\"Dry operation\" and \"wet operation\" mentioned in API610 Edition 11”
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In API610, version 11, the definition of a traditional rigid rotor is as follows: \"The first-order critical speed is 20% higher than the maximum allowable continuous speed at which bouncing can occur: (1) For rotors designed for operation only in wet conditions\"； (2) For those involving a rotor capable of dry operation at 30%, what do “dry operation” and “wet operation” mean respectively?
Dry running means there is no fluid in the pump, only air. Wet operation means there is a liquid medium inside the pump. The liquid provides support for the pump rotor, thereby increasing the rotor’s stiffness and critical speed.
After checking this issue thoroughly, no results were found. In my opinion, it can be understood as follows: 1. Wet rotation means that the pump has liquid inside it as it rotates, that is, a pump operating normally ； 2. Dry rotation refers to the rotation of the pump without water inside it. Note that this dry rotation is different from the situation during cavitation; during cavitation, there is actually water inside the pump. 3. Generally speaking, pumps should not be operated dry, as this can easily burn out the mechanical seal. But in fact, if the mechanical seal uses an external cooling fluid, such as Plan 32, it’s actually no problem for it to run dry for a few minutes. At least I can’t think of any other problems that could arise. 4. In terms of technology, the above situation may occur in fire pumps. For more details, refer to NFPA20/NFPA25 (especially NFPA25, which includes the no-flow test), as well as the relevant FM/UL standards. However, NFPA20 doesn’t seem to recommend mechanical seals. I can’t think of any other process conditions that could lead to dry running. In any case, it’s just my own speculation; it’s not necessarily correct.
After checking this issue thoroughly, no results were found. In my opinion, it can be understood as follows: 1. Wet rotation means that the pump has liquid inside it as it rotates, that is, a pump operating normally ； 2. Dry rotation refers to the rotation of the pump without water inside it. Note that this dry rotation is different from the situation during cavitation; during cavitation, there is actually water inside the pump. 3. Generally speaking, pumps should not be operated dry, as this can easily burn out the mechanical seal. But in fact, if the mechanical seal uses an external cooling fluid, such as Plan 32, it’s actually no problem for it to run dry for a few minutes. At least I can’t think of any other problems that could arise. 4. In terms of technology, the above situation may occur in fire pumps. For more details, refer to NFPA20/NFPA25 (especially NFPA25, which includes the no-flow test), as well as the relevant FM/UL standards. However, NFPA20 doesn’t seem to recommend mechanical seals. I can’t think of any other process conditions that could lead to dry running. In any case, it’s just my own speculation; it’s not necessarily correct.
Thank you for your reply! I’ve reviewed quite a few documents but didn’t find any results; it’s probably as you guessed. However, I happened to come across another similar term: drier speed, whose meaning is completely different from that of the former. I’d like to share this here. Drier speed – actually, according to the translations in the literature, it should be referred to as “rotational speed of the drying drum”, meaning that there is no transmission mechanism at all, with the drive unit and the driven unit being connected directly to each other. Of course, this is something different from what we call dry speed. Finally, thank you so much for your guidance!
This is a concept in the field of pump design: the critical speed of a pump under dry operation and the critical speed under wet operation. For wet rotation, the critical speed must be calculated taking into account the support stiffness and damping of the mouth ring
I know the dry critical speed and the wet critical speed; these are not the same concept as dry operation and wet operation. API610 also provides explanations regarding the dry critical speed and the wet critical speed. In fact, the dry critical speed is equivalent to the critical speed under rigid support, while the wet critical speed is equivalent to the critical speed under flexible support. For a detailed explanation, please refer to the book \"Rotor Dynamics\" by Tsinghua University.
The person on the 8th floor is really skilled. . . . .
We are talking about the same thing. Don’t get stuck on the words.
Dry operation refers to running without material, while wet operation refers to running with material