Without question, liquid storage terminals play an integral part in the ongoing success and relevance of a wide array of industries worldwide. They serve a vital role in the global economy as transfer points from one mode of transportation to another and as safe, secure storage locations until product transfer is needed. The list of products that move through and are stored at liquid terminals is long: from raw crude oil to refined petroleum products, from animal fats to solvents and caustics.
Sometimes, however, money- and time-wasting "soft spots" exist in the liquid-handling systems that deliver the goods. Not all systems are created equal, nor are they created to take optimal advantage of the systems as they have evolved. The problem is, how does a terminal operator ensure time, money and energy are not wasted as they play their part in the supply chain?
For the purposes of our discussion, the classification of liquid storage terminals falls into two general categories:
- Bulk Terminal: A facility used primarily for the storage and/or marketing of petroleum products or chemicals, which has a total bulk-storage capacity of 50,000 barrels or more and/or receives products by tanker barge or pipeline. Estimates put the number of bulk-terminal operators in the United States at roughly 1,500 companies.
- Bulk Station: A facility used primarily for the storage and/or marketing of petroleum or chemical products, which has total bulk capacity of less than 50,000 barrels and receives its products by rail tank car or truck. There are approximately 2,860 companies that operate bulk stations in the United States.
A generic term for both bulk terminals and bulk stations is tank farm, which is defined as "a group of supply or storage tanks placed together for storage of oil, chemicals, etc." Using the definitions above, all bulk terminals and bulk stations can be described as tank farms, but not all tank farms can be called bulk terminals or bulk stations.
While these general classifications regarding the capacities of liquid storage terminals remain appropriate, the change in terminal operation comes in the constantly modifying and more specific product configurations that pass through them, as well as the types of ancillary operations that terminal managers are now asked to perform on a regular basis.
Figure 1. Sliding vane principle
Diversify and Conquer
When most people think of liquid storage terminals, the first image that comes to mind is the giant holding tanks located at petroleum-refining complexes. These tank farms feature acres of storage tanks, with capacities reaching 50,000 gallons per tank. These facilities serve as a vital hub in the storage and dispersal of numerous types of liquids, including petroleum products and petrochemicals, which are crucial in the world's transportation and manufacturing sectors.
In reality, refinery tank farms represent a small portion of the liquid-storage terminal universe. In addition to crude oil and its petroleum derivatives, tank farms serve as an essential link in the distribution of a wide variety of other products, including:
- Mainstream and niche chemicals (solvents, fertilizers, pesticides and acids)
- Alternative fuels (ethanol and biodiesel)
- Vegetable oils (for food products)
- Animal fats and oils (for cosmetics)
At some point, any liquid that can be transported in bulk-by ocean-going tank ship, barge, railcar, tank truck or pipeline-is stored and transferred at a liquid terminal with the storage tank operating as the interface between the various transportation methods.
Transferring, handling and storing these liquids can be a daunting task for the facility manager, but these terminals are not just being asked to be a link in the supply chain; they are asked to do much more, especially among chemical distributors. For example, while the large port terminals may just load and unload raw and finished products, the bulk plants may later add blending operations (i.e., ethanol, biodiesel, petroleum additives, etc.) to the loading and unloading duties. Then, at the distributor level, loading, unloading and blending routines are typically joined by mixing and packaging operations before finished products are shipped to the end-user.
Somewhat oddly, when liquid-storage facilities are initially built, they often do not make use of the best equipment, relying instead on brands and technologies that get the facility "up and running." Then, after the facility has been in operation for a while, the operators identify the inefficiencies and weak links in the enterprise and look to "find a better way." One possibility is sliding vane pumps.