Questions, Questions, Questions - WaterWorld Magazine

The other challenge was the very poor soil on which the water tank was installed. Cleveland says construction involved driving concrete precast piles into the ground to support the tank and associated pump station. This impacted both the cost of the project and its schedule. “It’s also a very noisy operation,” he says, so communication with the neighbors and sensitivity to working hours were important considerations.

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What Are Your Options?
Containment Solutions Inc. manufactures fiberglass tanks in sizes up to 60,000 gallons that can be tethered together for larger storage and buried underground. According to David Heiman, director of marketing, business for its tanks has been exploding in the last 10 years.

Heiman attributes this growth to the increased popularity of green projects, including water capture and water conservation, which are important for point collection with Leadership in Energy and Environmental Design (LEED) buildings applying for certification. Reducing the consumption of potable water for non-potable use by capturing rainwater and/or graywater for irrigation will earn points toward gold, silver, or platinum certification.

Historically, municipal water agencies were not interested in fiberglass water tanks, but Heiman says this is changing in a time with little or no funding. He says these agencies are looking for alternate water conservation methods and are encouraging customers to conserve water in tanks. New developments are installing fiberglass tanks in rural areas where there are no municipal services.

Customers prefer multiple large tanks, says Heiman. The ability to build a hybrid system for customers, such as schools and hospitals who are routinely buying fiberglass tanks creates opportunities for water conservation, particularly in summer peak demand periods. Rainwater can be captured in one tank, graywater in a second, and water condensate in a third. Heiman says the University of Binghamton in New York did just that. It recently bought four 50,000-gallon tanks with separate outlets to store rainwater in some and graywater in others.

American Structures designs, fabricates, installs, and services bolted and welded stainless steel storage tanks for the agricultural, industrial, municipal, and wastewater industries. Its water tanks are used to store potable, recycled, and stormwater, as well as water for fire protection. They are made to order, and come in all sizes.

Earl Wildenberg, president of American Structures, says, “People are getting really excited about stainless steel. It doesn’t have to be painted; it is resistant to corrosion, rust, and relatively maintenance-free; it is environmentally friendly; it blends into the landscape.”

Municipal water agencies don’t have to worry about refurbishing a stainless steel tank in five years, he adds. Water agencies are now looking at the cost of refurbishing existing tanks and comparing those numbers with the costs of a stainless steel tank.

Wildenberg says the company has installed a lot of smaller tanks, which can be designed for expansion later. The tank is unbolted at the bottom, the tank is jacked up and new panels are installed. They recently installed two 100,000-gallon tanks in North Dakota for a mining company. There are no differences in installing small or large tanks.

“It’s like building a garage,” he says. “Once you build an envelope, you can put anything in it.”

United Tank Systems is a distributor for Fusion Tanks, manufacturer of glass-fused steel tanks, headquartered in England. It also manufactures both epoxy-lined steel tanks and stainless steel tanks in all sizes. Joel Portmann, company president, says glass-fused bolted steel water tanks are like putting water in a glass.

Glass-fused steel tanks have advantages over other types of tanks. They can be built up to accommodate growth, they can be moved to another location for other uses, and they have near-zero life-cycle costs, compared to concrete and welded steel tanks, which must be recoated about every 10 years and be maintained to avoid biofilm growth, says Portmann.

What About the Price?
Glass-fused steel tanks are price competitive with concrete tanks, stainless steel and welded steel tanks as size increases beyond 200,000 gallons, but pricing is dependent on region and customer requirements, Portmann says. For example, in Wisconsin, a tank has to be built to handle snow on its roof, but in California, seismic regulations require a heavier tank–these variations all impact price. The cost of stainless steel tanks is tied to the price of the metal itself and becomes less competitive pricewise as the size increases.

“There have been times when stainless steel is a lot cheaper and times when it is more expensive,” says Portmann. Operations and maintenance is similar to that recommended for glass-fused steel tanks.

Wildenberg agrees that stainless steel is cost-competitive initially and has low operations and maintenance costs since it is resistant to corrosion and rust, making it cheaper to maintain.

Another element affecting price is the ability to assemble the tank at the factory if it is small enough and can be trucked to the site, thereby decreasing costs. The cutoff is 20,000 gallons, Portmann says. However, transportation of the tank materials outside of the region where they are manufactured also increases the total price.

Portmann says epoxy-lined steel tanks are the least expensive type, and are usually purchased by private companies for chemical and other liquid storage uses. New improved epoxies are now coming on the market. The original epoxies are holding up well on tanks, he says, although some require special coatings. It is still too soon to say how well the new epoxies will endure, he says.

Pricing can be a challenge, says Heiman, and can vary depending on the fittings and accessories customers request for the tanks. Fiberglass is easy to customize, but still economies of scale rule, he says. If changes are called for in the field during installation, they can be made there, in contrast to concrete or steel tanks.

