BECA 804

BECA 804
beca_804_3d_v1
beca_804_3d_v2

Description

The BECA 804 is a shaft seal composed of a filled PTFE primary sealing lip, a rubber counter-seal and a metal cage.

Advantages

Excellent chemical inertia
May be used in the food industry
Very good friction coefficient; no stick-slip effect
Machined outside diameter for precise mounting in the housing

Technical data

Temperature

-60°C/+200°C

Pressure

0.5 MPa

Speed

50 m/s

Applications

Motors
Crankshafts
Food & Beverage

Materials

Sealing lip

Virgin PTFE
Glass-filled PTFE
Carbon-filled PTFE

Metal cage

Steel - AISI 1010
Stainless steel - AISI 304
Stainless steel - AISI 316

Dimensions
Materials
Conditions
for use
Seal design
Shaft design
Housing design

Dimensions

Installation drawingLogement pour bague d'étanchéité - Housing Groove for shaft seal

Materials

Metal cage

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

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 Chrome-nickel-molybdenum steel AISI 316
(DIN 1.4401 - V4A)
Stainless steel highly resistant to corrosion

PTFE

PTFE is a thermoplastic polymer made of tetrafluoroethylene with exceptional properties - very low friction coefficient (adhesive friction and sliding friction are almost equal), physiologically safe for temperatures up to +200°C, excellent electrical insulation properties, and excellent chemical compatibility with the majority of fluids. On the other hand, as this material is plastic and not elastic, so it cannot easily replace rubber bases.

Conditions for use

Speed

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

Maximum speed for standard shaft seals with spring

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

The linear speed cannot exceed 50 m/s.

Temperature

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

Media Maximum temperature depending on the materials
PTFE
Mineral oils Oils for motors +150°C
Oils for gearboxes +150°C
Oils for hypoid gears +150°C
ATF oils +150°C
Hydraulic oils +150°C
Greases +150°C
Fire-resistant
fluids
HFA group - Emulsion with more than 80% water +
HFB group - Opposite solution (water in oil) +
HFC group - Polymer aqueous solution +
HFD group - Water-free synthetic fluids +150°C
Other fluids EL + L heating oil +
Air +150°C
Water +
Water for washing +
Temperature range Min. -60°C
Max. +200°C

+: resistant but not commonly used with these fluids

Fluids

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 outside diameter of the seal (ØD)

The table below indicates the pre-tightening for shaft seals on the housing diameter according to standard ISO 6194-1.

Bore diameter
ØD1 (mm)
Tolerances on the outside diameter ØD of the ring Roundness tolerance
Apparent metal cage Rubber coating Coating with grooves Apparent metal cage Rubber coating
ØD1 ≤ 50.0 +0.10 / +0.20 +0.15 / +0.30 +0.20 / +0.40 0.18 0.25
50.0 < ØD1 ≤ 80.0 +0.13 / +0.23 +0.20 / +0.35 +0.25 / +0.45 0.25 0.35
80.0 < ØD1 ≤ 120.0 +0.15 / +0.25 +0.20 / +0.35 +0.25 / +0.45 0.30 0.50
120.0 < ØD1 ≤ 180.0 +0.18 / +0.28 +0.25 / +0.45 +0.30 / +0.55 0.40 0.65
180.0 < ØD1 ≤ 300.0 +0.20 / +0.30 +0.25 / +0.45 +0.30 / +0.55 0.25% of ØD 0.80
300.0 < ØD1 ≤ 500.0 +0.23 / +0.35 +0.30 / +0.55 +0.35 / +0.65 0.25% of ØD 1.00
500.0 < ØD1 ≤ 630.0 +0.23 / +0.35 +0.35 / +0.65 +0.40 / +0.75 - -
630.0 < ØD1 ≤ 800.0 +0.28 / +0.43 +0.40 / +0.75 +0.45 / +0.85 - -

Shaft design

Shaft installation for the shaft seal

Shaft 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:

  • chrome coatings solidified through non-uniform 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

Shaft hardness

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

Rotation speed Hardness in HRC
s ≤ 4.0 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 shaft surface area.

Standard conditions:

  • Ra = 0.1 to 0.4 µm
  • Rz = 1.0 to 4.0 µm
  • Rmax ≤ 6.3 µm

Shaft tolerance

The shaft must have a tolerance of h11, in line with standard ISO 286-2

Shaft diameter
Ød1 (mm)
Tolerance
h11 (mm)
Ød1 ≤ 3.0 -0.060 / 0
3.0 < Ød1 ≤ 6.0 -0.075 / 0
6.0 < Ød1 ≤ 10.0 -0.090 / 0
10.0 < Ød1 ≤ 18.0 -0.110 / 0
18.0 < Ød1 ≤ 30.0 -0.130 / 0
30.0 < Ød1 ≤ 50.0 -0.160 / 0
50.0 < Ød1 ≤ 80.0 -0.190 / 0
80.0 < Ød1 ≤ 120.0 -0.220 / 0
120.0 < Ød1 ≤ 180.0 -0.250 / 0
180.0 < Ød1 ≤ 250.0 -0.290 / 0
250.0 < Ød1 ≤ 315.0 -0.320 / 0
315.0 < Ød1 ≤ 400.0 -0.360 / 0
400.0 < Ød1 ≤ 500.0 -0.400 / 0

Chamfer and radius

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

Shaft 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

Shaft run out

The shaft run out is a deviation between the current shaft axis and the theoretical rotation axis. It is important to reduce the shaft run out as much as possible by positioning the 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.

Shaft run-out for shaft seals with spring

Eccentricity

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

Eccentricity for shaft seal with PTFE lips

Shaft machining

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

  • Plunge grinding: preferred machining method that ensures the absence of striations on the shaft (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, min. 30 secs
Passing depth > Rmax of the old machining operation
Eccentricity of the tool and part to be machined the best possible

Housing design

Housing installation for the shaft seals

Surface roughness

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

Standard conditions for rings with an apparent metal cage:

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

Tolerance of the bore diameter of the housing

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

Bore diameter
ØD1 (mm)
Tolerance
H8 (mm)
3.0 < ØD1 ≤ 6.0 0 / +0.018
6.0 < ØD1 ≤ 10.0 0 / +0.022
10.0 < ØD1 ≤ 18.0 0 / +0.027
18.0 < ØD1 ≤ 30.0 0 / +0.033
30.0 < ØD1 ≤ 50.0 0 / +0.039
50.0 < ØD1 ≤ 80.0 0 / +0.046
80.0 < ØD1 ≤ 120.0 0 / +0.054
120.0 < ØD1 ≤ 180.0 0 / +0.063
180.0 < ØD1 ≤ 250.0 0 / +0.072
250.0 < ØD1 ≤ 315.0 0 / +0.081
315.0 < ØD1 ≤ 400.0 0 / +0.089
400.0 < ØD1 ≤ 500.0 0 / +0.097
500.0 < ØD1 ≤ 630.0 0 / +0.110

Groove width

The table below provides information on the recommended groove width.

Height
H1 (mm)
Width
L2 min (mm) L1 min (mm)
7.00 5.95 7.50
8.00 6.80 8.50
10.00 8.50 11.00
12.00 10.30 13.00
15.00 12.75 16.00
20.00 17.00 21.00

 

Groove radius

The table below provides information on the recommended radius.

Height
H1 (mm)
Radius
R2 max (mm)
7.00 0.50
8.00
10.00
12.00 0.70
15.00
20.00

Only on request