Circulation water pump---Modular self-flushing mechanical seal

The modular type is in contrast to conventional mechanical seals; it combines components such as the rotating and stationary rings as well as springs into a single unit. In conventional mechanical seals, the rotating and stationary rings are separate. The installation of modular seals is simpler than that of conventional seals, but maintenance is more complex, requiring return to the manufacturer or consultation with a specialized seal manufacturer for repair

Self-flushing is the 11-flushing scheme

The modular type refers to a seal that features shaft sleeves, sealed end caps, an active ring, and a static ring

Self-flushing refers to flushing that relies on the medium itself; the commonly used flushing scheme is PLAN11, from the pump outlet to the sealing chamber

Firstly, the concept of “containers” in transportation led to the development of containerized sealing. The rotating and stationary parts of this seal are pre-assembled into one unit before installation; after passing inspection and pressure testing, they are installed on the shaft within the shaft seal housing and fixed to the shaft with set screws. Once the gland bolts are tightened and the positioning plates are removed, the mechanical seal can operate in a parallel plane configuration and begin to function. This not only makes assembly easier but also ensures the quality of the assembly. Currently, mechanical seals for welded metal bellows are all designed as modular seals, which possess the aforementioned advantages. Cartridge sealing is also a type of modular mechanical seal. Before installation, this type of sealed static ring, dynamic ring, shaft sleeve, gland, as well as auxiliary seals are all assembled together using a shaft sleeve, which facilitates the inspection of the assembly quality. After passing the inspection, simply seal it tightly and tighten the screws. Sealing components that are assembled, inspected, and tested in advance in this way make it easier to ensure the quality of installation and assembly. This type of modular seal has the following characteristics: (1) No measurement of the seal’s operating length is required during installation ； (2) The axis can be adjusted at any time ； (3) There will be no leakage issues at startup, as the seals have been pre-tested ； (4) During installation, only the sealing cover bolts need to be tightened, making it easy to ensure proper assembly quality ； (5) Protect the sealing surface from contamination by debris or damage due to operational errors before installation or startup ； (6) The machine equipment can be readjusted after thermal expansion ； (7) Centering can be adjusted using cooperation ； (8) The seal can be easily removed for cleaning and inspection without having to disassemble the pump equipment. Standard API682 recommends that all mechanical seals use modular mechanical seals.

After loosening the 4 bolts of the sealed gland for container sealing, the sealed shaft sleeve and the gland can be removed from the pump at the same time, while remaining assembled together. Before installing it on the pump, seal all the parts so that they can be assembled together to form a single unit. Self-flushing sealing falls under sealing flushing scheme 11: a thin pipeline is led from the pump outlet or the high-pressure side of the pump to the seal gland (with a flow-limiting orifice plate of 2 mm in diameter in between), and water pumped by the pump is used to flush the stationary and rotating rings of the seal. This ensures the formation of a strong liquid film between the two sealing surfaces. Meanwhile, the flushing water carries away the heat generated due to friction between the rotating and stationary rings as they move relative to each other; a high temperature of the liquid film can lead to its vaporization, resulting in dry friction between the rings and accelerating their wear and damage. Therefore, the purpose of this system is primarily to cool the rotating and stationary rings

The advantage is that a complete replacement is carried out, which ensures better assembly dimensions and effectively prevents the leakage of hazardous substances. The downside is that it requires repair by a specialized external manufacturer, and it’s also expensive.

The static ring gland and shaft sleeve can be reused; only the static and dynamic rings need to be replaced. The O-rings and seals need to be replaced, which helps to reduce costs effectively.