Knowledge Popularization of Mechanical Seal for Pump of Desulfurization

The main components of the mechanical seal for pump of desulfurization include the pump shaft, the dynamic ring component assembled on the pump shaft, and the stationary ring component. The dynamic ring component includes the inner shaft sleeve, the driving seat shaft sleeve mounted on the inner shaft sleeve through a locking disc, the dynamic ring connected to the driving seat shaft sleeve, the O-ring seal on the inner shaft sleeve, and the O-ring seal on the driving seat shaft sleeve. The stationary ring component includes the stationary ring, the gland placed on the other end of the stationary ring, the spring, the spring seat with guide bushing, the flange seat, and the O-ring seal of the stationary ring. The mechanical seal for pump of desulfurization is a more precise mechanical component, and the correct installation has a great influence on its service life. We generally follow the standards of the Petrochemical Department.

The technical requirements for the pump and mechanical seal cooperation parts of the mechanical seal for pump of desulfurization are as follows

  • Shaft bending: not more than 0.05 mm.

  • Rotor swing: the clearance between the shaft sleeve at the dynamic seal ring is not more than 0.06mm.

  • The axial movement of the shaft must not exceed ±0.5mm. If with a shaft sleeve, there must be no looseness of the shaft sleeve.

  • The alignment error of the coupling: for the gear coupling, it should not be greater than 0.08-0.10mm (P2008C), and for the flexible coupling, it should not be greater than 0.05-0.06mm.

  • The concentricity allowable deviation of the pressure cover (stationary ring seat) and the sealing joint with the shaft centerline is 0.05mm, and the perpendicularity value of the contact surface centerline with the gasket allows a deviation of 0.03-0.05mm. If these requirements are not met, the sealing chamber must be processed.

  • The end of the shaft sleeve where the dynamic seal ring is installed and the end of the gland (or housing) where the stationary seal ring is installed should be chamfered and polished.

  • During the installation and dismantling of this type of mechanical seal for pump of desulfurization, carefulness is required to avoid damaging the sealing elements. Do not use a hammer or flat shovel. If it is difficult to dismantle due to scaling, it should be cleaned before the dismantling process.

  • If this type of mechanical seal is used on both ends of the pump, it is necessary to take care of each other during the assembly and dismantling process to avoid interference.

  • For the used mechanical seal, if the cover becomes loose and causes the seal to move, the dynamic and static ring components must be replaced, and it should not be tightened again for continued use. Because the working trajectory of the mating parts will change after looseness, the sealing performance of the contact surface will be easily destroyed.

The clearance between the stationary ring and the housing and the clearance between the dynamic ring and the shaft of the mechanical seal for pump of desulfurization is sealed with forming filler. A relative sliding surface is formed on the end face where the dynamic and stationary rings are in contact, i.e., the dynamic seal surface. The dynamic seal surface should be very flat and smooth to ensure good sealing. The spring force and the pressure of the sealed fluid make the dynamic ring tightly adhere to the stationary ring. Since the dynamic ring is connected to the shaft through a spring, the fitting of the dynamic and stationary rings is less affected by the vibration and swing of the shaft. A soft material with good lubricity, such as graphite and filled polytetrafluoroethylene, is generally used for the stationary ring, while a hard alloy, ceramics, and other materials are used for the dynamic ring.

After taking corresponding measures in the structure, the mechanical seal for pump of desulfurization can be used for the sealing of high-temperature, high-pressure, high-vacuum, high-speed, corrosive working media. When the pressure in the chamber is equivalent, the gate is closed to form an initial seal. When the valve is opened or closed each time, the seat ring can automatically clean the two sides of the gate. The pressure acting on the gate forces it to press against the PTFE ring on the outlet seat and compress it until the gate stops on the steel seat. Thus, a double seal is formed: first, PTFE against metal, then metal against metal. The seat is firmly pushed into the groove, and the O-ring prevents any backflow of the medium at this point.

To form the inlet seal, the pressure of the pipeline acts on the inlet seat, pushing it towards the gate. At this time, a PTFE-metal seal is formed, and the O-ring and the valve seat groove form a tight seal. When the pressure in the valve chamber is greater than that in the pipeline, due to thermal expansion, the inlet seat is pushed toward the groove. The excess pressure in the valve chamber is released between the seat and the gate and flows back to the pipeline.

The mechanical seal for pump of desulfurization adopts a filler structure with self-sealing ability

The mechanical seal for pump of desulfurization does not need to be adjusted frequently, and the opening and closing are very light. The sealing is reliable. The filler box is equipped with an auxiliary sealing grease injection structure, and the whole cast bracket has a locking device, and the valve disc assembled by positioning the bracket is more stable and reliable. The shaft or shaft sleeve is basically not worn, and the end face wear can be automatically compensated. Under normal circumstances, it does not require frequent maintenance. The mechanical seal for pump of desulfurization can be used for the sealing of high-temperature, low-temperature, high-pressure, vacuum, different rotating frequencies, as well as various corrosive media and abrasive media. Its sealing state is very stable and the leakage is very low, which is about 1% of that of a soft-packed seal.

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