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Selection principle of mechanical seals

Selection principle of mechanical seals

Apr 21,2021
Mechanical seal selection is a more complex system engineering. It is necessary to consider a variety of process parameters and select more suitable sealing structure types.

(A) Body pressure seal chamber

For the sake of good lubrication, high viscosity medium, more than 0.8MPa should choose balance seal, unbalanced seals;

Poor lubrication, low viscosity medium, more than 0.5MPa should choose balance seal, opposite unbalance sealing; 

For light hydrocarbon medium, no matter how much pressure sealed room, will choose the balance seal. Pressure is particularly high, such as: 5 ~ 6MPa, select multi-stage seal;

For bellows seals, the chamber pressure is > 2MPa, double bellows shall be used, otherwise a single bellows shall be selected;

(B) Frictional wire speed

Friction velocity is greater than or equal to 25m/ s, select the static seal;
Friction line speed <25m / s, optional rotary seal;
(C) The temperature of the sealing cavity medium
1. To determine the structure and the two sealing material NBR temperature of -40〜120℃, ethylene propylene rubber ≤-57〜150℃,Viton-34〜204℃,Teflon~250 C , kalrez≥260℃ .
2. Determine the temperature of the sealing system solution according to the medium.
3. Sealed room temperature more than 200 DEG C, applied to the welded metal bellows mechanical seal principle.
The influence of available space in the seal chamber:
The radial seal chamber is smaller in size and larger in axial size. The spring menu structure can be used; the radial dimensions are becoming larger and larger in size; multiple springs can be used; the wave spring can be sealed with the shortest axial dimension.
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