Examples ofExamples of
5.4 APPLICATION APPLICATION TO TO OPERATING PROCEDURES OPERATING PROCEDURES
5.4 APPLICATION APPLICATION TO TO OPERATING PROCEDURESOPERATING PROCEDURES
Start-up/Shutdown Procedures Start-up/Shutdown Procedures
The standard HAZOP technique may be used for analysis of stepwise procedures (startup, The standard HAZOP technique may be used for analysis of stepwise procedures (startup, shutdown, emergency, batch, etc.) with relatively minor modifications. Normal operating shutdown, emergency, batch, etc.) with relatively minor modifications. Normal operating procedures, however, are best treated as part of the P&ID HAZOP and are reviewed procedures, however, are best treated as part of the P&ID HAZOP and are reviewed separately.
separately.
Nodes should be selected to represent the largest group of actions for which a single clear Nodes should be selected to represent the largest group of actions for which a single clear intention can be defined (e.g. “start the Acid Rerun System”). The study would then proceed intention can be defined (e.g. “start the Acid Rerun System”). The study would then proceed as follows:
as follows:
•
• Parameter : StepParameter : Step
•
• Guide Word : NoGuide Word : No
•
• Deviation : No Step (i.e., step is omitted)Deviation : No Step (i.e., step is omitted)
•
• CausesCauses
—
— Is the iIs the intenntention otion of the nf the node uode unmistnmistakabakable?le?
—
— Are all of the aAre all of the actionctions requis required stared stated in the prted in the procedocedure?ure?
—
— Are the Are the actions actions sufficiently sufficiently explicit to explicit to ensure thensure that all oat all operatorsperators will execute them properly?
will execute them properly?
—
— Are cheAre checklists ancklists and othd other externer external docal documents uments complete complete and and areare they referenced as needed?
they referenced as needed?
•
• Consequences: e.g. Loss of ContainmentConsequences: e.g. Loss of Containment
•
• Safeguards: e.g. Procedures & TrainingSafeguards: e.g. Procedures & Training
•
• Recommendations may be general (e.g. Provide detailed proceduresRecommendations may be general (e.g. Provide detailed procedures and checklists) or may list
and checklists) or may list specific procedure changespecific procedure changes.s.
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The main steps in
The main steps in HAZOPing the start up/shutdown procedHAZOPing the start up/shutdown procedures are:ures are:
List each action required to complete the step as a separate cause.
List each action required to complete the step as a separate cause.
Review the consequences if each action is not done, is done Review the consequences if each action is not done, is done improperly, or is done out of order.
improperly, or is done out of order.
Review safeguards (note disabled alarms and interlocks).
Review safeguards (note disabled alarms and interlocks).
Recommend appropriate warnings, procedure changes, or Recommend appropriate warnings, procedure changes, or equipment modifications to help ensure that the action is done equipment modifications to help ensure that the action is done properly.
properly.
The following example demonstrates how the HAZOP technique is applied to the start-up The following example demonstrates how the HAZOP technique is applied to the start-up procedures for a typical
procedures for a typical distillation column:distillation column:
Deviation:
Deviation: No StepNo Step Causes:
Causes: Incomplete or inexplicit procedureIncomplete or inexplicit procedure Consequences:
Consequences: Possible hydrocarbon releasePossible hydrocarbon release Recommendations:
Recommendations: Consider providing a detailed checklist and initialsConsider providing a detailed checklist and initials for all steps
for all steps
Deviation:
Deviation: No StepNo Step Causes:
Causes: Batchwise steps not Batchwise steps not referencedreferenced Consequences:
Consequences: Possible pump damage and vessel overfillPossible pump damage and vessel overfill Recommendations:
Recommendations: Consider providing an introductory stepConsider providing an introductory step describing batch requirements and parallel describing batch requirements and parallel operations (Note: start-up is essentially operations (Note: start-up is essentially
batchwise on each major unit and major units batchwise on each major unit and major units may be started-up in parallel)
may be started-up in parallel)
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Deviation:
Deviation: No StepNo Step Causes:
Causes: Reflux pump self-flush not lined upReflux pump self-flush not lined up Consequences:
Consequences: Pump damage and possible hydrocarbonPump damage and possible hydrocarbon release
release Recommendations:
Recommendations: Add a state Add a statement requiring tment requiring the reflux pump he reflux pump self- self-flush to be lined up
flush to be lined up
Deviation:
Deviation: Less StepLess Step Causes:
Causes: Heat input to column not increased as neededHeat input to column not increased as needed Consequences:
Consequences: High level resulting in column flooding andHigh level resulting in column flooding and aborted start-up
aborted start-up Recommendations:
Recommendations: Clarify procedure by referencing “steam flow”Clarify procedure by referencing “steam flow”
rather than “heat input”
rather than “heat input”
Normal Operating Procedures Normal Operating Procedures
The basic steps involved in HAZOPing the normal operating procedures are:
The basic steps involved in HAZOPing the normal operating procedures are:
•
• Identify the major hazards associated with Identify the major hazards associated with the procedure.the procedure.
