Fire in a refinery

A fire started as a result of an explosion in the process section of a refinery. An open structure of steelwork protected with reinforced concrete housed the usual furnaces, reactors, heat exchangers, storage vessels, overhead pipe racking, pumps and ancillary equipment associated with the refining of crude oils.
Also included in the area were three 46m (150 ft.) high stripping and drying columns built on a concrete base approximately 91m x 21m (300 ft. x 70 ft).

The origin of the fire was the rupture of a pipe in a gasoline hydrogen-treating unit; a mixture of superheated naphtha and hydrogen under pressure leaked from the fracture and either exploded on contact with a hot process line or was ignited by static electricity. The fire reached its maximum severity within a few minutes.

Plant controllers operated an immediate shutdown but the contents of the many pipes and vessels, which had been superheated and were under high pressure, continued to flow from fractured pipes and distorted flanges cascading burning liquid through the plant.

The fracture occurred at a point where the water was injected into the system to improve the flow of materials. The corrosion tolerance was accepted at 1mm (0.05 in.) per year but due partly to the presence of corrosive contaminants and an unfavourable flow pattern inside the pipe, corrosion and erosion were much higher than expected, contributing to excessive thinning of pipework, leading to its ultimate failure.

The explosion and fire destroyed the stripping and drying columns associated with two hydrogen treating plants and severily damaged other parts of the processing equipment .

The INITIATING CAUSE was the failure of a pipe due to unexpectedly high thinning of the pipe wall, due to the combination of internal corrosion and erosion.

The ROOT CAUSE is linked to the under-estimation of the corrosion rate of the pipe. It highlights shortcoming in operative and material design knowledge. Moreover, it reveal the lack of (proper) inspection and an underestimation of the related risks in term of severity of consequences.

pipework, flange, pump, heat exchanger and furnace

The explosion and fire destroyed the stripping and drying columns associated with two hydrogen treating plants; other parts of the processing equipment were severely damaged. The remainder of the process area, offices and ancillary buildings, though seriously threatened remained unaffected by the fire. Part of the concrete cladding protecting the main load-bearing steel columns, and the underside of the platform at first-storey level was affected by spalling but the steel structure itself was undamaged and will not need to be replaced.

The statement of the source regarding " ...no serious casualties" is too vague to exclude injuries.

The loss of confinement was caused by the structural failure of a pipe under internal pressure, due to internal corrosion and erosion. The operator was aware that corrosion and erosion was causing thinning of the pipe wall, but it under-estimated the thinning rate.
This case highlights the importance of regular and effective inspection of the pipeline integrity. Theoretical assumption on material behaviour should not be taken as the only input to the risk assessment, without some kind of validation based on real operative conditions.
The case shows also that failing to perform a proper risk assessment considering hazards of individual components and materials may have massive consequences for the whole plant.