Shares of Robbins & Myers Inc., an industrial products maker with operations in Dayton and Springfield, climbed 27 percent on Thursday after the company announced it had agreed to be acquired by a Houston drilling equipment firm.

National Oilwell Varco Inc. will acquire Robbins in an all-cash transaction that values Robbins at about $2.5 billion, the company said.

Under the agreement, Robbins shareholders will receive $60 per share in cash in return for each of the approximately 42.4 million shares.

Shares of Robbins (NYSE: RBN) closed Thursday at $59.63, up $12.83. Trading volume exceeded 19 million shares, compared with an average daily trading volume of 462,859 shares.

Shares of National Oilwell (NYSE: NOV) closed at $76.97, up 63 cents, or 0.8 percent, on below-average trading volume.

The boards for both companies have unanimously approved the deal, which requires approval by two-thirds of Robbins shareholders. The deal could be completed late this year, Robbins said.

Robbins makes equipment used by energy, chemical, industrial and pharmaceutical companies worldwide. Early this year, the company moved its headquarters operations from The Greene in Beavercreek to Willis, Texas, about 50 miles north of Houston.

News of deal comes two weeks after employees returned to work at Robbins subsidiary Moyno Inc. in Springfield after a four-month strike. United Auto Workers Local 902, which represents 128 local employees and 150 retirees, ratified a contract in July after Robbins threatened to fire all workers or move production permanently from Springfield.

In a letter to employees, Robbins made no mention of what will happen with employees, just that there would be meetings to address any questions.

“For the time being nothing changes — our focus continues to be serving our customers,” said Robbins CEO Pete Wallace in the letter.

But Moyno workers are concerned, one employee said.

“We just took a beating on the contract,” said Denny Parrett, who has worked at Moyno for 24 years. “It’s so uncertain, especially with the way companies are going overseas like crazy.”

Moyno employees said they conceded to the company on several issues. Employees said they lost pension and attendance bonuses, have higher insurance costs, are on a two-tier wage system and will receive pay cuts.

“We’re back to work and trying to get things back in order on the floor and now there’s just a lot of uncertainty,” Parrett said.

Moyno has about 240 employees, while another subsidiary, Dayton-based Chemineer, has about 140 workers.

Robbins’ largest shareholder, M.H.M. & Co., Ltd, which owns about 10 percent of Robbins’ outstanding common shares, has agreed to support the transaction, Robbins said.