Every industry professional understands in theory that outdated instrumentation costs money – but making a change can seem more costly and vastly time consuming . One producer of liquid asphalt, however, proved how important updated instrumentation technology is in harsh reality for all to see.
The producer had 42 tanks for liquid asphalt and its level devices were manual tape-type instruments that were very unreliable, as they were prone to sticking, breaking, and freezing, and the guide cables would get gunky build-up. In fact, these route-based measurements could not provide data to indicate product loss or track wrong product transfers, and there was no compensation for dramatic level swings in very large tanks due to temperature changes.
The issues caused by the outdated system were twofold – a huge impact on inventory management and an even more significant issue of safety. The company needed to reconcile inventory to the nearest 1000th, but inaccurate level created a monthly error rate of up to +/-5 percent, which could equal up to $1,125,000. These kinds of inventory swings were a critical financial risk since it’s difficult to defend the errors in an audit for revenue reporting and tax purposes.
The safety issues were realized a few years earlier when a tank exploded and it was determined the cause was a frozen tape gauge. The plant engineers and operations also realized that if a leak had happened over a weekend, it could have gone undetected for days, leading to a major safety and environmental risk.
The plant realized it needed to bring automation to a 1940s terminal with a solution that provided continuous, accurate level measurement; was easy to convert to tonnage for inventory management; included a ground-level display for visual redundancy, which was a new insurance requirement after the accident; and was easily accessible and maintainable. However, the size of the plant footprint and limited existing wiring to tanks made wired pressure instruments cost-prohibitive.
The solution was to install a wireless gateway in the center of the site grounds and build a wireless mesh network that connected each of the RosemountTM Wireless 2051L pressure transmitters that were outfitted on each tank. Emerson Wireless THUM™ Adapters were added to existing radars on mix tanks and two Rosemount 648 wireless temperature transmitters were added on pipe clamp sensors to boost signal strength in some areas. With the new system, all product is stored, tracked, and inventoried, and volume is calculated using API density and temperature correction formulas.
Since the implementation, there haven’t been any safety incidents related to poor level control and the company has had no irreversible off-spec product blends. In addition, the company has saved between 40 and 80 hours per month by the accounting team reconciling inventory, and dropped from having potential average error rates of $500,000 or more to around $2,000, and as a result, they have less uncertainty with tax audits.
Earlier this year, the new system more than proved its worth. A 6-inch valve containing 1.5 million gallons of liquid asphalt cement at 300o F broke in half on a Friday evening. The asphalt cement began draining from the tank at a rate of 800 gpm. The wireless system notified the terminal manager via text and e-mail, so it was caught and addressed very quickly. If they had the manual system, that leak would likely not have been discovered until the following week and would have lost approximately $3.5M worth of liquid value, plus clean-up costs and construction costs would have exceeded $5M.
The implementation of 21st century instrumentation has given the plant the ability to more effectively control inventory and batch processes as well as improved safety.
Have you seen examples where updated instrument technology has saved you money?
Lance Berry | General Manager | Rosemount Tank Gauging North America, Inc.
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