Radial Lip Shaft Seals
There are two sealing products referred to in the industry as “mechanical seals”. Face seals and radial lip seals both claimed the phrase mechanicals seals in the mid 1950’s.
Mechanical seals
Radial Lip Shaft Seals
Lip seals are probably the most common rotating shaft sealing device. Your car has multiple lip seals holding grease on your driveshaft, the coolant in your radiator, hydraulic oil in your brake lines, and gasoline in fuel tank. Pretty much any piece of equipment that moves a fluid will use a lip seal, a face seal, or braided packing.
Rotary shaft seals are an integral part of any rotating and moving part assembly and are used to seal between the shaft and rotating bore. The object of the oil seal is to retain lubricant or exclude contaminants or to separate dissimilar media. Oil seals need to seal both dynamically (on the shaft) and statically (on the outer diameter of the seal).
Rotary Shaft Seal Design:
There are many types of rotary shaft seals they generally consist of a flexible rubber sealing element, the metal insert/case, and are energized with a garter spring.
The purpose of the sealing element (generally NBR or FKM) is to stop the fluid from leaking between the shaft and housing. The sealing lip may be molded or molded with hydrodynamic aids to assist sealing in demanding applications. The metal insert will give rigidity and strength to the seal while it is being held in the bore or recessed groove. The garter spring helps to make the rubber sealing element more effective. (shown on the right) shows
a typical type of seal and its component lables.
Fabric supported lip seals
Cross Section / Type:
AFL/LUP
Application:
General Purpose. Shaft Seal that are used wherever the adequate lubrication is provided by the hydraulic fluid. It can be installed back to back with a metal spacer
(lantern ring) to provide lubricant between the seals.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
15mm – 1524mm
Cross Section / Type:
AFQ
Application:
General Purpose. Shaft Seal
Shaft Surface Speed (m/min) – Pressure Rating
Thru 2953 FPM – 15 m/s
Pressure: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
15mm – 1524mm
Cross Section / Type:
AFF
Application:
General Purpose. Shaft Seal
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
HOW A LIP SEAL WORKS:
The area between the sealing edge and the shaft is the most critical. The sealing effect is obtained by preloading the sealing lip, making its inner diameter slightly smaller than the diameter of the shaft. The garter spring maintains constant mechanical pressure on the shaft. The radial force from the spring extends the sealing lip to the shaft.
Sealing is guaranteed by the surface tension of the oil film between the flattened area of the seal and the shaft. The oil thickness must be between 1 and 3 mm to avoid leakage. The meniscus (film) acts as an interface between the outside air and the fluid. Any rupture of the film will
cause a leak. This can occur if the shaft contains scratches along the surface of the shaft contact area.
METAL CASE:
Shaft surface finish plays a vital role in the performance of the seal and ensures maximum life of the seal. The shaft hardness should increase for faster running applications to avoid frictional wear. Poor shaft conditions including pitted and grooved surfaces result in higher friction,
resulting in higher temperatures and reducing the life of the seal or the overall seal capacity. Machining faults, scratches or groove marks existing on the shaft should be avoided. The better the shaft tolerance and the runout tolerance the longer your seal will last.
The shaft shall have a diametral tolerance not greater than h11 (ISO 286-2).
