OTBC

Dimensions

Materials

Metal cage - Spring

The table below shows the materials that we can offer for metal cages and springs.

Application	Material	Standard	Characteristics
Metal cage	Non-alloy standard steel	AISI 1010 (DIN 1624)	Cold rolled steel
Metal cage	Nickel chrome steel	AISI 304 (DIN 1.4301 - V2A)	Standard stainless steel
Metal cage and spring	Chrome-nickel-molybdenum steel	AISI 316 (DIN 1.4401 - V4A)	Stainless steel highly resistant to corrosion
Spring	Steel for springs	AISI 1070 - 1090 DIN 17223	Cold drawn carbon steel wire
Spring	Nickel chrome steel	AISI 302 (DIN 1.4300)	Stainless steel for springs with a high carbon content

Rubbers

ACM (Polyacrylate)

Polymers containing ethyl acrylate (or butyl acrylate) have a small amount of monomer, which is necessary for cross-linking; ACM is a material with better heat resistance than NBR. It is often used for automatic gearboxes.

Chemical resistance	Mineral oils (motor oils, gear box oils, ATF oils) Atmospheric and ozone agents
Compatibility issue	Glycol-based brake fluids (Dot 3 & 4) Aromatic and chlorinated hydrocarbons Water and steam Acids, alkalis and amines
Temperature range	-25°C to + 150°C (short-term peak at +160°C) -35°C / +150°C with particular ACMs

AEM (ethylene acrylate rubber)

As a methyl acrylate and ethylene copolymer, AEM is considered to be more resistant to heat than ACM. Its characteristics make it an intermediary between ACM and FKM.

Chemical resistance	Cooling fluids Aggressive mineral oils Atmospheric agents Water
Compatibility issue	Aromatic solvents Strong acids Brake fluids Gearbox oils ATF oils
Temperature range	- 40°C to + 150°C

CR (Polychloroprene)

This CR-based rubber is used in the refrigeration industry and for ventilation systems. This chloroprene was the first synthetic rubber to be developed and marketed.

Chemical resistance	Paraffinic mineral oils Silicone oils and greases Water and water-based solvents for use at low temperatures Refrigerant fluids Ammoniac Carbon dioxide Atmospheric and ozone agents
Limited chemical resistance	Naphthenic mineral oils Aliphatic hydrocarbons (propane, butane, petroleum) Glycol-based brake fluids
Compatibility issue	Aromatic hydrocarbons (benzene) Chlorinated hydrocarbons (trichlorethylene) Polar solvents (ketone, acetone, acetic acid, ethylene-ester)
Temperature range	-40°C / +100°C (short-term peak at +120°C)

EPDM (Ethylene Propylene Diene Monomer rubber)

As an Ethylene Propylene Diene Monomer copolymer, EPDM is commonly used for hot water taps, cooling systems, brake systems, dishwashers and washing machines.

Chemical resistance	Hot water and steam up to +150°C Glycol-based brake fluids (Dot 3 & 4) and silicone-based brake fluids (Dot 5) Organic and inorganic acids Cleaning agents, sodium and potassium alkalis Hydraulic fluids (HFD-R) Silicone oils and greases Polar solvents (alcohols, ketones and esters) Atmospheric and ozone agents
Compatibility issue	Mineral oils and greases Hydrocarbons Low impermeability to gas
Temperature range	-45°C / +150°C (short-term peak at +175°C)

FFKM (perfluorinated rubber)

FFKM has the best characteristics for resistance to high temperatures, with an excellent chemical inertia. This FKM-based rubber is very often used for high-temperature hydraulic and pneumatic systems, industrial valves, injection/fuel systems, motor seals and high-vacuum systems.

Chemical resistance	Aliphatic and aromatic hydrocarbons Polar solvents (ketones, esters and ethers) Organic and inorganic acids Water and steam High-vacuum system
Compatibility issue	Coolants (R11, R12, R13, R113, R114, etc.) PFPE
Temperature range	-15°C/+320°C

FKM (fluorinated rubber)

Depending on their structure and fluorine content, the chemical resistance and resistance to the cold in fluororubbers can vary. This FKM-based rubber is very often used for high-temperature hydraulics and pneumatics, for industrial valves, injection/fuel systems, motor seals and high-vacuum systems.

