The deal will create a third operational base for Glacier, in addition to its sites in the west of Scotland and in Aberdeen. Glacier is moving its west of Scotland base from Motherwell to the Clyde Gateway development in the east end of Glasgow.
Glacier said that the acquisition of Site Machining Services, a specialist provider of pipe-cutting and preparation services to the global oil and gas industry which had turnover of about £750,000 in its last financial year, would increase its annual turnover to nearly £10m.
Roberts is a pipeline machining company, while Wellclad is a welding services specialist.
Jeff Milne, founding director of Site Machining Services, will remain with the Site Machining Services business alongside his existing staff of 12. The deal will thus increase Glacier's workforce, who operate in the UK and internationally, to about 60.
The acquisition was enabled by further investment from Glasgow-based Maven Capital Partners and Simmons Parallel Energy. Together, these private equity providers invested £8m to back Glacier's purchase of Roberts and Wellclad from MB Aerospace Holdings back in 2011.
The MB Aerospace Holdings business came into being through a management buyout from Motherwell Bridge in 2007.
Dave Sturrock, chief executive of Glacier, highlighted plans to ramp up activity on the back of the Site Machining Services deal.
He said: "This is a key business area which we believe will help us achieve further growth, and we intend on investing in additional technicians and equipment to facilitate an increased workload.
"Glacier harnesses the combined manufacturing capability, technology and expert staff of three very well known and respected companies in Roberts, Wellclad and now Site Machining Services, delivering for clients across the production and processing equipment, intervention, and pipeline component disciplines."
Ewan MacKinnon, investment director at Maven, said: "Glacier ...has developed a solid reputation and the acquisition of Site Machining Services will further enhance the group's standing and will play a key role in achieving further growth."
