DEUTSCHE NORM SeDtember 1996 ~ ~~

DIN 3760

Rotary shaft lip seals

ICs 21.120.10

Descriptors: Fluid power, lip seals.

Supersedes April 1972 edition

Radial-Wellendichtringe

In keeping with current practice in standards published by the International Organization for Standardization (ISO), a comma has been used throughout as the decimal marker.

Foreword This standard has been prepared by the Normenausschuß Kautschuktechnik (Rubber Technology Standards Committee). It is based on IS0 6194-1 : 1982.

Amendments The following amendments have been made to the April 1972 edition.

a) For shaft diameters 32, 35, 38 and 40 mm, a nominal width of 8 mm has been introduced to account for new designs. b) Information to be provided by both the manufacturer and the purchaser has been included. c) The standard has been editorially revised.

Previo us edit ions DIN 3760: 1962-02, 1972-04.

Dimensions in mm

1 Scope and field of application This standard specifies dimensions and requirements for materials, marking, use and installation of rotary shaft lip seals used for retaining fluid or grease in unpressurized equipment, or equipment with a low differential pressure, that has rotating shafts. Where seals are intended for use in applications other than those specified in this standard, the seal manufacturer should be consulted.

2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For undated references, the latest edition of the publication referred to applies. DIN 51 524-1 Type HL hydraulic oils - Minimum requirements DIN 51 524-2 Type HLP hydraulic oils - Minimum requirements DIN 51524-3 Type HVLP hydraulic oils - Minimum requirements IS0 1629 : 1995 Rubbers and latices - Nomenclature IS0 4287-1 : 1984 Surface roughness - Terminology - Part 1: Surface and its parameters IS0 61 94-1 : 1982 Rotary shaft lip type seals - Part 1 : Nominal dimensions and tolerances

Continued on pages 2 to 13

Translation by DI N-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text.

No pari of this translation may be reproduced without the prior permission of Ref. No. DIN 3760 : 1996-0 V Deutsches Institut für Nonung e. V., Berlin. Luth Verlag GmbH, D-10772 Berlin, has the exclusive right of sale for German Standards (DIN-Normen).

~- English price group O9

~ ..

Sales No .~

.o109 08.98

Page 2 DIN 3760 : 1996-09

VDMA-finheitsblatt (VDMA Code of practice) 2431 7 Fluid power systems - Hydraulics - Fire-resistant hy- draulic fluids, guidelines

ASTM D 141 8 : 1992*) Rubber and rubber latices - Nomenclature

3 Dimensions and designations Rotary shaft lip seals are not expected to conform to the designs illustrated here; compliance is only required in the case of the dimensions specified.

Type A Type AS

i 1

a) Elastomeric component b) Metal insert c) Garter spring d) Sealing lip

a) Minor lip Dimensions and details as for type A.

Figure 1: Rotary shaft lip seal without minor lip Figure 2: Rotary shaft lip seal with minor lip

Designation of a type A rotary shaft lip seal intended for a shaft diameter,d,, of 25 mm, with an outside diameter, d,, of 40 mm and a width, b, of 7 mm, with an elastomeric component of acrylonitrile/butadiene rubber (NBR): EXAMPLE 1:

Lip seal DIN 3760 - A25 x 40 x 7 - NBR If seals are to be marked with a symbol denoting the material of the elastomeric component used (cf. subclause 5.2), a ‘G’ shall be included in the designation. EXAMPLE 2:

Lip seal DIN 3760 - A25 x 40 x 7 - NBR - G If it is required that metal inserts and springs be provided with an improved corrosion protection, a ‘K’ shall be included in the designation. EXAMPLE 3:

Lip seal DIN 3760 - A25 x 40 x 7 - FKM - K or Lip seal DIN 3760 - A25 x 40 x 7 - FKM - GK

*) Obtainable from Beuth Verlag GmbH (Auslandsnormen-Sen/ice), D-10772 Berlin.

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Page 3 DIN 3760 : 1996-09

Table 1 : Nominal dimensions

c2)

min. dl i 02

Shaft diameter,

d21) b

12 120 125 120

95

0,4

1 O0 125 12 130

Shaft diameter, &i) b

dl I 0 . 2

C 2)

min.

