food and beverage liquid ring

The drawbacks of liquid ring pumps

April 6, 2021


Liquid ring pumps in the food and beverage industry

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.

Drawbacks of liquid ring pumps

When compared to other types of mechanical vacuum pumps, the liquid ring pump has the following drawbacks:

Higher capital equipment cost

While the initial purchase price of a liquid ring pump (LRVP) 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.)

· Separators

· Motors

· Frames

· Material (SS, Hastelloy, brass, etc.)

· Seal material and packing

· Control panels

· Larger wiring and components for the motor

· Piping for water

· Floor space “footprint”

Energy consumption

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.

Water consumption

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 an 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 shortens 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 temperature of the cooling water becomes warmer.

To decrease the risk of cavitation, an “anti-cavitation line,” or a relief valve, can be installed to protect the equipment.

Limited performance

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.

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Pros and cons of liquid ring pumps

When deciding on the appropriate vacuum pump for your business, it's important to consider 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 choose, proper maintenance can help extend the life of your machinery and reduce the risk of damage.

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