* Watchdog identifies "serious breaches" of regulations
* Orders improvements in maintenance, documentation
* Equinor recruiting more engineers (Adds quote, detail, reaction)
By Nora Buli and Terje Solsvik
OSLO, June 24 (Reuters) - There were serious breaches of regulations at an Equinor methanol plant that caught fire last year, Norway's petroleum safety watchdog (PSA) said on Thursday, ordering the company to improve maintenance practices and documentation.
No one was hurt in the Dec. 2 fire at Tjeldbergodden, western Europe's largest methanol plant.
It was caused by a runaway steam turbine when its shutdown valve malfunctioned, Equinor's own investigation concluded in May. The blaze shut the plant in central Norway for around 12 weeks.
"The PSA's assessment is that the incident had a major accident potential and could have caused serious personal injury or death as well as substantial financial loss," the regulator said in a report.
"The PSA's investigation has identified serious breaches of the regulations," it added.
Coming just months after a fire that incapacitated Equinor's Hammerfest liquefied natural gas (LNG) plant, the Tjeldbergodden incident led to questions over whether the company's staffing and training had been adequate.
Maintenance issues were a common factor of the two fires, PSA chief Anne Myhrvold told a news conference.
Equinor last month said it would recruit more engineers for a range of onshore facilities.
"We've already embarked upon an extensive learning and improvement effort at the plant to prevent similar incidents from ever occurring again," an Equinor spokesperson said on Thursday.
The report found Equinor had failed to properly identify and classify equipment that was critical to plant safety and also criticised the facility's maintenance and technical documentation.
"The investigation confirms that this was serious, and maybe even more serious than first assumed," Myhrvold said.
The agency ordered Equinor to ensure that any equipment that has a safety function at Tjeldbergodden is identified and classified to enable correct follow-up and proper handling.
The methanol plant accounts for more than 25% of European production and has an annual capacity of around 900,000 tonnes, according to Equinor data. The Norwegian firm owns an 82% stake while ConocoPhillips owns the remaining 18%. (Additional reporting by Nerijus Adomaitis. Editing by Gwladys Fouche and Mark Potter)