HAZOP 0
Loss Prevention
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Loss Prevention
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What is HAZOP? •
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HAZOP Study • •
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HAZOP Team HAZOP studies are carried out using a `brainstorming' approach by a team, chaired and coordinated by a qualified person experienced in HAZOPs:
• Team Leader
• Team Secretary
• Process Engineer • Mechanical Engineer
• Commissioning/Operations • Engineer/Manager • Instrument Engineer
Strength of HAZOP •
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Weakness of HAZOP •
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Guide Words NONE /No
e.g .,
NO FLOW caused by blockage; pump failure; valve closed or jammed :
REVERSE
Opposite, failure
MORE
Quantitative increase, e.g ., MORE FLOW, Temp,
LESS
Quantitative increase,
As Well As
Qualitative increase, e.g. impurity
PART OF
Qualitative decrease, Change in composition high or low concentration of mixture; additional reactions in reactor or other location ; feed change.
Other than
Nothing of the intent happen, completely different occurs 8
e.g .,
REVERSE FLOW caused by pump
e.g .,
LESS FLOW, Temp,
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HAZOP Steps •
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This process enables a comprehensive evaluation of Hazard control systems and produces recommendations for any necessary modifications. The overall result is a reduction in both hazards and potential operational problems
HAZOP STUDY REPORT FORM TITLE :
HAZOP Study Form Sheet 1 of
LINE 1 : CAUSES DEVIATION
CONSEQUENCES
EXISTING PROVISIONS
ACTIONS, QUESTIONS OR RECOMMENDATIONS
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Storage Tank To atmosphere RV-1
Nitrogen
PV-2
To flare
H
PICA
Equipment & Valve FV Flow control valve T Tank P Pump PV Pressure control valve RV Relief valve V Valve
PV-1
V-8 V-7
V-5 H From tank trucks
Storage Tank
TIA H
LIA
L
V-1
V-2
FICA
PI
L To process V-4
V-3
FV-1
Instrument L Level T Temperature P Pressure F Flow I Indicator C Controller A Alarm
HAZOP Table - level Cause
Deviation
Consequences
Safe guard
Action
Level
Less
More
NO
1. Rupture discharge line
Reagent release
Potential fire
LIA
Estimate release quantity
2. V3 open or broken
Reagent release
Potential fire
LIA
Estimate release quantity
3. V1 open or broken
Reagent release
Potential fire
LIA
V1 protection
4. Tank rupture
Reagent release
Potential fire
LIA
What external event cause tank rupture
5. Too much truck unload
Overfill
Reagent release via RV1
LIA
Does RV1 allow for liquid release? Consider high level alarm shutoff
6. Reverse flow from process
Overfill
Reagent release via RV1
LIA
Consider check valve at pump discharge Consider high level alarm shutoff at feed
Same as less
HAZOP Table - pressure Pressure
Less
More
9. Break in nitrogen or flare line
Reagent release
Potential fire
PICA
Consider independent PLA
10. Lose nitrogen
Tank implode
Reagent release
PICA
Consider vacuum break valve
11. PV2 fails closed
Tank implodes
Reagent release
PICA
Consider PAL
12. PICA fails, closing PV2
Tank implodes
Reagent release
13. PICA fails, closing PV1
Reagent release via RV1
Tank rupture if RV1 fails
PICA
What PV1 and RV1 capacity
14. PV1 fails closed
Reagent release via RV1
Tank rupture if RV1 fails
PICA
Consider independent PAH
15. V7 closed
Reagent release via RV1
Tank rupture if RV1 fails
PICA
Is V7 locked open
16. Overfill tank
Truck unload
Tank rupture if RV1 fails
PICA
Consider second high level shutoff
17. Temperature of inlet higher than normal
Reagent release in RV1
Tank rupture if RV1 fails
PICA
What prevent high temp of feed Consider PAH
18. Volatile impurities in feed
Reagent release in RV1
Tank rupture if RV1 fails
PICA
Consider PAH Consider sampling before unloading
Tank not designed for vacuum
Hazop Table - composition Cause
Deviation
Consequences
Safe guard
Action
Composition
Other than
7. Wrong reagent
Possible reaction
As well as
8. Impurities in reagent
Problem in reactor
Tank rupture
Consider sampling before unload Are other material delivered in tank Are unloading connection different
HAZOP Table - Temperature Temperature
Less
High
19. Temperature of inlet cooler than usual
Possible vacuum
Thermal stress on tank
What are temp limits of tank
20. Low tank pressure
See 9-12
Thermal stress on tank
What are pressure limits of tank
21. temperature of inlet is higher than usual
See 17
Thermal stress on tank
What are temp limits on tank
22. external fire
Tank fails
Reagent release
What could cause external fire What are fire protection capabilities Is fire protection adequate
Preliminary HAZOP Example Cooling Coils Monomer Feed
Refer to reactor system shown.