•
• Describe the steps of a model Describe the steps of a model or ideal procedure.or ideal procedure.
•
• Evaluate the existing procedure (if there is Evaluate the existing procedure (if there is one) to determine whether one) to determine whether it accommodates the hazards that were identified and listed, and if it it accommodates the hazards that were identified and listed, and if it follows the model.
follows the model.
The first step in reviewing a procedure, or “software” element, is to identify the major hazards The first step in reviewing a procedure, or “software” element, is to identify the major hazards associated with the process. These items will have been identified during the HAZOP of the associated with the process. These items will have been identified during the HAZOP of the
“hardware” if a process HAZOP was
“hardware” if a process HAZOP was previously done.previously done.
It is best to list the hazards associated with the process. This helps ensure the hazards are It is best to list the hazards associated with the process. This helps ensure the hazards are avoided when reviewing the procedures.
avoided when reviewing the procedures.
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In addition to the obvious physical and chemical hazards, recognize that there may be In addition to the obvious physical and chemical hazards, recognize that there may be ergonomic hazards. In other words, incompatibilities between what the procedure says to do ergonomic hazards. In other words, incompatibilities between what the procedure says to do and what the body can actually do.
and what the body can actually do.
The hazards may be those inherent in performing the procedure or hazards associated with The hazards may be those inherent in performing the procedure or hazards associated with the process that the procedure must avoid. For example, in
the process that the procedure must avoid. For example, in using a torch to using a torch to light off a furnace,light off a furnace, an example of a physical hazard may be the potential for spilling and igniting the flammable an example of a physical hazard may be the potential for spilling and igniting the flammable liquid used to light the torch. An example of a chemical hazard might be the burning of a toxic liquid used to light the torch. An example of a chemical hazard might be the burning of a toxic waste material in the furnace. And an ergonomic hazard may be the improper positioning of waste material in the furnace. And an ergonomic hazard may be the improper positioning of the torch hole that requires the employee to get
the torch hole that requires the employee to get into an unsafe position to perform his into an unsafe position to perform his duties.duties.
The next step will be to list the major steps that would be required in the actual procedure.
The next step will be to list the major steps that would be required in the actual procedure.
There may be decision criteria, such as minimums and maximums, that the employee should There may be decision criteria, such as minimums and maximums, that the employee should know and act upon in order to accomplish the tasks without an accident. These may be time, know and act upon in order to accomplish the tasks without an accident. These may be time, repetitions, pressure, temperature
repetitions, pressure, temperature, etc. And , etc. And this may be this may be further complicated by an exact further complicated by an exact order order in which the steps must be taken, such as in the case of certain regeneration processes. The in which the steps must be taken, such as in the case of certain regeneration processes. The model procedure must also be specific as to who will perform the steps and how they will be model procedure must also be specific as to who will perform the steps and how they will be performed. The intent at this point in
performed. The intent at this point in the procedure review process is not to the procedure review process is not to write a procedure,write a procedure, but to quickly highlight those items the procedure should include, as well as any criteria or but to quickly highlight those items the procedure should include, as well as any criteria or important variables.
important variables.
The next step is to determine whether the actual procedure compensates for the hazards The next step is to determine whether the actual procedure compensates for the hazards identified and how well the existing procedure compares with the ideal procedure that the identified and how well the existing procedure compares with the ideal procedure that the team has prepared. If there are deficiencies in the existing procedure, they should be team has prepared. If there are deficiencies in the existing procedure, they should be highlighted and corrected.
highlighted and corrected.
