RU2318151C1 - Face seal - Google Patents

Abstract

FIELD: sealing engineering.

SUBSTANCE: face seal comprises movable contact that is formed by interacting members of nonrotating and rotating units one of which is movable in the axial direction and is made of a friction ring whose one end is connected with the fluoroplastic bellows having corrugations provided with the straight-line sections at the top and hollow. The grooves are made between the sections. The second end of the bellows is secured inside the housing or to the shaft above the bellows or a spring is mounted inside it. The spring is provided with slots. The width of the grooves of the springs is less than the width of the straight-line section at the top of the corrugation of the bellows, and the width of its shelf is greater than the width of the straight-line section at the top of the corrugation of the bellows. The height of the side of the corrugation relates to the width of the groove between the corrugations as 3.5-5.5.

EFFECT: enhanced reliability.

5 cl, 4 dwg

Description

The invention relates to a sealing technique and can be used for mechanical seals having a PTFE bellows and operating at high pressure and temperature.

A mechanical shaft seal is known, the sealing movable contact of which is formed by the elements of non-rotating and rotating assemblies interacting along the sealing belt, one of which is axially movable and consists of a friction ring fixed at one end of the fluoroplastic bellows, which has grooves between the corrugations, the second end of the bellows is fixed in the housing or on the shaft, above the bellows there is a spring and a protective metal sleeve that is sensitive to the overpressure in the bellows (see Cr catalog ane Packing Ltd, B5. 800A / 8/77, p. 5).

The disadvantage of this seal is that the metal sleeve prevents the radial and angular deflection of the bellows, thereby reducing the reliability of the mechanical seal.

The closest technical solution is a mechanical shaft seal, the sealing movable contact of which is formed by the elements of non-rotating and rotating nodes interacting along the sealing belt, one of which is axially movable and consists of a friction ring fixed at one end of the fluoroplastic bellows having grooves between the corrugations made rectangular in shape with straight sections at the apex and trough, the second end of the bellows is fixed in the housing or on the shaft, above the bellows are located dinners and protective metal sleeve, the perceptive effect of overpressure in the bellows (see. FLOWSERVE FSO company directory 126 Rev 07/02 EUR).

The disadvantage of this device is the unreliability of the design of the seal due to the large pitch of the bellows corrugation, the same thickness of the top and bottom of the bellows corrugation, the large length of the straight sections on the top and bottom of the corrugation, the small number of load-bearing walls of the bellows corrugation, and, as a result, the need for the introduction of a metal sleeve, which in turn prevents the radial movement and angular bending of the bellows.

The objective of the invention is to increase the reliability of the mechanical seal.

The technical result from the use of the invention is to increase the technical characteristics, reliability of the mechanical seal and increase its service life.

The specified technical result is achieved by the fact that the spring is slotted, while the width of the grooves B of the spring is less than the width of the straight section B at the top of the bellows corrugation, and the width of its shelf C is greater than the width of the straight section B at the top of the bellows corrugation, and the ratio of the height of the working part of the wall of the corrugation N to the width of the groove M between the corrugations is 3.5-5.5.

At the mechanical seal of the shaft, the width of the grooves B of the slotted spring is 0.3-0.8 of the width of the straight section B on the top of the bellows corrugation. For a bellows, the thickness of the rectilinear section h at the depression of the corrugation is at least 1.3 the thickness of the rectilinear section h ₁ at the top of the corrugation. The width of the flange C of the slotted spring is 1.1-1.5 of the width of the rectilinear portion B of the bellows at the top of the corrugation. In a bellows, the width of the groove between the corrugations M is less than two thicknesses S of the corrugation wall.

The spring can be placed in a protective cover made of thin-walled polymeric material.

Figure 1 shows a longitudinal section of a mechanical seal.

Figure 2 presents a longitudinal section of a slotted spring.

Figure 3 presents a longitudinal section of a bellows.

Figure 4 presents the node I of figure 1.

