Type A and AO Shaft Seals

21.04.2023

What is a Simmering Seal?

A Simmering seal, also known as an oil seal or rotary shaft seal, is a technical sealing component designed to prevent oil and grease leaks in machines and equipment where rotary or oscillating motion is present—primarily on shafts. Additionally, these seals protect against the ingress of moisture, dust, dirt and other contaminants from the external environment.

A rotary shaft seal typically consists of a rigid metal case and a flexible sealing lip, which may include a spring to ensure tight contact with the shaft. The design may vary depending on the specific seal type.

Common Applications

At Power Rubber, radial shaft seals are manufactured using high-quality materials to ensure reliable sealing across a wide range of applications, including:

Household appliances (e.g. washing machines, dishwashers)
Powertrain systems (e.g. agricultural machinery, construction equipment)
Heavy industrial machinery (e.g. wind turbines, rolling mills)
Engines (electric motors, internal combustion engines)
Gearboxes (industrial gear systems)
Hydraulic power units
Pumps

Simmering Type A

Type A shaft seals are composed of an elastomer outer casing, a metal reinforcing insert, and a sealing lip with a tension spring to ensure a tight fit around the shaft. They do not feature an additional dust lip.

They are commonly used in components with rotary or pivoting motion such as shafts, hubs, and axles.

Simmering Type AO

AO-type seals feature an elastomer outer shell, metal insert, and a self-sealing elastomer lip. Unlike type A, they include an additional dust lip that blocks contaminants like dust, dirt, and moisture from entering the system. AO seals also ensure leakage prevention of lubricating media.

They are ideal for sealing rotating and oscillating machine parts.

Industry Standardisation of Shaft Seals

Simmering seals are among the most widely used sealing solutions across various industries. As a result, standardisation of dimensions, materials, and types has been implemented to meet consistent industry requirements.

Shaft Sealing Rings – Types A and AO

Common Rubber Compounds for Simmering Seals

At Power Rubber, the most frequently used rubber materials for manufacturing type A and AO shaft seals include NBR (Nitrile Rubber), FKM/FPM (Fluoroelastomer), ACM (Acrylic Rubber), and VMQ/MVQ (Silicone Rubber). Below is a brief overview:

NBR – Nitrile Rubber
Temperature range: -40°C to +100°C
Excellent resistance to engine oils, gear oils, heating oils, hydraulic fluids, oil-water emulsions, greases, and water.

ACM – Acrylic Rubber
Temperature range: -20°C to +130°C
Resistant to engine and transmission oils, as well as hydraulic fluids.

VMQ/MVQ – Silicone Rubber
Temperature range: -50°C to +150°C
Highly resistant to engine and gear oils, oil-water emulsions, and hydraulic fluids.

FKM/FPM – Fluoroelastomer
Temperature range: -30°C to +180°C
Offers exceptional resistance to engine and transmission oils, heating oils, oil-water emulsions, hydraulic fluids, and synthetic fire-resistant liquids.

Standards for Type A and AO Shaft Seals

At Power Rubber, our Simmering seals conform to the following standards:

PN-72/M-86964 – Rubber sealing rings for shafts with metal reinforcement (dimensions)
PN-72/M-86965 – Shaft seals with metal outer casings (dimensions)
PN-88/M-73067 – Rotary shaft seals as per ISO nominal dimensions and tolerances
PN-81/M-86960 – General requirements and testing procedures for rotary shaft rubber seals

We deliver Simmering seals that meet strict quality and dimensional standards. Our products ensure reliable sealing of bearing assemblies, protect against lubricant leakage (both during operation and downtime), and guard internal components against contamination.

PN-72/M-86964 – Type A Seal Dimensions

This standard defines the dimensions for type A shaft seals with a metal insert.

Example:
Seal A 6x22x7 NBR

d (inner diameter) = 6 mm
D (outer diameter) = 22 mm
b (width/thickness) = 7 mm
NBR = material type (Nitrile Rubber)

PN-72/M-86965 – Type B Seal Dimensions

This standard specifies the dimensions for type B shaft seals with a full metal outer casing and no elastomer coating.

Example:
Seal B 52x72x10 NBR

d (inner diameter) = 52 mm
D (outer diameter) = 72 mm
b (width/thickness) = 10 mm
NBR = material type

PN-88/M-73067 – ISO Shaft Seal Standards

This ISO-based standard defines nominal dimensions and tolerances for rotary shaft seals, facilitating international standardisation.

PN-81/M-86960 – General Requirements and Tests

This standard outlines general testing methods and technical requirements for rotary shaft seals with rubber lips, metal inserts, or external metal housings. These Simmering seals are designed for use in applications where pressure does not exceed 0.02 MPa. Seal selection depends on the working environment's temperature and the shaft material. For shafts with diameters over 200 mm, the recommended speed and surface velocity must be agreed upon between manufacturer and client.

Need Type A or AO Shaft Seals That Comply with These Standards?