (38) is connected to the seal gland (40) by at least one anti-rotation pin (41) and seal gland (40) is connected to the equipment housing (42) of the item of rotating equipment (37) by at least one bolt member (43).
The experienced reader will therefore understand that as the equipment housing (43) is stationary, so is the seal gland (41) and stationary seal face (40).
Elastomeric members (44) and (45) seal the interface between the rotary seal face (31) and cartridge sleeve (32), and the cartridge sleeve (32) and the shaft (36).
Likewise, elastomeric member 46 and gasket 47 seal the interface between the stationary seal face (38) and seal gland (40) and seal gland (40) and equipment housing (42).
Therefore in the equipment non-rotating condition, process media (48) in the seal chamber (48) is contained and unable to escape to the atmospheric side (49) of the mechanical seal (30).
Figure 3 corresponds to Figure 2 and shows longitudinal section through the first embodiment of the current invention.
The rotary seal face assembly (50) comprises of a rotary seal face insert (51) and a rotary seal face holder (52). On the outer most radial surface of the rotary seal face assembly (50) and substantially adjacent to the equipment seal chamber inner most radial surface (53), there is at least one radially extending groove (54).
Preferably, as shown, the radially extending groove (54) has an inclined surface (55) that preferably extends radially outwardly in the longitudinal direction towards the seal face insert (51) at an angle between 5 and 95 degrees from the longitudinal axis of the shaft (56) of the rotating equipment.
Figure 4 corresponds to Figure 3 and shows debris and particles (60) adjacent to the seal faces in the seal chamber (61) when the equipment is not rotating.
From Figure 4 product media particles (60) collate in the seal chamber (61) of the rotating equipment. In most industrial applications, the rotary seal face insert (62) is manufactured from a relatively soft material such as carbon or PTFE. Said product media particles (60) chip, damage or become embedded in the fluid film (63) between the rotary seal face insert (62) and the stationary seal face (64). This causes the rotary seal face insert (62) to prematurely wear resulting in a leaking mechanical seal (65) and leaking rotating equipment.
Figure 5 corresponds to Figure 4 and shows the debris and particles (70) being radially and longitudinally displaced by the first embodiment of the current invention as the rotary seal face assembly (71) rotates (69) with the equipment shaft.
As shown, the inclined surface (72) of the rotary seal face assembly (71) creates centrifugal forces to longitudinally displace the heavy debris particles (70) away from the fluid film (73) and the seal face insert (74). Preferably, multiple inclined surfaces (72) are employed along the length of the rotating seal face assembly (71). An experienced reader will understand that this embodiment of the first invention can also be applied to any rotating surface of the mechanical seal (71), including but not limited to, the cartridge sleeve (32) of Figure 2.
Figure 6 corresponds to Figure 3 and shows an alternate design of the first embodiment of the current invention.
From Figure 6, the rotary seal face assembly (80) comprises of a rotary seal face insert (81) and rotary holder (82). The rotary holder (82) has an inclined surface (83) that radially outwardly extends in the longitudinal direction towards the seal face insert (81) and the fluid film (84). Again, as the shaft (85) rotates (86) the rotary seal face assembly (80) acts to centrifugally migrate the process fluid particles, debris and solids away from the fluid film (84).
Figure 7 corresponds to Figure 3 and shows a further alternate design of the first embodiment of the current invention, wherein, the rotary seal face assembly (90) comprises of a seal face insert (91) and a seal face holder (92), and again in accordance with the first embodiment of the invention, said rotary seal face assembly (90) has a radially extending cavity (93) with an inclined surface (94) adjacent to the rotating equipment seal chamber’s inner most radial surface (95). As shown, as the equipment shaft (99) and mechanical seal assembly (100) starts to rotate (96), debris and particles (97) in the seal chamber (95) migrate away from the mechanical seals fluid film (98).
Figure 8 corresponds to Figure 1 and shows a partial longitudinal cross section of a conventional prior art mechanical seal (101) installed in a stuffing box bore (102) of an item of rotating equipment (103).
As previously explained, the stuffing box bore (102) of traditional equipment, by design, has a very small cross-sectional area which is defined by the equipment housing inner most radial surface (104) and the equipment shaft outer most radial surface (105).
When conventional mechanical seals are installed in such equipment, as shown in Figure 8, the outer most radial surface (106) of the rotary seal face assembly (107) comes in very close proximity to the housing inner surface 104.
To provide reader perspective, the radial distance between housing inner surface (104) and rotary seal assembly outer surface (106) is typically between 0.5mm and 1.0mm. The experienced reader will therefore understand that the process fluid volume in and around this very small stuffing box radial cross-sectional area is very limited.
As the rotational equipment operates, it is easy to see that the limited volume of process fluid will increase rapidly in temperature given the frictional heat generated from the sealing interface. The high temperature, lack of processed fluid movement and replacement in said area, breaks down the fluid film at the sealing interface, leading to mechanical seal failure.
Figure 9 corresponds to Figure 6 and shows a partial longitudinal cross section of the first embodiment of the current invention, showing a mechanical seal (111) installed in a stuffing box bore (112) of an item of rotating equipment (113).
Given the same traditional equipment stuffing box bore (112) constraints as previously explained in relation to Figure 8, the reader will see the advantage of the first embodiment of the current invention, given the specifically engineered outer most radial surface (116) of the rotary seal face assembly (117).
The reader can see that given the inclined surfaces of the rotary seal face assembly (117), the current invention has more than triple the volume of process fluid (118) in and around the mechanical seal faces.
