The company said the purchase of Melbourne-based Valve Tech Engineering was the first of five acquisitions planned for the next six months.
The deal heralds a big push for growth in Australia by Aberdeen-based EnerMech, which specialises in mechanical services such as the maintenance and engineering of cranes, valves and hydraulic equipment.
EnerMech said it expected to invest £10 million in developing its Australian operations over the next two years. Target markets include oil and gas, mining and power.
The company, which has a valves supply and servicing operation in Perth, Western Australia, expects to more than double its workforce in the country to 180 in the next 12 months.
Managing director Doug Duguid said: "Valve Tech is an excellent strategic fit for our business and gives us significant maintenance and repair capabilities in addition to our existing offering in the region. It strengthens our geographic reach in eastern Australia and introduces EnerMech to Valve Tech's broad client portfolio."
Backed by the Lime Rock private equity business, EnerMech has used acquisitions to help cash in on booming activity in oil and gas and related markets at home and overseas.
It has bases in 15 countries and annual sales of £140m. Last month EnerMech bought South Africa's Water Weights International for £3m, increasing its exposure to the region's fast-growing oil and gas industry.
The company said it had £40m funding to support organic growth and further acquisitions, including a facility provided by Lloyds Banking Group.