ISO gives users of lip-type seals requirements and guidance on the careful storage, handling and proper installation of rotary shaft lip-type seals;. ISO (E). PDF disclaimer. This PDF file contain embedded typefaces. In accordance with Adobe's licensing policy, this file . et montage. ISO. First edi tion. Reference number. ISO ( Standards is normally carried out through ISO technical committees.
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ISO. Second edition. Rotary shaft lip-type seals .. ISO , Rotary shaft lip-type seals incorporating elastomeric. BS ISO Document Year Format, unit price, price in USD. PDF Version, GBP , USD , Add to Wishlist. Secured PDF. Print Version, GBP. ISO PDF - ISO. Second edition. Rotary shaft lip-type seals.. ISO, Rotary shaft lip-type seals incorporating elastomeric. Find the most up-to-date version.
Typically, the radial force related to the circumference of the radial shaft seal approximately ranges between 0.
In case of pressure-loaded radial shaft seals the radial force may increase by a factor of 2 to 5, which results in a higher development of heat in operating conditions.
D Outer diameter d Shaft diameter a Elastomer part b Metal insert c Garter spring d Sealing lip a In many drive systems conditions may occur in which a higher incidence of external ambient dirt or dust must be anticipated. In these cases it is advisable to use radial shaft seals with one or more moulded-in dust lips.
The dust lip prevents contaminants being dragged underneath the sealing lip, which would lead to faster seal wear. The dust lip thus considerably contributes to the functional reliability of the sealing system. The preload of the dust lip is merely achieved by a dimensional overlap to the shaft diameter and the elastic properties of the seal compound. The dust lip is designed flexibly enough to allow it to follow the radial movements of the shaft without a radial gap occurring during operation.
In case of a simultaneous pressure build-up this could result in leakage due to the sealing lip lifting up in extreme cases. Since in specified operating conditions dry running tends to occur at the dust lip the dust lip is designed with significantly less overlap and preload than the actual sealing lip. To avoid permanent dry operation, which would lead to wear of the dust lip, lubrication is recommended when the seal is installed.
The space between the two lips can be used as a grease depot. Static sealing is achieved by the radial interference fit in the housing bore. Due to the geometry of the sealing lip and the position of the spring effect line an asymmetric distribution of compression occurs in the contact area on the shaft with a steep gradient towards the pressure side. In addition to the sealing lip geometry, this distribution of compression has a crucial influence on the dynamic sealing capability of a radial shaft seal.
When the shaft rotates a mixed-friction condition occurs in which the sealing lip partially lifts off of the shaft and lubricant can migrate into the resulting gap. As a result of micro-structures occurring in the contact area of the sealing lip, radial shaft seals have a certain pump-back capacity which ensures that the medium cannot escape in the contact area and can be pumped back into the pressure chamber.
At the same time, there is always a sufficient amount of lubricant present in the sealing gap when the shaft rotates, which prevents dry running of the seal. This has a crucial influence on wear of the sealing lip and thus the service life of the sealing element.
In case of pressure-loaded shaft seals the contact width increases with rising pressure and may amount to as much as 1. This even applies to housing materials with higher temperature coefficients of expansion such as aluminium.
Depending on the type of shaft seal rubber-covered or without rubber cover on the outer diameter , the diameter-relevant press fit allowances used are specified in applicable standards e. For shaft seals with grooved outer contours on the outer diameter, a slightly larger press fit allowance has generally been selected.
For seals with a grooved surface, other press fit allowances are required and should be agreed between the manufacturer and the user. The performance limits of the compounds may vary, depending on the composition of the compound.
Good heat removal from the sealed area must be ensured as a general rule. Sufficient spark-out time should be assured during the grinding process. This prevents the introduction or retention of conveying structures on the shaft surface. Conveying structures can be compared with a multiplestart thread which, depending on the rotational direction, delivers fluid to the air side and promotes leakage at the shaft seal.
In case of doubt, a simple string test can be performed. This usually suffices to demonstrate the presence of conveying structures on the shaft surface.
Description of the String Method: A finished shaft is slightly wetted with oil and rotated in a lathe. A light weight is suspended from a string so that the string is slightly tensioned against the shaft surface.
If, as a result of machining, the shaft surface exhibits a conveying structure the string is deflected towards one side. To achieve a clear result, the shaft must be accurately aligned in the lathe.
When the required surface roughness and absence of helical structures have been confirmed, the shaft can be precision-turned, planished or blasted. After hardening, the sliding surface must be polished. For the shaft diameter d, the ISO tolerance zone h11 should be selected in the area of the sliding surface. In case of varying tolerance zones the seal supplier should be contacted.
Installation To protect the sealing edges, lead-in chamfers with smooth surfaces and rounded edges should be used.
The sealing lip must always face the side to be sealed and be exposed. The radial shaft seal must be in a centred and perpendicular position to the shaft during installation. 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. Translation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text.
Edges chamfered or rounded optional. Page 4 DIN : Table 2: Interference allowance and tolerance on d2 Outside diameter, d2 Up to 50 Over 50 up to 80 Over 80 up to Over up to Over up to Over up to 1 Interference allowance1 Tolerance on d 22 The average value for d2 taken from a number of measurements shall not be greater than the value specified for d2 plus the interference allowance.
For seals having grooved outside surfaces, additional interference allowances are to be agreed upon. For materials to be used for the elastomeric component, see table 3. If requested, the seal itself shall also be marked with this symbol.
The following methods of applying the marking to the seal are permissible: a vulcanization; b using a durable colour resistant to both mineral oil and fat; c using a label that is the same colour as the seal. Page 5 DIN : 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 order to 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.
If all of these limits will be reached simultaneously, or if individual limits will be exceeded, the seal manufacturer should be consulted cf. The heat transfer system shall be capable of maintaining the permissible temperature of the test fluid and shall be vented to atmosphere.
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