In the fluid machinery, the parts with the most demanding working conditions are counted as the mechanical seal. It is difficult to achieve a static seal in high temperature, high pressure, and easy corrosion, but it is more difficult to achieve a dynamic seal at the end of a seal of several millimeters wide in high-speed rotation. In order to solve this thorny problem, after long-term practice, people have found two ways: one is from the mechanical sealing structure and material, to make it adapt to the harsh working conditions. The second is to add the auxiliary system, so that the effect of mechanical sealing is greatly improved, the scope of use and conditions are also more broad.

　　The cost of mechanical sealing is high, however, it cannot fundamentally solve the problem. Once the seal fails, the consequences are serious. Another way is to improve the working environment through ancillary facilities.For now, mechanical seals without any auxiliary facilities are rare in practice. Through auxiliary facilities, some harsh working environment is changed into a sealed acceptable environment, and washing is very helpful to the long cycle temperature operation of the seal: 1. Irrigation to dissipate heat. The heat generated from the fluid seal must be controlled. This can be achieved by flushing the sealed chamber with a liquid to remove heat and control the temperature rise.2. Reduce the liquid temperature. In some cases, the liquid temperature is too high so as to affect the sealing performance. In such cases, the temperature must be lowered to improve the liquid performance.3. Change the sealing cavity pressure. In some cases, an increased or lower sealing chamber pressure is required to improve performance. This can be achieved by controlling evaporation or reducing the heat load of the seals.4. Clean the process liquid. If the process fluid contains improper solid particles or contaminants, clean the fluid in the sealing cavity. In extreme cases, it may also be necessary to provide clean fluids from outside the sealing system.5. Control the atmospheric side of the seal. Because the process liquids are in contact with the atmosphere, they may solidify, crystallize, or focus, affecting the sealing properties. In order to prevent the interaction with the atmosphere, so as not to have adverse effects on the sealing performance.

　　According to the latest standard API Std 682 standard, the characteristics of each washing scheme are summarized as follows:

Single mechanical seal:

　　PLAN 01 (Single-end surface self-flushing, in-pump flushing, machine seal without interface)

　　PLAN 02 (Jacket cooling is associated with heat, cooling by heat conduction, machine seal without interface)

　　PLAN 11 (Self-flushing, 1 interface in seal)

　　PLAN 12 (Self-flushing, sealed with 1 interface, with filter)

　　PLAN 13 (Reverse flushing, 1 interface for vertical pump)

　　PLAN 14 (Positive + reverse flushing, sealed with two interfaces)

　　PLAN 21 (Self-flushing with cooling with 1 interface)

　　PLAN 22 (Self-flushing with cooling, sealed with 1 interface, with filter)

　　PLAN 23 (Internal flushing with pumping ring, seal with 2 interfaces)

　　PLAN 31 (Self-flushing with suspension separator, machine seal with 1 interface)

　　PLAN 32 (External flushing with 1 interface)

　　PLAN 41 (Self-flush with suspension separator and heat exchanger with 1 interface)

Double mechanical seal:

　　PLAN 52 (Series seal with pressure buffer tank, sealed with 2 interfaces)

　　PLAN 53A (Double end seal with pressure sealing fluid, two interfaces)

　　PLAN 53B (Double end sealing of forced circulation sealing fluid with two interfaces)

　　PLAN 53C (Double end face seal with booster tank, sealed with 2 interfaces)

　　PLAN 54 (Double end seal with external introduction seal fluid, sealed with two interfaces)

　　PLAN 55 (Double end sealing with external guide seal fluid, two interfaces, buffer is not pressurized)

Cooling seal:

　　PLAN 61 (The PLAN 72 interface is reserved and blocked with wire)

　　PLAN 62 (External washing or rapid cooling to prevent the accumulation of solid particles on the sealing surface, sealed with two interfaces)

　　PLAN 65A (With liquid level transmitter, measure the seal leakage, the seal has 2 interfaces)

　　PLAN 65B (Drainage valve control leakage, seal has two interfaces)

Dry gas seal:

　　PLAN 71 (The PLAN 72 interface is reserved and blocked with wire)

　　PLAN 72 (Series dry gas seal with isolated nitrogen for volatile medium)

　　PLAN 74(Double-end surface dry air sealing)

　　PLAN 76 (Tandem dry air seal with external lead seal gas)