Cooling Water to Sewer
The reaction is exothermic. A cooling system is provided to remove the excess energy of reaction. In the event of cooling function is lost, the temperature of reactor would increase. This would lead to an increase in reaction rate leading to additional energy release.
Cooling Water In
The result could be a runaway reaction with pressures exceeding the bursting pressure of the reactor. The temperature within the reactor is measured and is used to control the cooling water flow rate by a valve. Perform HAZOP Study T C
Thermocouple
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Preliminary HAZOP on Reactor Guide Word
Deviation
Causes
Consequences
Action
NO
No cooling
Cooling water valve malfunction
Temperature increase in reactor
Install high temperature alarm (TAH)
REVERSE
Reverse cooling flow
Failure of water source resulting in backward flow
Less cooling, possible runaway reaction
Install check valve
MORE
More cooling flow
Control valve failure, operator fails to take action on alarm
Too much cooling, reactor cool
Instruct operators on procedures
AS WELL AS
Reactor product in coils
More pressure in reactor
Off-spec product
Check maintenance procedures and schedules
OTHER THAN
Another material besides cooling water
Water source contaminated
May be cooling inefffective and effect on the reaction
If less cooling, TAH will detect. If detected, isolate water source. Back up water source?
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Case Study – Shell & Tube Heat Exchanger •
Using relevant guide works, perform HAZOP study on shell & tube heat exchanger
Process fluid
Cooling water 19
HAZOP on Heat Exchanger Guide Word
Deviation
Causes
Consequences
Action
NONE
No cooling water flow
Failure of inlet cooling water valve to open
Process fluid temperature is not lowered accordingly
Install Temperature indicator before and after the process fluid line Install TAH
MORE
More cooling water flow
Failure of inlet cooling water valve to close
Output of Process fluid temperature too low
Install Temperature indicator before and after process fluid line Install TAL
LESS
Less cooling water
Pipe leakage
Process fluid temperature too low
Installation of flow meter
REVERSE
Reverse process fluid flow
Failure of process fluid inlet valve
Product off set
Install check valve (whether it is crucial have to check?)
CONTAMINATION
Process fluid contamination
Contamination in cooling water
Outlet temperature too low
Proper maintenance and operator alert
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Documents needed for HAZOP Study • For Preliminary HAZOP – Process Flow Sheet ( PFS or PFD ) – Description of the Process • For Detailed HAZOP – Piping and Instrumentation Diagram ( P & ID ) – Process Calculations – Process Data Sheets – Instrument Data Sheets – Interlock Schedules – Layout Requirements – Hazardous Area Classification – Description of the Process
Planning for HAZOP : • Safety procedures documents • Relief/venting philosophy
• Chemical involved • Piping specifications • Previous HAZOP report
Planning for HAZOP • •
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Responsibility of HAZOP Team Members Plan sessions and timetable Control discussion Limit discussion Encourage team to draw conclusion Ensure secretary has time for taking note Keep team in focus Encourage imagination of team members Motivate members • Discourage recriminations • Judge importance issues • • • • • • • •
Responsibility of HAZOP Team Members • Take adequate notes • Record documentations • Inform leader if more time required in taking
notes • If unclear, check wording before writing
• Produce interim lists of recommendations • Produce draft report of study • Check progress of chase action • Produce final report
Responsibility of HAZOP Team Members • Provide a simple description
• Provide design intention for each process
unit • Provide information on process conditions
and design conditions • Provide a simple description • Provide design intention for each process
unit • Provide information on process conditions
Responsibility of HAZOP Team Members • Provide specification details
• Provide vendor package details • Provide equipment and piping layout
information • Provide details of control philosophy • Provide interlock and alarm details • Provide info on shutdown, safety features
Responsibility of HAZOP Team Members • Provide information on compatibility with any
existing adjacent plant • Provide details of site utilities and services • Provide (for study on existing plant) any update on maintenance access and modifications • Provide guidance on control instrumentation
integrity from an operating experience view point • Provide (for study on existing plant) information on plant stability at the specified control parameters • Provide information on experienced operability deviations of hazard potential