Chemical resistance	Mineral oils and greases, ASTM n°1, IRM 902 and IRM 903 oils. Fire-resistant liquids (HFD) Silicone oils and greases Mineral and vegetable oils and greases Aliphatic hydrocarbons (propane, butane, petroleum) Aromatic hydrocarbons (benzene, toluene) Chlorinated hydrocarbons (trichlorethylene) Fuel (including high alcohol content) Atmospheric and ozone agents
Compatibility issue	Glycol-based brake fluids Ammonia gas Organic acids with a low molecular weight (formic and acetic acids)
Temperature range	-20°C / +200°C (short-term peak at +230°C) -40°C / +200°C with particular FKMs

FVMQ (fluorosilicone rubber)

The FVMQ has mechanical and physical properties that are very similar to those of the VMQ. However, the FVMQ offers better resistance to fuels and mineral oils. However, resistance to hot air is not as good as that of the VMQ.

Chemical resistance	Aromatic mineral oils (IRM 903 oil) Fuels Aromatic hydrocarbons with low molecular weights (benzene, toluene)
Temperature range	-70°C/+175°C

HNBR (Hydrogenated Nitrile Butadiene Rubber)

This HNBR-based rubber is obtained through selective hydrogenation of the NBR's butadiene groups. It is commonly used for power-assisted steering and for air conditioning.

Chemical resistance	Aliphatic hydrocarbons Mineral and vegetable oils and greases Fire-resistant fluids (HFA, HFB and HFC) Diluted acids, saline solutions and bases for operation at an average temperature Water and steam up to +150°C Atmospheric and ozone agents
Compatibility issue	Chlorinated hydrocarbons Polar solvents (ketones, esters and ethers) Strong acids
Temperature range	-30°C / +150°C (short-term peak at +160°C) -40°C / +150°C with particular HNBRs

NBR (Nitrile Butadiene Rubber)

Nitrile rubber (NBR) is the general term for acrylonitrile-butadiene copolymer. The ACN content can vary between 18% and 50%. While the acrylonitrile content is important, the resistance to oil and fuel is more so. Conversely, the elasticity and compression set are not as good. The NBR has good mechanical properties and good wear resistance. However, its resistance to atmospheric agents and the ozone is relatively low.

Chemical resistance	Aliphatic hydrocarbons (propane, butane, petroleum, diesel fuel) Mineral oils and greases Fire-resistant fluids (HFA, HFB and HFC) Diluted acids, low-temperature alkaline and saline solutions Water (up to +100°C max)
Compatibility issue	Fuels with high aromatic content Aromatic hydrocarbons (benzene) Chlorinated hydrocarbons (trichlorethylene) Polar solvents (ketone, acetone, acetic acid, ethylene-ester) Strong acids Glycol-based brake fluids Atmospheric and ozone agents
Temperature range	-30°C / +100°C (short-term peak at +120°C) -40°C / +100°C with particular NBRs

VMQ (silicone rubber: methyl vinyl polysiloxane)

This FVMQ-based rubber is very often used in fuel systems.

Chemical resistance	Animal and vegetable oils and greases Water for operation at an average temperature Diluted saline solutions Atmospheric and ozone agents
Compatibility issue	Superheated steam up to +120°C Chlorinated hydrocarbons with a low molecular weight (trichlorethylene) Aromatic hydrocarbons (benzene, toluene)
Temperature range	-60°C / +200°C (short-term peak at +230°C)

The table below gives an overview of the physical, chemical and mechanical characteristics for each of the materials.

Characteristics/Materials	ACM	AEM	CR	EPDM	FFKM	FKM	FVMQ	HNBR	NBR	VMQ
Abrasion resistant	2	3	2	2	4	2	4	2	2	4
Resistance to acids	4	3	2	2	1	1	3	1	3	3
Chemical resistance	4	2	2	1	1	1	1	2	2	2
Resistance to cold	4	2	2	2	3	4	2	2	2	2
Dynamic properties	3	3	3	2	3	2	4	1	2	4
Electrical properties	3	3	3	2	1	4	1	3	3	1
Flame resistant	4	4	2	4	1	1	2	4	4	3
Heat resistant	1	1	2	2	1	1	1	1	2	1
Sealing water	1	1	2	2	2	2	4	2	2	4
Oil resistant	1	3	2	4	1	1	2	1	1	2
Ozone resistant	1	1	2	1	1	1	1	2	4	1
Tearing resistant	2	3	3	1	4	3	4	2	2	4
Traction resistant	3	2	2	1	2	1	3	1	2	4
Water/vapour resistant	4	4	3	1	2	3	3	1	2	3
Resistance to atmospheric agents	1	1	1	1	1	1	1	2	3	1

1. Excellent properties 2. Good properties 3. Average properties 4. Poor properties

Chemical compatibility

A "Chemical compatibility guide" catalogue can be downloaded from the Documentation section. You can also use our online "Chemical compatibility" tool free of charge.

