CE1400 Environment And Safety Engineering Lecture 21 & 22 PDF

CE1400 ENVIRONMENT AND SAFETY ENGINEERING Lecture 21 & 22 Safety Engineering HAZOP Dr. Soukat Das Assistant Professor Department of Civil Engineering National Institute of Technology Rourkela Safety Analysis Meth...

CE1400 ENVIRONMENT AND SAFETY ENGINEERING Lecture 21 & 22 Safety Engineering HAZOP Dr. Soukat Das Assistant Professor Department of Civil Engineering National Institute of Technology Rourkela Safety Analysis Methods Failure Modes and Effect Analysis (FMEA) Fault Tress analysis (FTA) Hazard and Operability Analysis (HAZOP) Job Hazard analysis (JHA) Markov Method Control Charts  HAZOP Study The HAZard and OPerability study, commonly referred to as the HAZOP study HAZOP is a systematic technique for identifying all plant or equipment hazards and operability problems. HAZOP is a process to identify and assess risk. In this technique, each segment (pipeline, piece of equipment, instrument, etc.) is carefully examined, and all possible deviations from normal operating conditions are identified. HAZOP is an identifying technique and not intended as a means of solving problems When to conduct HAZOP study ? Documents needed for HAZOP study Features of HAZOP study Subsystems of interest Line, valve, equipment, vessels, etc Modes of operation Normal operation Start -up mode Shutdown mode Maintenance /construction / inspection mode Trigger events Human failure Equipment/instrument/component failure Supply failure Emergency environment event Effects within plant Changes in chemical conditions Changes in inventory Change in chemical physical conditions Features of HAZOP study How would During normal operation hazardous conditions Upon human failure detected ? Upon component failure In other circumstances Contingency actions Improve isolation Improve protection Corrective actions Change of process design Change of operating limits Change of system reliability Improvement of material Change control system Add/remove materials  GUIDE WORDS Guide Words Meaning No, None Negation of Intention (No flow) More Of Quantitative Increase (e.g., higher Temp). Less Of Quantitative Decrease (e.g., lower Pressure) As Well As (More Than) Qualitative Increase (e.g., an impurity) Part Of Qualitative Decrease (e.g., only one of two components in a mixture) Reverse Opposite of Intention (e.g., backflow). Other Than Complete Substitution (e.g., flow of wrong material Process elements Flow Composition pH Pressure Temperature Reaction Time Stirring Speed Maintain Level Particle Size Viscosity, etc., STUDY NODES The locations (on P&ID or procedures) at which the process parameters are investigated for deviations. These nodes are points where the process parameters (P, T, F etc.) have an identified design intent. INTENTION The intention defines how the plant is expected to operate in the absence of deviations at the study nodes. DEVIATIONS A deviation is a way in which the process conditions may depart from their design/process intent. Guide-word + Parameter = Deviation Example: No + Flow = No Flow  CAUSES: The reason(s) why the deviation could occur. Several causes may be identified for one deviation. It is often recommended to start with the causes that may result in the worst possible consequence. CONSEQUENCES: The results of the deviation, in case it occurs. Consequences may both comprise process hazards and operability problems, like plant shut-down or reduced quality of the product Several consequences may follow from one cause and, in turn, one consequence can have several causes.  PRINCIPLES OF HAZOPS GUIDE WORDS* NONE MORE OF LESS OF PART OF MORE THAN OTHER CAUSE DEVIATION CONSEQUENCES (from standard (trivial, important, condition catastrophic) or intention) -hazard -operating difficulties *COVERING EVERY PARAMETER RELEVANT TO THE SYSTEM UNDER REVIEW: i.e. Flow Rate. Flow Quantity, Pressure, Temperature, Viscosity, Components Safeguards Facilities that help to reduce the occurrence frequency of the deviation or to mitigate its consequences. There are five types of safeguards that: 1.Identify the deviation: 2.Compensate for the deviation: 3.Prevent the deviation from occurring: 4.Prevent further escalation of the deviation: 5.Relieve the process from the hazardous deviation.  HAZOP procedure 1. Divide the system into sections (i.e., reactor, storage) 2. Choose a study node (i.e., line, vessel, pump, etc.,) 3. Describe the design intent 4. Select a process parameter 5. Apply a guide-word 6. Determine cause(s) 7. Evaluate consequences/problems 8. Recommend action: What? When? Who? 9. Record information 10. Repeat procedure (from step 2) HAZOP procedure HAZOP TEAM HAZOP STUDY - TEAM COMPOSITION A Team Leader, an expert in the HAZOP Technique Technical Members, for example New Design Existing Plant Design or Project Engineer Plant Superintendent Process Engineer Process Supervisor (Foreman) Commissioning Manager Maintenance Engineer Instrument Design Engineer Instrument Engineer Chemist Technical Engineer Example Phosphoric acid + ammonia = DAP (non-hazardous) Too little phosphoric acid hazardous ammonia Too little ammonia safe but undesirable product. 1) Choose a study node Study Node 1 2) Choose a process parameter Flow 3) Apply a guide word to the process parameter to suggest possible deviations  Deviation Possible Possible Action (Guide-word) Causes Consequences Required NO (no flow at i. valve A falls excess ammonia in automatic closure study node 1) closed reactor and release of valve B on loss to work area of flow from ii. phosphoric acid phosphoric acid supply supply exhausted iii. plug in pipe, pipe ruptures  Deviation Possible Possible Action (Guide-word) Causes Consequences Required LESS (reduced i. valve A excess ammonia in automatic closure flow at study node partially closed reactor and release of valve B based on 1) to work area reduced flow in ii. partial plug or pipe from leak in pipe phosphoric acid supply  Deviation Possible Possible Action (Guide-word) Causes Consequences Required MORE (increased excess phosphoric flow at study node acid degrades 1) product but presents no hazard to workplace  Deviation Possible Possible Action (Guide-word) Causes Consequences Required PART OF i. vendor delivers excess ammonia in Add check of (decreased wrong material reactor and release phosphoric acid concentration of or concentration to work area supply tank phosphoric acid at concentration after ii. error in study node 1) charging charging procedures phosphoric acid supply tank  Deviation Possible Possible Action (Guide-word) Causes Consequences Required AS WELL AS (increased concentration of phosphoric acid at study node 1) REVERSE (reverse flow at study node 1) OTHER THAN (material other than phosphoric acid in line A) 1. Repeat steps until all applicable guide words have been applied to the chosen process parameter 2. Repeat steps until all applicable process parameters have been considered for the given study node 3. Repeat steps until all study nodes have been considered Case Study Shell & Tube Heat Exchanger Case Study Shell & Tube Heat Exchanger Case Study Shell & Tube Heat Exchanger HAZOP Advantages HAZOP Disadvantages Thank you