Week 5

Question 1

What is the HAZOP Procedure?

Answer 1

1. Begin with a detailed flowsheet. Break the flow sheet into a number of study nodes.
2. Select a study node for study.
3. Describe the design intent of the study node.
4. Pick a process parameter: flow, level, temperature, pressure, concentration, pH, viscosity, state (solid, liquid, or gas), agitation,
   volume, reaction, sample, component, start,
   stop, stability, power, inert.
5. Apply a guide word to the process parameter to suggest possible deviations. Some of the guide word process parameter combinations are meaningless for some processes.
6. If the deviation is applicable, determine possible causes and note any protective systems.
7. Evaluate the consequences of the deviation (if any).
8. Recommend action (what? by whom? by when?)
9. Record all information.
10. Repeat steps 5 through 9 until all applicable guide words have been applied to the chosen process parameter.
11. Repeat steps 4 through 10 until all applicable process parameters have been considered for the given study node.
12. Repeat steps 2 through 11 until all study nodes have been considered for the given section and proceed to the next section on the flow sheet

Question 2

Guideword

Answer 2

A short word to create the imagination of a DEVIATION of the INTENTION. The mostly used set of Guidewords is: NO, MORE,LESS, AS WELL AS, PART OF, OTHER THAN and REVERSE. The GUIDEWORDS are applied, in turn, to all the PARAMETERS, in order to identify unexpected and yet credible DEVIATIONS from the INTENTION.

Question 3

Cause:

Answer 3

The reason(s) why the DEVIATION could occur. More CAUSES can be identified for one
DEVIATION.

Question 4

Comments:

Answer 4

Any remarks to be given to the RECOMMENDATIONS or which, in another way, showed up during the HAZOP sessions.

Question 5

Consequences:

Answer 5

The results of the DEVIATION, in case it occurs. CONSEQUENCES may both comprise process hazards and operability problems, like plant shutdown. More CONSEQUENCES can follow from one cause and, in turn, one CONSEQUENCE can have several CAUSES.

Question 6

Action:

Answer 6

Where a credible cause results in a consequence, it must be decided whether some action should be taken. It is at this stage that consequences and associated safeguards are considered. If it is deemed that the protective measures are adequate, then no action need be taken, and words to that effect are recorded in the Action column.

Question 7

Safeguard:

Answer 7

Facilities that help to reduce the occurrence frequency of the DEVIATION or to mitigate its
CONSEQUENCES.

Question 8

Five types of safeguards

Answer 8

1. Facilities that identify the DEVIATION. These comprise, among others, alarm instrumentation and human operator detection.
2. Facilities that compensate the DEVIATION, e.g., an automatic control system that reduces
   the feed to a vessel in case of overfilling it (increase of level). These usually are an
   integrated part of the process control.
3. Facilities that prevent the DEVIATION to occur. An example is an inert blanket gas such as argon in storages of flammable substances.
4. Facilities that prevent a further escalation of the DEVIATION, e.g., by trip of the activity.
5. Facilities that relieve the process from the hazardous DEVIATION. These comprise for
   instance: pressure safety valves (PSV) and vent systems.

Question 9

HAZOP pros

Answer 9

1.Systematic, creative and open-ended highly
2.thorough and structured, yet still versatile
3. covers safety and operational aspects
4. uses a multidisciplinary team approach
5.solutions to problems may be identified
6. results are recorded (also for legal reasons)

Question 10

HAZOP cons

Answer 10

1. dependent on the accuracy of drawings and data
   2.requires the right mix of team members with the proper technical experience and insight
2. tiring and difficult to perform over extended periods
3. requires the commitment of the team, and management, for the duration of the study
4. Very expensive
   6.HAZOPs assume that the plant is built as
   intended, and operated as intended - but it might not be the case.

Question 11

What is nodes are too small?

Answer 11

Time consuming and tedious.

Question 12

What if nodes are too large?

Answer 12

Can miss some problems

Question 13

Deviation

Answer 13

How the process or equipment can stray away from intended design

Question 14

The 2 Action groups

Answer 14

1. Actions that remove cause
2. Actions that mitigate or eliminate consequences

Question 15

Who is on a HAZOP team

Answer 15

Chair, Secretory, Design team member, operator, specialists eg. Engineers, maintenance supervisor

Question 16

Part of guideword meaning

Answer 16

Only some of the design intentions are achieved, some are not. Eg. Lower concentration