These two tools give you the option of measuring the behaviour of our materials that come into contact with the majority of existing fluids. The data displayed is the result of rigorous testing of the ambient temperature and in consultation with previous publications. Test results are not fully representative due to the specific features of your application. The tests performed actually do not consider additives and impurities that may exist under the actual conditions of use, nor the potential elevation of temperatures. Other parameters can also alter the behaviour of our materials, such as the hardness, persistence, abrasion, etc. We therefore recommend performing your own tests to verify the compatibility of our materials according to your specific application. Our technical team can provide you with any additional information.

Conditions for use

Speed

The table below indicates the relationships between the linear speed, the rotation speed and the recommended material.

Linear speed calculation: s (m/s) = [Ø rotating hub (mm) x speed (rpm) x π] / 60,000

Pressure

The inverted shaft seals are generally used in unpressurised environments, or for pressures between 0.02 and 0.05 MPa (maximum).

Temperature

The table below indicates the temperature limits, depending on the materials and fluids used.

Media		Maximum temperature, depending on the materials
		ACM	AEM	EPDM	FKM	HNBR	NBR	VMQ
Mineral oils	Oils for motors	+130°C	+130°C	-	+170°C	+130°C	+100°C	+150°C
	Oils for gearboxes	+120°C	+130°C	-	+150°C	+110°C	+80°C	+130°C
	Oils for hypoid gears	+120°C	+130°C	-	+150°C	+110°C	+80°C	-
	ATF oils	+120°C	+130°C	-	+170°C	+130°C	+100°C	-
	Hydraulic oils	+120°C	+130°C		+150°C	+130°C	+90°C	-
	Greases	-	+130°C	-	-	+100°C	+90°C	-
Fire-resistant fluids	HFA group - Emulsion with more than 80% water	-	-	-	-	+70°C	+70°C	+60°C
	HFB group - Opposite solution (water in oil)	-	-	-	-	+70°C	+70°C	+60°C
	HFC group - Polymer aqueous solution	-	-	+60°C	-	+70°C	+70°C	-
	HFD group - Water-free synthetic fluids	-	-	-	+150°C	-	-	-
Other fluids	EL + L heating oil	-	-	-	-	+100°C	+90°C	-
	Air	+150°C	+150°C	+150°C	+200°C	+130°C	+90°C	+200°C
	Water	-	-	+150°C	+100°C	+100°C	+90°C	-
	Water for washing	-	-	+130°C	+100°C	+100°C	+100°C	-
Temperature range	Min.	-25°C	-40°C	-45°C	-20°C	-30°C	-30°C	-60°C
	Max.	+150°C	+150°C	+150°C	+200°C	+150°C	+100°C	+200°C

The lip of the seal is subjected to a higher temperature due to the hub rotation, and the significant pressure and friction on the mechanical parts. Good lubrication is therefore necessary to allow for a better release of heat and thus limits the temperature rise in the parts subjected to friction.

Fluids

The data below refers mainly to standard shaft seals, but it can also apply to inverted shaft seals.

Mineral oils

In general, this type of oil has few additives and is therefore perfectly suitable for all of the rubbers used for the rotary shaft seals. The following oils are suitable for revolving applications:

• motor oils
• gearbox oils
• hypoid oils
• ATF oils for automatic gearboxes
• transmission oils

synthetic oils

This type of oil is used to improve different characteristics such as the resistance to ageing, resistance to high temperatures, viscosity, etc. and has a good compatibility with the majority of rubbers used for the seals for the rotary shaft. Tests may need to be performed beforehand to measure the degree of compatibility of this type of oil with the materials used. Among the synthetic oils are:

• brake fluids
• fluids for automatic gearboxes
• fluids for suspensions
• fluids for steering systems
• fluids for hydraulic transmissions

Hypoid oils

This type of oil contains special components such as EP additives. These enable lubrication and thus limit any seizing at the bearings, for example. When affected by heat, these additives have the tendency to lead to deposits on the sealing lip. That is why we recommend using seals for the rotating shaft with a sealing lip comprising return pumping leads in order to limit the increase in temperature and above all, to reduce these potential carbon deposits.

Greases

Greases are generally applied to bearings etc. and require specific adaptation to provide favourable operating conditions for the rotary shaft seal. To prevent the lip of the seal from sustaining more significant pressures than planned, we recommend positioning the lip seal on one side of the bearing in such a way so that the lip is not prematurely destroyed. We also recommend reducing the rotation speed by 50% when lubricated, to ensure that less heat escapes during friction.

