fbpx

This website uses its own cookies and third party cookies to analyze and enhance your browsing experience.

By continuing to browse, we understand that you agree to its use.

Shaft seals, Type: A, B, C, AUP, BUP, CUP - GUMAPLAST VP

Seals have a crucial influence on the system’s performance. The life and reliability of what is often considered a simple component can make a difference to your products and operations.

Radial shaft seals are elements that seal the inside of the medium on rotating machine parts and prevent the ingress of impurities from the atmospheric outer environment.

Radial shaft seals specifications

The working principle of the Basic rotary seal

The surface between the sealing edge and the shaft is the most important. The sealing effect is achieved by pre-loading the sealing lip, making its internal diameter slightly smaller than the shaft diameter. The garter spring provides constant mechanical pressure and maintains the radial force to the shaft, flattening the sealing edge to defined width. Sealing is the result of the surface tension of the hydrodynamic oil layer between the seal flattened area and the shaft. Oil thickness must be between 1 and 3 micro millimeters as to avoid leakage. The meniscus acts as an interface between the outside air and the fluid. Any break in the meniscus will result in leakage. This can happen if the shaft contains scratches along the seal path.

The working principle Radial Shaft Seals
Diagram the principle of operation Radial shaft seals

The metal case

The metal insert or case is used to give the seal strength and rigidity. It is usually made of cold rolled steel in accordance with the standard DIN 1624. Stainless steel can be used to avoid rust or chemical corrosion attack. Chromium-Nickel AISI 304 (DIN 1.4301 - V4A), Chromium-Nickel Molybdenum AISI 316 (DIN 1.4401 - V4A).

The garter spring

The garter spring maintains the radial force exerted by the sealing lip around the shaft surface. It is usually made of SAE 1074 spring harmonic steel wire (DIN 17223) or AISI 302 chromium nickel stainless steel wire (DIN 1.4300).

Types of radial shaft seals

Installation and operation

Shaft

The shaft hardness and surface finish are of prime importance for achieving a useful lifetime. Basically, the hardness should increase along with the increase in peripheral velocity. According to DIN 3760, minimum hardness required is 45 HRC. At a peripheral speed of 4 m/s, the hardness should be 55 HRC and at 10 m/s it should be 60 HRC. In case that the shaft is not fully hardened, the recommended hardness depth is 0.3 mm. Lubrication is also very important. Surface treatment according to DIN 37600 should be Ra 0.2 to 0.8μm, Rz 1 to 5μm, with Rmax 6.3µm. Rougher surfaces generate higher friction, and therefore higher temperatures. Machining defects and scratches on the shaft must be avoided. Even the slightest defects can be sufficient to increase layer thickness, eventually damaging the meniscus and causing leakage. It is also important to avoid spiral grinding or marks, as they may result in pumping effect and leakage. Recommended mechanical processing tolerance is ISO h11 according to DIN 3760 (see table).

Shaft diameter

Tolerance

od

do

h11

6

10

0
-0.090

10

18

0
-0.110

18

30

0
-0.130

30

50

0
-0.160

50

80

0
-0.190

80

120

0
-0.220

120

180

0
-0.250

189

250

0
-0.290

250

315

0
-0.320

310

400

0
-0.360

Temperature

Diagram of the radial shaft seals temperature

Permissible speeds in a pressure-free state according to DIN 3760

Sealing lip temperature is the mean temperature increased by the temperature caused by the friction heat. The higher the effective working temperature, the faster the aging of the elastomer will be, thus affecting the performance of the sealing lip and the shaft. Friction heat depends on the design and the material of the seal, peripheral speed, sealing lip preloading spring force, the design of the shaft and surface finish, lubrication, medium, etc.