0.8

22 24

8 7

0.8 9 22 7

22 10 25 7

26 22

12 25 7 30

24 30

26

14 7

15 30 7 35 30 35

10 . 7

0.8

125 150

1 30 0,4

0.8

40

1

=E 35

1

280 1 0,4 300

25 7 320

I 52 I 340

360 I 40 I 28 I 47 I 7 380

400 52 40 42 47 52 45 47 73) 52 45 47 8

52

30 7

32

420

440 460 480 500

I) Limit deviations for d, are given in table 2 ,) Edges chamfered or rounded (optional). 3) These values are not specified in IS0 6194 and should therefore not be used for new designs.

Page 4 DIN 3760 : 1996-09

Outside Interference diameter, d, aiiowance?)

Tolerance on d,,)

0.25 + 0,3 + 0,15

+ 0,35 + 0,2

Up to 50

Over 50 up to 80 0,35

~~

Fluorinated rubber

I I Over 80 up to 120 I

FKM

0,65 + 0,45 + 0,25 Over 120 up to 180

I I + 0.45 1 + 0,25 I Over 180 up to 300

1 ,o + 0,55 + 0.3 Over 300 up to 500

I) The average value ford, taken from a number of meas- urements shall not be greater than the value specified ford, plus the interference allowance. For seals having grooved outside surfaces, additional interference al- lowances are to be agreed upon.

,) The tolerance on d, (¡.e. dpmax- d2min) is to be deter- mined by taking three or more measurements equally spaced around the circumference.

4 Materials and surface protection Metal inserts and garter springs shall be made from steel, the grade and surface protection being at the manufacturer?s discretion. Where seals are exposed to fluids which will cause corrosive damage to the steel, a ?K? shall be included in the designation (see example 3 in clause 3) and agreement should be reached between manufacturer and user with regard to the corrosion protection of the metal insert and the material for the garter spring. For materials to be used for the elastomeric component, see table 3.

Table 3: Materials

I Material designation to IS0 1629 and ASTM D 1418 I Base elastomer

I ~~

NBR butadiene rubber Acryl o nit ri I e/

*) Colours according to the RAL 840 HR Colour index, which is obtainable from Beuth Verlag GrnbH, Burggrafenstraße 6, D-10787 Berlin.

Page 5 DIN 3760 : 1996-09

Maximum differential pressure,

in bar

0.5

0,35

6 Use Type A or AS seals are capable of providing a fluid-tight fit suitable for all operating temperatures and housing materials with differing coefficients of linear thermal expansion. The advantage of the minor lip on type AS seals is that it prevents the ingress of contaminants. In orderto reduce wear, the space between the sealing lip and minor lip shall be filled with a suitable lubricant so as to increase the resistance of shafts to corrosion. The lubricant used shall be compatible with the base elastomer; both the elastomer and the lubricant shall be chemically resistant to the fluids present in the shaft assembly. Limits for the operating conditions (e.g. fluid pressure, shaft speed, chemical and thermal resistance of the elastomere used) are given in subclauses 6.1 and 6.2. If all of these limits will be reached simultaneously, or if individual limits will be exceeded, the seal manufacturer should be consulted (cf. annexes A and B).

Shaft

Maximum Resulting maxi- rotational speed, mum peripheral

in min-’ speed, in m/s,

up to 1000 2,a

up to 2000 3,15

up to 3000 5,6

6.1 Maximum permissible shaft speed 6.1.1 Unpressurized operation The maximum permissible rotational speed of the shaft during unpressurized operation is given in figure 3 as a function of the elastomeric component material. The heat transfer system shall be capable of maintaining the permissible temperature of the test fluid and shall be vented to atmosphere.

6.1.2 Pressurized operation Lip seals shall be capable of retaining fluid or grease at low differential pressures, as well as air (provided there is sufficient lubrication). Table 4 gives the maximum differential pressure as a function of the rotational and peripheral speeds.

7 Seal installation 7.1 General In addition to the manufacturer’s instructions, the following guidelines shall be observed when installing seals. The sealing lip shall face the fluid to be sealed and shall be unobstructed. The seal shall be pressed home and completely square by means of suitable installation tools, taking care to prevent misalignment and to ensure that the seal does not carry any load in service. To prevent damage to the sealing lip during installation, it is recommended that

a) the shaft be rounded (with a corner radius of r , ) or chamfered (if the shaft is fitted in directionz or the seal fitted in direction y , as in figure 4) or b) the shaft be chamfered (if the shaft is fitted in direction y or the seal fitted in direction z, as in figure 4).

