Today’s tank buyers face tough questions: What kind of tank is needed? What features work best for the material to be stored and handled? What size tank should be considered? Which are the best vendors? Will the tank chosen meet the specified budget?
Tank buyers often make purchase decisions based on cost. Companies in the market to buy a tank or silo think about longevity–which translates into getting the most economical tank that lasts the longest time.
While cost is important, several other factors will also affect your level of satisfaction when purchasing a tank. To this end, the five key points to consider when researching a tank purchase include: construction materials, proper design, coatings, characteristics of the material to be stored and total lifecycle cost.
Proper DesignThe material you choose for tank construction will likely depend on the volume of material to be stored. Concrete and field-welded tanks are well suited for storing an exceptionally large volume of material.
However, for most storage jobs, bolted and factory-welded tanks are an appropriate choice as they require less manpower to install, are quicker and easier to erect, and offer more features and options.
Common construction materials for field-welded, factory-welded and bolted tanks are carbon steel, stainless steel and aluminum.
To ensure the most effective design of your tank or silo, you must first determine the parameters of the product to be stored. Consider the product’s characteristics, features that will provide the best flow for your product, the tank’s ease of use and expandability, and your organization’s unique needs, such as available space.
Another critical element to consider when choosing a tank, moreover, is the characteristics of the material to be stored. Are you familiar with your product’s flow requirements? They are best determined by a flow test, which should be done prior to considering a tank.
Flow testing will determine the proper degree for the hopper and hopper outlet, in addition to providing you with the requirements for flow or blending equipment.
Also consider your product’s abrasiveness and the bulk density of the product. Each material has its own unique characteristics, whether dry or liquid chemicals, plastics, minerals, wood, food, potable water or wastewater, etc. Understanding the material’s unique characteristics will help you figure out the features you need (and don’t need) to construct the most effective tank for the job.
Design CriteriaThe available space in which you have to build the tank is another key consideration. Tanks come in all shapes and sizes–tall and slender to short and wide. Design criteria, such as natural boundaries, wind loads, deck loads and seismic conditions, will affect the design you choose.
Tanks built in areas with high wind and seismic conditions, for example, are better built with a shorter height and wider diameter. On the other hand, tanks that must fit into tight spaces will likely be tall and slender.
Additionally, be sure to consider whether the tank may need to be expanded or moved in the future. Concrete and field-welded tanks can be costly and time-consuming to expand. Bolted tanks are expandable; however, the foundation and lower half of the tank must be originally built to accommodate the additional weight of an expansion.
Keep in mind that vertical expansion of an existing bolted tank is often more cost effective than constructing a new tank. If available space is a limitation, consider constructing a small expandable foundation with a tank design that is capable of expansion.
Features & OptionsThe world’s leading tank manufacturers offer the ability to design a tank or silo customized to suit your specific storage and handling needs. Some manufacturers also have the ability to install components provided by the customer at the factory, which reduces time and cost for field installation. Common factory-installed components include bin activators, blending tubes, flow devices and bin vents. Be sure to ask your vendor about these items.
In the same vein, a variety of custom features and options are available for today’s tanks, such as:
- Access platforms.
- Spiral stairways.
- Elevated drive-through designs (accessible by both railcars and trucks).
- Custom components.
- Support structures.
- Deck filter flanges.
- A cone-hopper or flat bottom (which is dependent upon the frequency of filling and emptying needs).
- Level indicator openings and nozzles.
- Pressure relief devices.
- Other safety features.
Factory application offers the most durable and controlled coatings on all pieces. Examples of coatings include epoxy (which bends without cracking or tearing), glass fused to steel (Vitrium™), plus coatings specifically designed to withstand high heat and cold environments, or even acidity.
Additionally, bolted and factory-welded tanks may receive their coatings at the factory. Field-welded tanks obtain coatings after being fully erected in the field. Extensive surface preparation, such as abrasive blast cleaning, must be done to assure maximum coating adhesion and performance. Likewise, if concrete is being field-coated, blast cleaning of surfaces to provide profile is required for immersion service applications.
Be aware that field-coated tanks are subject to the environment during the drying process: The quality of the coating process may be affected by not only rain, humidity, dust and temperature, but also the quality of the on-site team erecting and coating the tank.
Weather may also play a role in the timetable for installation and hookup of field-welded and concrete tanks.
Choosing A VendorChoosing a vendor may be just as important as choosing a tank. Consider the experience of the manufacturer–for example, how long has the company been in business, what is their volume sold, what is their experience in your country and market, etc.
Ask whether the company uses the highest quality materials available or “commercial” grade. Tank manufacturers should be familiar with your industry’s standards and unique product requirements. It is also wise to choose a tank manufacturer with third party accreditation, such as ISO 9001 quality certification.
Total Lifecycle CostFinally, when it comes to cost, be sure to analyze the total lifecycle cost of each tank that you consider. Reviewing only initial construction costs will not take into consideration future maintenance and expansion. It is a good idea, furthermore, to request that all tank manufacturers provide an analysis of life expectancy and cost.
For some extra guidance, you can find an example of a total lifecycle analysis for epoxy-coated and glass-fused-to-steel-coated tanks at www.columbiantectank.com. While your decision may rely on cost in the end, make sure you compare apples to apples with each cost estimate.
Columbian TecTank Power Generation Product Manager Dave Davis has more than 27 years of experience in bolted tanks for both liquid and dry bulk use. Columbian TecTank, an ISO 9001-certified company, manufactures both bolted and shop-welded tanks.