Shaft Seals For Chemical Reactor
A chemical reactor is an enclosed volume in which a chemical reaction takes place. In chemical engineering, it is generally understood to be a process vessel used to carry out a chemical reaction which is one of the classic unit operations in chemical process analysis.Chemical reactor is a kind of pressure vessel used to complete the processes of vulcanization, nitration, hydrogenation, hydrocarbonation, polymerization, esterification, condensation, etc. , which has been widely use in petroleum, chemical, rubber, pesticide, dye, medicine, food. Generally, chemical reactor consists of vessel, driving device, agitator/stirring system, heating/cooling system, shaft seal device. The shaft seal device of chemical reactor included Packing seal type, end-face mechanical seal type, magnetic seal type and etc. Main function of shaft seal device is to help agitator/stirring shaft join together with pressure vessel by preventing leakage, keeping vessel pressure, or excluding contamination.
Features of Mechanical Seal For Agitating/Stirring Reactor
The top-inserted agitating/stirring shaft type reactor is widely used. Because the seal is placed in the top of the vessel, it is in the gas phase space (liquid phase when the material is full). To avoid dry friction in the seal, a certain method of lubrication with cooling device is required. The top-inserted vertical-mounted agitating/stirring shaft has a large aspect ratio and may have low processing and installation accuracy, so it will inevitably produce large deflections.
When the shaft rotating, the following factors will increase the vibration of the shaft: Uneven weight distribution of agitator/stirrer blade; Liquid level is too low or have eddy in the vessel; Uneven medium inlet or not control well of the reaction;Pressure and temperature fluctuations; Deformation of agitating/stirring shaft and vessel caused by pressure and temperature changed; Suddenly changed of agitator speed or viscosity increased of mesium by temperature drop, etc. The top-inserted vertical-mounted agitating/stirring shaft has a large aspect ratio,an intermediate bearing is usually installed to provide a relatively vibration-free working environment for the seal to make the seal running smoothly.
Classifications Of Mechanical Seal
|
Classifying MethoClassifying Method |
Classificationion |
Application |
|
By set of sealing end-face |
Single sealing face |
Pressure of vessel: ≤0.6Mpa-a |
|
Double sealing face |
Pressure of vessel: ≤1.6Mpa-a* |
|
By the pressure of the sealed fluid acting on the seal ring |
Balance type |
For high & middle pressure reactor |
|
Non-balance type |
For low pressure reactor |
|
By if the position of spring is in/not in the sealed fluid |
In in the sealed fluid |
For non-corrosive medium |
|
Not in the sealed fluid |
For corrosive medium |
|
By the number of spring |
Single spring |
For light load with small shaft diameter |
|
Multiple springs |
For large load with big shaft diameter |
|
By if the spring is rotating with the shaft |
Rotating type |
Used in most equipment |
|
Stationary type |
Use in large sizes or at high rotational speeds |
|
By if end-face is contacted |
Contact type |
For commonly orking medium |
|
None-contact type |
For flammable, explosive and highly toxic medium |
Design of Mechanical Seal For Agitating/Stirring Reactor
Generally, the rotating speed of mechanical seal used for the top-inserted agitating/stirring shaft type reactor is lower, so the specific pressure of the spring can be set larger; the vibration of the stirring shaft would be larger, so the sealling element should be designed more strong and friction ring should adopt the overall structure when sealing the gas; considering the large amount of swing when the stirring shaft rotates, the gap between the mating ring and the shaft should take a larger value. When calculating the specific pressure of the end face of the mechanical seal using for the large shaft diameter top plug-in reactor, the weight of the compensation ring cannot be ignored.
Generally, the type selection of mechanical seal should according to the working medium in reactor, working pressure & temperature, agitating/stirring speed, diameter of agitating/stirring shaft & power of driving motor. Material selection of mechanical seal should according to the working medium & temperature in reactor: sleeve material of mating ring seat: glass lined steel, SiC, Al2O3 Ceramics, Reinforced PTFE, and etc; material of end-face(seal ring & mating ring): SiC-SiC, SiC--Reinforced PTFE, Al2O3 Ceramics-Reinforced PTFE, Al2O3 Ceramics-Modified graphite, and etc. When working pressure lower than 0.4Mpa-a, commonly use single end-face mechanical seal; pressure higher than 0.4Mpa-a use double end-face mechanical seal; pressure higher than 0.6Mpa-a should use double end-face type mechanical seal with auxiliary device; when working temperature higher than 150 deg.C, it can not use material of PTFE; use Integrated with bearing structure type during diameter of agitating/stirring shaft & the power of the stirring motor are relatively large.
Typical Structure of Mechanical Seal For Agitating/Stirring Reactor
Typical Application Model of Mechanical Seal For Agitating/Stirring Reactor
Auxiliary Device Of Mechanical Seal For Agitating/Stirring Reactor
COMMON FAULTS AND PROCESSING METHOD OF MECHANICAL SEAL
CONTACT
SHANDONG PIONEER HEAVY INDUSTRY TECHNOLOGY CO.,LTD.
Address : Changwang Industrial Park, Liushan Town, Linqu County, Weifang City, Shandong Province, P.R.China
Mr. Conan WEI
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