Minimizing Risks

Chemical-circulation unit significantly reduces equipment and manpower required for cleaning projects.
Minimizing Risks
Vollie Pendergrass (left) and Nicole Nix, lead service engineers, clean heat exchangers at a California petroleum refinery. After they were decontaminated, an inspection revealed a significant amount of iron sulfides (FeS) remained in the exchangers and would require an acid wash to dissolve them. The H2S rig was utilized for this cleaning because hydrogen sulfide gas is liberated during the acid wash and the rig scrubs the H2S.

Decontaminating various oil-refinery equipment – pressure vessels, pipelines, exchangers, condensers and the like – used to be an equipment- and labor-intensive job for crews at Delta Tech Service Inc., a national chemical-cleaning company based in Benicia, Calif.

But that changed dramatically when Jeremy Siebels, the company’s project manager and supervisor, fabricated a closed-loop, trailer-mounted, chemical-circulation unit that significantly reduces the amount of on-site equipment and manpower required for cleaning projects. That, in turn, boosts long-term productivity because those freed-up workers can instead work on other projects.

“Before, we used three circulation tanks, portable pumps and scrubbers, all connected with hoses, which increased the risk of leaks because of all the connections,” Siebels explains. “This closed-circulation unit minimizes those risks.

“In addition, we also needed more people on site to monitor each tank and pump … and the setup time was quite a bit longer compared to what it is now,” he adds. “Depending on the size of a job, we might have needed six to eight guys and three to four trucks, compared to four guys and one truck now. It’s more cost-effective for our customers too, so it’s a win-win situation. We can do more jobs with the same amount of people.”

The Delta Tech crews often work during scheduled maintenance shutdowns at refineries, where speed, safety and efficiency are top of mind. With so many other contractors also working at the same time, it really helps that the circulating unit occupies a much smaller footprint – the trailer is 8 feet wide and 20 feet long – than when the crews needed three separate tanks and trucks.

“We used to take up about triple the space we take up now,” notes Siebels, who studied civil and structural engineering and designed the rig with input from field crews. “And it’s safer to work too, because there aren’t so many hoses to trip on. Plus, the unit includes a work platform [catwalk] instead of using a ladder welded to the side of a tank, so that offers a much safer way to monitor the tank.”

The unit primarily consists of a centrifugal pump made by Summit Pump (rated at 2,200 rpm at 68 psi); two carbon-steel tanks manufactured by Industrial Service & Fabricators Inc.; and a tandem-axle trailer fabricated by Pac West Trailer Co. The larger tank (800-gallon capacity and rated at 100 psi at 200 degrees) holds cleaning solutions; in the smaller tank (420 gallons rated at 100 psi at 200 degrees), dangerous gases – mainly hydrogen sulfide – get “scrubbed,” rendering them safe for disposal.

The unit was designed for a gross vehicle weight of less than 10,000, so drivers do not require a commercial driver’s license (CDL). “That gives us a huge advantage,” Siebels says. “We’re a 24-hour-a-day company – customers could call us at any time. But since it doesn’t require a CDL, all our employees can drive it.”

More often than not, crews at Delta Tech – which also offers hydroblasting, decontamination and vapor-cleaning services – encounter hydrogen sulfide gas on jobs; it’s either present as a byproduct of the crude-oil refining process or produced when crews use a cleaner like sulfuric acid. Delta Tech mainly uses the unit for descaling with acids in oil refineries because it can scrub the dangerous, highly flammable H2S gas, but Siebels notes that it’s designed to be utilized in aspects of the company’s cleaning services. It can clean with the company’s proprietary soap products or other solutions.

Here’s how the unit works: After a cleaning solution is mixed in the main tank, it’s pumped through a refinery’s process equipment and returns to the main tank. The vapors that enter the main tank are routed to the scrubber tank. The scrubber tank is filled with a predetermined amount of water and concentrated sodium hydroxide. As the toxic H2S vapors bubble through the solution, the resulting chemical reaction dissolves the vapors.

Multiple valves enable operators to isolate the two tanks and use them independently, and the inclusion of a third suction point allows crews to use just the pump alone.


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