Reprinted from May 2010 | HydrocarbonEnginEEring |

Tanks - Gary Carson, Equamark Inc., USA, describes the design of a Florida tank facility with high tech manifolds to speed loading and unloading.

silent links vital to energy distribution

Steel aboveground storage tanks are a key link in the energy transportation system, a system that ensures adequate supplies reach the locations of demand when needed. Yet tanks are sometimes taken for granted and their

important roles in distribution not well understood. Often hidden from view in industrial locations, tanks play vital roles at key stages of getting the product from source to the end user, and they handle

a lot of product.

Supply versus demand locations, a major mismatchIn 2008, the US imported a net 11.1 million bpd of crude oil and consumed approximately 7.14 billion bbls of oil overall.

Approximately 57% of US consumption is imported. Most of Europe is even more dependent upon imported crude oil as are the large industrialised and industrialising economies of Asia such as Japan, China and India.

Because of the wide variation between the locations of production and the locations of heavy demand for crude oil and petroleum products, the transport and storage of crude oil and petroleum products is critical to ensuring that the product gets to where it is needed at the time it is needed. Billions of bbls of crude oil and petroleum products are transported to meet this demand.

According to Global Storage Agency Limited, the global tank storage market capacity today is approximately 2.75 billion m3 (726.9 billion gal.), which is approximately 60 days of total refinery throughput. Of this, approximately 2.4 billion m3 (87.3%) is captive, or

| HydrocarbonEnginEEring | Reprinted from May 2010

controlled directly by the crude oil producer, processor or transporter, and 0.35 billion m3 (12.7%) of capacity falls within the independent tank storage sector, facilities whose owners lease storage capacity to owners and operators involved in production, marketing, transport and/or refining.

Storage tanks may be located at a tank farm, a terminal used for transport purposes, a gathering system near a production site or a refining operation. These facilities interconnect with modes of bulk liquid carriers such as oceangoing tank ships, tank barges, tank trucks, tank rail cars and pipelines.

new storage tanks to meet demandIn January 2007, UNI Engineering, Inc. (UNI), a provider of engineering and design services to industrial, commercial and governmental clients, started the detailed design of a new bulk storage tank terminal in Port Canaveral, Florida. Established in 1977 with headquarters in Hightstown, New Jersey, USA, UNI services refineries as well as the pharmaceutical, chemical, manufacturing and processing industries. The Florida project falls into the transportation sector. This sector includes many of the larger tanks, with over 1600 tanks of 100 000 bbls (4.2 million gal.) capacity or greater. The marketing and refining sectors also have higher numbers of large tanks as a proportion to their totals. The production sector tanks tend to be smaller, due in part to their often remote locations and transportation considerations.

High tech automation speeds loading and unloadingThis grassroots facility in Florida designed and engineered by UNI consisted of 24 bulk storage tanks, which varied in capacity from 10 000 - 150 000 bbls. These include both conical fixed roof and internal floating roof tanks designed for the storage and eventual distribution of gasoline, blend components, distillate and residual fuel oils.

A key part of the scope of work were three marine loading platforms with an inbound loading capacity of up to 20 000 bph and an outbound capacity of up to 10 000 bph, designed to expedite the process of being served by the worldwide market. Loading and unloading was to be performed through two 18 in. product transfer manifolds, which were also included as a design deliverable. The manifolds allow loading and unloading bulk product to and from the tanks to be done efficiently and safely, and with as much automation as possible, while delivering the lowest piping and equipment costs. This automation of the loading and unloading process delivers efficiencies that benefit the owner as well as the transporter and ultimate consumer of the product.

Increasingly stringent tank standardsWhen it comes to the construction of these types of storage tanks, designers and engineers today must follow a number of stringent guidelines and regulations that have evolved over the years.

In 1922 Underwriters Laboratories created the first US standard for aboveground storage tanks. UL 142 - Steel Aboveground Tanks for Flammable and Combustible Liquids was created to provide standards that people could trust and facilities that insurance companies would insure. Formed in 1919, the American Petroleum Institute (API) developed its first standard, which was API-12A for steel aboveground storage tanks with riveted shells. In 1935 API-12C was issued for welded oil storage tanks. The transition from riveted to welded tanks was slow at first, due in part to suspicion regarding variable weld quality at the time.

By 1951 API-12C was superseded by API Standard 650, which is still the standard for designing new tanks in much of the world today. Welded tanks for oil storage, such as those in the Florida project, fall under API 650. This standard establishes the minimum requirements for material, design, fabrication, erection and testing of vertical, cylindrical, aboveground, closed and open top welded carbon or stainless steel storage tanks. The sizes and capacities vary although internal pressures approximate atmospheric pressure. This standard applies only to tanks whose entire bottom is uniformly supported and to tanks in non-refrigerated service. Appendix M of the code allows design temperatures of up to 260 ˚C (500 ˚F).

