NHBB official: Nitric acid transfer led to explosion

PETERBOROUGH — The explosion on Feb. 10 at New Hampshire Ball Bearings’ Peterborough plant occurred when nitric acid was transferred into a drum containing an acidic waste mixture, according to a letter to company employees posted on the NHBB website.

In the letter, company President and Chief Executive Office Gary Yomantas wrote, “Since the evening of Feb. 10, we have been working with the Fire Marshal’s Office, OSHA, and independent experts to determine the cause of the blast. We have determined that a chemical reaction occurred when nitric acid from a non-production process was transferred to a 55 gallon drum containing an acidic waste mixture. The acids in question are commonly used in industry for surface treatment and testing of metals.”

The letter did not address why the acid mixture was in the drum or discuss what safety procedures were followed. Hans Baker, a company spokesperson in Peterborough, said Wednesday that the company could not comment at this time beyond what is stated in the letter.

Investigator Keith Rodenhiser of the State Fire Marshall’s Office said Wednesday that the office’s investigation is nearly complete. A report that should provide additional details about the explosion is expected to be released soon, he said.

Rose Ohar, the Concord area director for OSHA, said the OSHA investigation is still open. OSHA has a six-month time frame in which to complete an investigation, Ohar said.

Fifteen workers were injured in the accident on Feb. 10, when an explosion ripped through the first floor of the manufacturing plant on Route 202, blowing out a row of windows on the side of the building facing the state highway.

Two seriously injured workers were airlifted after the explosion — one to Massachusetts General Hospital in Boston and the other to UMass Medical Center in Worcester, Mass. They were released from the hospital a few days apart in mid-March and are currently recovering at home, according to Baker.

A few days after the explosion, an initial investigation conducted by the State Fire Marshal’s Office determined the blast was caused by a nitric acid reaction. Nitric acid is an oxidizing agent commonly used in industrial processes, including at N.H. Ball Bearings, where workers use it in the ball plant for surface treatment of ball bearings.

The plant was closed for two days after the explosion, but most employees had returned to work within a week after the explosion and the company resumed full production by March.

In his letter, Yomantas wrote that the company is evaluating its policies, procedures and training and organizational structure at all its facilities.

“We are confident that we are taking the necessary steps to prevent anything like this from happening again,” he wrote.

Yomantas also expressed appreciation for the support of the local community and gratitude for the response to the accident from NHBB employees. The complete text of his letter is printed at right.

Baker said the explosion was an unprecedented event and nothing similar had ever occurred at any of the company’s facilities. The company, which is owned by the Japanese firm Minebea, is headquartered in Chatsworth, Calif., has plants in Peterborough, Laconia and Chatsworth.

“We are looking at all our procedures related to safety,” Baker said. “We’re looking at everything, at all of our facilities.”

Dave Anderson can be reached at 924-7172, ext. 233 or He’s on Twitter at @DaveAndersonMLT.

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