A single spark could cause a fireball: 32-hour op that averted propylene gas disaster on Pune–Mumbai Expressway

PUNE: A meticulously executed 32-hour hazardous materials operation—marked by split-second decisions, specialised expertise and round-the-clock coordination—averted what could have been a catastrophic propylene gas disaster on the busy Pune–Mumbai Expressway.

The incident unfolded around 7.30 pm on Tuesday when a propylene tanker carrying nearly 21,000 kg of highly flammable compressed gas overturned onto its side near Adoshi tunnel on the expressway0.





ZN Gawade, technical director of Mec Elec Industrial Services, Thane, a private agency, which played a crucial role in the operation, told TOI that the situation on the ground was extremely volatile and critical.

“All three top-mounted ball valves on the tanker were damaged in the rollover and were leaking. Liquid propylene was discharging from every connection, forcing authorities to stop traffic in both directions. Lower Explosive Limit readings were alarmingly high even 500 metres from the site, underscoring the severe explosion risk,” he said.

Working under life-threatening conditions, the response team managed to arrest two of the three leaks—one liquid and one vapour valve. The third valve, however, posed a formidable challenge. Bent sharply during the impact, its handle had jammed against the weld cap, making operation impossible while liquid propylene continued to escape.

Gawade reached the site the following morning, travelling against traffic flow in a police-escorted ambulance. After a detailed technical assessment, the team opted for a high-risk decanting strategy—transferring the tanker’s contents through the single operable vapour valve into multiple empty propylene tankers.

“The objective was to reduce the liquid level inside the damaged tanker until the leaking valve began releasing vapour instead of liquid, significantly lowering the hazard,” he said.

By around 4.30 pm, specialised transfer hoses were connected and liquid transfer was initiated using pressure differential, with receiving tankers carefully depressurised. The process was repeated three times, each transfer conducted with extreme caution due to loosened valves and mechanical instability.

Once the leaking valve began venting vapour—indicating the liquid level had dropped below roughly 50%—authorities prepared for the next critical phase: lifting the overturned tanker.

The operation was carried out with extensive multi-agency support, including the police, NDRF, fire brigade and other state and local agencies. Four cranes and multiple fire tenders were deployed, and the lifting plan was rehearsed in detail before execution.

As anticipated, the leak briefly intensified when residual liquid contacted the damaged valve via the dip pipe. The response team swiftly arrested the final leak, preventing escalation at a critical moment.

At around 1.30 am, the tanker was escorted through the ghat section under strict safety supervision. Despite still containing a significant quantity of propylene, another delicate operation was undertaken—partially opening the bent liquid valve to decant additional product into a fourth tanker.

The tanker was finally transported to the Khalapur tanker testing station, reaching the facility at around 5.00 am.

By then, the technical team had worked continuously for over 32 hours, navigating one of the most complex and hazardous compressed-gas response operations witnessed on an Indian highway in recent years.

Officials said the incident underscored not only the dangers associated with hazardous material transport but also the critical importance of specialised expertise, precise execution and seamless inter-agency coordination in preventing a large-scale disaster.