Metal supported lip seals
Cross Section / Type:
ACA
Application:
The metal-encased on the outer diameter
and the non-fluid sealing side ensures better resistance to thermal
expansion, when compared to the rubber, encased metal insert rotary
shaft seal.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(15mm-1524mm)
Cross Section / Type:
ACB Lip Seal
Application:
ACB type rotary shaft seal is a closed, spring-loaded built-up seal with
two metal cup inserts. The complete metal-encased ensures strength
especially for seals with small cross-section or even large diameters.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(16-1500mm)
Cross Section / Type:
ACI
Application:
ACI style rotary seal is mostly used in hot rolled or cold rolled steel rolling mills for sealing expensive bearing in the work rolls, intermediate rolls, and backup roll chocks. Extremely long life is assured compared to other seals. Due to a robust design providing a steel spacer and a hard
CRC outer cup, this seal provides excellent retention in the housing thus increasing seal resistance to rotate or distort with the shaft as seen with conventional seals.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(15mm-1524mm)
Cross Section / Type:
ACJ
Application:
ACJ style rotary seal is similar to ACI but supplies with a rubber
spacer.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
Cross Section / Type:
ACK
Application:
ACK style Rotary Seal commonly use in heavy-duty gearboxes. Due to
its two-metal case, this seal becomes robust and with additional cup type
spring creates good contact with the rotating shaft thus gives long term
sealing ability in severe operating conditions.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 2953 FPM – 15 m/s
Pressure: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
Cross Section / Type:
ACE
Application:
Used in gearboxes, Pumps and Motors. This rotary shaft seal can be used for sealing two separate fluids. e.g. coolant from shaft side to enter the bearing or to avoid the leakage of bearing lubricant from the opposite side.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 1968.5 FPM 10 m/s
Pressure Rating: 7.25 PSI (.5 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
High Pressure Lip Seals
Cross Section / Type:
AFF
Application:
AHI seals are mainly for use as an end-seal in all rotary transmissions of
construction machinery, mobile hydraulics, and machine tool hydraulics,
as well as for low-pressure swivel joints.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 984 FPM 5 m/s
Pressure Rating: 145 PSI (10 Bar)
Shaft Size Range Inches(mm)
5/8″-60″
(15mm-1524mm)
PTFE Lip Seals
Cross Section / Type:
ATA
Application:
The ATA is a single lip rotary shaft seal for rotating or pivoting shafts offering a very long service life. The ATA seal has excellent sealing performance is guaranteed by
the pre-stressed PTFE sealing lip which has a very low friction coefficient providing lower starting resistance and avoiding stick-slip problems. These seals are used where there is insufficient lubrication or dry running.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 7874 FPM 40 m/s
Pressure Rating: 145 PSI (10 Bar)
Temperature Range : -22 F (-30 C) to + 500 F (260 C)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
Cross Section / Type:
ATB
Application:
Used in motors, gearboxes, pumps, compressors, blowers, etc. Two lips separate oil and other media.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 7874 FPM 40 m/s
Pressure Rating: 145 PSI (10 Bar)
Temperature Range : -22 F (-30 C) to + 500 F (260 C)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
Cross Section / Type:
ATK
Application:
Used in chemical, pharmaceutical, and food industries.
Shaft Surface Speed (m/min) – Pressure Rating
Thru 5906 FPM 30 m/s
Pressure Rating: 217 PSI (15 Bar)
Temperature Range : -22 F (-30 C) to + 500 F (260 C)
Shaft Size Range Inches(mm)
5/8″-60″
(16mm-1524mm)
SURFACE ROUGHNESS:
The contact surface area of the shaft should adhere to Ra = 0.2 – 0.8 μm. The surface roughness should lie within the stipulated
ranges. Shaft surfaces with higher roughness create increased wear on the sealing edge and lead to a decrease in the lifespan.
Even very small defects could be enough to increase the thickness of the film, which could eventually rupture the meniscus and
cause leakage. It is also important to avoid spiral or groove grinding marks. This could cause a pumping effect or dry running
resulting in leakage or failure.
Mechanical Seals
When should I use a lip seal, rather than a “face seal”?
The advantage of lip seals is that they require very little space. They do have limitations on pressure, speed, minimal, and media compatibility. As long as the application is within the parameters of the materials of construction they can last many years. Mechanical face seals are required when the application is over 25 psig but will require more space.
We can help you to have the success you want out of your lip seals. Materials of construction include Nitrile, Viton, FKM, PTFE, EPDM, and Neoprene.
Get In Touch
(888) 654-SEAL
Location:
1537 E. McFadden Ave-A
Santa Ana, CA. 92705
Email:
sales@usseal.com
Technical Support:
technicalsupport@usseal.com
Open Hours:
Mon: 7:30am - 5pm
Tue: 7:30am - 5pm
Wed: 7:30am - 5pm
Thur: 7:30am - 5pm
Fri: 7:30am - 5pm
Sat: Closed
Sun: Closed