In the considered example, the axially movable assembly is made non-rotating. However, it is obvious that this technical solution can also be implemented if the non-rotating assembly is made rotating and the rotating assembly is non-rotating. In this example, the spring is located above the bellows, and the overpressure acts from the inside of the bellows. In the event of pressure acting outside the bellows, the spring is located inside the bellows.

The mechanical seal consists of a housing 1, the movable sealing contact of which is formed along the sealing girdle 2 by the elements of the rotating assembly 3 and the non-rotating assembly 4, movable in the axial direction. The non-rotating assembly 4 consists of a friction ring 5 fixed at one end of the fluoroplastic bellows 6, which has grooves 7 (see FIG. 3) between the corrugation walls 8, which are rectangular in shape with straight sections 9 at the top and straight sections 10 at the depression. The second end of the bellows is fixed in the housing 1. Above the bellows is a spring 11. The spring is slotted, and the width of the grooves B of the spring is less than the width B of the straight section at the top of the bellows corrugation (see figure 2). The width C of the spring shelf 12 is greater than the width B of the corrugation top, and the ratio of the height H of the wall 8 of the corrugation to the width M of the groove 7 between the corrugations is 3.5-5.5 (see table). The bellows has an inner diameter d and an outer diameter D.

At the mechanical seal of the shaft, the width B of the grooves of the slotted spring should preferably be 0.3-0.8 of the width B of the straight section at the top of the bellows corrugation. In a bellows, the thickness h of the straight portion at the corrugation depression is at least 1.3 thickness h _{1 of the} straight portion B of the corrugation at its apex. The width of the flange f slotted spring is selected based on a given axial stiffness. In a bellows, the width M of the groove between the corrugations is less than two thicknesses S of the corrugation wall.

The spring is placed in a protective shell 14 of thin-walled polymeric material (see figure 4).

Below is a table with comparative characteristics of mechanical seals with fluoroplastic bellows.

No. p / p Country, Company, year Seal type Sizes, mm Worker couples. D _corrugation d _corrugation S, _corrugation N _corrugation N, pcs _{number of corrugations} Step t, _corrugation Bellows stroke The length of the bellows is it. L Seal length. at ⌀50 Pressure MPa Pace. ° C K = n / m one Poland "ANGA", 2002 A13a 75 65 1,2 3,5 3,5 3,5 four 41 61 1,2 +80 2-2.5 12 A10
A11 75 52 7.5 2,5 3 43 68.3 0.9 +120 7-10 2 JAPAN Epil _{(Eagle poonawalla Indusry) Ltd} Y29 75 52 6.5 3 5 34.93 0.5 -75
+100 2-3 3 England "John Crane" 10T / 10R 72 52 1,5 6 2,5 6 2 43 2-3 950 71 51 1,5 5 four 6 3 53 53 0.8 +25 2-3 0.3 +125 Tetraflex 78 fifty 1,5 10 7 5 39 80 80 0.23
0.02 +20
+200 2,5-
3.2 four Germany "Merkel" No. 633 80 fifty 1,5 12 n fourteen 5.5 * l ₀ 1,5 +20 2-3 D n 0.5 +200 5 The proposed solution according to the invention fifty UTD
C100 77 53 1,5 7 four 7 6 63 155 1.8
1,0 +25
+200 3,5-
5.5

Analysis of the designs of bellows mechanical seals of various companies listed above in the table shows that the ratio K is used in the ranges of 2-3.2 and 7.0-10.0. The proposed bellows design uses a ratio of 3.5-5.5. This ratio is selected taking into account the optimal combination of strength and rigidity of the bellows. If you use a ratio of less than 3.5, the bellows will be very stiff and strong, which leads to high loads at the ends of the bellows and increased wear of the seal. If you use a ratio of more than 5.5, the bellows becomes very soft and does not withstand high pressure. The proposed ratio allows the seal to be used at significantly higher pressures and to select a specified value of the axial stiffness of the seal, which increases the durability and reliability of the seal.

