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Hydraulic Seals

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Hydraulic seals

Types and Definitions

Standard Loaded Lip Seal

Loaded Lip Seals are very versatile and can be used as rod seals or piston seals.  They are considered to be multi-purpose hydraulic seals and are designed for significantly improved performance.  American Seal & Packing Loaded Lip Seals are molded from 92 Durometer Urethane with a 70 Durometer Nitrile energizer.  The energizer ensures constant pressure on the sealing lips.


Temperature:  -65˚F to +300˚F

Pressure:  0 to 5000 psi

Fluids:  Petroleum based Hydraulic Fluids


Standard Loaded Lip Seal


The Standard Loaded Lip Seal is the most widely used design of Loaded Lip Seal.  By energizing the sealing lips with an endless O-ring, you are assured of uniform, positive lip contact and excellent low-pressure sealing.  The seal depth is equal to the radial width, which results in a square design.  Standard Loaded Lip Seals can be widely used to interchange with existing hydraulic packing and/or O-rings without changing dimensions.


Loaded Lip Seal Type B


The Loaded Lip Seal Type B features a back-beveled sealing lip.  This provides greater film breaking and increased unit loading at the sealing surface.  The seal depth is generally 1 times the radial width to ensure hydraulic seal stability in the most rugged applications.  It is most commonly used as a rod seal.


Loaded Lip Seal-Deep Style


The Loaded Lip Seal-Deep Style incorporates the same unique design as the Sthard Loaded Lip Seal, plus its depth is 1 times greater than the radial width.  This increases seal stability to withstand rugged, high shock, heavy-duty applications.  This seal will replace many kinds of Vee Packing.  When minimum drag is needed, use Standard Loaded Lip Seals or Loaded Lip Seals-Deep Style.





U-Cups derive their name from their shape and are self-sealing on both the inside diameter and outside diameter.  They are most often used for sealing rams or rods and are very popular due to the small gland space required.  They are especially adapted to low speed, low pressure environments for both pneumatic and hydraulic cylinders.  They provide an extremely smooth, steady movement because of their inherent low friction.


The seal is obtained by means of the flared, flexible lips coming in contact with the rod or cylinder wall.  Clearance is provided at the heel for minimum friction.  Through this design, the packing is preloaded when installed.  Sealing effectiveness is increased by internal pressure of the air or fluid (hydraulic seal) against the inner surface of the lips.  For continued sealing effectiveness and long seal life, the surface finish of the working surface of either rods or bores should be a maximum of 16 micro-inches.  It is not recommended that U-cups or any other single lip seal be used in any application where there is excessive side loading.

The 6226 Series U-Cups has a flat sealing lip and is available at American Seal & Packing in 70 Durometer Nitrile.


U-Cup Installation Data


The lips of the U-Cup should always be toward the pressure force.


The U-Cup is a floating seal which means the height of the U-Cup should be between .015 to .090 shorter than the depth of the gland.  This added gland space allows the pressure to equalize on both lips, thus keeping the U-Cup from rolling.


The surface finish for a static seal surface should be 32 RMS maximum.  The dynamic surface should be in the range of 8 to 16 RMS.  Finishes rougher than 16 RMS could cause premature lip wear and finishes finer than 8 RMS can result in failure of the seal due to loss of lubrication.



Rod Wipers

The main function of the Rod Wiper is to keep the rod and cylinder clean and free from foreign matter; thus preventing premature failure.  The Rod Wiper is not a pressure sealing element, yet it avoids possible abrasive effects which may result if contaminates were to reach the sealing and rod bearing elements.


Style WD Rod Wipers


One-piece snap-in type rod wiper scrapers for heavy duty applications.  WD wipers are continuous (not split) and conform with wear and side motion for effective wiping action over the entire life span of the seal.  Part numbers listed below are molded from 90 durometer urethane for maximum strength and abrasion resistance.  American Seal & Packing also stocks selected sizes in 90 durometer fluoroelastomer.  Please inquire.



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Loaded Lip Seal
Spring Loaded

Lip Seal
Lip Seals

O-Ring Kits

Hydraulic Seals


Piston Cups


Type B
Type B


Rod Wipers

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American Seal & Packing, Inc., Santa Ana, CA. 92705 • 
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