Mechanical seal for kettle Normal operation and maintenance

1. Preparations and precautions before startup

a. Comprehensively check whether the mechanical seal, accessory devices and pipeline installation are complete and meet the technical requirements.

b. Static pressure test shall be carried out before starting the mechanical seal to check whether there is leakage of the mechanical seal. If there are many leaks, find out the causes and try to eliminate them. If it is still invalid, it shall be disassembled, checked and reinstalled. The general hydrostatic test pressure is 2~3 kg/cm2.

c. Turn the gear according to the rotation direction of the pump and check whether it is light and even. If the turning gear is hard or does not move, check whether the assembly size is wrong and the installation is reasonable.

2. Installation and shutdown

a. The sealing chamber shall be kept full of liquid before starting. When transporting solidified medium, the sealing chamber shall be heated by steam to melt the medium. The turning gear must be turned before starting to prevent the soft ring from breaking due to sudden starting.

b. For the mechanical seal using the external sealing oil system of the pump, the sealing oil system shall be started first. Finally stop the oil sealing system after shutdown.

c. After the hot oil pump is shut down, the cooling water of the seal oil chamber and the end face seal cannot be stopped immediately. The cooling water can only be stopped when the oil temperature at the end face seal drops below 80 degrees to avoid damaging the sealing parts.

3. Operation

a. If there is slight leakage after the pump is started, observe for a period of time. If the leakage does not decrease after 4 hours of continuous operation, stop the pump for inspection.

b. The operating pressure of the pump shall be stable, and the pressure fluctuation shall not exceed 1kg/cm2.

c. During the operation of the pump, evacuation shall be avoided to avoid dry friction on the sealing surface and seal damage.

d. The sealing condition shall be checked frequently. During operation, when the leakage exceeds the standard, the heavy oil shall not be more than 5 drops/min and the light oil shall not be more than 10/min. If there is no improvement trend within 2-3 days, the pump shall be stopped and the sealing device shall be checked.

The development of "seal" in China has a long history. The ancients used cotton, hemp and other fibers as the seals of water lifting machinery, while foreign countries only used filler in 1782. The importance of sealing will not be mentioned here. Now there has been a discipline of studying sealing laws, sealing device design technology and applied scientific principles abroad - "sealing science". Scientific research institutions also have professional courses specialized in sealing science. In China, so far, as far as I know, there are courses of fluid mechanics and hydraulic transmission in universities, However, there is no "sealing system" specialized in sealing, so our research level is still lagging behind that of foreign countries.

There are many professional fields of seal design, including mechanics (including fluid mechanics, boundary layer theory, etc.), tribology, automatic control, etc. in addition to materials and machinery. Therefore, for sealing, the research is relatively difficult. Personally, I think the gap between the domestic sealing industry and foreign sealing industry should not be less than 50 years. So all of us must refuel!