DNV GL © 2013 SAFER, SMARTER, GREENERDNV GL © 2013

Writing HAZOP Recommendations

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Overview

�Learning goals – Develop understanding of how to

write effective recommendations

�Topics– Effective recommendations

– Examples of recommendations

Slide 2

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Writing HAZOP Recommendations

� Purpose of HAZOP

– Critical Review

� Intermediate Output

– Recommendations

� Final Output

– Plant where hazards are understood and minimised

– Plant where operability is considered and optimised

Slide 3

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Writing HAZOP Recommendations

� Recommendation must be :

– Clear

– Unambiguous

– Concise

– Relevant

– Prioritised (depending on criticality)

Slide 4

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Before writing recommendations

� Identify problem

� Understand problem

� Agree

– Is present situation unacceptable?

– what is to be changed?

or

– not enough information available

Slide 5

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Writing HAZOP Recommendations

� Recommendations must make clear:

– Scenario reviewed

– Outcome to be avoided

– Suggested change

or

– Scope and objective of further study

Slide 6

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Information available elsewhere?

� Log sheet header

– indicates Line/Section (and sometimes Guideword) being considered

� “Causes”

– identifies scenario

� “Consequences”

– defines outcome

� Log sheet is the chain of arguments

Slide 7

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What is needed in recommendations?

� Enough detail to carry out the action

� Clarity and no chance of misunderstanding

� Avoid using “consider”

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If further study is required

� When team cannot make a recommendation, ask for further study

� Must clearly define:

– Problem

– Objective – in detail

– Scope and extent

– Target date for completion

Slide 9

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The “3Ws” Rule

� What do you want?

� Where do you want it?

� Why do you want it?

Slide 10

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Quality Control of recommendations

� Is it relevant to the problem?

� Does it solve the problem?

� Does it introduce any other problems?

� Is it easy to understand?

Slide 11

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Examples of HAZOP Recommendations (1)

Slide 12

NotesRemove the manual valve

Full RecommendationRemove the manual valve on the drain line from pH meter AT21015, to prevent the meter being over-pressurised if the valve is closed.

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Examples of HAZOP Recommendations (2)

Slide 13

NotesAdd a check valve

Full RecommendationAdd a check valve on line 2”-11015-HD between E5041 and TV-1015, to reduce the risk of backflow, which could lead to major damage to the compressor.

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Examples of HAZOP Recommendations (3)

Slide 14

NotesChange to a coarse mesh filter, or remove the filter

Full RecommendationReplace existing filter in line 6”-10501-AL with a half inch mesh filter below the feed hopper, to prevent large objects damaging the screw feeder.

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Examples of HAZOP Recommendations (4)

Slide 15

NotesAdd a pressure gauge on the filter

Full RecommendationAdd a pressure gauge on the lid of filter FA-6407 to indicate pressure before the element, so operator can check that filter is depressurised before opening, to avoid injury.

Add to operating instructions.

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Examples of HAZOP Recommendations (5)

Slide 16

NotesProvide more protection for operator when taking a sample

Full RecommendationProvide an enclosure around the sample spout 4”-5117-HN, to prevent the operator being splashed.

Modify the operator instructions to include required protective clothing, to ensure that operator cannot be injured.

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Examples of HAZOP Recommendations (6)

Slide 17

NotesChange pipe specification after manual valve on nitrogen line

Full RecommendationMake piping specification change on line 10005-HB, after the downstream manual valve, not after reducing valve PRV-78341, as currently the valve and piping could be over-pressurised.

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Examples of HAZOP Recommendations (7)

Slide 18

NotesFurther study needed

Full RecommendationAn explosion in vessel V2301 may be possible if gas composition control is lost.Carry out a study of explosion peak pressures and rate of pressure rise for representative vapour/oxygen/nitrogen mixtures, to identify whether detonation could occur. Include experiments with bursting discs, to help design interlocks and vents to reduce probability of rupture of vessel V2301.Results required before Jan 1st.

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Examples of HAZOP Recommendations (8)

Slide 19

NotesCheck relief valve sizing

Full RecommendationA fire in the unit could envelop vessels V257, V628, V629 and V2103 and might overload the manifold.Ensure that relief valve RV628, tail pipe and manifold are sized for external fire and that back pressure in the manifold from other fire related discharges would not restrict the vent capacity.

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Examples of HAZOP Recommendations (9)

Slide 20

NotesConsider more fire protection

Full RecommendationA fire in the solvent recovery unit could cause a major loss in terms of down time and lost market share. Review the current active and passive fire protection systems and make recommendations on justifiable improvements on the basis of a cost/benefit analysis.

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Examples of HAZOP Recommendations (10)

Slide 21

NotesUpdate drawing

Full RecommendationUpdate P&ID F201/1086/R to show last year’s modifications to the piping of the catalyst injection system to Reactor R791 and its sampling arrangements.

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