Self-contained rotary mechanical seals

Self-contained rotary mechanical seals

A self-contained rotary mechanical seal is provided for mounting on a rotating shaft to form a seal between the shaft and structure on a housing through which the shaft extends. The seal includes an annular lug holder to be secured to the shaft as by set screws. A plurality of lugs extend from the lug holder parallel to the shaft.

Tines extend circumferentially from the ends of the lugs concentric to the axis of the lug holder. A belleville washer assembly is disposed within the lugs. An annular carbon seal washer also is disposed at least partially within the lugs. The seal washer includes radially extending shoulders dimensioned to engage the lugs and tines. In assembled form, the shoulders 15 of the carbon seal washer are urged by the spring force of the belleville washers against the tines. The tines retain the carbon seal washer in a position partially within the lugs.

In a rotary mechanical seal of the type having an annular base adapted for mounting on a rotating shaft, a seal washer, and a spring means located between the base and the seal washer for urging said seal washer against a housing through which the shaft extends to form a seal, the improvement comprising:a plurality of longitudinal lugs extending from said annular base in circumferentially and radially spaced-apart relationship with said shaft such that said spring means and seal washer can be received between said lugs and shaft;circumferential projections extending away from said lugs on the ends of said lugs opposite said base; and a plurality of circumferential projections extending radially outward from said seal washer in circumferential spaced-apart relationship sufficient for receiving said lugs there between so that said seal washer and base can be engaged for rotation and secured against longitudinal separation under the action of the spring means by inserting said seal washer under said lugs and twisting said seal washer until the seal washer projections are locked behind the lug projections.

Mechanical seals have long been known and used for forming a seal between a rotating shaft and a housing through which the shaft extends. Typically, a carbon seal washer is mounted to rotate on the rotating shaft and to slidably engage a seal seat mounted in the housing. The sliding engagement between the carbon seal washer and the seat forms a fluid-tight seal that, in conjunction with additional stationary seals, is operable to complete a fluid-tight seal between the shaft and the housing.

Often a plurality of coil springs are provided to force the carbon seal washer against the seal seat on the housing. In this assembly, the carbon seal washer is continuously urged along the shaft toward the seal seat so that the washer and the seat are maintained in a firm engagement even after both have been used for long periods of time.

However, problems have been encountered with the use of mechanical seals having coil spring forced carbon seal washers. Conventional mechanical seals utilizing a multiple coil spring arrangement often utilize coil springs mounted in a recess in the seal housing. The coil springs located in such recesses are susceptible to fouling and clogging by suspended particles and the like. The fouling of the springs may cause the seal to malfunction.

Further, in the assembly of a mechanical seal utilizing a multiple coil spring arrangement, usually, each individual spring must be properly positioned in the mechanical seal housing, and then the carbon seal washer must be forced into the seal against the spring force. Finally, some measure must be taken to retain the carbon seal washer within the seal housing resisting the spring force. This assembly procedure has proved difficult, and installation of such seal was often cumbersome. Mechanical seals of this type are generally expensive to manufacture.

The present invention overcomes the foregoing problems and others long associated with mechanical seals by using an anti-clog, self-cleaning, belleville spring arrangement and by using an annular seal housing designed to facilitate assembly. In the present invention, a mechanical seal includes an annular base for mounting on a rotating shaft within a housing. A plurality of lugs extend from the base and circumferential projections extend from the ends of the lugs. A seal washer is provided for being mounted at least partially within the lugs and is dimensioned for snuggly encompassing the shaft. The seal washer includes radial projections for engaging the circumferential projections. A spring is provided within the lugs between the base and the seal washer for urging the radial projections of the seal washer against the circumferential projections extending from the lugs. In this manner, the seal washer is retained partially within the lugs and mounted on the mechanical seal. When the mechanical seal is mounted on the shaft, the spring structure is operable to urge the seal washer against housing structure to form a seal. Also, the lugs will engage the radial projections to force the seal washer to rotate with the lugs and shaft.

