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How to Move a Molecule


In todays society, particularly developed regions of the world, many necessities are taken for granted. Clean and abundant drinking water, a safe environment and readily available products are considered the norm. Turn on a tap, and one expects water. Go to the service station, and one expects an uninterrupted flow of gasoline or diesel fuel.

The same is true with the lubricants industry. Consumers expect high quality consistent with standards mandated by original equipment manufacturers (OEMs). They also expect uninterrupted supply. These expectations form challenges to the lubricants industry and its transition from a regional to global operation.

Base stocks are the lifeblood of the lubricants industry. As performance demands have continued to advance, so has the quality and quantity of high-performance base stocks. The demand for API Group III base stocks has increased rapidly over the past decade, with Asia Pacific now the dominant supply source for the global market. North America remains the primary source for exports of Group II and heavy-viscosity Group I including bright stock. Western Europe has long been the key exporting region of Group I stocks for Africa, the Middle East, Central/Eastern Europe and Latin America. Naphthenics, too, are produced worldwide yet remain a strategic base stock for intercontinental trade.

As this shows, the proximity of base stocks to the target marketplace is not always ideal. This has resulted in the development of an integrated supply network and supporting quality-assurance system to deliver on-specification base stocks to distant customers in a timely and cost-effective manner. Acceptance of this concept took several years to develop, particularly for the merchant marketer.

The global movement of base stocks includes Groups I and II, naphthenics and specialties such as white oils and transformer oils. There are also car-goes of synthetic base stocks, including but not limited to polyalphaolefins from Chevron Phillips Chemical, ExxonMobil Chemical, Ineos Oligomers, Neste and others, and Group III stocks such as ExxonMobil Visom, Petro-Canada VHVI, Shell XHVI, SK Yubase, S-Oil Ultra, and more.

Each base stock requires its own special handling to minimize contamination and maintain integrity. The higher-quality and specialized base stocks require the highest degree of quality assurance. This is a challenge to suppliers, as shipments can include several transfers that can threaten overall consistency and integrity.

Ship to Shore

Consider the transfer of a Group II or Group III base stock from Asia Pacific to a customer in the U.S. Midwest. Geographically, this roughly represents an 8,000-mile journey over several months, and involves product transfers by pipeline, ship, barge, railcar, truck and in selected instances smaller packages (e.g. flexi-tanks or drums). The base stock is initially manufactured to a specification consistent with the feed and refinery operation. For Group III base stocks that are used in synthetic and partial synthetic engine oils and driveline products, care is required to minimize contamination while maintaining key base stock properties like viscosity index (V.I.), NOACK volatility and Cold Cranking Simulator (CCS) viscosity.

There are a number of testing protocols and quality checks observed during the manufacturing process. Some properties are estimated during production using online analyzers or spot sampling. After a production run, the output is fully inspected consistent with its manufacturing specifications and typical properties where specified.

Base stocks are stored on site and, prior to transcontinental shipment, they may be transferred to a tank with proximity to the shipping area. A second sample is taken prior to shipment and fully inspected. The resulting report represents the Certificate of Analysis, or C of A document that will be used for the final destination.

The C of A should describe properties consistent with the manufacturing process, and some selected non-routine tests. For Group II and Group III base stocks, for example, saturates and sulfur contents are measured to ensure compliance with American Petroleum Institute and/or Europes ATIEL definitions for base oil groups. These properties usually are measured once, though additional testing may be required based on customer needs. For some Group IIs, where saturates can be near the 90 percent by weight minimum specification, more frequent testing is required versus those base stocks where saturates are usually in the 95 percent to 100 percent range. The latter is normally observed with Group III and many Group II base stocks produced using a full hydroprocessing scheme.

One property that may be reported on the C of A is polycyclic aromatics (i.e. PCA by IP method 346). This is required to confirm acceptable toxicological properties, and is not an issue for highly refined paraffinic base stocks (i.e., Group III, Group II and most Group I). Other properties that may be reported include foam, demulsibility, copper corrosion, carbon residue, total acid number and water content. These are base stock and application specific. Additional testing will also be required for white oils and transformer oils.

