Liquid ring vacuum pumps are commonly used to optimize food and beverage production. They have a wide range of applications, including evaporating liquids, evacuating processing chambers, and removing air during the food packaging process.
The liquid ring pump has several advantages, including its simple structure, low upfront price, minimal wear and tear, and long operating life. Years ago, when industry concerns over water usage and cost did not exist, liquid ring pumps were inexpensive and simple to use.
However, times have changed, and so has the industry’s consideration of water usage. Liquid ring pumps aren’t the most viable option for energy efficiency, production, or maintaining a consistent vacuum.
While the initial purchase price of a liquid ring pump might be lower than that of a dry pump, industry concerns have created the need to systemize LRVPs, shrinking the cost delta between LRVP and dry technology type pumps. This systemization cost can include:
Recirculation systems (pumps, chillers, etc.)
Material (SS, Hastelloy, brass, etc.)
Seal material and packing
Larger wiring and components for the motor
Piping for water
Floor space “footprint”
Liquid ring pumps also require more power in order to form and maintain the liquid ring. This means that they require larger motors that use around 20 to 25 percent more energy than other pumps.
When equipped with a water recirculation system, there may be additional motors, chillers, or other accessories that add to your power consumption.
Despite the comparatively low maintenance cost, energy consumption over the lifespan of the pump can cost up to five times more than its initial purchase price.
Liquid ring pumps rely on a liquid seal to achieve a vacuum — typically a steady flow of water. A cooling water system may also be in place to decrease the heat produced during operation.
For this reason, water consumption is one of the most significant drawbacks. The cost for water disposal can be as much as three to four times the cost of supply.
Even if you are using well or pond water, there are costs involved and additional strain on your supply and treatment plants.
During the process, contaminants from the gas may become trapped in the water, causing damage as it continues to recirculate. This can lead to additional costs for treatment of the contaminated fluid and shorten the life of the pump.
Risk of Cavitation
Cavitation occurs when pressure drops below a certain limit, leading to the formation of small gas bubbles in the liquid. When subjected to higher pressure, these bubbles collapse and can damage the internal machinery.
If a liquid ring pump is operated below this limit — the “cavitation limit” — it can cause damage to the pump. This phenomenon often leads to pump damage in the summer months, when the cooling temperature water becomes warmer.
To decrease the risk of cavitation, an “anti-cavitation line,” or a relief valve, can be installed to protect the equipment.
The performance of a liquid ring pump relies on the temperature of the liquid. The achievable vacuum is limited by the vapor pressure of the sealant fluid at operating temperature.
Not only does this limit pump performance, but it can also lead to increased operating costs and water consumption through the coolant system.
When deciding on the appropriate vacuum pump for your business, it's important to weigh all the factors. While the liquid ring pump can be more affordable up front and may minimize wear and tear, it also comes with high energy and water costs.
No matter what pump you end up choosing, proper maintenance can help extend the life of your machinery and reduce the risk of damage.
Encompassing Technical Service, writing Vacuum Product Manuals, Managing Trade Shows, Sales Account Manager for direct and distributor sales and lastly Product Sales Development.
My 34 years of vacuum industry experience have covered a very broad spectrum of vacuum applications and markets. Food, chemical, plastics, heat treating, metals, vacuum centralization, universities, R&D and a host of others.
I take great pride and joy using this experience to help customers and colleagues learn the intricacies of vacuum, how best to utilize and apply to their applications for appreciated results.