The working principle or theory of a mechanical seal
Mechanical seal is a shaft seal device that relies on one or several pairs of end faces that slide against to the shaft and are held in contact under the fluid pressure and the elastic force (or magnetic force) of the compensation mechanism to assist in seal function and prevent from leakage.
Selection of material
Clean water: normal temperature; (Dynamic ring) Silicon carbide, (Static ring) resin impregnated graphite,
River water (including sediment): normal temperature (Dynamic ring) tungsten carbide, (static ring) tungsten carbide
seawater: normal temperature; (Dynamic ring) tungsten carbide, (Static ring) resin impregnated graphite, tungsten carbide
Hot water at 100 degrees Celsius: (Dynamic ring) tungsten carbide, (Static ring) resin impregnated graphite, tungsten carbide
Gasoline, lubricating oil, liquid hydrocarbons: normal temperature; (Dynamic ring) tungsten carbide, (Static ring) resin or antimony graphite.
Classification of mechanical seals
1, Classification by structure of mechanical seal: rubber bellow type, spring push type, metal bellow type
2, Classification by theroy of seal: wet seal, dry running seal, dry gas seal.
3, Classfication by equipment: Pump seal, Compressor seal or blower seal.
Mechanical seal auxiliary system
For single seal, we always choose Plan 11, 21, 23 or 32.
Plan 11: Flushing come from discharge side of pump and come to chamber through F hole with orifice application.
Plan 21: Flushing route same with Plan 11, but orifice was been placed by heat exchanger. FYI: Need to confirm if cooling water is available at site.
Plan 23: Medium was been circulated by pump screw setted on mechanical seal. With heat exchanger to cool medium down in chamber of mechanical seal.
For dual seal, Plan 52, 53A or 53B is very common to be used.
Plan 52: Unpressurized buffer fluid applied in system, commonly used for medium are not allowed buffer fluid come in and kind of dangerous if leakage happen. I.E.: Light hydrocarbon(Methane, ethane, propane, and hydrocarbons)
Plan 53A & 53 B: Both are pressuized barrier fluid applied in system, but pressure come from different source. For 53A it comes from nitrogen, 53B comes from accumulator. Both of them commonly used in medium with solid particle or medium is not allowed to leak.
