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April 8, 2016
Atlas Copco Rental provides quick solution when unscheduled compressor maintenance poses risk to processing for Dominican gold mine.
A trio of stationary compressors produce 630,000 m3/hr of air for the oxygen plant at Pueblo Viejo gold mine in the Dominican Republic. The oxygen is used by its autoclave processing facility to treat roughly 24,000 tons per day of refractory ore for the 60/40 joint venture between Barrick and Goldcorp Inc., operated by Barrick as Pueblo Viejo Dominicana Corporation.
Normal compressor maintenance at the mine takes one of its three units offline. The remaining two units share the load while one compressor undergoes maintenance, though production dips slightly.
In late 2015, while one compressor was down for repair, an unexpected motor failure in another compressor reduced production capability by 30%. It was too risky to rely on just one compressor. The plant needed a backup plan.
The failure had occurred right in the middle of the holiday season, a time of extended vacations and a burdensome surge on the international shipping industry.
Barrick’s Capital Project - Barry Hummer called the Atlas Copco Rental sales representative, Paul Morgan, in Florida. Hummer was relieved to learn Atlas Copco Rental had an immediately available solution: seven ZH6000 and seven ZH9000 portable air compressors complete with a technical team.
The units are rented by a variety of industries for scheduled stationary compressor maintenance or for emergency bypass, as in Pueblo Viejo’s case. Response time was quick. Morgan contacted Clayton Jones, key account manager of Atlas Copco Rental centrifugal air compressors. Jones immediately assembled a four-man technical team led by David Moessinger, who built the ZH-series compressors.
“We fill a sort of niche with this product,” Jones said, explaining that truly oil-free, centrifugal compressors capable of 6,000 and 9,000 cfm are hard to find outside of Atlas Copco.”
Atlas Copco ZH6000 and ZH9000 units are self-contained, 100 percent oil-free, three-stage centrifugal air compressors that fit completely within a standard 40-foot shipping container. Electrically powered, the units have zero risk of exhaust contamination that can be a problem with diesel units.
Jones added: “And, technically, Atlas Copco is one of a few manufacturers of truly 100 percent oil-free air compressors. Others reduce oil to a minimum and then filter it out. But our air has zero oil. There’s no need for a filter. And as for volume, you just can't compress that much air with a screw or piston. A centrifugal is just so much more efficient.”
The fundamental components of a centrifugal compressor are stainless steel impellers, efficient turbines that provide constant positive pressure. The three-stage ZH compressors have one low pressure impeller closest to the intake, which feeds primary stage compressed air to be stepped up by two high-pressure impellers. From inlet to discharge, neither coolant nor lubrication ever comes in contact with the compressed air. To manage heat from compressions, the system uses integrated stainless steel inter- and after-coolers.
It took just 31 days from the time Hummer contacted Morgan for the first compressor to be up and running, with much of that time taken up by shipping and site prep. Having determined the job’s specifications and logistics during onsite visits, the Atlas Copco team was ready at Pueblo Viejo before the compressors arrived. The containerized units make installation and start up simple. Only a few connections need to be made at each compressor: the electrical hook up in back, with hoses for water in/out and an air discharge pipe in front.
After setup and motor alignment, the Atlas Copco Rental technicians served as supplemental labor, joining Barrick’s team in a time of operational need. They worked around the clock in two-man 12-hour shifts right through Christmas and well into the new year.
The containerized units provided plenty of room to work in comfort, protecting technicians from the elements while they cleaned filters, monitored gauges, tuned performance with digital controls and logged six-hour readings. Elektronikon control and monitoring systems are integral to the units, mounted just inside at eye level for ease of use.
“Hummer said, “We’ve worked with Atlas Copco before. I had no doubt this would work. And I would do this again, no problem whatsoever. The self-contained units just make it go so smoothly. The Atlas Copco team deserve credit. I can’t say enough about how this was managed, administrative level on down. They did very good work and should be complimented for it.””
For 50 days the ZH compressors ran full capacity, sustaining a steady 105,000 cfm flow of ISO-quality, 100-percent-pure air at 75 psi. Production was maintained throughout the repair. And then as easily as they were installed, when the original overhauled stationary compressors came online, the Atlas Copco containerized compressors were unplugged and shipped back to the U.S.