Aggressive fluids

It is critical to choose the correct material to better resist different aggressive fluids (acids, solvents, chemical products, etc.). For applications in a rotating environment, we recommend using materials such as FKM rather than NBR. For operations that are dry or use very little lubrication, and where the rubbers do not resist certain aggressive fluids, we advise you to use our PTFE seals for the rotary shaft.

Seal design

Tolerance for the inside diameter of the seal (Ød)

The table below sets out the pre-tightening for shaft seals on the diameter of the fixed shaft.

Shaft diameter Ød1 (mm)	Tolerances on the inside diameter Ød of the ring			Roundness tolerance
	Apparent metal cage	Rubber coating	Coating with grooves	Apparent metal cage	Rubber coating
Ød1 ≤ 50.0	-0.20 / -0.10	-0.30 / -0.15	-0.40 / -0.20	0.18	0.25
50.0 < Ød1 ≤ 80.0	-0.23 / -0.13	-0.35 / -0.20	-0.45 / -0.25	0.25	0.35
80.0 < Ød1 ≤ 120.0	-0.25 / -0.15	-0.35 / -0.20	-0.45 / -0.25	0.30	0.50
120.0 < Ød1 ≤ 180.0	-0.28 / -0.18	-0.45 / -0.25	-0.55 / -0.30	0.40	0.65
180.0 < Ød1 ≤ 300.0	-0.30 / -0.20	-0.45 / -0.25	-0.55 / -0.30	0.25% of ØD	0.80
300.0 < Ød1 ≤ 500.0	-0.35 / -0.23	-0.55 / -0.30	-0.65 / -0.35	0.25% of ØD	1.00
500.0 < Ød1 ≤ 630.0	-0.35 / -0.23	-0.65 / -0.35	-0.75 / -0.40	-	-
630.0 < Ød1 ≤ 800.0	-0.43 / -0.28	-0.75 / -0.40	-0.85 / -0.45	-	-

Tolerance for the outside diameter of the seal (ØD)

Free and without constraint, the outside diameter of the sealing lip is always bigger than the diameter of the rotating hub. The pre-tightening or interference denotes the difference between these two values. Depending on the hub diameter, the diameter of the sealing lip is generally considered to be greater, between 0.8 and 3.5 mm.

Pumping leads

The sealing lip operates with low lubrication and significant heating at the point of contact with the rotating hub during higher stresses with elevated temperatures and speeds, and with the seal close to the bearing exercising a considerable pumping effect.

To maintain the lubrication, we recommend integrating diagonal pumping leads on the primary sealing lip, on the air side oriented in the direction of the support's rotation, which reinforces the pumping effect of the rubber's micro-striations. Below are the types of return pumping leads that can be made:

Shaft design

Surface roughness

The recommendations below must be considered for the quality of the shaft surface area.

Standard conditions for inverted shaft seals with an apparent metal cage:

• Ra = 0.8 to 3.2 µm
• Rz = 6.3 to 16.0 µm
• Rmax ≤ 16.0 µm

Shaft diameter tolerance

The shaft diameter must have a tolerance of H8, in line with standard ISO 286-2

Shaft diameter Ød1 (mm)	Tolerance H8 (mm)
3.0 < Ød1 ≤ 6.0	- 0.018 / 0
6.0 < Ød1 ≤ 10.0	-0.022 / 0
10.0 < Ød1 ≤ 18.0	-0.027 / 0
18.0 < Ød1 ≤ 30.0	-0.033 / 0
30.0 < Ød1 ≤ 50.0	-0.039 / 0
50.0 < Ød1 ≤ 80.0	-0.046 / 0
80.0 < Ød1 ≤ 120.0	-0.054 / 0
120.0 < Ød1 ≤ 180.0	-0.063 / 0
180.0 < Ød1 ≤ 250.0	-0.072 / 0
250.0 < Ød1 ≤ 315.0	- 0.081 / 0
315.0 < Ød1 ≤ 400.0	-0.089 / 0
400.0 < Ød1 ≤ 500.0	-0.097 / 0

Fixed shaft widths

The table below provides information on the width of the groove and the recommended radius.

