GB2419646A

GB2419646A - A modular gland member for use in a mechanical seal

Info

Publication number: GB2419646A
Application number: GB0521138A
Authority: GB
Inventors: Alan James Roddis
Original assignee: AES Engineering Ltd
Current assignee: AES Engineering Ltd
Priority date: 2004-10-18
Filing date: 2005-10-18
Publication date: 2006-05-03
Anticipated expiration: 2025-10-18
Also published as: US8011668B2; GB2419646B; GB0521138D0; US20060082071A1; GB0423087D0

Abstract

A modular gland member 41 for use in a mechanical seal 9, the gland member has a radially or axially extending cavity adjacent to a seal face 33, the cavity contains a solid or fluid thermal conducting member 60 to effectively dissipate heat from the seal face 33 into the surrounding components 41.

Description

CLOSE COUPLED MECHANICAL SEAL

Field of the Invention

This invention relates to mechanical seals and their use in rotating equipment, especially pumps, mixers, agitators and drying equipment.

submersible pumps. However, the use of such seals extends well beyond the use in such equipment and accordingly, while reference will be made below to pumps, it should be understood that this term is used, as far as the invention is concerned, in connection with such having wider uses.

A Mechanical seal comprises a "floating" component which is mounted axially movably around the rotary shaft of, for example, a pump and a "static" component which is axially fixed, typically being secured to a housing. The floating component has a flat annular end face, i.e. its seal face, directed :.:. 15 towards a complementary seal face of the static component. The floating S...

component is urged towards the static component to close the seal faces * together to form a sliding face seal, usually by means of one or more spring *S.S members. In use, one of the floating and static components rotates; this S.....

* component is therefore referred to as the rotary component. The other of S..

.. 20 the floating and static components does not rotate and is referred to as the stationary component...DTD: Those seals whose floating component is rotary are described as rotary seals. If the floating component is stationary, the seal is referred to as a stationary seal.

If the sliding seal between the Rotary and Stationary components are assembled and pre-set prior to despatch from the Mechanical seal manufacturing premises, the industry terminology for this is "cartridge seal".

If the Rotary and Stationary components are despatched individually (unassembled) from the Mechanical seal manufacturing premises, the industry terminology for this is "component seal" Mechanical seals are used in all types of industries to seal a variety of different process media and operating conditions. The general industry term which defines the area adjacent to the process media is "inboard". The industry term which defines the area adjacent to the atmospheric side is "outboard".

Background to the Invention

Mechanical seals are used in a wide variety of industrial applications.

Often, the sealing applications necessitate the use of a gas barrier system.

This means that the seal faces must run "dry", as herewith described.

An experienced reader will note that typically mechanical seal faces require a fluid film. This fluid film is positioned between the pair of seal faces and acts : to lubricate and cool the seal faces during dynamic operation. * 15 S..

If a pair of seal faces are required to seal a marginal lubrication fluid and/or a gas, for example Nitrogen, for ease of explanation the reader may also I...

consider the fluid film to be a gas. Such a fluid film provides very little seal face lubrication, which often results in a high amount of heat generation. * **

***** 20 Such heat is dissipated into the respective mechanical seal faces. There are many factors, which will increase the heat generated between the pair of mechanical seal faces. Pressure and counter rotational surface speed are two of such factors.

Heat between mechanical seal faces is highly undesirable as explained; Firstly, some environments contain gases which can auto ignite should said gas come into contact with heated surfaces. In the case of a mechanical seal, seal faces running at elevated temperatures increases the possibly of a problem and/or reduces the possibility of their wide application. The European directive which fully describes such environments is described in 94/9/EC. Further information is contained in DIN EN1127-1:1997, prEN 13463-1:2001, prEN 13463-5:2000 and prEN 13463-6:2002.

- Secondly, this condition may also increase seal face deterioration and reduce seal face life.

It is deemed particularly advantageous if a seal design is created which reduces the heat transferred into a seal face, which is operating in poor fluid film conditions.

Figure 1, shows a partial cross sectional view of a mechanical seal of the 1st embodiment of the invention, a close coupled stationary seat over the outboard seal face, of a double mechanical seal.

Figure 2, corresponds to Figure 1 and shows an enlarged view of the close:.:. 15 coupled stationary seat of the invention. S... * * S...

Figure 3a, corresponds to Figure 1 and shows the close coupled stationary S. S S * seat on the inboard side of a single cartridge mechanical seal, of the 2nd S.....

* embodiment of the invention. S.. * 20 S...

Figure 3b, corresponds to Figure 3a and shows the modular close coupled stationary seat on the inboard side of a single cartridge mechanical seal employed with a cooled seat, of the 2nd embodiment of the invention.

Figure 4, corresponds to Figure 1 and shows the modular close coupled stationary seat operating as a fluid cooled arrangement, of the 3rd embodiment of the invention.

From Figure 1, which shows a cross sectional view of a mechanical seal (9) of the 1st embodiment of the invention.

At the inboard side of the seal, the rotary and axially floating seal face (11) is spring biased towards an axially static stationary seal face (12). The rotary seal face (11) is allowed to slide on the stationary seal face (12). The interface between the rotary seal face (11) and stationary seal face (12) forms sealing area (13). This sealing area (13) is the primary seal that prevents the process media (14) from escaping from the process chamber (15).

