1. Read the following case study and answer the associated questions. Case study
ID: 1867425 • Letter: 1
Question
1. Read the following case study and answer the associated questions. Case study 1: An analysis was done by expert safety committee in Sohar refineries about control valve failure and they have list around 24 reasons and the failure rate in percent. Study them and answer the following questions i. Discuss the hazards that can effect from control valve failure ii. Recommend control measures for at least 20 reasons for avoiding control valve failures 1. Loss of demand si 2. Loss of s 3. Actuator failure 5.6% 4. Water in the airline 2% 5. Insufficient air s 6. IP out of calibration 4.590 7- Positioner out of calibration 6.7% 8. Valve -3.6% air (reg -2.6 % ssure or volume 8% cations for the a lication 0.5% 10. Sti 11. Leakage external and internal 23% 12. Incorrect valve 13. Misalignment of valve parts 1 1% 14. Overshoot of control devices 3.8% 15. Valve plug and trim failure 4.6% 16. Dead band 090 17. Nonlinear flow 0% 18. Controller signal unavailable 19. Sand Erosion 0.5% 20 21 22. Commissi 23. Materials deficient0% 24. Valve stem failure 5.8 % 25. Poor welding 090 18.8% and closing time 9% e maintenance 8% rator failure 23 error 7%Explanation / Answer
1. Provide accurate demand signal to control valve to prevent hazard.
2. Supply air is required to be check daily basis to prevent malfunction of valve.
3. Actauator should be checked on peroidic basis to prevent sudden failure of actuator.
4. Water should not be there in air line. Some sort of heating device should be there to prevent water entering in to air line.
5. Due to insfficient air supply pressure, some feature may not work. enough amount of air pressure should be applied to valve before any operation.
6. Periodic maintenance is required for I/P calibration to prevent failure.
7. Positioner should be placed on calibration or it should be replaced with new positioner.
8. Due to wrong valve specifications hazard may occur. Before using in application valve specification should be checked once again.
9. Some sort of chemical or other paints should be applied to prevent corrosion. valve should not be kept in humid environment else should be kept in cover.
10. medium which is flowing in valve should not get stick with valve surface. Some chemical should be applied inside valve surface to prevent sticking.
11. Leakage should be prevented. Fillers or any other sits should be provided to prevent leakage.
12. Before using valve, operator should be aware of all functions of valve and he should know when to open valve and for how much time it should be kept open.
13. Before fitting valve in any pipe or anywhere, erection should be done properly and enough amount of alignment should be there to prevent hazard.
14. Overshoot of control valve is one of reason for hazard. Overshooting should be prevented. While overhauling of valve, enough qualified person should be available for overhauling.
15. As far as possible valve plug in should be prevented for valve safety.
16. Dead bend should be avoided in valve line.
17. Nonlinear flow should not be there in valve. Non linear flow may increase turbulance and in turn stresses also increase on valve inside surface.
18. Controller signal should always be available for valve functioning. Electric source should be always available for valve functioning.
19. Sand Erosion should be prevented. When valve are kept in open environment for long time, sand erosion may occur after long time. Valve should be covered under roof or anything to prevent sand from valve.
20. Inadequate maintenance: Most of hazard occur due to inadequate maintenance. Periodic maintenance should be done to prevent long time cost and experienced person should be available for maintenance operation.
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