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Each of mechanical seals, used only within the provisions of the order to function effectively. Selection of misconduct, will significantly reduce sealing performance, shortened life expectancy, and even failure.
Selection of the main parameters are as follows
1¡¢A sealed cavity medium pressure P
Media lubricity, and the viscosity is high, the P ¡Ü 0.8 MPa use of non-equilibrium. Poor lubrication medium, low viscosity, P ¡Ý 0.5 Mpa
2¡¢Line speed V
V ¡Ü 25 m / s selection of rotation. V ¡Ý 25 m / s selection of static.
3¡¢PV values
PV value between the sealing surface of the fluid membrane stability (vaporization) of the wear and friction. PV limits, for example: |
| End composite material |
Media |
Non-equilibrium- |
Balanced |
| Tungsten cobalt-chromium alloy / Graphite |
Water |
2 |
7 |
| Tungsten Carbide / Graphite |
Water |
9 |
35.5 |
| Silicon Carbide / Graphite |
Water |
35.5 |
142 |
| SiC / WC |
Water |
7 |
26.6 |
| WC / WC |
Water |
2 |
9 |
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4¡¢Seal medium temperature T
In the absence of the cold conditions, the maximum temperature mechanical seal general auxiliary sealing materials on the safe use of temperature. The table below: |
| Materials |
Safe use of temperature ¡æ |
Remarks |
| NBR |
-30~100 |
Temperature over the safe use of corrugated metal pipe to use mechanical seals |
| MVQ |
-40~200 |
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| EPR |
-10~160 |
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| FPM |
-30~180 |
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| PTFE |
-100~220 |
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5¡¢ medium particularity.
(1)viscosity: medium-low viscosity to use stem friction balanced. High viscosity media, to the adoption of compulsory transmission structure.
(2) corrosion and chemical solvents: a strong, corrosion suitably-loaded PTFE bellows seal.
B, supporting different chemical medium sealed in the application form are as follows: |
| Materials |
Uses |
| NBR |
Mineral oil, gasoline, volatile oil, potassium carbonate, potassium hydroxide, water, phosphate, etc. |
| MVQ |
Alcohol and low swelling of mineral oil, weak acid, weak base, ammonia, etc. |
| EPR |
Acetone, alkali, sulphur dioxide, potassium dichromate, hydrogen peroxide, ammonia, etc. |
| FPM |
Hot oil, steam, inorganic acid, alcohol, chlorine family solvent |
| FCO |
Freon |
| PTFE |
Acid, alkali and solvents and various media |
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(3) suspended solid particles containing:
Central to move materials using tungsten carbide / tungsten carbide, or SiC / SiC, when particles easily blocked sealed cavity, the use of assistive devices to be filtered or separation after the wash-liquid, rinse end.
(4) toxic gases or medium:
Face to a dual mechanical seal. |
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