Lip seals are items which, if cut across, show the presence of one or more sealing lips on the inside or outside diameter. This type of seal is necessarily used for all types of dynamic seal. Lip seals are therefore used in the presence of parts moving against each other in order to obtain an effective seal, limiting abrasion and other problems of deterioration of the seal caused by the rubbing. The seal obtained by using lip seals is equally effective and appreciable under both very low and high pressures. Also the choice of the right quality of elastomer as well as the relative hardness are of basic importance for the life and quality of the sealing system. Less hardness ensures a greater seal with low or very low pressure, but suffers the effect of friction which increases in proportion to the increase in pressure. Vice versa, using a harder compound, the troubles due to friction are limited, but efficiency at low pressure is lost since the seal struggles to adapt to the sometimes minimum diametrical clearance between the parts. Elastotech makes these seals using a highly elastic, abrasion-resistance compound that has proved the most suitable for the majority of the more heavy-duty conditions of use. Lip seals may be made on request in materials with different chemical and mechanical resistance if so required by working conditions.
There are two processes normally used for producing lip seals.
The first consists of making the seal directly from the mould: this method is the most economical and is usually used for producing items with a semi-O-ring lip or with lip having different shapes but always in a seal with a movement between the parts that is relatively small and of brief duration.
The second method consists of making a moulded seal with a larger lip and then proceeding to "end trim" or cut the excess parts: this system is undoubtedly more expensive than the preceding method, but the resulting quality of seal is considerably better. The subsequent cut or trim of the deliberately excessive moulded part, guarantees the presence of a lip with a perfectly "sharp" edge, which in turn guarantees a perfect seal without a leak, even when used in extreme dynamic systems. This last form is necessarily used in all hydraulic and pneumatic systems and is strongly recommended for a dynamic seal with long or very fast longitudinal movement.
Dimentional and aesthetic tolerances
There is no table of dimensional tolerances applicable for this type of seal, since they are extremely variable depending on the real need for precision of the seal. Given the particular shape of the piece and the type of seal, particularly restrictive tolerances are rarely necessary. Elastotech makes this type of seal doing its utmost to limit tolerances as much as possible, compatibly with costs.
A Lip Seals Table is available, which contains a list of all the lip seals considered standard as well as the constructional measurements of the relative seats. These tables are in order of type of lip and then in order of size. The listed items are normally held in stock in the standard compounds and correspond to the measurements which are easily found on sale as hydraulic and pneumatic spare parts. Other measurements may, however, be made if necessary. With regard to lip seals with non-standard dimensions, please refer to the section below "Existing Moulds".
Other moulds than those for standard measurements are available for making lip seals. These other measurements are listed in the Gaco Table in order of outside diameter. Please note that the shape of the section of the sealing lip may be extremely different between one size and another. It is advisable to ask our Sales Office
for full relevant information.
This table only contains the dimensions obtainable from moulds that are fully owned by Elastotech.