In today’s economy, tank operators are seeking means of improving the financial and operational performance of their tank assets. Terminal operators and their customers are concerned more than ever with increasing working capacity, reducing heel, extending service life and reducing emissions and evaporative product loss. This article takes a closer look at these key concerns and considers some potential strategies to improve performance, increase tank working capacity and reduce heel.
Tank working capacity is driven by the distance the floating roof can travel when the tank is cycled. This distance is, in turn, driven by the constraints at the top and bottom of the tank and the depth of the floating roof system. Increasing working capacity can result in operational efficiencies and drive increased revenue. Heel reduction is a related, but separate issue. Heel refers to the inventory that is stranded at the bottom of the tank between the tank bottom and the floating roof when the roof is at its lowest operating position. For the owner of the stored product, this inventory acts, financially, just like a fixed asset, in essence tying up working capital indefinitely.
Reducing this heel has a direct positive impact on cash flow. For example, replacing a traditional steel pontoon IFR with a low profile, suspended IFR system can allow for up to an additional 2 feet in roof travel. On a 150 foot crude storage tank, this equates to over 6,200 barrels, or more than $620,000 of immediate positive cash flow. Design details, such as the use of drain dry sumps or low profile nozzles, can aid in achieving these results. The use of a mesa or plateau style bottom (a raised bottom which displaces a portion of the liquid) can also achieve significant heel reduction; however, this method does not result in the working capacity increases that can be achieved by lowering the IFR.
Many factors influence working capacity and heel:
- Depth of the floating roof and seal systems
- Floating roof support method and design details
- Equipment located under the floating roof (for example, mixers, diffusers, piping and hoses)
- Safety buffers above and below the floating roof
- Inlet type and position
- Bottom treatments such as drain dry sumps or mesa bottoms
Best practice #1 – Do the math
Begin with a thorough operational analysis to assess the current working capacity constraints and partner with a provider that can offer options. Options vary and can include flush mounted dome roofs; suspended, low profile IFRs and seals; pontoon modifications, and alternative bottom fill systems. These details can have a big impact on financial performance.
Extending service life
Increasing out of service intervals and reducing unplanned outages can add hundreds of thousands of dollars, even millions to the bottom line. In an effort to make tank operations more efficient and increase profitability, many operators are specifying materials with longer life spans and fewer maintenance requirements.
Storage terminals near ports typically have high cycle frequencies and flow rates, increasing repetitive stresses on floating roof and seal systems. Thoughtful selection and design of these systems can mean the difference between 10 and 20 year service intervals. In addition, most unplanned maintenance can be avoided by specifying systems and materials that are built to last and designed to perform under the types of dynamic loading situations the system can be expected to encounter.
Years ago, when the first aluminum IFRs were brought to market, these technologies were underdeveloped and unproven. Fast forward 40 years and multiple aluminum roof manufacturers have evolved and offer extremely high quality, well engineered and cost effective systems that offer significant benefits over traditional steel options.
Some of these benefits include:
- Aluminum does not require painting or coating
- Aluminum domes do not require the periodic structural repairs commonly required with cone roofs
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