In accordance with a particular aspect of the present invention, a mechanical seal is provided for use on a rotating shaft extending through a housing. An annular lug holder is dimensioned to snuggly engage the shaft and includes a plurality off asteners for mounting the lug holder on the shaft. The lug holder includes a plurality of slots, and a plurality of lugs are mounted in the slots and extend from the lug holder in a longitudinal direction parallel to the axis of the lug holder. A plurality of tines are provided with two tines extending circumferentially from the end of each lug in a direction perpendicular to the lugs and concentric to the axis of the lug holder.

A plurality of belleville washers are dimensioned to snuggly encompass the shaft and for being disposed between the lugs and the shaft adjacent to and engaging the lug holder. The belleville washers have sufficient elasticity to resilientlyoppose compression. A contact washer is provided for encompassing the shaft and for being disposed adjacent the belleville washers. An annular carbon seal washer is center-bored for snuggly encompassing the shaft and is disposed partially within the lugs adjacent the contact washer. The seal washer includes an annular recess adjacent the contact washer and an annular nose surface facing away from the lug holder. An O-ring and a back-up ring encompass the shaft and are disposed within the recess in the seal washer to form a seal between the shaft and the seal washer.

A plurality of shoulders extend radially outward from the seal washer for engaging the tines to retain the seal washer partially within the lugs. The shoulders have a sufficiently small width to pass between the confronting ends of the tines extending from adjacent lugs and have a sufficient radial extension to engage the tines and lugs. The mechanical seal may be assembled by inserting the seal washer partially within the lugs to engage the contact washer and to compress the belleville washers. The seal washer is then rotated until the shoulders engage the lugs. Then, when the seal washer is released, the belleville washers will urge the seal washer forward until the shoulders engage the tines to retain the washer on the mechanical seal.

A seal seat is mounted in the housing and includes a face surface for slidably engaging the annular nose surface of the seal washer to form a seal. The mechanical seal is positioned on the shaft relative to the housing such that the seal washer is urged against the seat by the spring force of the belleville washers. In this position, the seal washer is displaced rearwardly toward the lug holder such that the shoulders extending from the seal washer do not engage the tines.

Arrangement in connection with mechanical seal

An arrangement in connection with a mechanical seal includes at least two sliding surfaces pressing against each other, which are arranged to seal a gap between a rotating and a non-rotating machining part, and mechanism for providing a sealing fluid flow cooling the sliding surfaces. To provide an optimal consumption of sealing fluid, a valve mechanism is arranged to the mechanism for providing the cooling sealing fluid flow, the valve mechanism being arranged to react to the temperature of the seal and to open and close the flow of sealing fluid according to the cooling need.

The method of controlling sealing fluid flow according to seal cooling need, comprising: providing at least two sliding surfaces pressing against each other, which are arranged to seal a gap between a rotating and a non-rotating machine part, providing means for providing a sealing fluid flow cooling the sliding surfaces, and providing a valve means arranged in connection with the means for providing a cooling sealingfluid flow, the operation of the valve means being based on a memory metal element that is arranged to react to the temperature of the sealing fluid and to open and close the sealing fluid flow according to a cooling need, wherein the valve means isintegrated to the mechanical seal.

Mechanical seals are commonly used in different technical fields to seal gaps between a rotating and a non-rotating machine part. Examples of such rotating and non-rotating machine parts and gaps between them include the body and shaft of apump, for instance process pump, and the gap between them that needs to be sealed so that the pumped process fluid cannot leak out through the gap between the pump shaft and the pump body. The sealing is done between two exactly opposing slidingsurfaces that rotate against each other. In normal use, a mechanical seal naturally also heats up, in which case it is cooled by a fluid flow on the opposing side to the seal. Water, for instance, is used as the coolant. Mechanical seals often alsocontain a second sliding surface pair on the atmospheric side, in other words on the outside, to seal any leakage of sealing fluid to the atmosphere.