Loading Up

With the C of A completed, the base stock at last is ready to ship. To minimize contamination from other base stocks, transfer lines are usually dedicated at both the loading and unloading sites. Where a single line is used for multiple base stocks, it will be pigged to prevent cross-contamination and dedicated to common base stock qualities. A small section of a common line may exist at the transfer point to and from the ship; however this volume only represents a fraction of the total transferred volume – less than 0.01 percent. Dedicated flexible hosing is used for the shore-to-ship transfers to further eliminate contamination. In many instances, the hosing at both geographic transfer points is owned by the base stock supplier.

Additional care is employed when white oils or transformer oils are transferred, as trace contaminants including sulfur and nitrogen will reduce quality. With transformer oils, a clean and dry fluid is extremely important as water will reduce the dielectric strength of the finished fluid. Transfers to and from the ship may employ special coalescing filters to remove trace water, and nitrogen blanketing of the tank, transfer lines and onboard compartments can be used to exclude water vapor present in the air.

The ship, whether a parcel tanker or barge, will contain several compartments and cargoes, varying with the size of ship. Storing base stocks on a ship is like a jigsaw puzzle involving several quality-related criteria, like compatibility with tank coatings – most are stainless steel though zinc and epoxy may also exist. Base stocks should be compatible with adjacent cargoes to eliminate chemical reactions, and consistent with adjacent storage temperatures to avoid unnecessary overheating and decomposition. Base stocks should be monitored daily for temperature, pressure and cargo level during their transcontinental voyage.

Prior to offloading, base stocks are sampled from each compartment from the ship and a consolidated sample prepared for testing. Samples are visually inspected for color, appearance and the presence of free water. If clear and bright – with no cloudy appearance suggesting the presence of moisture – the compartments are considered ready for offloading.

Coming Ashore

The ship or barge offloading procedure is consistent with loading. At the port or terminal, dedicated equipment is used including pigged or dedicated lines to minimize contamination. Samples are taken from onshore tanks (top, middle and bottom, combined sample for testing) and tested to ensure conformity to that reported at the point of shipment. Retesting occurs when deviations exist, consistent with ASTM protocols. The completed analysis is used to generate a final Certificate of Analysis for the customer.

One protocol frequently required in the overall quality assurance program is laboratory participation in ASTM round-robin studies. Round-robins provide a common sample that can be analyzed by base stock producer, inspection laboratory and customer to demonstrate their testing proficiency and establish a mechanism to address any test bias when observed.

From the terminal, base stocks are forwarded to regional and/or international (e.g. North to South America) customers by a number of transportation modes, including barge, rail or truck. For bulk loading, dedicated and/or pigged lines are again recommended to minimize contamination. The loading point should be shielded to limit water contamination from precipitation. The transport units are inspected prior to loading for cleanliness (i.e. water and visible particles) and the absence of light hydrocarbons. If the tank compartment or shipping container is found unfit, loading will be delayed until additional cleaning and certification is completed.

At the point of loading, a retain sample is collected from each compartment. A visual inspection is normally sufficient to approve the load for shipment, with the sample retained for a period, usually 30 to 60 days, in case a quality incident occurs during the transfer from terminal to customer. The time for shipment will vary with the destination and mode of transportation. Truck shipments are the fastest but most expensive due to the limited volume involved (6,500 gallons or less). Railcars and barges are more efficient – with capacities around 24,000 gallons for the former and 10,000 to 30,000 gallons for the latter – but mean a slower delivery to the final destination.

Point of Delivery

At the customer site, offloading includes quality procedures consistent with the loading process. This includes shielding for moisture control, and dedicated and/or pigged offloading lines. When a common line is used, the products are again segregated by family to minimize contamination. A final sample is collected by the customer and tested against the C of A.

Testing varies by customer, but will usually include appearance, water (i.e. crackle test), kinematic viscosity and V.I. Unique base stocks like white oils and transformer oils will undergo additional testing, consistent with their technical requirements.

Any discrepancies throughout the shipment from manufacturing site to customer can be traced using the series of samples collected during the transfer process. With transcontinental movements, six or more samples may be obtained. This reflects a highly managed quality system, and a key service offering from supplier to customer.

With sales of base stocks today, regardless of distance and delivery time, quality assurance is a key element of the delivery process. This has been successfully demonstrated for Group III base stocks over the past decade and led to an international trade where supply point no longer coincides with end-customer location.

As the global trade of base stocks and other valuable products continues to escalate, quality assurance and customer care remain key requirements. This seamless movement of consistent quality in a timely fashion creates a comfort level with customers – much like seeing a clean, clear and unlimited supply of water whenever they turn on the faucet.

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