Success Story in Overcoming Challenges on Contractor Management for Process Safety

Wakayama refinery started operation in 1941 and has current crude processing capacity of 127.5KBD with largest class lubes plants in Japan. The refinery experienced a fire incident on ILP in Jan 22, 2017. Equipment that located in approximately 400 square meters suffered significant damage, though no personnel injury occurred. Next is summary of the incident, lessons & learned and measures.

Likely Fire Development and Spread
Phase 1: Gas fire resulted from combustible gas leakage and its ignition (15:37-47)
PT-2 HD (Lube Solvent Extraction Unit Hydro-Treater Section) high pressure purge gas line at D-253 (high-pressure low-temperature separator drum) overhead failed and a large amount of flammable gas leaked and ignited.
Phase 2: Transition to oil fire (15:48-16:13)
PT-2 HD D-252 (high-pressure-high-temperature separator drum) /D-253 were filled with the oil from upstream and oil overflew into the high-pressure purge gas line. Oil leaked from the perforated pipe opening and caught fire with black smoke observed.
Phase 3: Transition to pool fire (16:14-)
As adjacent pipe lines were exposed to flame, PT-2 feed line pipe ruptured with severe bulging just upstream of flow control valve. Leaking feed oil and the fire spread inside the spill wall and developed to pool fire.

Opening location of high-pressure purge gas line
18 openings were found via field investigation. 12 openings were found in the high pressure purge gas line where pressure dropped first and only one opening was not appeared to be affected by the fire.

Summary of the direct cause
Processing rate of heavy feedstock in the hydrogenation unit increased gradually, and a corrosive environment with high concentration of ammonium hydrogen sulfide (ammonium bisulfude) was created at moisture condensation part, causing the severe alkaline sour water corrosion.

Measures against the direct cause
One of measure against the direct cause is installation of washing-water injecting equipment to improve operating condition on the API RP 932-B chart. Another measure is corrosion control improvement from the thickness measurement-based to comprehensive corrosion control including operation management.

Summary of the indirect cause
Evaluation of the equipment in question was omitted in past risk assessments due to lower desulfurization rate and denitrogenation rate than those of fuel oil desulfurizing units. So, it was regarded that quality of the risk assessment was not adequate.
As the corrosion control was conducted depending on only thickness measurement of representative inspection, it was regarded that knowledge about ammonium hydrosulfide corrosion in the lube oil manufacturing unit was not adequate.

Measures against the indirect cause
One of measures against the indirect cause is improvement of quality of risk assessments from viewpoint of making an individual actively think about causes and measures and then recognize again its responsibility.
Another measure is to increase knowledge about ammonium hydrosulfide corrosion. Corrosion mechanism about ammonium bisulfide shall be learnt with more research work and improve how lesson leant be applied when new findings be obtained.