Another standard for storage tanks, API 620, covers low pressure (up to 15 psig), cylindrical and non-cylindrical tanks and capabilities for low temperature operation. The API 653 standard covers the inspection, repair, alteration, testing and rerating of tanks after they have been put in service. It provides the minimum requirements for maintaining the integrity of welded or riveted, non-refrigerated, atmospheric pressure, aboveground storage tanks.

Stringent local regulationsFlorida, where this UNI project is located, has among the most comprehensive environmental regulations of any state in the US when it comes to steel aboveground storage tanks used for crude oil and petroleum products. This is primarily because 90% of the state’s drinking water comes from groundwater, with some less than 5 ft below the surface. This is why the Florida Department of Environmental Protection (FDEP) aboveground storage tank regulations, FAC 62-762, set very strict guidelines, to ensure the state’s environmental safety and a potable water supply for its citizens. The state is well known for its swamps and marshes with a diversity of fauna and flora, with much of it highly susceptible to easy damage from encroachment and other environmental conditions. Also many of these inland and coastal regions feature very slow moving tidal currents that make it very difficult to stop pollution ingress into this fragile environment once an incident, such as a leak or spill, takes place. This is why, even with an effective bund area, more stringent steps are needed to ensure the safety of the ground water.

addressing environmental concerns in FloridaA complete range of regulatory requirements had to be met, including site plan approvals, environmental permitting (air pollution, storm water discharge, wetlands, facility lighting impacting turtle breeding), Florida Coast Guard regulations, Florida Department of Law Enforcement and port authority security regulations, NFPA, and the Florida Building Code, plus the USEPA Oil Spill Prevention Program (40CFR Part 112), and the state aboveground storage tank regulations previously mentioned.

One requirement of FDEP outlined in FAC 62-762 is that all components utilised for spill prevention must be on an approved equipment list. Also, all tanks at the Port Canaveral facility were to be equipped with a leak collection system between the tank bottom and pile cap. In the event of a bottom leak, product would be detected in a leak detection sump. Groundwater is also protected from potential spills by

Figure 1. Port Canaveral, Florida, USA. Bulk storage tank manifolds, designed by Uni Engineering, new Jersey, USA, for the loading and unloading of bulk products and transportation tanker charging. The manifold design includes 20 pumps, 300 valves and almost 13 000 ft of pipe.

Reprinted from May 2010 | HydrocarbonEnginEEring |

virtue of an HDPE liner system within the entire secondary containment system. In addition, all tanks are equipped with a real time tank gauging system as well as a redundant high level alarm system.

Soil and subsoil conditions were also a critical consideration for the tanks’ foundation design. The tanks were placed on 12 in.2 square, 120 t precast concrete piles supporting a reinforced concrete pile cap that would eventually bear the load of these tanks, with a full weight of up to 23 000 t each. Optimising foundation design was key to enabling the client to build at this site along the Florida coast. These tanks were to sit within a bund area, with 6 ft high perimeter walls, designed to contain any spills. Regulations specify that the volume of walled area should be greater than 110% of the capacity of the largest tank in the bund area. All

storm water collected within the bund areas is treated with a coalescing type oil/water separator prior to being discharged to surface water under the facility’s NPDES permit.

Switch to 3d expedited UnI project, saving time and moneyInitially UNI began the design of the tank terminal project in 2D using AutoCAD. While the design of the tank field was straightforward, the complexity of the two manifolds would prove too difficult to develop in a 2D format. The decision was made to move forward and design the manifolds in 3D using an existing inhouse 3D software package. However, the existing software did not offer the level of intelligence and flexibility that was needed to properly create a design of this magnitude. Delays were caused by problems using the cumbersome interface.

Realising it could not continue in this manner and complete the project, UNI decided to look for another 3D package. It reviewed several piping packages based on the following criteria: ease of 3D modelling, isometric extraction including bills of material, fully customisable to accommodate pipe support location and callouts, compatibility with Intergraph Caesar II for pipe stress analysis, structural modelling, ability to interface with process and instrumentation diagram (P&ID) software, project scalability, minimal hardware investment and, critically important, a short learning curve.

After review, Intergraph CADWorx Plant Professional was selected because it was able to meet both expectations of UNI and the client’s needs. After a brief familiarisation with the software, the company’s lead piping designer was able to easily customise CADWorx Plant’s piping specifications and user shapes required to proceed with the design.

CADWorx Plant allowed the company to develop three manifold concepts, extract isometrics and provide a preliminary structural support and platform package for the bidding process on schedule. As the design process continued, the piping group used the CADWorx Plant bidirectional link with Intergraph CAESAR II for stress analysis to provide adequate flexibility in the piping system.

When completed, the manifold incorporated eight bulk transfer pumps, 12 truck rack loading pumps, 160 automated and 140 block valves, controlling product through 13 000 ft of mostly 10 - 18 in. diameter pipe. A more traditional method would have been to locate a dedicated pump at each tank. However, a centralised manifold allowed much greater operational flexibility and redundancy, and a reduction in the number of pumps. In all, the total area taken up by the manifold was 190 x 150 ft; a very tight area considering the piping and controls involved in creating a workable and stress approved design.

