Civil Engineering Reference
In-Depth Information
huge fl ammable gas cloud and that the confi nement
and obstructions within the plant caused high explosion
pressures.
The HSE's subsequent report identifi ed the following
failings in technical measures:
2.
A major hazard on a refurbishment project is fi re.
(a)
Identify
THREE activities that represent an
increased fi re risk in such a situation.
(3)
(b)
Outline
the precautions that may be taken
to prevent a fi re from occurring.
(5)
3.
Outline
the measures that should be taken to
minimise the risk of fi re from electrical
➤
A plant modifi cation occurred without a full HAZOP
assessment of the potential consequences. Only
limited calculations were undertaken on the integrity
of the bypass line. No calculations were undertaken
for the dog-legged shaped line or for the bellows. No
drawing of the proposed modifi cation was produced
equipment.
(8)
(a)
Identify
two sources of oxygen which can
be found in the workplace.
(2)
(b) State the ways in which the potential sources
of oxygen supply to a fi re can be reduced.
(4)
➤
With regard to the use of fl exible pipes no pressure
testing was carried out on the installed pipework
modifi cation
(c)
Defi ne
the terms 'explosive atmosphere'.
(2)
4.
Defi ne
the following terms:
(a) Defl agration
(2)
➤
In relation to maintenance procedures there appeared
to be ad hoc recommissioning arrangements
(b) Detonation
(2)
(c) Upper fl ammable limit (UFL)
(2)
➤
Those concerned with the design, construction and
layout of the plant did not consider the potential for
a major disaster happening instantaneously
(d) Lower fl ammable limit (LFL).
(2)
5.
Explain
with the use of a diagram the method of
operation of an automatic explosion suppression
➤
The plant layout was poor in relation to the position-
ing of occupied buildings
system.
(8)
6.
Describe
the three zones that may be identifi ed
within a workplace that has fl ammable gases
and vapours that may produce an explosive
➤
Control room design did not take into account struc-
tural design to withstand major hazards events
➤
The incident happened during start-up when critical
decisions were made under operational stress. In
particular the shortage of nitrogen for inerting would
tend to inhibit the venting of off-gas as a method of
pressure control/reduction
➤
Operating procedures were lacking particularly with
regard to the number of critical decisions to be made
atmosphere.
(8)
7.
Identify four
methods of heat transfer and
explain how each can cause the spread of fi re.
(8)
➤
In relation to inerting the atmosphere reliability/back-
up/proof testing appeared inadequate.
7.7
Example NEBOSH questions for
Chapter 7
1. (a)
Explain
the meaning of the term 'fl ash
point'.
(2)
(b)
Outline
the precautions to take to reduce
the risk of fi re when using fl ammable
solvents in the workplace.
(6)