Prices for fiberglass tanks are comparable to those for concrete tanks, and with water rates rising, paybacks are improving, Heiman says. Life-cycle costs for fiberglass tanks are much lower, since they don’t rust, because biofilm such as bacteria and algae can find no home in the underground environment due to their smooth inner surfaces. Heiman says biofilm needs a textured wall to grow on, as well as sunlight. Once installed correctly, fiberglass tanks will operate for decades without maintenance, he says.

Heiman contractors like fiberglass tanks because of the ease with which they are installed. Anchors can be transported on the same truck as the tanks, and smaller cranes are needed.

Good O&M Will Protect Assets
Operations and maintenance (O&M) standards for water tanks developed by the American Water Works Association (AWWA) have been established long enough that they have become the industry standard and adopted by virtually all the states and some countries abroad.

AWWA M42, Manual for Steel Water Storage Tanks is referenced several times in this story. Standards are found in D100 for welded steel, D102 for coating steel water storage tanks, C652 for disinfection of water storage facilities, and G200 for distribution systems operation and management. Standards for concrete tanks can be found in D110 and D115, and standards for fiberglass tanks are found in D120-09.

The following discussion was drawn from a white paper written by Randall L. Moore, vice president of special products and technical services at Utility Service Company, and an April Web seminar organized by AWWA featuring Moore as moderator with speakers Kirt Ervin, vice president for Water Quality at Utility Service Company, and Mark Johnson, director of metropolitan water operations at the Massachusetts Water Resources Authority.

The white paper, “A Sustainable Approach to Potable Water Quality Management,” can be found on the PAX Water Technologies website, under resources/white papers. The Web seminar, “Tank Inspections and Sustainable O&M Best Practices to Manage Water Quality” is available through AWWA’s education services. Additional comments were provided by Moore and Johnson in interviews.

Moore cautions that it is best to confirm you are viewing the most recent updates when you read the standards. The most recent update of AWWA’s reference book, Steel Water Storage Tanks: Design, Construction, Maintenance, and Repair, for example, was released in , he says.

Moore, Ervin, and Johnson stressed chemical cleaning, active mixing, and tank asset management as tools that will provide plant managers and operators the ability to comply with the myriad new regulations governing contaminants and disinfection by-products.

Inspections Are Important
In the Web seminar, Ervin recommends that all water agencies have a written inspection plan outlining frequency, procedures, and maintenance of records. A good inspection program can extend the life of an existing tank indefinitely, he says.

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Types of inspections include weekly visual, plus once-per-year inspections via remotely operated vehicles if sedimentation is a problem, in which tanks can remain full and sediments can be removed. Dive inspections can be done every three years or longer. When tanks are drained for chemical washouts, every aspect of the tank, and distribution system can be inspected.

Johnson says that remotely operated vehicles (ROVs) are doing a great job now. A crawler tank can soak up sediment to produce a clean tank as a result. Once materials dredged from the tank are allowed to settle and dry out the remaining liquid can be discharged, he says.

Areas that should be inspected on a regular basis, says Ervin, include the roof and its coverings, low spots on roof plates, access hatches that may get unlatched and vents, which should be kept in good condition. Overflow pipes should have a good catch basin.

Openings through roofs or access hatches have allowed birds, squirrels, beer cans, and, yes, even eels, to get into the water. Roofs with low spots are prone to rust where water and snow can gather. Vents should be inspected at least once a year, and kept in good condition. A good vent has a fine mesh screen preventing wind-borne particles from entering the tank.

Johnson recommends taking outbound water samples from tanks weekly, and having them laboratory tested for bacteria. The monitored data and chlorine residuals, for example, can be plotted each week. He recommends using 1.0 milligram per liter (mg/l) chlorine residual as a measurement for an action threshold.

Furthermore, this schedule is a weekly opportunity to confirm access is intact, gates are locked, the fences are secure, there are no obvious tank problems, screens, vents, and hatches all secure, and there is no leakage due to rust or penetrations. Finally, Johnson cautions that tank ladders should not become cable trays for cell vendors. Renting space to cell vendors is a great source of needed income, he says, but don’t forget that these are water tanks, not antenna bases.

Johnson recommends AWWA’s G200-09, “Distribution systems Operations and Maintenance,” section 4.3.1, which provides a great inspection checklist.

Maintain Water Quality
When potable water sits in a storage tank, problems occur and the water stagnates. Johnson says to try and keep the age as low as possible. He quoted a white paper published by EPA and a Water Research Foundation study, which reviewed turnover rates and found they varied from one to three days and as much as five days. The Water Research Foundation study found that a turnover rate of 2.5 days of 40% of water in the tank became the optimum level.

