Hg announced the sale of JLA - a major UK player for critical assets solutions in the commercial laundry, catering, heating and fire safety markets - to Cinven on Monday.
The London-listed firm said the closing of the transaction remained subject to regulatory approval, and the terms were not disclosed.
It explained that JLA provides equipment, supply and services solutions across commercial laundry, catering, heating and fire safety to customers across the UK, primarily through its 'Total Care' offering.
Total Care provides customers with a solution for running critical areas of their business, minimising downtime and maximising peace of mind for business owners.
Hg's services team invested in JLA at the beginning of 2010, identifying it as a 'hidden champion' services business.
JLA displayed best-in-class services characteristics: stable and predictable revenue streams, growth from both existing and new customers, and a wide customer base with high customer satisfaction levels, the Hg board explained.
Since 2010, in addition to the organic development of new product offerings in the catering, heating and fire safety markets, JLA had successfully completed 16 bolt-on M&A transactions.
During that time, Hg said the business had more than doubled in size, with employment increasing from 310 to 900 across the UK.
"JLA has been a strong performing business, displayed by its 25 year-on-year unbroken growth track record," said Hg's Thorsten Toepfer and Joris Van Gool in a joint statement.
"Hg has supported management to enable this growth during our 8-year investment period, including a variety of operational projects covering new product development, digital marketing and acquisitions."
Toepfer and Van Gool said Hg's investment returns had been driven by a combination of "impressive" revenue and EBITDA growth, as well as accretive mergers and acquisitions delivered by a "world-class" management team.
"We have really enjoyed working with the JLA team and we wish them well as they continue their success."
Stephen Baxter, CEO of JLA, added that his company had enjoyed an "incredibly successful" period during its partnership with Hg.
"The operational projects we have undertaken together have proved valuable, whilst the M&A activity has helped expand and diversify our services.
"We look forward to working with Cinven, who we're confident will help us maintain this momentum and continue JLA's future growth."
The Hg board said the sale of JLA would deliver an overall return to Hg6 clients of 4.9x original cost, generating a gross internal rate of return of 26%.
It said the realisation of JLA represented the 17th exit from Hg6 to-date, and the fifth exit from Hg in 2018.