Selection between water ring vacuum pumps and water jet vacuum pumps
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This post was last edited by meinijiuok on 2018-8-14 08:01. Dear colleagues in the chemical industry dealing with pharmaceutical intermediates and pesticide intermediates: Do you use water ring vacuum pumps more often, or water jet vacuum pumps (commonly known as water-driven pumps)? The ultimate vacuum of both is 3.3 KPa, and the power required for the same pumping rate is roughly the same (meaning the electricity cost for operation is also similar). Water ring pumps are expensive, while water jet pumps are cheap ； Water ring pumps produce less wastewater, while water jet pumps generate more wastewater ； Water ring pumps are small in size, while water jet pumps require a large footprint. How should I make a choice? In the fine chemical plants I’ve encountered, water jet pumps are used more frequently, while water ring pumps are used less often. I’m asking for everyone’s help, thank you!
I use water ring vacuum pumps quite often here. While ensuring a proper vacuum level, the water ring vacuum pump effectively reduces water contamination; it only requires a heat exchanger connected to the vacuum pump for recycling purposes. The gas drawn out can be separated into gas and liquid phases before being disposed of.
I have only gotten a basic understanding of these two types of pumps. Let me share my opinion: when using a water ring pump to achieve a pressure of 3300 Pa, it is essential to pay attention to controlling the water temperature. This is especially true in summer, as many factories rely on brine at that time. I’m not sure if you have taken into account the energy consumption associated with cooling. A water jet pump is essentially a momentum transfer pump; if the substance you want to pump is quite viscous, it is recommended to use a water jet pump
Water ring pumps indeed produce much less wastewater. I’ve heard that in areas with strict environmental regulations, using water to clean pumps is no longer allowed; I’m not sure if this is true
I hadn’t noticed that with your reminder; the temperature of tap water is indeed very high in summer. If saltwater is used, the operating costs will be much higher than those of a water-driven pump. Do you know the relationship between the vacuum level of a water ring pump and the water temperature? Could you let me know?
Regarding what was mentioned on the 4th floor, in summer the water ring pump needs brine to increase the vacuum. Do you experience such a phenomenon there? In summer, without salt water, what level of vacuum can be achieved?
When a liquid is present in a vacuum system, the ultimate pressure that the system can achieve is the saturated vapor pressure of that liquid at a specific temperature. Therefore, the ultimate pressure that a water ring pump can achieve is the saturated vapor pressure corresponding to the water temperature.
Under normal circumstances, in summer the temperature of the water entering the water ring pump (the circulating water) is around 32–35°C (in hot regions in the south). It is difficult to maintain a vacuum pressure at the design limit of 3.3 kPa; generally, 5–6 kPa is already a good achievement. If such a vacuum level meets the requirements of your process, it is recommended to use a water ring pump. These pumps operate stably, cause less pollution, require less water for circulation, have lower maintenance costs, and involve a simpler system.
It’s not that using water to flush the pump is prohibited; rather, it’s not allowed for the wastewater generated by this process to be discharged without being treated first. This processing fee is also a significant expense.
Thank you for your advice! ! ! It seems that the water ring pump is better than the water jet pump. However, during operation of the water ring pump, the saturated vapor pressure of the circulating water should be higher than that of pure water (as volatile solvents are drawn into the water during the vacuum creation process). This level is sufficient to meet our process requirements; for high-vacuum systems where such requirements are not met, I plan to design a Roots pump. Thank you again; it was very informative!