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Mechanical Seal Running

mechanical seal means a means for preventing fluid leakage caused by at least one pair of end faces perpendicular to the axis of rotation which are retained and slid under the action of the fluid pressure and the resilient force (or magnetic force) of the compensating mechanism and the auxiliary seal.

The elastic loading mechanism with the auxiliary seal is the metal seal of the mechanical seal we call the metal bellows seal. In the light seal, there are rubber bellows for auxiliary sealing, rubber corrugated tube is limited, generally need to supplement the spring to meet the loading elastic. "Mechanical seal" is often referred to as "seal".

mechanical seal is a shaft seal for a rotating machine. Such as centrifugal pumps, centrifuges, reactors and compressors. As the drive shaft penetrates inside and outside the equipment, there is a circumferential gap between the shaft and the device, and the media in the equipment leaks out through the gap. If the pressure in the equipment is below atmospheric pressure, the air leaks into the equipment, so there must be a A shaft seal that prevents leakage. Many types of shaft seals, because the mechanical seal with less leakage and long life, etc., so the world's mechanical seal is the most important shaft seal in these devices. The mechanical seal, also known as the end seal, is defined in the relevant national standard: "The end faces of at least one pair of faces perpendicular to the axis of rotation remain in contact with the action of the fluid pressure and the resilient (or magnetic) of the compensating mechanism and the auxiliary seal A device that prevents fluid leakage from moving relative to each other.

System Components

Shaft seal

In the past, the mechanical seal of the shaft seal is a packing for the design of the soft packing. It is not suitable for the use of mechanical seals, not only the size is too small, the gap is too narrow, and simple cylinder shape is not appropriate.

Abroad has been developed to increase the size of the mechanical seal shaft seal the standard. In addition, both the United States and the British Fluid Mechanics Research Group are studying a reasonable mechanical seal shaft seal, its shape should not only be conducive to fluid flow and heat dissipation, but also should be conducive to the removal of solid particles, to The seal creates a good surrounding environment.

Volatile matter escape control

In the past, only attention was paid to the removal of visible fluid leaks, without regard to the control of the amount of invisible volatiles, which caused environmental pollution and was dangerous to the device and the person. (Such as the American Society of Tribology and the Society of Lubricants) has developed the control of mechanical seal rotary machines, compressors and screw systems for SP-30 (1994), SP-32 (1990) and SP-33 (1991) Guidelines for Volatile Degeneration. SP-30 is implemented in three phases. Which clearly defines the definition of blocking fluid and buffer fluid, clarifying the concept of error, confusion. The blocking fluid is a fluid that introduces a double seal between the completely blocked process fluid leakage into the surrounding environment. The pressure of the blocking fluid is always higher than the pressure of the process fluid being sealed. The buffer fluid is a double seal between the fluid used as a lubricant or a buffer, and the buffer fluid pressure is always lower than the pressure of the sealed process fluid.

Auxiliary system support

Mechanical seal of the auxiliary system in the cooling, heating, washing and other systems need to support the pump cycle needs to be optimized, the state monitoring system and other issues in the study to solve. The API-682 standard specifies the supporting system.

Gas blockage system

In the past to block the sealing system commonly used liquid blocking liquid or liquid blocking gas In order to simplify the huge blocking liquid system, use blocking gas to block the liquid or gas blockage system can be used in the spiral groove gas seal and blocking gas, floating sets and blocking gas To block the gas and liquid.

Maintenance issues

Pre-start preparation

1, a comprehensive inspection of mechanical seals, as well as ancillary equipment and pipeline installation is complete, whether in line with technical requirements.

2, mechanical seal before starting static pressure test, check whether the mechanical seal leakage phenomenon. If the leak more, should find out the reasons to try to eliminate. If it is still invalid, it should be disassembled and reinstalled. General static pressure test pressure with 2 to 3 kg / square centimeter.

3, according to the pump to turn the car, check whether the light evenly. If the cart is difficult or does not move, you should check the assembly size is wrong, the installation is reasonable.

Installation and outage

1, should be kept before the start of the sealed cavity filled with liquid. For the transport of solidified media, the application of steam to seal the cavity heating the media to melt. Must be set before starting to prevent a sudden start and cause soft ring fragmentation.

2, for the use of pump outside the sealing system of mechanical seals, should first start the sealing system. Stop after the last stop sealing system.

3, the heat pump can not immediately stop after the closure of the oil seal and the end of the sealed cooling water, should be sealed at the end of the oil temperature dropped to 80 degrees below, can stop the cooling water, so as not to damage the sealing parts.


1, if the pump after a slight leak, should be observed for some time. Such as continuous operation for 4 hours, the leakage is still not reduced, you should stop the pump check.

2, the pump operating pressure should be smooth, the pressure fluctuation is not greater than 1 kg / square centimeter.

3, the pump in operation, should avoid the occurrence of evacuation phenomenon, so as to avoid dry sealing and sealing seal damage.

4, sealed to be regularly checked. During operation, when the leakage exceeds the standard, the heavy oil is not more than 5 drops / min, light oil is not more than 10 drops / min, such as 2-3 days there is no better trend, you should stop the pump check the sealing device.