From Figure 9, this significant increase in process fluid volume helps to keep the mechanical seal faces much cooler in the like-for-like operating environment as defined by Figure 8. Tests have shown that the mechanical seal faces can run up to 60% cooler using the design of the current invention. This has significant advantages for seal longevity and rotating equipment operational performance.
Figure 10 shows an isometric view, front and back, of the second embodiment of the current invention, a mechanical seal gland (200).
From Figure 10, the seal gland (200) has a series of longitudinally extending cavities (201) in the back face of the gland (200) and a further series of longitudinally extending cavities (202) in the front face of the gland (200).
Said cavities are spaced around the gland (200) face periphery between the slots (203) which facilitate the connection of said gland (200) to the equipment housing by one or more bolts.
From the design and spacing of said cavities 201 and 202 the reader can see that the surface area of the gland (200) is significantly increased to that of a non-cavity prior-art gland. This increased surface area of the second embodiment of the current invention is typically up to 50% greater than a non-cavity prior-art gland, facilitating significant additional heat removal from the mechanical seal assembly.
Figure 11 corresponds to Figure 10 and shows a partial longitudinal section through a mechanical seal (210) of the second embodiment of the current invention, together with an end-view of the mechanical seal gland (211) adjacent to the housing (212) of the item of rotating equipment (213).
Longitudinal cavity (214) in the rear face of gland (211) and longitudinal cavity (215) in the front face of the gland (211) are shown in context with the mechanical seal assembly (200).
Figure 12 shows a longitudinal section through a mechanical seal (300) of the third embodiment of the current invention.
Heat transfer in a mechanical seal occurs in three main ways: through radiation, conduction, and natural convention.
Radiation heat transfer is a function of the location in which the mechanical seal is installed, i.e. the radiation heat transfer of a seal installed in a country such as India will be very different to the same mechanical seal installed in Alaska. The summary being that the problem of dissipating the heat from a mechanical seal is exacerbated in a hot climate.
Conduction heat transfer in a mechanical seal is a function of the surface contact with the heat source and materials of construction of the seal members to transfer the heat away.
From Figure 12, heat generated by the primary heat source (306) when the equipment is operational, is conducted through the stationary seal face (307) and the stationary elastomer (308) and into the gland (301). Facilitating conduction heat transfer is thereby largely limited to the selection of materials for the aforementioned members. The present invention maximises conduction heat transfer through the careful selection of materials of construction.
Convention heat transfer in a mechanical seal can be significantly enhanced by the design of the mechanical seal, as in the case of the third embodiment of the current invention
From Figure 12, a seal gland (301) incorporates an inter-connecting orifice (302) between the rear cavity (303) and front cavity (304) of the gland (301). Said inter-connecting orifice (302) facilitates air-flow from the front to back of said gland (301).
Furthermore, from Figure 12, a second inter-connecting cavity (305) is shown in the rear face of the gland (301). This second inter-connecting cavity (305) connects the periphery of rear face cavities (303) together thereby permitting bi-directional airflow around the entire gland (301) of the mechanical seal (300). This helps to convention heat transfer from the atmospheric air/fluid side.
Furthermore, from Figure 12, the seal gland (301) incorporates a large internal cavity (309) adjacent to the primary heat source (307) when the equipment is operational. The extended surface area of said internal cavity (309) helps to convention heat transfer from the process fluid side.
The reader will therefore understand the significant heat transfer benefits of airflow across the surface of a component of the present invention.
Figure 13 corresponds to Figure 12 and shows an end view of the seal gland (310), from arrow “Y” of Figure 12, for the third embodiment of the present invention.
From Figure 13, the inter-connecting cavity orifices (311) are shown. Clearly, the current invention anticipates various shapes of said orifices (311) and not just the circular orifices shown.
Figure 14 corresponds to Figure 13, Section B-B and shows a longitudinal section through a mechanical seal (320) of the third embodiment of the current invention with bi-directional airflow circulation cavities.
As shown, air (321) circulates across the surfaces of both the front and rear faces of the gland (322) facilitating convection heat transfer (323).
Figure 15 shows a longitudinal section through a mechanical seal (400) of the fourth embodiment of the current invention.
The reader will understand that heat transfer is accelerated through forced convention. The faster the air flow rate, the more readily the surface cools as air forming a boundary layer is replaced.
From Figure 15, a mechanical seal (400) is shown as a cartridge seal in that the rotary seal face assembly (401) is connected to a cartridge sleeve (402) which is connected to a clamp ring (403). The clamp ring (403) contains one or more screws (404) for connecting the mechanical seal (400) to the equipment shaft (405).
An air-fan assembly (406) is connected to the clamp ring (403) by one or more screws (407). The air-fan assembly (406) contains one or more fan blades (408) which are angularly positioned, shaped and curved to induce longitudinal air flow towards the gland (409) when the equipment is operation.
Clearly, as the fan (408) is rotating with the shaft (405) and in the potential operator vicinity at the atmospheric side of the mechanical seal (400), the current invention anticipates a fan shield (410), in the form of a solid or wire-mesh guard.
Said fan shield (410) is connected to the stationary gland (409) by one or more screws (411).
This fourth embodiment arrangement thereby creates forced convection to, and around, the gland (409) to significantly improve convection heat transfer.
Figure 16 corresponds to Figure 15 and shows an end view of the mechanical seal air-fan assembly (420). As shown, the air fan assembly (420) has one or more blades (421) which are connected to a central ring (422) with orifices for connection to the mechanical seal (or equipment shaft) by the use of screws (423).
The foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

