Risk and Safety Engineering - Assignment Example

Task a a) List 5 possible hazards and carry out a hazard analysis bases on a check list Hazard associated with the systems include Spilling of the gas mixture due along the pipe work Explosion of the tank due to failure of relieve valve Pump failure Rupture at heat exchanger Check list Is the relief valve (RV) in good working condition? Is Level Indicator (LI) in working condition? Is low level indicator (LLA) in good working condition? Is the pump in good working condition? Is pump of the appropriate size? Is Flow Recorder Controller (FRC) in good working condition? Task b Use of HAZOP technique in identification of causal events and hazards HAZOP means is important as it entails detailed hazard and operability problem identification process which is undertaken in teamwork and this definition is a clear indicator of how the process is important in identifying the causal events and hazards. Use of HAZOP will involve identifying potential deviation in the design intent, the possible cause of deviation is examined and a consequence of the same is also assessed. The main features associated with HAZOP are The process of examination is creative and it proceeds in a system way where a series of guide words are used in identification of any likely deviation in the design. The deviations are used to trigger team members discern the way the deviations are likely to happen and the consequences of the same. The examination is to be undertaken with guidance being offered by a study leader who is trained and who will ensure that the system is covered comprehensively where there will be logical and analytical thinking. All the proceedings are recorded by recorder who is assigned to help the study leader with this task and the and this makes it possible for further evaluation to be done on the hazards and operational disturbances Specialists from relevant fields are relied upon for examination and this ensures that intuition and good judgment as they have the required skills and experience. The examination is carried in an atmosphere of positive thinking and free discussion and any problem identified is recorded so that it can undergo further assessment and resolution HAZOP is based on a “guide word examination” where there is deliberation to search for deviations in design intent. Examination is facilitated by putting the system into parts in a manner that will make it possible for design intent for the parts can be defined adequately. The choice of the size part is dependant on how complex the system and severity of the hazard. The design intent for a part of a system will be composed of items that convey the important features the part and this will enable the part to be divided naturally. The HAZOP studies have a lot of importance attached to the such that if a nominated team member happens to fail to attend any session, this would be regarded as being a very serious breach of plant safety management procedures. This failure to attend means that the other attendees would have put their time to waste as they wait input from the absent team member. After the assembling of the data and drawings, the team leader would be in a position to plan review meetings with estimation of meeting time for the study being the first priority. The role of the thumb is that a process section would be expected to last 20-30 minutes. For examp application of the rule would require a vessel having two inlets and two exits and a vent to take a total of two hours. This makes it possible for the leader to be able to make an approximation HAZOP meeting time requirement by putting into consideration the process sections that are to be dealt with. Allowing two to three hours for major equipment is another way of making an approximation. The leader goes on to make arrangements for review meeting upon making estimations for meeting time. Carrying on too long in a sitting or taking too many hours in a day or having many days in a week are considered undesirable. Thus the desire is an individual meeting not going beyond three hours non stop and two sessions per day preferably one in the morning and the second in the afternoon. If the HAZOP studies are require about six hours it is recommended that time per week should not go beyond three or four days a week. No Guide word Element Deviation Possible causes Consequences Safeguards Comments Actions required 1 LESS TRANSFER PRODUCT LESS PRODUCT TRANSFERED Wrong pump Fitted FRC fail Rupture in heat exchanger None unacceptable Check pump 2 MORE TRANSFER PRESSURE More pressure RV fail Tank bursts None Unacceptable Check pump Check RV 3 AS WELL AS Valves /pipes As well as to valve Valves/pipe leaks Environmental contamination Possible explosion Use accepted piping standard Use flow sensor 4 NO Transfer material No transfer of material Pump fails Explosion Unacceptable Check pump 5 NO Transfer material No transfer of material Valve fail Explosion Unacceptable Check valve Task c Describe how you might use the FMECA approach to identify system hazards and produce a fragment of the FMECA table of the system described above (include about 5 items). FMECA approach is useful in the identification of system. In this approach all failure modes for each level of assembly or function analyzed is identified a description given and analysis done. Which the chance of a failure mode having more than one cause, all likely causes at lower assembly levels or what is regarded as subordinate functions are usually put into consideration. In the FMECA approach failure modes such as premature operation; intermittent operation, operation not taking place at the expected time etc. the failure focuses on specific assembly or function that is being affected by the mode of failure under consideration. The approach takes note of the fact that failure modes are likely to effects on other levels assemblies or functions and thus each failure mode is established in terms of local effect, effect on next higher level of function and the effect on the system in totality. It is also a requirement that FMECA be conducted by reliability engineers, design staff and any other party who may be interested. FAILURE MODE EFFECT AND CRITICALITY ANALYSIS System Assessor Date assessed Subsystem Sheet Date reviewed Reference Or Item No Function Process Function Potential Failure mode Potential effect Potential cost Risk rating Corrective action Revised risk OCC SEV DET RPN OCC SEV DET RPN 1 TRANSFER PRODUCT Wrong pump Fitted FRC fail Rupture in heat exchanger 3 10 3 90 2 TRANSFER PRESSURE RV fail Tank bursts 2 10 2 40 3 Valves /pipes Valves/pipe leaks Environmental contamination Possible explosion 3 10 3 90 4 Transfer material Pump fails Explosion 2 10 3 50 5 Transfer material Valve fail Explosion 2 10 3 50 Task d Task e (1) Tolerable Risk Criteria There are a number of methods which may be used in expressing risk tolerability where there is variation from one operator to another, variation in cultural setting as well as regulatory environment in the setting of the project. In qualitative criteria there will be use of descriptive words such us remote, probable, frequent unlikely in describing likelihood that the event will occur and the consequences of occurrence will be described by words like catastrophic, major or minor. In order to ensure that there is consistency in application of the criteria quantitative numbers are introduced so as to provide a definition on how the words are to be interpreted unlikely may mean occurrence that is may be witnessed once in 10 to 100 years. Qualitative interpretation is involved because the numerical predictions that are made have some level of uncertainty. Task e (2) E is consequence parameter for this case E4 (catastrophic) = 1 P is possibility of failing to avoid hazard parameter =P2 = 0.01 Therefore SIL = 1x0.01= 0.01 References Dean S. (1999) IEC 61508 – Understanding Functional Safety Assessment. Sauf Consulting Ltd Read More