Compressor manufacturer improves cutting process

It wouldn’t be much of an exaggeration to say that natural gas is nature’s wonder fuel. Also known as methane, this abundant, inexpensive, versatile compound (CH4) is used by utility companies to generate electricity; in homes to provide the heat for furnaces, ovens, and clothes dryers; and by a small but growing number of vehicles for power. It’s also used as a feedstock for many other products and industrial processes. For producing heat and power, it’s favored over other fossil fuels because of its environmental advantages. It produces about 30 percent less carbon dioxide than petroleum and about 45 percent less than coal.

Despite its many advantages, natural gas often presents two difficulties: extraction and transportation.

First, because vast amounts of natural gas are locked up in shale deposits, which are impermeable, they can’t be extracted economically by using traditional drilling. Instead, hydraulic fracturing (fracking) creates fissures in the shale, freeing the gas, and horizontal drilling makes it recoverable. This combination of processes has made many of these formerly hard-to-reach deposits economically viable in recent years.

Second, because natural gas deposits are rarely found where the gas is consumed, it must be transported. Decades ago no efficient transportation method existed, so much of it couldn’t be put to good use. Natural gas compressor systems can compress natural gas up to 3,600 pounds per square inch (PSI), reducing its volume 99 percent, making transportation viable.

While these technologies aren’t new, the combination of capable processes and increasing demand, for this energy source has fueled the increase in natural gas extraction in recent years. Until July 2000, the retail price never exceeded $9 per thousand cubic feet (MCF), and monthly production rarely exceeded 2.1 trillion cubic feet (TCF). In July 2000, the price finally broke through the $10-per-MCF barrier and it kept climbing. Producers responded by extracting and processing much more natural gas than ever before.

Compressor Systems Inc., Midland, Texas, a manufacturer of natural gas compressors, recently upgraded its cutting equipment to improve its ability to serve this growing market.

Compress It, Ship It

CSI was founded in 1971 to fabricate, sell, lease, and maintain custom-made natural gas compressors. It manufactures two compressor styles, reciprocating (piston) and rotary (screw), powered primarily by Caterpillar and Waukesha engines. It also fabricates the vessels used for storing natural gas.

Because natural gas is flammable, it goes without saying that the quality of the compressor systems and storage vessels must be first-rate. Internal explosions aren’t a hazard—oxygen isn’t normally present in natural gas deposits, and without oxygen, combustion is impossible—but the systems cannot leak.

“All of the piping in our compressor systems and all of the components in our pressure vessels must comply with AMSE boiler code,” said Curtis Stone, manager of the company’s support shops.

For the most part, the pressure vessels require round holes, but on occasion they need oblong holes. For cutting to length and making holes, the company used a 4-axis NC oxyfuel machine. The process was suitable for its needs, but the hole quality wasn’t quite up to par.

“The pipes always needed a lot of manual work—deburring and cleanup,” Stone said. “Another problem was that the machine had a chuck at one end that clamped 30 in. of pipe, so we’d often waste 30 in. on each length of pipe we fabricated. We worked around that by keeping an inventory of 30-in. sections, and we’d tack one to the pipe end, but then we had a storage problem. We had to keep 30-in. lengths of pipe in every diameter we used,” he said.

When CSI was looking to upgrade its cutting machine, VERNON Tool™ Co. came to CSI’s attention. Its MPM model, capable of oxyfuel and plasma cutting, emerged as a contender. A fifth axis provides more control than CSI’s previous machine, and it provides a better cut quality. Also, it uses servo-driven rollers to rotate the pipe, rather than chucks, so CSI can use the entire length of material of every pipe. Built-in lifter conveyors make material handling easier and safer.

It handles diameters from 3 to 48 in. OD, lengths greater than 20 feet, and weights up to 15,000 lbs.

Better Holes, Better Throughput

In September 2005 U.S. gas producers extracted 1.77 TCF; in August 2012 they produced 2.37 TCF. This is a 34 percent increase in less than seven years. The new cutting machine has helped CSI keep up with the growing demand for compressor systems and storage vessels.

“When we had the previous system, we had two equipment operators, and they provided material to 12 welders,” Stone said. In recent years, the number of welders in its support shop has doubled, but the number of operators running the profiling machine hasn’t. “With the new machine, two operators can keep up with 24 welders,” he said.