Hydraulic Seals - Compact Double Acting

M78 and M79 are compact double acting seals for rod and piston seals. They can replace O-ring seals, without hardware modifications, to improve performance for existing equipment.

Unless space is a premium, it is advisable to use larger section seals such as M74/M75 if possible.

Advantages Surface Roughness Operating Ranges
  • Simple and stable design
  • Compatibility and temperature limited only by elastomer material
  • Good extrusion resistance
  • No vulcanising to hardware
  • Compact seal envelope
  • Good wear resistance
  • Cylinder/bore: Ra=0.05 - 0.6µm
  • Rod/shaft: Ra=0.02 - 0.5µm
  • GrooveØ: Ra<2.5µm
  • Groove walls: Ra<4µm
  • Up to 350 bar
  • Oscillatory up to 5m/s. High frequencies over 5Hz - please consult Moontown
  • Temperature from -25°C to + 25°C limited by the O-ring material
Table for Type M78 Rod Seals
Type

Groove
Width

L1 + 0.2

Type GROOVE
WIDTH
L2 + 0.2

ROD

 ​ØC

f8/h9

Groove

​ØD

H9

Groove
Depth X
Radius
R Max
Diametral
Clearance
E Max
O-RING
Series C/S
M78A 2.40 M78F 3.8 4 - 9.9 C + 2.9 1.45 0.4 0.13 000 1.78
M78B 3.60 M78G 4.65 10 - 19.9 C + 4.5 2.25 0.4 0.13 100 2.62
M78C 4.80 M78H 5.70 20 - 39.9 C + 6.2 3.10 0.6 0.15 200 3.53
M78D 7.10 M78J 8.50 40 - 119.9 C + 9.4 4.70 0.8 0.17 300 5.33
M78E 7.10 M78K 11.20 120 - 400.9 C + 12.2 6.10 0.8 0.25 400 7.00
Table for Type M79 Piston Seals
Type

Groove
Width

L1 + 0.2

Type GROOVE
WIDTH
L2 + 0.2

BORE

ØA 

H9

Groove 

ØB

h9

Groove
Depth X
Radius
R Max
Diametral
Clearance
E Max
O-RING
Series C/S
M79A 2.40 M79F 3.8 8 - 13.9 A -2.9 1.45 0.4 0.13 000 1.78
M79B 3.60 M79G 4.65 14 = 24.9 A -4.5 2.25 0.4 0.13 100 2.62
M79C 4.80 M79H 5.70 25 - 45.9 A -6.2 3.10 0.6 0.15 200 3.53
M79D 7.10 M79J 8.50 46 - 124.9 A -9.4 4.70 0.8 0.17 300 5.33
M79E 9.50 M79K 11.20 125 - 400.9 A -12.2 6.10 0.8 0.25 400 7.00

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