1. HAZOP
(Alfredo Ruggiero)
The Hazop technique is recently expanding, and has been developed by the giant ICI to analyze
the chemical plants, it is a qualitative technique driven by keywords and requires a team of people
coordinated by a cross-functional team leader. The Hazop study should be performed as soon as
possible at the design stage of the production processes. For the analysis required shop drawings
(P & ID; the technique can still be used:
a) in the phase of maximum design drawings of block
b) in the process of design review with final drawings
c) during construction and commissioning
d) during its operation.
The composition of the team must be open to:
1) process designers
2) process engineers
3) maintenance responsible
4) software experts
5) technical supplier companies.
The activity of Hazop team must be recorded on a form where they are registered:
1) No reference
2) word help
3) This deviation
4) causes
5) consequences
6) protection used
7) recommendations
8) responsibility.
The study can start when they are available:
1) the process flow diagram
2) P & ID
3) Lay out the process
4) data sheet of the materials, components, instrumentation, equipment
5) Operating instructions
6) Emergency procedures.
The process of analysis consists of the following phases:
1) dividing the entire system into sections (pumping, mixing, reaction, distillation, solvent recovery
etc)
2) choice of the node in the section that has a set of components and is well defined . A node is
for example a process line or an apparatus.
3) description of the purpose of the node (that is how it should work the process)
4) choice of a process parameter characterizing the node (eg, flow, temperature, pressure,
composition)

2. 5) application of the word help (eg plus, minus, of etc.)
6) identification of deviations in the process. For deviation means the way in which the process
disregards the purpose indicated
7) determination of the causes of deviations
8) assessment of the consequences. The consequences can be both from a safety point of view
and from the point of view of the operability of the system.
9) protection to be provided for preventing the consequences
10) identification of countermeasures, actions to be taken to combat the causes of the deviations
The guide words are the heart dell'hazop, their proper use results in a well-made HAZOP; the most
used words are:
1) no;
1.1 significance: the function is absent, the purpose of the project is not reached
2) more
2.1 meaning: excessive function, beyond the designed
3) less
3.1 significance: insufficient function, lower than planned
4) as well as
4.1 meaning: this is an unwanted function in parallel
5) part of
5.1 significance: only part of the purpose of the planned has been reached
6) other than
6.1 significance: This is an unwanted feature instead of waiting dl project function
7) reverse;
7.1 significance: the opposite activities designed to sample function (flow back to the time of the
shutdown)
8) other words used guide are:
8.1 soon / later
8.2 before / after
8.3 faster / slower
8.4 in any other place.
These words guide together with the process parameters (flow, temperature, pressure,
composition, pH, speed 'tce) give rise to a number of combinations to be analyzed.
Example for reactor batch Checklist
PROBLEMS TO REAGENTS
1) incorrect reagents
2) impurities
3) insufficient amount / high
4) flow rate too fast / slow
5) contamination
EXHAUST PRESSURE SYSTEM
1) packing
2) vent condition biphasic

3. 3) back pressure
4) Corrosion
MALFUNCTION MIXER
1) Insufficient mixing
2) mechanical failure
3) stop for lack EE
4) resulting layering liquid phases
INADEGUATE COOLING
1) ability to inadequate cooling system
2) lack electricity
3) system block pumping / flow
4) failure to coolers / cooling towers
5) failure to Fittings
6) failure to the control system
7) Loss of Coolant
TEMPERATURE
1) sensor failure
2) failure of the control system
3) in erroneous position sensor
FAILURE CONTROL SYSTEM
1) incorrect setting
2) Lack of Air / voltage
3) electrical / mechanical failure
It Is possible to suggest some corrective actions to mitigate the consequences of possible
deviations:
• Failure Alarm stirring with power reagent block
• High temperature alarm and high temperature of the reactor independently from the temperature
control system
• fail safe valves (open) on the cooling system
• flow switches and pressure on the cooling system with alarm and reagent supply blocks
• cooling water temperature indicator output
• maintenance of control procedures on safety valves or bursting disc
• reactor equipped with sprinkler system
• maximum level indicator
• any of the batch discharge tank
• Quality analysis to detect contaminants on reagents
In conclusion the Hazop technique has the advantage of having a series of guide words to identify
deviations spent neglected by other techniques, but it has the disadvantage of being only
qualitative and not to consider the simultaneity of occurrences.
Reference :
1)La prevenzione nell’industria chimica fine e farmaceutica- M. Mazzoli (Ge Specialities)
2)L’analisi dei rischi per la qualità e per l’ingegneria-Tartari .R.- Franco angeli