Harsco Industrial Air-X-Changers has shipped the largest coolers in the Tulsa-based company’s 60-year history. Weighing in at 180,000 pounds, the Model 204-3Z coolers are 75 feet long, 25.9 feet wide and 14 feet tall. In late September, Harsco AXC shipped the first of four units to be delivered by the end of the year for a customer that will use the coolers in offshore natural gas operations in the Gulf of Mexico. A second unit left the Harsco AXC plant in mid-October.
“We knew from the beginning that the sheer size and complexity of these coolers would pose unique challenges, but I was confident all along that our experienced staff and well established processes would make us successful,” said Harsco Vice President and General Manager Eric Clower.
Maximum Cooling Per Square Foot
Initial planning for the giant coolers began in late 2012, said Mike Thomas of Eads & Associates, the Houston-based sales firm representing Harsco AXC in the project. “Our goal was to deliver units that would give the customer the greatest amount of natural gas cooling possible” for the available space of the offshore platform.
AXC Model Z – a bolt-together horizontal cooler designed for high-horsepower, high-volume applications – was the ideal choice, Thomas added. “It’s a flexible, scalable design suited to a wide range of applications in gas compression and processing – and its increased deck-height means easier drive maintenance, an important benefit on an offshore platform.”
To achieve the needed cooling, gas will flow from the compressor through a six-row assembly of 64-feet-long finned cooling tubes in the Harsco AXC unit. Three 17-foot diameter fans, each driven by a 60-HP electric motor, will force air across the tubes to cool the gas.
With over 315,000 square feet-of dedicated manufacturing space, Harsco AXC had plenty of room to build the giant coolers. Still, inserting the XXL cooler into plant workflow took careful planning, starting with floor space.
The challenges of size were compounded since the coolers will be used in “sour gas” compression, which means natural gas loaded with toxic hydrogen sulfide (H2S) will flow through the unit. As a result, the coolers have to meet strict ASME requirements for coolers used in “lethal service” – standards designed to eliminate leakage of toxics into the atmosphere.
“Basically, it means no leaks – period – with strict weld-inspection to guarantee it,” explained Harsco AXC Manufacturing Engineer Allen S. James.
Manufacturing the headers and cooling tube assembly of each of these giant coolers requires no fewer than 6,000 welds, James said. “With the 4-inch header-plate thickness of these coolers, that would be a tall order even for the best TIG welders we have on board – and for inspectors as well.”
Breaking New Ground: Automated Welding
To maximize both manufacturing efficiency and weld-consistency, Harsco AXC broke new ground, putting automated orbital welding technology from Maus Italia to work in the project, supplementing a labor-intensive, manual TIG process. As the project progressed, Harsco AXC came to rely on this cutting-edge technology for most of the welds required to build the giant coolers, James said – with the company’s top TIG welders driving the automated process.
The human-hi-tech combination – highly skilled welders driving a highly consistent and repeatable automated process – paid off in significant reductions in manufacturing time.
The Maus system cut weld-time by over 50% with comparable improvements in weld quality. Like any other piece of automation, the Maus will do the same job over and over, hundreds of times, in exactly the same way, according to James.
“Being able to put a complex, exacting process on auto-pilot is a big advantage,” James said. “But as any airline pilot will tell you, you still need an experienced, qualified human being in the driver’s seat, to make sure things stay on course.”
Before final shipping, James added, the cooler and its components are subjected to an array of quality-control tests, from X-ray dye-penetrant and microscopic weld exams to vibration, pressure and full run tests.
Harsco AXC plans to ship two more of the jumbo coolers this year. “These coolers will play an important role in solving a big problem the customer has confronted – natural gas shortages in Mexico,” Clower said.