Issues related to bellows mechanical seals
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It is a VIKING internal gear pump with a speed of 180; its designed viscosity range is 30–100. The medium in use was changed on-site, and the viscosity has not been measured; it appears to be quite low, so a value of 10 is assumed. The pump uses double-end diaphragm seals, but it is said that mechanical seals leak during operation. Is it possible that the low speed of the pump prevents a liquid film from being formed, resulting in sealing leakage due to factors such as reduced medium viscosity or surface tension? PS: I inspected the idler wheel, crescent plate, and small shafts on site yesterday, and found wear of varying degrees on all of them. The mechanical seal using bellows here is made of flexible graphite, and no spare parts are available; I’m worried that the flexible graphite might get damaged after it’s removed.
This post was last edited by foam_ZPTK on 2018-7-16 at 11:21: Is the mixer’s speed even lower, and can’t the tank seal be used anymore? Can seals with a lower viscosity, like water, not be used?
Mixers shouldn’t be used with media that have an extremely low viscosity; a mechanical seal designed for pumping water cannot operate at just 180 RPM
Seals for kettles with double ends use 5-15# white oil as the isolation fluid, which is quite useful. What’s the viscosity of that?
Double-end face mechanical seals for kettles generally use the PLAN53C sealing design, with a lubricating oil of certain viscosity as the isolation fluid, rather than the process medium itself; here, speeds of 80 r/min are used without any problems. You should specify what type of double-end face mechanical seal you have What sealing scheme is being used? Let’s discuss it together.
This post was last edited by asd6692569 on 2018-7-17 at 13:54: serpentine tube series double-end face sealing, PLAN54, oil station installed outside the pump. I haven’t seen any signs of leakage; it was used right after production and has been left unused ever since. VIKING internal gear pump, designed for a temperature of 300 degrees Celsius, with a viscosity range of 30–100; the medium is asphalt, and the rotational speed is 180. Later, the medium used on site was changed to a light oil with very low viscosity; there was a possibility of vaporization of this medium, and that indeed occurred. The idler shaft sleeves wore out, and pitting occurred on the crescent plates, which is likely due to cavitation. After disassembling the mechanical seal for inspection, the sealing surfaces appeared fine to the naked eye, and the friction pairs were able to hold together through mutual attraction; it was difficult to assess the condition of the flexible graphite. That’s the basic situation
The leakage point of a mechanical seal is not just the interface between the rotating and stationary rings! ! The O-rings of the moving ring and stationary ring can also cause leaks due to improper selection or installation! ! ! It is also possible for the medium to cause the O-ring to swell and lead to leakage! ! !
Bellows mechanical seals are generally used with high-temperature media, employing flexible graphite gaskets instead of rubber O-rings.
API682 Type B refers to the O-rings used for bellows sealing; medium range: -40–176℃