Passing the acid test

In chemical manufacturing, hazardous commodities need to be safely handled along the production and supply chain. Fully aware of the potential risks, chemical manufacturers are extremely vigilant and take great pains to ensure that only the safest, most reliable equipment is placed on the railcars that are used to transport all classes of hazardous chemicals.

Sulfuric acid (H2SO4) is a highly corrosive acid that is indispensable to a number of industries—agricultural, automotive, manufacturing, mining, paper, oil refinery, water treatment—that use it as a commodity chemical in a number of different industrial production processes. In the U.S., the Belgian chemical company Solvay, one of the world’s largest, through its Cranbury, N.J.-based Eco Services business unit, is one of the most prominent producers, suppliers, and transporters of sulfuric acid in North America.

Solvay operates six sulfuric acid production plants—one in Hammond, Ind., three on the Gulf Coast (Baytown and Houston, Tex., and Baton Rouge, La.) and two on the West Coast (Martinez and Dominguez, Calif.)—from which it transports the sulfuric acid to its industrial customer base with a fleet of 800 tank cars. In addition, Solvay Eco Services is the nation’s largest regenerator of sulfuric acid.

“Half of our sulfuric acid volume goes out and is consumed like any other commodity, and after the customer uses it, an empty railcar is sent back to us,” explains Solvay Eco Services Rail Fleet Manager Nick Bizzarrot. “We’re also the leader in the regeneration process. We’ll send high-strength sulfuric acid to customers who use it as a catalyst. When they are done, they send us back the ‘used’ sulfuric acid, which then contains organics. That used sulfuric acid is regenerated, meaning we reburn it, build it back up to strength, remove any impurities, so it’s ready to be used as a catalyst again.”

The breadth of its operation means that Solvay Eco Services has a large amount of sulfuric acid riding the nation’s rails at any one time, which dictates that the tank cars used to transport the commodity must offer the highest level of safety and protection against a catastrophic accident, spill, or release.

Though Solvay leases all but 19 of the 800 tank cars that are used to transport its sulfuric acid, since 1998 the company has mandated that, when possible, pressure relief valves (PRVs) from Midland Manufacturing, Skokie, Ill., be used on any railcars that it leases.

“All of our tank cars are equipped with safety PRVs, and 85% are equipped with Midland valves,” says Bizzarrot. “Ninety-five percent of our tank cars have been built within the past 10 or 11 years. We designed them with full stainless-steel pressure plates, stainless-steel nozzles, stainless-steel manways, and full domes with lids equipped with safety valves. The railcar owners let us execute the valve changeovers; we send them an invoice after the work is completed.“

Data mining through remanufacturing

Solvay had been working off the premise that the PRVs on its tank cars should be inspected and requalified every three years, an expensive process that can also keep a large portion of rolling stock in the shop for maintenance at one time. However, in 2010 Solvay began using Midland’s Valve Remanufacturing Program, in which customers can send valves that have been in the field back to Midland for testing, inspection, and cleaning before they are remanufactured to OEM standards and returned to the owner with a new manufacturer’s warranty.

One of the program’s ancillary benefits is that anytime a valve is sent in to be remanufactured, comprehensive performance data is collected that allows Midland to compare the valve’s performance to industry standards and let end-users make informed decisions regarding maintenance and compliance intervals.

“We approached Midland in 2010 and asked, if we pulled the valves and returned them, could they not only requalify them, but also study them and let us know if three years was too long or too short an interval between inspections?” says Bizzarrot. “That’s where our relationship with Midland as a fact-gatherer began. Since then, we’ve sent about 150 valves to Midland to rebuild and collect data. To date, Midland’s findings are that the interval for the valves can be extended to five years or more, so we have chosen to go to a five-year interval, which is a big savings for us.”

Now, Solvay’s fleet of sulfuric acid tank cars not only benefits from using Midland’s PRV technology, but also takes advantage of Midland’s ability to identify and implement a valve-maintenance and requalification cycle that is both ideal for Solvay as a transporter of sulfuric acid and as a way to ensure the safest handling of a highly hazardous commodity.

“The Midland folks do the best they can to make sure our valves meet our ‘absolute reliability’ standards for safety when handling sulfuric acid,” says Bizzarrot. “To have the valve manufacturer gather the data and validate the data at a single location is a huge benefit. To date, it’s worked like a charm.”