INGENIEUR
CASE STUDY
Inherent Safe Design for Bulk
Storage of Flammable Liquids
By Ir. Dr Nor Halim Hasan
Director, Department of Occupational Safety and Health Sarawak
Muhamed Hayeri bin Abdul Rashi
Deputy Director, Department of Occupational Safety and Health Sarawak
B
ulk storage of flammable liquids, either as
raw materials or final products are common
in downstream industries where crude oil
(hydrocarbons) is refined into multiple products.
Flammable liquid storage tanks are also found
in industrial facilities such as refineries, marine
terminals, power plants, and large manufacturing
facilities such as automotive and steel plants. For
the purpose of this article, the flammable liquids
discussed are at atmospheric pressure and thus
liquefied natural gas will not be taken into account.
Construction of bulk storage for flammable liquids
requires strict adherence to common design
standards, such as those of the American Petroleum
Institute (API). The design standards are a set of
(minimum) engineering guidelines which have been
agreed upon to ensure sound engineering of the
tanks as containers for flammable liquid, but care
must be taken to address the potentially hazardous
situations which may arise in the event of loss of
containment and the possibility of fire. In line with
the “As Low As Reasonably Practicable (ALARP)”
philosophy of minimising risks associated with
the nature of bulk storage, inherently safe design
practices must be taken into account during the
detailed design phase and carried over during
the construction phase, and not treated as an
afterthought during the operation phase. As the
Department of Occupational Safety and Health
(DOSH) does not provide specific requirements
on the inherent safety of atmospheric tanks, the
recent case where bulk storage fires escalated and
caused major damage and losses shook the nation.
On July 5, 2018, a 40,000 litre oil tank caught fire
at Kemaman Bitumen Company and spread to two
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adjacent tanks, resulting in major losses (1). . The
fire required more than 48 hours and numerous
personnel to put out in a controlled and safe
manner. This article therefore aims to highlight
inherent safe designs as lessons learned from the
Kemaman Bitumen Company incident. The design
of the plant revealed that bulk storage tanks were
located closely adjacent to each other, with a high
potential of fire carry-over to adjacent tanks. The
disaster could have been minimised if inherent safe
design had been practised, in line with the ALARP
philosophy.
Layers of Protection
A good design requires safety aspects to be
incorporated throughout the project lifecycle-
starting from Front-End-Engineering-Design (FEED)
phase and continued in Engineering-Procurement-
Construction (EPC) phase, as this will address
risks related to hazard and operability of the
project during its operation. For this purpose, the
concept of Layers of Protection Analysis (LOPA) will
be introduced as a rough guide as to how inherent
safe design could play a major part in plant safety.
LOPA is based on the concept of using
protection layers to mitigate risks, such as fire
and explosion. The LOPA tool is an effective way
of analysing the adequacy of these independent
protection layers. As there is no perfect protection
barrier, several layers may be needed to achieve a
risk that is as low as reasonably practicable. The
above figure is an example of LOPA analysis for
bulk flammable storage in the event of tank fire.