Height H1 (mm)	Width		Radius R2 max (mm)
	L2 min H1 x 0.85	L1 min H1 + 0.30
7.00	5.95	7.30	0.50
8.00	6.80	8.30
10.00	8.50	10.30
12.00	10.30	12.30	0.70
15.00	12.75	15.30
20.00	17.00	20.30

Housing design

Rotating hub material

Suitable materials are:

• ordinary C35 and C45 steels used in mechanical construction
• 1.4300 and 1.4112 stainless steels for sealing water
• sprayed carbide coatings
• graphite
• malleable cast iron
• materials with a CVD and PVD coating

Not appropriate:

• hard chrome coatings due to irregular wear
• plastic materials resulting from low thermal conductivity, which can lead to a disturbance in the transport of heat, an increase in temperature in friction areas with the shaft seal, as well as a potential softening

Rotating hub hardness

The hardness of the rotating hub will depend on the linear speed (in m/s) and the level of pollution.

Rotation speed	Hardness in HRC
s ≤ 4 m/s	45 HRC
4.0 < s ≤ 10.0 m/s	55 HRC
s > 10.0 m/s	60 HRC

Surface roughness

The recommendations below must be considered for the quality of the housing surface area.

Standard conditions:

• Ra = 0.2 to 0.8 µm and 0.1 for demanding applications
• Rz = 1.0 to 4.0 µm
• Rmax ≤ 6.3 µm

For pressurev > 0.1 MPa:

• Ra = 0.2 to 0.4 µm and 0.1 for demanding applications
• Rz = 1.0 to 3.0 µm
• Rmax ≤ 6.3 µm

Rotating hub tolerance

The hub must have a tolerance of H11, in line with standard ISO 286-2

Rotating hub diameter ØD1 (mm)	Tolerance H11 (mm)
3.0 < ØD1 ≤ 6.0	0 / +0.075
6.0 < ØD1 ≤ 10.0	0 / +0.090
10.0 < ØD1 ≤ 18.0	0 / +0.110
18.0 < ØD1 ≤ 30.0	0 / +0.130
30.0 < ØD1 ≤ 50.0	0 / +0.160
50.0 < ØD1 ≤ 80.0	0 / +0.190
80.0 < ØD1 ≤ 120.0	0 / +0.220
120.0 < ØD1 ≤ 180.0	0 / +0.250
180.0 < ØD1 ≤ 250.0	0 / +0.290
250.0 < ØD1 ≤ 315.0	0 / +0.320
315.0 < ØD1 ≤ 400.0	0 / +0.360
400.0 < ØD1 ≤ 500.0	0 / +0.400
500.0 < ØD1 ≤ 630.0	0 / +0.440

Chamfer and radius

You are strongly advised to install a chamfer on the hub so as not to alter the primary sealing sealing lip of the shaft seal during assembly. Please refer to the table below.

Rotating hub diameter ØD1 (mm)	Chamfer diameter ØD3 (mm)	Radius R (mm)
ØD1 ≤ 10.0	ØD1 + 1.50	2.00
10.0 < ØD1 ≤ 20.0	ØD1 + 2.00	2.00
20.0 < ØD1 ≤ 30.0	ØD1 + 2.50	3.00
30.0 < ØD1 ≤ 40.0	ØD1 + 3.00	3.00
40.0 < ØD1 ≤ 50.0	ØD1 + 3.50	4.00
50.0 < ØD1 ≤ 70.0	ØD1 + 4.00	4.00
70.0 < ØD1 ≤ 95.0	ØD1 + 4.50	5.00
95.0 < ØD1 ≤ 130.0	ØD1 + 5.50	6.00
130.0 < ØD1 ≤ 240.0	ØD1 + 7.00	8.00
240.0 < ØD1 ≤ 500.0	ØD1 + 11.00	12.00

Hub run out

The hub run out represents a deviation between the current axis of the rotating hub and the theoretical rotation axis. It is important to reduce the rotating hub run out as much as possible by positioning the inverted shaft seal as close as possible to the bearing. The table below sets out the maximum permissible values depending on the rotation speed and the sealing lip material.

Eccentricity

The shaft and hub must be assembled centred on one another in order to remove any unilateral radial load at the sealing lip of the ring.

Rotating hub machining

Correct machining of the rotating hub is essential to the proper operation of the sealing system.

• Plunge grinding: preferred machining method to ensure the absence of striations on the hub (0 +/- 0.05°)
• Turning: suitable for shafts used with a unidirectional sense of rotation

Machining guidelines for surface adjustments

Parameters	Requirements
Speed of the part to be machined	30 to 300 rpm
Wheel speed	1500 to 1700 rpm
Surfacing feed	< 0.02 mm/turn
Dressing tool	multi-grain dressing diamond, single drain dressing diamond
Grinding rate feed	approximately 0.02 mm
Spark duration	full spark, 30 secs min.
Passing depth	> Rmax of the old machining operation
Eccentricity of the tool and part to be machined	the best possible