US factory automation equipment maker Emerson Electric Co said on Thursday it would buy pump manufacturer Pentair Plc's valves and controls business for $3.15 billion in cash, as it expand its core businesses.

Emerson, which has been shedding non-core businesses, is focusing on growing its industrial automation business, along with process management, and commercial and residential heating and air conditioning businesses.

Reuters reported in July that Emerson had made an offer to acquire Pentair's valves and controls division, which makes fittings and controls used in machinery in the chemical, power generation, oil and gas and power generation sectors.

Pentair's valves and controls business will help Emerson capture a nearly 10 per cent share of the $105 billion global process automation market, up from 7 per cent currently, Emerson said.

Process automation involves precision measurement, control, and monitoring of industrial processes. Emerson's process management business, its biggest, reported revenue of $8.52 billion in fiscal year 2015 and accounted for about 38 per cent of its total revenue.

Pentair's valves and controls business is headquartered in Schaffhausen, Switzerland, and had revenue of $1.84 billion in 2015.

Pentair, which has been under pressure from activist hedge fund Trian Fund Management LP to improve its performance, inherited the business as part of its $10 billion all-stock merger with Tyco International Ltd's flow control unit in 2012.

Earlier in August, Emerson agreed to sell its network power unit to investment firm Platinum Equity in a deal valued at $4 billion.

The business provides equipment and services that stop mission-critical systems from failing including surge prevention, uninterruptible power supplies and precision cooling.

Emerson also said this month that Japan's Nidec Corp would buy its motors and electric power generation unit for $1.2 billion.

The valves and controls deal is expected to close in the next four to six months, Emerson said on Thursday. The business will be cash accretive in 2018.

Greenhill & Co LLC is Emerson's financial adviser and Davis Polk & Wardwell LLP the legal adviser. - Reuters