Tanks that are well mixed are sustainable, because they consume less disinfectant, minimize the formation of disinfectant by-products, and avoid the need to empty the tank should nitrification occur, which depletes disinfectant residual. With active mixing, the common operational practices of “deep cycling” storage tanks, onsite chlorine boosting, and tank/main flushing used to remedy problems due to poor mixing can be reduced or eliminated within the storage tank.

Also, an active mixing system can minimize icing in tanks located in northern climates and reduce ice damage to the tank interior coatings, thereby helping to minimize biofilm growth and corrosion by-products, ultimately improving water quality.

Three water quality management tools can be used to maintain water quality. Washouts at least every three years are recommended in AWWA’s M42 Manual for Steel Water Storage Tanks to remove sediments and clean the tank. But neither pressure washing nor the disinfection process will kill and remove biofilm on interior surfaces.

As biofilm builds up, an increasing amount of disinfectant is required. However, a low-pressure NSF standard 60-certified chemical washout can remove all biological growth from the empty tank, as well as the mineral staining typically associated with the biofilm.

Removing biofilm and stain, while the water tank is empty makes inspection and failure repairs in the coating much easier and more thorough. Maintaining the integrity of the coating will minimize biological regrowth by eliminating anchor sites where colonization occurs. Eliminating surface roughness will reduce biofilm growth.

An active mixing system certified by NSF Standard 61 which operates 24 hours a day seven days a week is highly recommended to eliminate thermal stratification and achieve homogenous water chemistry within the storage tank. Moore sites a study, which shows that passive mixing of the water when the tank fills will restratify both thermally and chemically within four hours after pumping water into the tank.

I have a tank and need a sight glass.  What are my options?  Although this may seem like an innocuous question… many factors come into play.  While the choice is clear for some customers, there are many more for whom this choice is anything but clear.

Sight glasses allow you to safely observe processes inside your tanks, vessels, pipes, and reactors. It is a window that allows operators to inspect the process media, observe reactions, observe the functioning of mixing equipment, verify the presence or absence of media, see liquid level, etc. It consists of metal, glass, and gasket components.  In order to ensure optimal performance, a variety of factors need to be considered. Here are 5 critical things to consider when specifying a sight glass for your process.

Let’s get started.

1. PRESSURE

The glass materials selected, the unsupported diameter, and the glass thickness all play a role in determining the pressure capabilities of a sight glass assembly.

There are two types of sight glasses: a conventional glass disc and a glass disc fused to a metal ring during manufacturing. The metal ring squeezes the glass and holds it in radial compression.  Glass typically fails as a result of being subjected to significant tension. With fused sight glass windows, the compressive force of the metal ring exceeds the tensional force (i.e., pressure) and, as a result, the sight glass is extremely resistant to failure. Fused sight glass windows offer high-pressure ratings and high safety margins.

The strongest fused sight glasses are made from duplex stainless steel and borosilicate glass; this combination creates the highest compression.

2. TEMPERATURE

The temperature will determine the glass type and more commonly the gasket material.

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3. MATERIAL OF CONSTRUCTION

Carbon steel and stainless steel are the two most common metals used.  Stainless steel offers better corrosion resistance and is standard in pharmaceutical applications.

4. METHOD OF CONNECTION 

There are three methods to connection:

• Weld-on. If the sight glass will be welded on, consider the following:
  • What will be the temperature and pressure inside the vessel? Sight glasses are rated for maximum temperature and pressure.
  • If the sight glass is going to be welded into place, the vessel onto which it will be welded likely hasn’t been created yet. The size of the hole for the sight glass should be specified before the vessel is made.
  • Is the tank ASME? If so be sure to only use ASME wetted parts.
• Bolt-on. When your sight glass is mounted to an existing flange, bear in mind the following:
  • Bolt-on sight glasses come with existing bolt holes. Be sure to let the sight glass supplier know the size of the flange to which the sight glass will be connected so that the bolt holes match up.
  • There are pressure limitations depending on the type of flange used. Bolt-on sight glasses are generally specified as 1) good to 15 lbs. psi or 2) for anything over 15 lbs. psi. Sizes should follow ANSI specification guidelines and materials should follow ASME standards.
• Clamp-on. The pharmaceutical industry uses clamp-on sight glasses so that all components can be easily disassembled for cleaning.

5. PRODUCT CONTACT CONCERNS

Will the sight glass come into contact with corrosive process media? Will it be subject to sanitize in place/clean in place processes? Will it be exposed to thermal cycles or extreme heat? Your L.J. Star expert can guide you to the specific glass, gaskets, linings, and shields that you will need.

Now that we have walked through the process and took a deeper look at what needs to be considered in choosing your sight glass if you still have questions our sales team is happy to assist you so you can begin to see more clearly.

The company is the world’s best GFS Tank supplier. We are your one-stop shop for all needs. Our staff are highly-specialized and will help you find the product you need.

How to Select the Right Sight Glass