A derrick arm collapsed while lifting a motor at an oil refinery, causing the motor to fall on equipment below. An investigation found that corrosion in an empty space in the derrick's structural foundation weakened and ultimately failed the arm under the weight of the motor. The corrosion was caused by accumulated rainwater in the empty foundation space. Lessons from the incident include filling empty spaces in structures to prevent water accumulation and corrosion, regularly inspecting derricks, and ensuring lifting equipment is sound before use.

1. Safety Talk
A.K.Singh, Chief Manager (F&S), Indian Oil Corporation Ltd, Mathura Refinery
Failure of Derrick
arm due to
corrosion
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Mathura Refinery

2. Incident : The incident happened in one of the refinery .A
motor after repair
from workshop was brought at site for placing on its mounting
frame. It was lifted
through a rotating derrick arm by a Chain pulley block. The
derrick got collapsed
under weight of the motor as it fractured and gave way little above
the pedestal Graphics of failure
foundation support. The motor fell down on the running motor
meant to move crude
booster pump of refinery. Because of tension in cable , it tripped
causing shutdown
of the plant. Failure occurred at
the base
Crude booster Pumps in Pit
Empty /Void space at foundation
bottom corroded and failed during
loading of motor
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Mathura Refinery

3. Root cause:
Corrosion of empty space in structural foundation
caused failure
of derrick arm .
Analysis:
• Basically structural members are not included in the
inspection and also during construction , little care
is taken on possibility of accumulation of rain water
in empty space in the structural and hardly any
preventive measure is taken from beginning for
corrosion failures .
• Due to rain water accumulation in empty space in
derrick bottom
corrosion and weakening of derrick structural
foundation caused
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Mathura Refinery

4. • Lack of inspection & maintenance of
derrick lifting channel
• Faulty judgment by rigging group on the
soundness of the derrick lifting channel.
Lessons
• Empty space in derrick structural to be
cemented or filled to avoid water
accumulation and corrosion
• Inspection of derricks to be done during
testing of other lifting tools and tackles .
• Soundness of all lifting tools to be
ensured before executing any job.
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Mathura Refinery