One of the important factors in the selection of sealing elements is the working environment and ambient temperature. Although the ideal temperature for the sealing element and systems is 50 ° C, the application temperature can reach up to 100 ° C. Since the sealing elements come into direct contact with the sliding surfaces in dynamic applications, they are directly affected by the heat generated by friction. For this reason, the temperature to be reached by the system in the selection of the sealing element should be below the temperature allowed to use the sealing element. Sealing elements consisting of FKM and PTFE are recommended for systems operating at high temperatures. Although it is thought that the sealing element cannot fulfill its function by hardening (glassization) in applications at low temperatures, it works up to -40 ° C without any problems depending on the behavior of the fluid in which it works. Depending on the material from which the sealing element is produced, its design and the place of use, the working speed of the cylinders can be up to 15m / sec. Sliding speed is one of the most important factors in oil film formation and friction forces. In the table below, it is seen that the friction force increases as the oil film thickness decreases with the increase of speed.
The dynamic surfaces that come into contact with the sealing elements should be subjected to honing or grinding process to bring the desired surface roughness to the desired surface roughness, so that more efficiency and a long life should be provided.
Surface roughness measurements are made with devices called profilimeters and are expressed in micron meters. Sample impressions of surface roughness are shown below.
As seen above, NBR adapts more easily to the rough form of the surface on which it is located. Teflon is the material with the lowest coefficient of friction.
Measurement Calculation with Profilimeter Device
Rz = Rz1 + Rz2 + Rz3 + Rz4 + Rz5 / 5 - SURFACE ROUGHNESS VALUE
Rmr = [(x1 + x2 + x3 + x4 + x5 + x6) / L] x100 - PERCENT OF SURFACE CONTACT AREA
| Machinery Parts |
Rz |
|
Machinery Parts |
Rz |
|
1-Plain bearings and shafts |
8-Worm screw and gear |
|||
| bronze bed |
0,8-1,6 |
On their outer surface: | ||
| Shaft |
02-0,8 |
Genesis |
0,8 |
|
| heavy duty |
0,4 |
|||
|
2-holes |
||||
| for hydraulic cylinder |
0,2 |
On other surfaces: | ||
| for automobile cylinders |
0,4 |
Outer diameter |
3,2 |
|
| for O-ring |
0,4 |
docking surface |
1,6 |
|
| For gears (according to tolerance) |
0,8-1,6 |
|||
| crocheted |
0,8 |
9-sliding surfaces |
||
| reamed |
0,8 |
General |
0,4-0,8 |
|
drilled |
3,2 |
Mechanically sealed ring |
0,005-0,2 |
|
|
3-Miller |
10-Frictional surfaces |
|||
| For gears (according to tolerance) |
0,8-1,6 |
Brakes |
0,4 |
|
| Spline shafts for cars |
0,4 |
Concepts |
0,4 |
|
| fine turned |
0,8-1,6 |
|||
| Medium precision turned |
1,6-3,2 |
11-Channels (cavities) |
||
| rough turned |
6,3 |
For movable o-ring |
0,1 |
|
| For non-moving O-ring |
0,4 |
|||
| 4-Exercises | for segments |
3,2 |
||
| Blank exercises: | ||||
|
Tolerans≤0,025 |
1,6(max) |
12-Co-working surfaces | ||
|
Tolerans≥0,025 |
3,2(min) |
Gasketed: | ||
| Intermediate exercises |
0,8(max) |
With copper gasket |
0,8 |
|
| rigorous exercises |
6,3 |
soft seal |
3,2 |
|
| 5-Wedge channels | Without gasket: | |||
| General |
3,2 |
Greaseproof |
0,4 |
|
| Sensitive |
1,6 |
Grease-proof |
0,8 |
|
| 6-Screw Threads | 13-Infinitives | |||
| rolled |
0,2 |
setting gauges |
0,025-0,1 |
|
| milled |
1,6 |
Manufacturing gauges |
0,2 |
|
| Stoned |
0,4 |
|||
| Opened with a sheet |
3,2 |
|||
| 7-Gear wheels | ||||
| On tooth surfaces: | ||||
|
m≥2,5 için |
1,6 |
|||
|
m≤2,5 için |
0,8 |
|||
| Heavy duty gears |
0,4-1,6 |
|||
| Precision gears |
0,4 |
|||
| sprockets |
3,2 |
|||
| On other surfaces: | ||||
| Outer diameter |
3,2 |
|||
| docking surfaces |
1,6 |
|||
| lateral surfaces of the hub |
3,2 |
|