Page 6 DIN 3760 : 1996-09

- Rotational speed

U a, a, Q cn

Figure 3: Maximum permissible rotational speed for unpressurized operation

z Direction of installation

c_

a) Fluid side b) Edges rounded

Figure 4: Installation

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Page 7 DIN 3760 : 1996-09

100

1

90 90 - - 80 80 100 90 90 90 70 70 i$+ - 30 150

Table 5: Chemical stability of base elastomers

1

150 140 150 130 e e 150 O . .

Co i~; +

Shaft diameter, d , I (4 - d3) ' ) I di (4 - d3) '1

Fluids based on petroleum products

I

I I L

Shaft diameter, dl (4 - d3) ' ) di

< 10 1 3 Over 50 up to 70

Over 10 up to 20 290 over 70 up to 95

over 20 up to 30 2 3 over 95 up to 130

over 30 up to 40 3,O over 130 up to 240

over 40 up to 50 3,5 over 240 up to 500

Fluids present

(4 - d3) '1

4 0

4,5

5.5

7.0

11 ,o

Co a, Co l3 a, L a -

~

< 10 1 3 Over 50 up to 70

Over 10 up to 20 290 over 70 up to 95

over 20 up to 30 2 3 over 95 up to 130

Non-flammable pressure fluids as in VDMA 2431 7

4 0

4,5

5.5

S O 3 O

3 a,

.- + - S

.- O Co - Co L

- E,

2 8

O Q Co 3 S

L O a, a, + 3

k - .- ? .-

over 30 up to 40

over 40 up to 50

3,O

3,5

over 130 up to 240

over 240 up to 500

I Maximum continuous operating temperature of fluid, in "C

7.0

11 ,o

7.2 Shaft Shafts shall meet the requirements specified in subclauses 7.2.1 to 7.2.3 and table 6.

I I I ) If there is a shaft lead-in chamfer, its radius shall be no less than this difference.

7.2.1 Surface roughness of shafts In order to ensure a tight fit between seal and shaft, the seal land (cf. subclause 7.2.3) shall have a surface roughness, Ra*), of 0,2 to 0,8 pm or R,*), of 1 to 5 pm, with R,,*) = 6,3 pm.

7.2.2 Surface hardness The service life of seals depends on the surface hardness at the seal land. It should be at least 45 HRC. Where ingress of contaminated fluid is to be expected, or where the peripheral speed exceeds 4 m/s, the hardness should be at least 55 HRC. Where shafts are not fully hardened, the effective depth of hardening should be at least 0,3 mm. After nitriding, shafts shall be provided with a smooth surface finish.

7.2.3 Seal land The valuesfor surface roughness and hardness specified in subclauses 7.2.1 and 7.2.2 shall be maintained over the entire seal land, whose dimensions shall be as specified in table 7. It is essential that the shaft is not subject to eccentric running, to prevent leakage.

*) In accordance with IS0 4287-1: Ra-arithmetical mean deviation of the profile; R, - ten point height of irreglarities; Rmax - maximum two point height of the profile.

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Page 8 DIN 3760 : 1996-09

b

- 7

8

-II-

with sealing lip only

el e2 min.

3.5 6 1

3.5 68

495 83

5 10

6 12

9 18.5

a) No eccentric running b) Seal land

with sealing lip and minor lip

e3 e4 min.

1.5 7,6

1 r5 83

2 10,5

2 12

3 15

3 19.5

10

12

15

20

u b l

a) No eccentric running b) Seal land

Figure 5: Seal land (notation)

7.3 Housing bore The housing bore shall be subject to a class H8 tolerance and shall have a maximum surface roughness Ra*), of 1,6 to 6,3 pm or R,*), of 10 to 20 pm, with R,,*) = 25 pm. The bore shall have the dimensions specified in table 8 and a lead-in chamfer of about 1 O to 20".

1 O" to 20"

Figure 6: Housing bore (notation)

*) In accordance with IS0 4287-1 : Ra - arithmetical mean deviation of the profile; R , - ten point height of irreglarities; Rmax - maximum two point height of the profile.

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Page 9 DIN 3760 : 1996-09

Nominal t l bore (0,85. b)

depth, b min.

7 5.95

8 6 8

10 83

12 10,3

15 12,75

20 17

t2 r2 ( b + 0,3)

min. max.

