Issues related to water ring vacuum pumps
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Is the angle of the impeller blades in a water ring vacuum pump inclined forward or backward (in other words, what is the rotation direction of the impeller)? Are there blades that are straight or curved, or are all the blades straight? Is the width of the water ring formed during the operation of a water ring vacuum pump equal at all radial positions in its axial cross-section? Is it true that the wider the water ring, the smaller the working chamber becomes relatively, and thus the poorer the pump’s performance? (Does that mean there shouldn’t be too much water inside the pump casing?) ) So what is the width of the water ring for which the pump performs best? And how can the width of the water ring be controlled? Our vacuum pumps use graphite packing for sealing; during operation, a large amount of working water leaks from the shaft seal area. Will this lead to a decrease in the pump’s performance? (Our pump is designed to operate at -8 KPa, but currently it can only achieve -3 KPa.) During normal operation, all the water inside the pump casing forms a water ring; there is no water at the axial height position. So how can there be leakage at the shaft seal? Is it because we have enabled automatic water replenishment, resulting in too much water inside the pump casing? So, should it be auto-watering or manual watering? The excess water that is added inside the pump casing will either leak out through the shaft seal or be used in a wasted cycle (by \"wasted cycle\" I mean that part of the useful energy that could have been used for pumping air is instead wasted on pumping water). Please provide an answer along with images; there are many pictures available online, or you can use actual photos from your own factory. Thank you! (Please do not copy the text descriptions from the Internet.)
In the axial cross-section of the water ring formed during the operation of a water ring vacuum pump, the width at various radial positions is theoretically equal; however, due to the eccentricity of the shaft, the widths of the water ring are not equal. The wider the water ring, the relatively smaller the working chamber. The pump performs best when the width of the water ring is such that the exhaust gas is completely discharged without any water being released. It is difficult to control the width of the water ring.
1. So far, I have only seen straight blades with a clockwise rotation direction, which is mainly to facilitate the formation of the working chamber. It’s pretty much the same as the pictures online. 2. The width of the water ring affects the volume of the working chamber, thereby influencing the pumping rate and vacuum level. The amount of working fluid to be added generally needs to be adjusted according to the operating conditions. During our previous debugging, the engineers from the equipment manufacturer said it was somewhere between 1/2 and 2/3, but in reality, different liquid levels do result in certain differences in the final outcome. 3. During normal operation, under the action of centrifugal force and the impeller, water inside the pump casing forms a water ring; theoretically, there is no water at the axis position. However, given the reasons for unstable liquid levels (with a higher likelihood of high liquid levels), leakage at the axis position is inevitable. 4. Sealing leaks will inevitably lead to a decrease in the system’s vacuum level and exhaust volume.
The ultimate vacuum achievable by water ring vacuum pumps is also around –93 KPa. This value is already quite close to absolute vacuum, so why are they still called rough vacuum pumps?
How is this even close to a vacuum? In KPa units, the difference is huge! Rough vacuum: 10^3~10^Pa; Low vacuum: 10^-1~10^3Pa; High vacuum: 10^-6~10^-1Pa
Generally, it features straight blades that are bent forward; the leakage pit inevitably leads to a decrease in vacuum level. A single-spring mechanical seal can be used to eliminate leaks