Critical operating values in the operation of a mechanical rotary shaft seal include pressure, temperature and a few other factors. Pressure includes the pressure of the sealed product, the pressure inside the seal, or the sealing fluidpressure, the ratio of the above-mentioned pressures with respect to each other, and any changes occurring in the pressures.

As regards temperature, the related issues are the temperature of the sealed product, the temperature of sealing fluid, the temperature of the environment, the temperature of the parts of the seal, especially the sliding surfaces, and any changesin temperature.

Mechanical rotary shaft seals are cooled by means of a sealing fluid that flows continuously through them. The flow is in some cases limited, i.e. the flow is adjusted in such a manner that cooling is sufficient for the conditions prevailingduring the adjustment. In some cases, the water connection from the seal is plugged completely. These solutions use a sealing water adjustment and control unit, for instance, to adjust the flow and pressure of the sealing water of the mechanical seal. The apparatus comprises a flow meter and any necessary adjustment devices for adjusting the flow and pressure of the sealing water.

The flow rate of sealing water is determined using the above-mentioned arrangement. One important task of the sealingwater is to cool the mechanical seal, as stated above. It is, however, difficult to adjust the flow of the sealing water to be optimal according to the temperature of the outflowing sealing water. The above-mentioned solution helps find out the amountof used sealing water, but, for safety, water consumption is often adjusted to be too high.

Further, there is the problem that if the flow of the sealing water is adjusted to be low, the flow orifice is easily blocked by particles in the water, eventhough the orifice were designed to allow water impurities to pass. Flow low-limit alerts caused by orifice blockage are also problematic in practice. Plugging the sealing water outflow connection provides good conditions for a mechanical seal, butthis arrangement does not provide heat removal from the seal. If the temperature rises higher than the temperature designed for a mechanical seal, the seal may suffer damage. The solution is thus not suitable for situations, in which the temperature ofthe seal rises easily. An advantage of the solution is naturally that it does not waste expensive sealing water.

The mechanical seal comprises two sliding surfaces pressing against each other, which are arranged to seal the gap between the rotating and the non-rotating machine part. The seal further comprises an input unit and an output unit for directingcooling sealing fluid to and from the mechanical seal. The seal may also comprise a second sliding surface pair to seal any leakage of sealing fluid to the surroundings.

Mechanical seal incorporating a pusher ring for safe

Mechanical seal incorporating a pusher ring for safe

An improved mechanical seal incorporating a pusher ring to hold the integral parts of the seal together, in lieu of a typical retaining ring and snap ring aligning and compressing the gland plate. The improvement consists of a pusher ring, fixedly attached to the seal body gland face with cap screws, which retains the gland plate, allowing for easy and safe repair and assembling.

A mechanical seal provides a hydraulic seal between a rotatable element, typically, a shaft and a stationary housing of the apparatus. Such seals are associated with a fluid pump having a shaft extending through a pump housing wall, handling fluids of varying viscosity. The lower the viscosity of the fluid being handled, the tighter the seal required within the pump design.

Although these seals are most commonly employed on pump equipment, other fluid handling equipment also utilize mechanical seals. So, although the present invention is addressed in terms of pump applications, the invention is not restricted therein, but may be employed on all such equipment having mechanical seals.

The pump shaft is typically coupled to a motor through a motor shaft. The mechanical seal forms a seal between the pump shaft and the outer surface of the pump housing. Mechanical seals for such applications are commercially available and have been available for more than 25 years.

Seals, Generally

Seals, in their most common and most basic form, are known in the art and comprise rotatable components and stationary components which contact to form a seal at opposing sealing surfaces. The rotatable components include a shaft attachment means. Such a means is typically a sleeve having an inner perimeter surface which sealingly fits over the outer perimeter surface of the shaft and is connected to the shaft, by connecting means such as set screws. An “O” ring typically provides a seal between the shaft and the sleeve. There is a rotatable circumferential seal element interconnected to the sleeve so as to rotate when the shaft and sleeve rotate. The sleeve extends axially along the shaft.

