Infinity offers a wide range of services, including mechanical construction, fabrication, project management, turnarounds and maintenance services.
It also provides heavy civil works, site preparation, and electrical and instrumentation services.
The acquired business will be included in the Wood Group PSN Americas business unit, establishing a brownfield service offering to the downstream market.
It will support the existing services of Wood Group PSN Australia Asia Pacific within the refining, chemicals and LNG sectors.
Under the deal, the existing management team will continue run the business, which employs around 2,500 personnel.
The acquisition will also provide a chance to offer a turnkey design and construct industrial service offering, in collaboration with Wood Group Mustang.
Wood Group PSN CEO Dave Stewart said: "The addition of The Infinity Group gives Wood Group PSN service line expansion, sector diversification, and entry into the US petrochemical and other downstream sectors, coupled with access to new clientele.
"Their 60-year history is a testament to the relationships they have built that we look forward to continuing and growing."
Subject to multiple conditions, including US anti-trust approval, the deal is expected to complete by the end of this year.