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The following is an example of how the HAZOP technique can be used to evaluate existing The following is an example of how the HAZOP technique can be used to evaluate existing normal operating procedures:
normal operating procedures:
Deviation:
Deviation: No StepNo Step Causes:
Causes: Poor organization of procedure for chemicalPoor organization of procedure for chemical injection in overhead system
injection in overhead system Consequences:
Consequences: Possible confusion resulting in insufficientPossible confusion resulting in insufficient chemical addition and rapid downstream heat chemical addition and rapid downstream heat exchanger fouling
exchanger fouling Recommendations:
Recommendations: Consider eliminating step 4 and incorporatingConsider eliminating step 4 and incorporating information into steps 3, 45-47
information into steps 3, 45-47
Deviation:
Deviation: Other Than StepOther Than Step Causes:
Causes: Incomplete or inexplicit procedureIncomplete or inexplicit procedure Consequences:
Consequences: Possible HF acid or hydrocarbon releasePossible HF acid or hydrocarbon release Recommendations:
Recommendations: Consider adding operating condition targets toConsider adding operating condition targets to individual steps
individual steps
Deviation:
Deviation: Less stepLess step Causes:
Causes: Depropanizer bottoms temperature not properlyDepropanizer bottoms temperature not properly adjusted
adjusted Consequences:
Consequences: Process upset and possible isostripper Process upset and possible isostripper overpressure due to increased light ends overpressure due to increased light ends concentration
concentration Recommendations:
Recommendations: Add a warnin Add a warning note to thg note to the procedures e procedures regardingregarding possible consequences to the isostripper due to possible consequences to the isostripper due to low depropanizer bottoms temperature
low depropanizer bottoms temperature
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Deviation:
Deviation: More stepMore step Causes:
Causes: Acid storage Acid storage drum pressure drum pressure increased aboincreased aboveve 140 psig
140 psig Consequences:
Consequences: Possible HF release to ARNPossible HF release to ARN Recommendations:
Recommendations: Add a high Add a high pressure alarm tpressure alarm to the acid stoo the acid storagerage drum and arrange to alarm in
drum and arrange to alarm in the control roomthe control room
Deviation:
Deviation: As Well As ste As Well As stepp Causes:
Causes: Normal butane storage tank lined up too earlyNormal butane storage tank lined up too early Consequences:
Consequences: Product contamination and process upsetProduct contamination and process upset Recommendations:
Recommendations: Clarify switching procedure and include specificClarify switching procedure and include specific time to make switch
time to make switch from isobutane to normalfrom isobutane to normal butane storage
butane storage
Although
Although the the guide guide words words used used for for the the hardware hardware review review do do not not necessarily necessarily fit fit well well whenwhen reviewing procedures, similar guide words may be helpful as a double check to insure the reviewing procedures, similar guide words may be helpful as a double check to insure the comprehensiveness of the review. A set of guide words, helpful in reviewing procedures is comprehensiveness of the review. A set of guide words, helpful in reviewing procedures is given in the table on the following page.
given in the table on the following page.
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Guide Words for
Guide Words for Procedure ReviewsProcedure Reviews
G
Guuiidde e WWoorrdd MMeeaanniinngg
N
NOO DDooeessnn’’t t ppeerrffoorrm m tthhe e sstteepp. . A A sstteep p oor r iimmppoorrttaannt t ccrriitteerriiaa, , iin n tthhee procedure is skipped.
procedure is skipped.
L
LEESSSS DDooees s lleesss s tthhaan n iis s ssppeecciiffiieed d oor r rreeqquuiirreed d qquuaannttiittaattiivve e ddeeccrreeaassee (e.g., purges a vessel for 5 minutes when the
(e.g., purges a vessel for 5 minutes when the procedure callsprocedure calls for 10 minutes)
for 10 minutes) M
MOORREE DDooees s mmoorre e tthhaan n iis s ssppeecciiffiieed d oor r rreeqquuiirreed d qquuaannttiittaattiivve e iinnccrreeaassee (e.g., opens a valve fully, when the
(e.g., opens a valve fully, when the procedure calls for procedure calls for
“cracking” the valve)
“cracking” the valve) P
PAARRT T OOFF PPeerrffoorrmms s ppaarrt ot of f tthhe se stteep p ( q( quuaalliittaattiivve de deeccrreeaasse (e (ee..gg.., , cclloosseess only one block valve when the procedure says to close a only one block valve when the procedure says to close a double block and open a
double block and open a bleed)bleed) AS WELL AS
AS WELL AS Does more than is specified ( qualitative increase (e.g.,Does more than is specified ( qualitative increase (e.g., opens the transfer valves to a number of
opens the transfer valves to a number of tanks when onlytanks when only one is to be filled)
one is to be filled) R
REEVVEERRSSEE DDooees ts thhe oe oppppoossiitte oe of wf whhaat it is ss sppeecciiffiieed (d (ee..gg.., o, oppeenns a s a vvaallvvee when the procedure says that it is to
when the procedure says that it is to be closed)be closed) OT
OTHEHER TR THAHANN CoCommplpletete se sububststititututioion (n (ee.g.g., ., opopeens ns vavalvlve A e A whwheen tn thhee procedure says to open valve B)
procedure says to open valve B) H
HOOWW HHoow w iis s tthhe e sstteep p tto o bbe e aaccccoommpplliisshheedd? ? AArre e aaddeeqquuaatte e ffaacciilliittiieess provided to allow the operator to
provided to allow the operator to perform the step asperform the step as specified?
specified?
C
CHHEECCKK HHoow w ccaan n iit t bbe e cchheecckkeedd, , oor r vveerriiffiieed d tthhaat t tthhe e sstteep p hhaas s bbeeeenn properly accomplished?
properly accomplished?
O
ORRDDEERR AArre e tthhe e oorrddeer r oof f sstteepps s iimmppoorrttaannt t aannd d ccoorrrreecctt?? W
WHHOO IIs s iit t cclleeaarrlly y oobbvviioouuss, , oor r ssttaatteedd, , wwhho o iis s tto o ppeerrffoorrm m eeaacch h ppaarrt t oof f the procedure?
the procedure?
W
WHHYY WWhhy y tteemmppeerraattuurre e sseet t ppooiinnt t iis s 33000 0 °°FF??