7,3

8,3 O S

10,3

12,3

15.3 0,7

20,3

7.4 Housing bore coaxiality The housing bore shall be coaxial with the shaft axis within the tolerances specified in figure 7. It should be noted that tolerances are to be smaller where sealing lips are thinner. Wider tolerances may apply if other types of elastomer or more flexible seal lip designs have been used to modify the performance of the seal.

i 0,8 E E .- c 0 , 6 aï

2 0 . 4

g 0 . 2

o C

a, O

x (u X (u O

- +

.-

O 0

280 to 500 Shaft diameter, d,, in mm +

Figure 7: Coaxiality tolerance 7.5 Shaft run-out The tolerances on shaft run-out shall be as shown in figure 8. It should be noted that in the case of higher shaft speeds, the sealing edge may not be able to follow any shaft movement due to its own inertia. If the shaft run- out results in the distance between sealing edge and shaft becoming larger than required for maintaining hydrodynamic lubrication, oil may leak from the seal. It is therefore advisable to position the seal as close as possible to the bearing to minimize the clearance between bearing elements.

5

4

3 5 3 25

2 15

1

o 5

O O 1000 2 0 0 0 3000 4 0 0 0 5 0 0 0 7000

Rotational speed of shaft, in min-l-

Figure 8: Run-out tolerance

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Page 1 O DIN 3760 : 1996-09

Annex A Information provided by the purchaser To allow the manufacturer to supply a seal suitable for the application in question, it is recommended that the purchaser provide the information given in the specimen form shown below. (The note in the margin on page 1 prohibiting reproduction of any part of this standard does not apply to the following specimen form.)

Table A: Information provided by the purchaser

Purchaser: Reference:

Application: Assembly drawing:

1 Shaft information

a) Diameter (d, ) mm max. mm min.

b) Material

c) Surface roughness Ra Iim, R Z w n Rmax I.lm

d) Type of finish

e) Hardness

f) Chamfer information

g) Rotation

1) Direction of rotation (viewed in direction of arrow as shown in drawing)

- Clockwise

- Anti-clockwise

- Birotational

2) Rotational speed min-'

3) Rotation cycle

(Time on Time off )

h) Other shaft motion (if applicable)

1) Reciprocation

- i) Length of stroke mm

-i¡) Cycles per minute

- iii) Reciprocation cycle

(Time on Time off )

2) Oscillation - i) Magnitude of oscillation (degrees)

-i¡) Cycles per minute

- iii)Oscillation cycle

(Time on Time off )

Bore depth, t ,

j) Additional information (e.g. regarding splines, holes, keyways, shaft lead, etc.)

(continued)

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Page 11 DIN 3760 : 1996-09

Table A (concluded)

2 Housing information

a) Bore diameter (D) mm max. mm min.

b) Bore depth mm max. mm min.

c) Material

d) Surface roughness Ra CLm, Rz ii.m, R,,, Pm

e) Chamfer information

f) Housing rotation (if applicable)

1) Direction of rotation (viewed in direction of arrow as shown in drawing overleaf)

-Clockwise

- Anti-clockwise

- Birotational

2) Rotational speed min-'

3 Contained fluid information

a) Type of fluid Grades

b) Fluid temperature Normal: "C "C Max. "C Min.

c) Temperature cycle

d) Fluid level

e) Fluid pressure bar kPa

f) Pressure cycle

4 Alignment

a) Housing bore eccentricity

b) Shaft run-out

5 External conditions

a) External pressure bar kPa

b) Materials to be excluded (¡.e. dust, mud, water, etc.)

Annex B Information provided by the manufacturer It is also recommended that the manufacturer provide the information given in the following specimen form. This information will ensure that the seal is compatible with the equipment design and the application in question, and will facilitate inspection and quality control as well. (The note in the margin on page 1 prohibiting reproduction of any part of this standard does not apply to the following specimen form.)

Page 12 DIN 3760 : 1996-09

Table B: Information provided by the manufacturer

Manufacturer: Part No.

Charge No. Date

Seal specifications:

Type:

Outside diameter, d,: mm max. mm min.

Seal width, b: mm max. mm min.

Sealing lip description (if applicable):

Plain Unirotational

Hydrodynamic Birotational

Sealing lip material specifications:

Material type: Specification:

Case specifications:

Case material: Inner case material:

Case thickness: Inner case thickness:

Spring material:

Optional information:

Assessment of results:

I

Sample drawing:

di

Page 13 DIN 3760 : 1996-09

Other relevant standards IS0 61 94-2 : 1991 Rotary shaft lip seals - Part 2: Vocabulary IS0 61 94-3 : 1988 Rotary shaft lip seals - Part 3: Storage, handling and installation IS0 61 94-4 : 1988 Rotary shaft lip seals - Part 4: Performance test procedures IS0 61 94-5 : 1990 Rotary shaft lip seals - Part 5: Identification of visual imperfections

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