The time saved using CADWorx Plant on the manifold area prompted UNI to convert the balance of the design project to 3D as well. Extracting bills of material was instant and accurate, design changes were easily achieved, and client review and comments were made with confidence, eliminating the ambiguities that can occur in 2D design. Facility wide the total length of pipe work in the design came to approximately 75 000 ft. An additional jet fuel filtering and delivery system is also in the works.

After seeing the savings and improved efficiencies on this Florida tank project, UNI then implemented CADWorx Plant in all new projects regardless of whether it was a grassroots facility or a retrofit project. It has been able to increase efficiency, improve overall accuracy, streamline costs and, most importantly, minimise construction errors, all of which save its clients time and money. It attributes the success to the capabilities of the software combined with the technical support provided by the Intergraph team.

ageing oil storage tanks, recipes for failureAnother ongoing challenge for the industry is the ever increasing age of existing storage tanks. According to the US Environmental Protection Agency (EPA), steel aboveground storage tanks begin to deteriorate at 15 years of age. An API study some years ago estimated

Figure 3. Ashland Oil tank failure, Floreffe, Pennsylvania, January 1988. A 120 ft diameter, 50 ft high tank catastrophically failed, without warning, discharging 3.7 million gal. of diesel. 500 000 gal. found its way into the local river. Failure was due to an undetected flaw in the base metal of the tank.

Figure 4. Amerada Hess tank failure, Perth Amboy, new Jersey, September 1990. A lake of oil covers the ground at the Amerada Hess facility, where 6 million gal. (22 700 m3) of oil was released when foundation collapse led to tank failure.

Figure 2. CAD image of the storage tank manifolds.

| HydrocarbonEnginEEring | Reprinted from May 2010

that 90% of aboveground steel storage tanks in the US were already over 11 years old, so the proportion of ageing tanks today is even higher. In the marketing, refining and transportation sectors, approximately 75% of tanks are over 20 years old, according to industry estimates.

On 2nd January 1988, a storage tank collapsed at the Ashland Oil facility in Floreffe, Pennsylvania, spilling 3.7 million gal. of diesel fuel, some of which found its way into the Monongahela River, covering the water and river ice with diesel. The tank, built in 1940, had been disassembled and reassembled at the site in 1987. When finished, the tank was 50 ft high and 120 ft in diameter, with a surrounding dike that would hold 150% of the tank capacity. The welds were x-rayed and leak tested, and the results indicated that none of the welds needed rework. However, the tank failed catastrophically, without warning, creating a tidal wave with at least 500 000 gal. of diesel ending up in the river, causing a major environmental problem so severe that the entire water supply of South Pittsburgh had to be shut down for two weeks. The investigative team determined that the failure was caused by an undetected flaw in the base metal of the original tank, rather than the actual welds, as had been considered initially as a possible cause. Ambient conditions as well as pressure from the filled tanks caused this flaw to yield catastrophically.

In September 1990, an Amerada Hess storage tank holding 6 million gal. (22 700 m3) of No. 6 oil failed in Perth Amboy, New Jersey, with a lake of oil soon covering the ground. This failure was caused by the collapse of an underground piling supporting a portion of the wall. An open valve on the inside of the surrounding concrete safety wall combined with a malfunctioning valve on the outside allowed 5000 gal. (19 m3) to reach the Arthur Kill Waterway. This incident was caused by a ‘perfect storm’ combining structural, maintenance and human failures.

The piled foundations and the installed leak protection, as incorporated on the Port Canaveral project, make the above disasters very

unlikely, by providing foundations with minimal chance of subsidence, and the early detection of the leaks that often lead to catastrophic and disastrous consequences.

conclusionFirms such as UNI and the owners and operators of tank storage facilities will require the most leading edge tools available as they are faced with the challenges of designing and engineering tank facilities in new environments and locations in the future, as energy demands shift globally and production and transportation services seek to address this demand.

According to the US Department of Energy, world energy consumption is projected to increase by 44% from 2006 - 2030. The largest projected increase in energy demand is for the non-OECD economies. In 2006, 51% of world energy consumption was in the OECD economies, but in 2030 their share is projected to fall to 41%. China and India together accounted for only approximately 10% of the world’s total energy consumption in 1990, which almost doubled to 19% in 2006. By 2040, they are projected to make up 28% of world energy consumption. In contrast, the US share is expected to fall from 21% in 2006 to approximately 17% in 2030, and Europe will also experience a similar proportional decline.

Many of the newer tank facilities that will be needed for storing product in transit will be in the midst of large and growing population centres in Asia and elsewhere. The engineering challenges will be many. Stringent environmental protections will be required to ensure the maintenance of supplies of potable water and food, plus a safe environment for people living nearby. All of these issues must be considered as the industry attempts to meet and keep up with the world’s growing and shifting demands for energy and the storage facilities that will be required.