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RS 17-A

description

asymmetric rod seal as RS 17 , but due to design with active back-up ring suitable for larger extrusion gaps or higher pressure range.

  • asymmetric single-acting rod lip seal, with the dynamic sealing lip being shorter than the static one.
  • interference fit on the outside diameter.
  • various materials are available for different purposes.
  • snaps into simple grooves (see notes on installation).
  • best sealing effect across a wide temperature range.
  • the active back up ring on the trailing side of the seal reduces extrusion wear andallows larger gap dimensions resp higher system pressure.
  • sealing effect enhanced by high recovery rate.
  • for pressures up to 700 bar as a seal between pressurized space and atmosphere.
  • good sealing in the low pressure range.
  • excellent static and dynamic sealing.
  • the secondary lip reduces the residual oil film.

application

not bolded symbols; please consult our technical for application limitations

category of profile

machined or molded/standard/trade product.

single acting

the RS17-A seal is designed  for use as a rod seal.

area of application: hydraulics

  • reciprocating rods on hydraulic cylinders,push rods, fittings.
  • rod seals for applications with large extrusion gap and without specific impact load.
  • commonly used as sealing element in telescopic cylinders (for large deflections increased preload may be necessary).

note

  • this seal has the correct functioning dimension only when mounted. when slipping the seal over the piston rod, it may appear too big.
  • the ratio between nominal width and sealing height cs/H should not drop below a value of 1/1.4, small cross sections demand values up to 1/1.6.
  • recovery volume  is limited.
  • on long strokes drag pressure may be built up between both lips,which can lead to disfunction.

function

RS17-A profiles are lip seals designed  to seal pressurised space against the atmosphere;  mainly for reciprocating movements. the secondary lip on the back ensures a increased stability in the housing. the design is based on application  in standard hydraulic systems with con- ventional hydraulic oils. the operating parameters are as defined in the sealing data sheet and material data. requirements deviating from these parameters can be met to a certain degree by changing the geometry in the software program.

 

operating parameters & material

material back-up ring temperature max. surface speed max. pressure 1 hydrolysis dry running wear resistance
PU  POM /  PA2 -30 °C … +110  °C 0,5 m/s 600 bar (60 MPa) – + +
HPU  POM /  PA2 -20 °C … +110  °C 0,5 m/s 600 bar (60 MPa) + + +
LTPU  POM /  PA2 -50 °C … +110  °C 0,5 m/s 600 bar (60 MPa) – + +
SPU POM / PA2 -20 °C … +110  °C 0,7 m/s 600 bar (60 MPa) + + +
CPU POM /  PA2 -30 °C … +100  °C 0,5 m/s 600 bar (60 MPa) + + +

the stated operation conditions represent general indications. it is recommended not to use all maximum  values simultaneously. surface speed limits apply only to the presence of adequate lubrication film.

1 pressure ratings are dependent on the size of the extrusion gap.

2 POM up to ø260 mm, PA above ø260 mm.

++ … particularly suitable                         o … conditional suitable

+ … suitable                                         – … not suitable

for detailed information regarding chemical resistance please refer to our „list of resistance“. for increased chemical and thermal resistance rubber

materials are to be preferred, attention  should be paid to restrictions for pressure range and wear resistance. for higher gliding  speeds another system should be used (e.g. PTFE materials)

note on special materials:

as the temperature limits are determined  by POM using special materials for the back up ring can expand the temperature limits.

 

gap dimension

operating pressure cs = (ØD – Ød)/2 mm
4 5 7.5 10 12.5 15
safe extrusion gap (mm)
200 bar (20 MPa) 0.60 0.75 0.90 1.20 1.30 1.50
400 bar (40 MPa) 0.25 0.40 0.45 0.50 0.60 0.75
600 bar (60 MPa) 0.10 0.10 0.13 0.15 0.20 0.25

important note:

the above data are maximum value and can’t be used at the same time. e.g. the maximum operating speed depend on material type, pressure, tem- perature and gap value. temperature range also dependent on medium.

the diagram applies to an operating temperature  of 70 °C.

surface quality

surface roughness

Rtmax (μm)

Ra (μm)
sliding surface ≤2,5 ≤0,1-0,5
bottom of groove ≤6,3 ≤1,6
groove face ≤15 ≤3

tolerance recommendation

seal housing tolerances
Ød f8
ØD H10

mode of installation

ffor inside diameters of 25 mm or more, and dependant  on radial cross section (cs), the seals may be snapped into the housing.

Ød type of installation
≤ 6•cs open mounting space required
> 6•cs …..≤ 10•cs snap mounting with tool
> 10•cs snap mounting by hand

recommended guide tolerance D1:

d f8 [mm]

p ≤ 100 [bar]

100 < p ≤ 200 [bar]

p > 200 [bar]
≤ 100 H10 H8 H8
> 100 ≤ 200 H10 H8 H7
>200 H9 H8 H7

insertion chamfer:

in order to avoid damage  to the rod seal during installation, the piston rod is to be chamfered  and rounded  as shown in the “recommended mounting space” drawing. the size of chamfer depends on the seal type and profile width.

cs (mm) c (mm)
α = 15⁰  … 20⁰ α = 20⁰  … 30⁰
4 3.5 2
5 4 2.5
6 4.5 3
7.5 5 4
10 6 5
12.5 8.5 6.5
15 10 7.5
20 13 10

seal & housing recommendations

please note that we are able to produce those profiles to your specific need or any non standard housing. for detail measurements, please see Jet seal pars catalog…

the ratio between nominal width and seal height cs/H depends on the cross section. therefore we recommend the following housing heights.

cs = (ØD – Ød)/2 [mm] L [mm]
8 4
9 5
11 6
14 7.5
17 10
20 12.5
25 15
32 20

fitted:

don’t hesitate to contact our technical department for further information or for special requirements (temperature, speed etc.), so that suitable materi- als and/or designs can be recommended.