5 ways to reduce or eliminate water waste

2. Precision installation of the ideal mechanical seal

Selecting the ideal seal for an application is important. Ensuring that the materials of construction are compatible with the process fluid and barrier fluid are critical. In addition, proper installation of the seal and setup of its environmental controls and barrier fluid system are just as important.

A cartridge seal simplifies installation, especially if your team is not fluent in seal installation. Selecting a vendor who provides training or assistance in installation is beneficial (see Figure 2). With training, the plant team will be able to carry out the next installation. While a cartridge setup may help the team install the seal correctly, they may need assistance from a sealing expert when setting up the environmental controls.

3. Appropriate flush arrangement and ideal barrier/flush fluid

Compression packing or a mechanical seal requires a cool, clean operating environment for success. To make sure the surroundings are appropriate, the following conditions must be met:

• The correct environmental control arrangement is selected.
• Ensure that the ideal flush/barrier fluid is used. Water or process fluid may not be robust enough.
• Properly set up and install the environmental controls.
• The lantern ring is unclogged and in the correct position to receive the flush fluid (see Figure 3).

4. Packing maintenance and reloading with the gland over time

Even precision-installed compression packing wears and will increase leakage above 10 to 12 drops per minute per inch of shaft diameter during operation. It has a finite lifetime within a stuffing box.

As the packing wears, the loading of the gland will need to be adjusted to decrease leakage to optimum levels. When the gland can no longer be adjusted, the packing must be replaced. Otherwise, flush water will be wasted.

5. Add a shaft-stabilizing bushing

A shaft-stabilizing bushing (separate from the lantern ring for ease of installation and removal) replaces two rings of packing. This solution also:

• may reduce flush water use by up to 80%
• increases flush water velocity and efficiency
• can be used with many packing configurations
• provides shaft stability
• has a low coefficient of friction, which allows for reduced power consumption.

Case studies

From oil & gas production to food & beverage and beyond, water is critical for almost any application in the process industries. These two case studies illustrate the risks and cost of allowing water to leak, causing waste and many other issues.

Ethanol

An ethanol plant’s engineer struggled with pump and seal failures. The slurry flowing through the evaporator pumps was problematic for many reasons. In addition to the fluid complications, the engineer had these other problems:

• detecting inboard seal failures (water leakage into the product)
• setting up the environmental controls
• premature seal failure
• improper training of the maintenance team.

In this ethanol application, the pumped fluid was being evaporated to remove water, resulting in a hot, sticky slurry moving through the pumps. When the inboard seal leaks and water is used as the barrier fluid, water leaks back into the process—the very process that is being sent through evaporators.

Once the pumped slurry leaves the evaporators, it moves to dryers. However, the cost to dry the material in dryers is many times more expensive than moving the material through the evaporator. Leakage that adds water back to this process causes water loss and increases the cost of production.

This plant needed a systems approach (see Figure 4) to solve the problem. The new system included:

• a new seal design to prevent seal failure with an integral pumping ring to ensure that the cooling barrier fluid was circulated properly
• new synthetic barrier fluid replaced water
• a convection tank with a new setup and installation position to ensure proper delivery to the seal.

The meantime between repair increased from 15 months to 37 months.

Pulp & paper

A pulp and paper plant experienced excess water leakage from a paper machine pump moving brown stock. The leakage to drain through the packing was 4.23 gallons per minute. This amounted to 2,102,400 gallons per year.

Water loss to the process (causing dilution) was 1.5 gallons per minute. The yearly amount was 262,448 gallons per year. The total water lost because of poor packing function was 2,628,000 gallons each year.

A systems approach (see Figure 5) helped solve the excess leakage problem. The system included:

• mandrel-cut, high-performance braided carbon packing; temperatures to 1250 °F, shaft speeds to 4,000 feet per minute
• 1-inch, high-performance, thermoplastic lantern ring
• schematic FA12579A environmental controls properly set up.

The system eliminated the leakage to drain, saving 2,102,400 gallons per year. The water into the process was decreased to 0.5 gallons per minute, saving 262,448 gallons per year. The total savings for the plant were 2,364,448 gallons each year.

This story originally appeared in the February 2022 issue of Plant Services. Subscribe to Plant Services here.

David Brewer is regional manager, Atlantic Region, for Sealing Equipment Products Company. Before this role, he served four years in the U.S. Navy and received three Letters of Commendation. He began his career in the fluid sealing industry with many manufacturers until he joined the SEPCO team. He has served many industries including pulp and paper, chemical processing, food and beverage, power generation, textile, and waste treatment. Contact Brewer at [email protected].