BOSTON- Today, the Department of Public Safety (DPS) issued its findings relative to the explosion of the boiler at the Salem Harbor generating station on November 6, 2007. The explosion led to the death of three plant workers. The DPS determined that the primary cause of the failure leading to the fatal explosion was a defective weld in combination with significant external corrosion of the tubes in an area of the boiler known as the dead air space. This caused a tube to spray steam and water onto the adjacent tubes. The collateral damage resulted in the catastrophic failure which sent steam, water and ash, at approximately 600°F, into the immediate area below the boiler.
The law requires a thorough internal and external inspection of the boiler, including the dead air space. DPS investigators were told during interviews of plant personnel and the insurance inspector that they could not recall this space being opened in at least 10 years.. The Department concluded that “[a]nnual inspection of this [dead air] space would have significantly abated the degree of corrosion in the space and observation of the current level of corrosion should have prompted further examination.” Accordingly, the Department is pursuing disciplinary actions against the engineer-in charge who is responsible for the operation and maintenance of the boiler as well as the insurance inspector who is responsible for annual inspections.
Since the failure, the Department has taken the following actions:
1. On November 19, 2007 the certificates of inspection for all four boilers at the Salem Harbor plant were revoked. This action prohibited the boilers from restarting until an inspection by Department inspectors was performed and a new certificate was issued.
2. Before the boilers were placed back in to service, the Department performed a thorough inspection for each of them which included non-destructive testing and pressure tests of the boilers.
3. The Department performed an assessment on all solid fuel fired boilers in the Commonwealth to ensure that other plants with solid fuel fired boilers were in compliance with the Code.
4. The Department is forming a Boiler Task Group to consider and submit proposed changes to the Board of Boiler Rules as a result of the incident.
A full copy of the report is available on the Departments web site mass.gov/dps
This incident was also investigated by the Essex District Attorney’s Office, the Massachusetts State Police, the Salem Police Department, and OSHA.