New Delhi: Hindustan Petroleum Corporation Ltd has said a leak from a pressure gauge in its crude distillation unit was the likely cause of the fire at its joint venture refinery in Rajasthan, and restoration work is expected to be completed within three to four weeks, after which operations at the refinery will restart in the second half of May. 

A major fire broke out at the newly built Rs 79,450-crore HPCL Rajasthan Refinery Ltd. on April 20, a day before the scheduled inauguration by Prime Minister Narendra Modi. The fire in the crude distillation unit -- the main unit of a refinery -- was likely caused by a hydrocarbon leak from a valve or flange in a heat exchanger circuit.

In a stock exchange filing, HPCL said a detailed investigation into the April 20 incident confirmed the fire was localised to the heat exchanger stack, impacting six exchangers and associated equipment.

"Basis circumstantial evidence, the cause of fire is suspected to be leakage from pressure gauge tapping point on the vacuum residue exchanger inlet line," it said.

"The restoration work is in progress and it is expected to get completed in next 3-4 weeks. CDU restart is anticipated in second fortnight of May 2026."

Other secondary units are at an advanced stage of commissioning and are progressing as planned, HPCL said.

Trial production of key fuels, including LPG, petrol, diesel and naphtha, is expected to begin within May, followed by stabilisation and full commissioning of the units.

The scheduled April 21 dedication of the refinery has been postponed, and the revised date will be announced later.

The Ministry of Petroleum and Natural Gas has instituted a separate inquiry into the incident, with MRPL's former Managing Director M. Venkatesh leading a four-member investigation team.

Refineries worldwide are highly susceptible to fires, explosions, and catastrophic failures during the commissioning and startup phases, as this period involves introducing hydrocarbons into new or maintained high-pressure, high-temperature systems.

The refinery project was scheduled to begin commercial operations on July 1, according to a Central government statement issued on April 8, announcing approval of the Union Cabinet to enhance the cost of the project.

The Rajasthan refinery will be India's 24th and the second most complex unit yet in India.

The refinery-cum-petrochemical complex, located in Rajasthan's Balotra district, is designed as a 9 million tonnes per annum facility with a strong petrochemical focus, reflecting India's strategy to boost value-added output and reduce import dependence.

It features a Nelson Complexity Index of 17 and petrochemical yields exceeding 26 per cent, aligning with global benchmarks for efficiency and sustainability, according to an official statement.

Refinery complexity -- often measured by the Nelson Complexity Index -- indicates the capability to handle heavier, dirtier crude oil (which is cheaper) and turn it into high-value products like gasoline and diesel.

HRRL is a joint venture between HPCL (74 per cent stake) and the Rajasthan government (26 per cent share).

Once operational, the complex will produce fuels, including petrol and diesel, along with petrochemicals such as polypropylene, polyethylene variants and key industrial chemicals like benzene and butadiene.

These products are widely used across sectors ranging from transportation and packaging to pharmaceuticals and construction.