Pressure

In practice, there is little or no differential pressure. When the rotary shaft seal is exposed to pressure, the sealing lip is pressed against the shaft, thereby increasing the temperature. In some cases, the pressure may cause overturning of the sealing lip.
At higher peripheral speed and pressure above 0.2 bars, or at a lower peripheral speed and pressure of 0.5 bars, spare rings or specially designed rotary shaft seals with a stronger sealing lip and supporting metal insert must be used. For lower speeds, we recommend our PP types. However, permissible overpressure with PP-type shaft seals is limited (see diagram).
On request, we can provide shaft seals with special reinforced lip to withstand pressure over the indicated value. If spare rings are installed, standard shaft seals may also be used. However, spare rings increase the cost, and often the space required for their installation is not available. Sometimes the use of spare rings is not even possible since it requires a very precise fitting as well as very low shaft eccentricity

Diagram of the pressure profile radial shaft seals

For this reason, rotary shaft seals (PP-type) are a better solution, even if more accurate fitting and lower shaft eccentricity are required than in usual cases.

Diagram pressuer radial shaft seals

Rotary shaft seal permissible overpressure.

Production and quality assurance

Our rotary shaft seals are manufactured according to DIN 3760 and Quality Assurance Standards ISO 9001: 2001, ISO SRPS 9001: 2008 and ISO SRPS 9001: 2015.

All production phases are checked and all measurements are recorded and stored for eventual data verification. Interference allowance and permissible eccentricity
In accordance with DIN 3760.

Radial shaft seals type A

Type
A

Scheme Radial shaft seals type AUP

Type
AUP

Scheme Radial shaft seals type B

Type
B

Scheme Radial shaft seals type BUP

Type
BUP

Scheme Radial shaft seals type C

Type
C

Scheme Radial shaft seals type CUP

Type
CUP

Seal outer diameter d2

Interference allowance(1)

Tolerance on
d2(2)

preko

do 80

Type
A, AUP

Type
B, BUP, C, CUP

Type
A, AUp, B, BUP, C, CUP

over 50

to 80

+0,30
+0,15

+0,23
+0,13

0,25

over 50

to 80

+0,35
+0,20

+0,25
+0,15

0,35

over 80

to 120

+0,35
+0,20

+0,28
+0,18

0,35

over 120

to 180

+0,45
+0,25

+0,28
+0,18

0,35

over 180

to 300

+0,45
+0,25

+0,30
+0,20

0,80

over 300

to 500

+0,55
+0,30

+0,35
+0,23

1,80

(1) The average value for d2 taken from a given number of measurements shall not exceed the indicated value of d2 with the interference allowance.

(2) The tolerance to d2 (e.g. d2 max - d2 min) is to be determined by taking three or more measurements equally spaced around the circumference.

Storage and handling

To avoid material aging, it must be properly stored. Rotary shaft seals should be stored in a dry, clean, dust-free place and in their original wrapping, which should only be opened just before installation. The obtained samples must be repacked after inspection. Excessive humidity will wear out the elastomers as well as cause corrosive damage to the metal casing and springs. Do not put rotary shaft seals on shelves or boxes, nor hang seals on hooks, wires or nails, as damage to the sealing lip may occur. Seals should be stored horizontally. Seals should be used in a first-in first-out basis to avoid aging on shelves. Avoid storage near sources of heat or near electrical equipment that may generate ozone. Also keep away from direct sunlight.

Shaft seals interchange table

Manufacturers

GUMAPLAST-VP type

A

AUP

AS-P

A-O

A-DUO

B

BUP

C

CUP

Simirit-Freundenberg

BA

BASL

BABSL

BAOF

BADUO

B1

B1SL

B2SL

Goetze

827N

827S

827SK

827NO

827D

822N

822S

824N

824S

Kako

DG

DGS

DGSP

DE

DGD

DF

DFS

DFK

DFSK

Simmerwerke

A

ASL

AOF

ADUO

B

BSL

C

CSL

Stefa

CB

CC

CF

CD

CK

BB

BC

DB

DC

Gaco

A

FA

SA

DUPLEX

AB

NOK

SC

TC

TCN

VC

DC

SB

TB

SA

TA