212

principle

Mechanical seal is a shaft sealing device that relies on one or several pairs of end faces that slide relative to the shaft and are maintained in contact and matched with auxiliary seals under the action of fluid pressure and the elastic force (or magnetic force) of the compensation mechanism to achieve leakage prevention.

The commonly used mechanical seal structure consists of a stationary ring, a rotating ring, an elastic element spring seat, a set screw, a rotating ring auxiliary sealing ring, and a stationary ring auxiliary sealing ring. The anti rotation pin is fixed on the cover to prevent the stationary ring from rotating.

Rotating rings and stationary rings can often be referred to as compensating rings or non compensating rings based on whether they have axial compensation capability.

System composition

Shaft seal box

The previous mechanical seal shaft seal box was designed as a stuffing box for soft packing seals. It is not suitable for accommodating mechanical seals, as its size is too small and the gap is too narrow, and its simple cylindrical shape is also not suitable. Foreign countries have established standards for enlarged mechanical seal shaft seal boxes. Beneficial for removing solid particles and creating a good surrounding environment for sealing.

Control of volatile emissions

In the past, only attention was paid to eliminating visible fluid leaks, without controlling the amount of volatile substances that were not visible, which caused environmental pollution and posed a danger to equipment and personnel. Blocking fluid refers to the fluid introduced between double seals that completely blocks the leakage of process fluid into the surrounding environment. The pressure of the blocked fluid is always higher than the pressure of the sealed process fluid. Buffer fluid is a fluid used as a lubricant or buffer between two seals, and the pressure of the buffer fluid is always lower than that of the sealed process fluid.

Supporting systems for auxiliary systems

In the auxiliary system of mechanical seals, there are cooling, heating, flushing and other systems that need to be matched, pump circulation needs to be optimized, and problems such as status monitoring systems are being studied and solved. The API-682 standard specifies the matching of auxiliary systems.

Gas blocking sealing system

In the past, liquid or liquid blocking gas was commonly used in blocking sealing systems. In order to simplify large blocking liquid systems, blocking gas was used to block liquid or gas. In blocking sealing systems, spiral groove gas seals and blocking gas, floating sleeves and blocking gas, etc. can be used to block gas and liquid.

212