, Claims:
1. A mechanical seal comprising of at least one rotary seal face and at least one stationary seal face, characterized in that both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member;
wherein, said rotary seal face member has one or more radially extending grooves with an inclined surface which runs radially outwardly in the direction of the longitudinal axis of the rotating equipment shaft, towards the counter-rotational sealing interface and fluid film.

2. The mechanical seal as claimed in claim 1, wherein said rotary seal face comprises of a seal face insert member and a seal face holder member forming a seal face assembly, characterised in that the seal face holder contains two or more radially extending grooves with inclined surfaces which run radially outwardly in the direction of the longitudinal axis of the rotating equipment shaft, towards the counter-rotational sealing interface and fluid film.

3. The mechanical seal as claimed in claim 1, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member;
wherein the stationary seal face is mounted in a stationary gland member that is connected to the stationary housing of the process equipment in an anti-rotational manner; and
wherein said seal gland member contains one or more longitudinally extending cavities.

4. The mechanical seal as claimed in claim 3, wherein the gland member contains at least one longitudinal extending cavity at the atmospheric side of the mechanical seal and at least one longitudinal extending cavity at the process side of the mechanical seal.
5. The mechanical seal as claimed in claim 4, wherein the said gland member contains a number of said cavities disposed around the periphery of the gland between the equipment housing connection slots/holes.

6. The mechanical seal as claimed in claim 3, wherein said seal gland member contains at least two longitudinally extending and inter-connected cavities which permit bi-directional airflow around the glands outermost surfaces.

7. The mechanical seal as claimed in claim 1, wherein said both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, characterised in that connected to the mechanical seal rotary member is one or more air-fan blades that facilitate atmospheric air movement.

8. The mechanical seal as claimed in claim 7, further comprising of a cartridge sleeve assembly connected to the rotary seal face assembly, and an air-fan member connected to the cartridge sleeve assembly.

9. The mechanical seal as claimed in claim 8, wherein the said air-fan member is substantially adjacent to the axial surface of the gland member.

10. The mechanical seal as claimed in claim 1, wherein the said rotary air-fan member is substantially shielded by a fan-guard member connected to the stationary member, such as the gland member or housing of the rotating equipment.