The width of the grooves In the slotted spring is selected from 0.3 to 0.8 of the width of the straight section B at the top of the bellows corrugation. If the width B is less than the width of 0.3 B, it is possible to cut into the material of the top 9 of the bellows corrugation. If the width B is greater than the width 0.8B, then it is possible that the surfaces 9 of the bellows will coincide with the grooves B of the slotted spring, which will entail the possibility of extruding the surfaces 9 into the gap B, thereby the slotted spring ceases to fulfill the protective function.

As shown by studies of the stresses of the material of the bellows, their value on the inner surface 10 is greater than the stresses on the outer surface 9 by 1.3-2.0 times. Therefore, for a uniform distribution of stresses in the material of the bellows, it is necessary to increase the wall thickness h by 1.3-2.0 times. The choice of the ratio depends on the size of the inner diameter d of the bellows.

The width C of the slotted spring shelf is selected from a ratio of 1.5-2.5 of the width of the rectangular portion B of the corrugation top. This is due to the need to overlap the width B and the gap M. This prevents squeezing the inner diameter of 10 corrugations to the outer diameter 9. In the above range, sections B and M overlap along the entire length of the corrugated part of the bellows.

The value M of the gap between the corrugations in the structure under consideration should always be less than 2S of the corrugation wall thicknesses.

Mechanical seal operates as follows.

When the mechanical seal is operating, radial, axial and angular movements are perceived by the non-rotating unit 4. The main working elements of the non-rotating unit are the polymer bellows 6 and the slotted spring 11, which compensate for the above beats.

Under the action of the working pressure inside the bellows, a uniform distribution of stresses occurs in the material of the bellows corrugation. The inner part of the bellows corrugation is always loaded more than its external part, in connection with this, the thickness of the rectilinear section of the corrugation at the cavity is increased and the number of load-bearing walls of the 8 corrugations is increased by reducing the width M of the groove 7. This has the effect of self-reinforcing the bellows and increasing the pressure the bellows can withstand. The introduction of the slotted spring 11 achieved an increase in pressure several times, due to the lack of the possibility of displacing the material at the trough of the corrugation into the width M of the groove 7. The slotted spring in the invention simultaneously serves as a protective metal sleeve for the prototype. The principal difference of the prototype is the possibility of displacing the material at the corrugation cavity into the gap between the metal sleeve and the body, and in another section, the rectilinear sections of the corrugation cavity are irreversibly deformed into the inner surface of the protective metal sleeve, which is eliminated in the present invention.

Industrial applicability is obvious. The mechanical shaft seal passed an experimental test at the Scientific and Production Center Anod LLC and proved its advantage over the prototype.

Claims (6)

1. The mechanical seal, the sealing movable contact of which is formed by the elements of the non-rotating and rotating nodes interacting along the sealing belt, one of which is axially movable and consists of a friction ring fixed at one end of the fluoroplastic bellows having corrugations made with straight sections at the apex and there is a groove between them, the second end of the bellows is fixed in the housing or on the shaft, a spring is located above or inside the bellows, characterized in that the spring is made It is notched, while the width of the grooves of the spring is less than the width of the straight section at the top of the bellows corrugation, and the width of its shelf is greater than the width of the straight section at the top of the bellows corrugation, and the ratio of the height of the side wall of the corrugation to the width of the groove between the corrugations is 3.5-5.5. 2. The mechanical seal according to claim 1, characterized in that the width of the grooves of the slotted spring is 0.3-0.8 of the width of the straight section at the top of the bellows corrugation. 3. The mechanical seal according to claim 1 or 2, characterized in that in the bellows the thickness of the straight section at the bottom of the corrugation is at least 1.3 times the thickness of the straight section of the corrugation at the top of the corrugation. 4. The mechanical seal according to claim 1, characterized in that the width of the groove of the slotted spring is 1.5-2.5 times the width of the straight portion of the bellows at the top of the corrugation. 5. The mechanical seal according to claim 1, characterized in that the bellows groove width between the corrugations is less than two thicknesses of the side wall of the corrugation. 6. The mechanical seal according to claim 1, characterized in that the spring is hermetically placed in a protective shell of thin-walled polymeric material.

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