In addition to the sliding seal face (13), the process media (14) is sealed by a sleeve elastomer (16) in contact with the shaft (17) and sleeve (18). This has been termed the first secondary sealing area (19).

The second secondary sealing area (20) is formed between stationary seal : face (12) and stationary gland (21) using elastomer (22).

**. * 15 The third secondary sealing area (23) is formed between the rotary seal face (11) and the sleeve (18) using elastomer (24). S...

SeS*SS * The fourth secondary sealing area (25) is formed between the gland (21) and *SS 20 the process chamber (15) using u-shape elastomer (26). S. * * . S * .*

The four secondary sealing devices and the primary sliding sealing interface prevent the process media (14) from escaping.

A clamp ring assembly (27) contains screws (28) which secure the sleeve (18) to the shaft (17) and transmit rotational drive from the shaft (17) into the clamp ring assembly (27) and sleeve (18). Said rotational drive is transmitted to the rotary seal face (11) by at least one drive mechanism (29).

At the outboard side of the seal, the rotary and axially floating seal face (31) is spring biased towards an axially static stationary seal face (32). The rotary seal face (31) is allowed to slide on the stationary seal face (32). The interface between the rotary seal face (31) and stationary seal face (32) forms sealing area (33). This sealing area (33) is the primary seal that prevents the barrier media (34) from escaping from the barrier chamber (35).

In addition to the sliding seal face (33), the barrier media (34) is sealed by a inner barrel elastomer (36) in contact with the sleeve (18). This has been termed the first secondary sealing area (39).

The second secondary sealing area (40) is formed between stationary seal face (32) and stationary gland (41) using elastomer (42).

The third secondary sealing area (43) is formed between the rotary seal face (31) and the inner barrel (30) using elastomer (45). * S.

:.: * 15 The three secondary sealing devices and the primary sliding sealing *..i.. interface prevent the barrier media (34) from escaping. S... * . S.

The inboard rotary seal face (11) and outboard rotary face (31) has damper members (50) and (51) supported by at least one damper elastomer (52) on **.

20 the respective outer circumferences of the rotaries. S. S * . S * *5

From Figure 2, axially adjacent to the outboard stationary elastomer (42) is a close coupled device (60) is radial contact with said stationary (32) on its inner most surface, and in radial contact with the gland (41) on its outer most surface.

Axially adjacent to the close coupled device (60) is a further stationary elastomer (61) which, in the case of Figure 2, is employed to help radially support the stationary seal face (32).

In dynamic operation, heat is created from the sliding surface (33). Said heat is transferred into the stationary seal face (32). With conventional seal faces, the stationary elastomer (42) and/or (61) acts to insulate the seal face and thus the heat generated can not effectively dissipate into the gland.

From Figure 2, the close coupled member (60) is preferably manufactured from a material, which is relatively conductive and acts to transfer heat from the stationary seal face (32) to the gland (41) and thus effectively dissipates the heat reducing the total heat build up in a given operating scenario.

It has been found that the larger the close coupled surface area (43), in contact with the seal face (32) and gland (41), the better the ability of the invention to remove undesirable heat build up.

By way of example only, Figure 3a, and shows the 2" embodiment of the * invention, the close coupled stationary seat (70) on the inboard side of a :.: 15 single cartridge mechanical seal (71), of the invention with conductive close *e** coupled member (72) between the stationary seat (70) and gland (73). *.** * * *.S

By way of example only, Figure 3b, corresponds to Figure 3a and shows the close coupled stationary seat (75) on the inboard side of a single cartridge **

.. 20 mechanical seal (76), of the invention with the conductive close coupled member missing leaving an open gland cavity (79) in gland (77). An heat transfer fluid orifice (78) connects the gland cavity (79) to the outer most radial area of the gland (77). As previously described, heat transfer fluid may then cool the stationary seat (75)...DTD: Figure 4, corresponds to Figure 1 and shows a cross sectional view of mechanical seal (80). From Figure 4, the modular close coupled stationary seat (90) operating as a fluid cooled arrangement of the invention. In such an application the gland cavity (91) in gland (92) is left unoccupied and without a heat transfer member. Said gland cavity (91) preferably has at least one inlet orifice (93) and preferable at least one outlet orifice (94).

A cooling medium and/or fluid such as water, enters the inlet orifice (93) , circulates around the outer radial portion of the stationary seat (90) and exits the outlet orifice (94). Heat is transferred from the stationary seat (92) into the heat transfer fluid.

The benefit of the invention is that a modular gland member can be employed for both close coupled product offerings and cooled seat product offerings thereby allowing the correct technical selection for an application without a commercial penalty being incurred. * ** * * *

**, 15 Se.. * I S... S... * I U* S *

* ....I * S S.. * U S... S. I * S * *0

Claims

1 A modular gland member containing a radially extending cavity adjacent to a seal face member, said radially extending cavity may be filled with a thermally conductive solid material or fluid.

2 A mechanical seal containing at least one pair of counter rotating seal faces which are axially biased together by one or more spring like members, at least one seal face is closely coupled to an adjacent member by a conductive solid or fluid means.

3. A mechanical seal in accordance with claim 1 and/or 2, which contains two or more stationary seal faces.

:

4. A cartridge mechanical seal in accordance with any preceding claim. * I S... * I *.*. * S * * . I. *

S I S * I.