The stationary components comprise a gland which extends circumferentially around the shaft. The gland abuts against the outer housing surface around the shaft. There is typically a sealing gasket interconnected to the gland and located between the gland and the housing. The gland functions as a base by which the seal is attached to the housing. The connection is typically accomplished by bolts extending from the outer housing wall. The bolts pass through slots or connecting extensions extending radially from the gland through the connecting slots or connecting extensions and secured with nuts. A stationary seal element is located between the inner circumferential surface of the gland facing the shaft (i.e. the gland inner surface) and the shaft. The stationary seal is directly or indirectly connected to the stationary gland. There are suitable means such as described in U.S. Pat. Nos. 4,832,351 and 4,989,882 to axially center the various stationary elements on the shaft. A circumferential spacing is maintained between the stationary elements, and the shaft and various of the rotating elements.

Mechanical Seals, Specifically

The mechanical seal also comprises rotatable components and stationary components. The rotatable components are interconnected to the shaft and rotate with the shaft. The stationary components are interconnected to the housing and do not rotate. The rotatable components and stationary components are positioned relative to each other so that a rotatable seal surface sealingly engages a stationary seal surface. Such a mechanical seal is particularly useful to form seals on machines which have rotatable shafts extending therefrom and fluid inside such as fluid pumps, i.e., water pumps, which have close tolerances, particularly in applications requiring the handling of caustic chemicals or flammable liquids. They are also widely used in nuclear reactor cooling systems to contain radioactive liquids. Typical mechanical seals are designed for leakage of less than one one-thousandth of one percent of the volume of the liquid pumped, per unit time.

The prior art mechanical seals date back to the early 1980′s. They have existed for many years, as relative to this art. There has existed, however, safety concerns over a number of the seals because they generally employ snap rings on the seal which, while being installed or removed, can become projectiles which pose a threat to the mechanics.

Original designs used a heavy duty snap ring just inside the gland to hold the integral parts of the seal together. This snap ring was rated at upwards of 80,000 ft. lbs. of axial thrust load. This is more axial thrust load than any pump would ever experience with these seals, and was extreme for a snap ring as applied to these seals. Therefore, when the snap ring was removed, special pliers had to be employed, and risk of severe injury was possible because of the loaded spring causing the threat of projectiles.

Mechanical seals known in the art have at least one “O” ring associated with the sealing element being acted on, and in most instances, acted on by the spring. The spring forces this element toward the opposing element to form a seal. The “O” ring must form a seal not withstanding the axial movement and is known as a “dynamic-O” ring. Additionally, the dynamic “O” ring is located in an “O” ring slot which can clog. The spring must, therefore, provide force to cause the sealing elements to come together under sufficient pressure to form a seal while overcoming the resistance of the dynamic-O ring.

It would be desirable to eliminate the metal spring installed in concert with the dynamic “O” ring, and that is the present sense of the invention disclosed and claimed herein. The present invention retains all the favorable characteristics of the “O” ring, but without the disadvantages of snap ring and retaining rings, the mechanisms which create the dangerous tendency of the spring mechanisms in current art.

Additionally, the means to connect the mechanical seal to the housing is integrated into the structure of the stationary components. The mechanical seal is often set in place and removed in the small space between the pump and motor. The means to attach the seal takes up space and make access to the mechanical seal difficult for both installation and removal. A design with easier access to the seal elements at the location where the shaft extends from the housing is desirable, also an attribute of the present invention.

Seals and Sealing Handbook, Fifth Edition

Seals and Sealing Handbook, Fifth Edition

Wherever machinery operates there will be seals of some kind ensuring that the machine remains lubricated, the fluid being pumped does not leak, or the gas does not enter the atmosphere. Seals are ubiquitous, in industry, the home, transport and many other places. This 5th edition of a long-established title covers all types of seal by application: static, rotary, reciprocating etc. The book bears little resemblance to its predecessors, and Robert Flitney has re-planned and re-written every aspe

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