L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Path Forward Introduction Advantages Layout & Location Foundation Types Mechanical Design Aspects Stress Analysis Design Guidelines Corrosion Protection Safety Aspects L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Introduction L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT What is Mounded Bullet ? • Mounded LPG Bullets are large, horizontal cylindrical steel vessels used for storage of pressurized gases (i.e. LPG) at ambient temperature. • Installed above the highest ground water level and the soil cover usually protrudes above grade, as an Earth mound, hence the term “Mounded Storage”. • Bullets sizes ranges between 3.5 to 7.0 meter diameter and lengths of 35 to 70 meters or more. • Mounded bullets allow storage of large quantities of LPG - up to 2,000 MT or more in a single location! L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Typical Detail of Mounded Bullet L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT BLEVE (Boiling Liquid Expanding Vapour Explosion) If a system catches fire due to leakage or there is any fire in the near by surroundings, the liquid inside the container starts expanding due to heat radiation. This will lead to rise in internal Pressure continuously and the container may explode causing huge damage. This can be avoided by using mounded storage concept. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Why Mounded Bullets ? • Mexico LPG Gas Terminal Incidence : 1600 m 3 LPG was stored after first BLEVE, Fireball Dia 350m,debris 1.2 km, 500 died, 7000 injured • Main Causes of Disaster : Close Spacing of Vessels within Plant Populated Built-Up Area within 300-400m of Plant Orientation Plant/ Layout not Conducive to good Safety. • Conclusion: Avoiding aboveground storage : A BLEVE would not have occurred & catastrophe could have been avoided: (NEED FOR MOUNDED STORAGE) BLEVE (Boiling Liquid Expanding Vapour Explosion) L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Advantages L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Advantages • BLEVE (Boiling Liquid Expanding Vapor Explosion) can be totally avoided. • Protection of equipment against. 1. Heat radiation from a nearby fire 2. Pressure wave originating from an explosion 3. Impact of flying objects. 4. Sabotage • It results in reduced site area due to less stringent inter-spacing requirements. • The safety distance to the site boundary can be reduced considerably. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Layout & Location L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Layout & Location Vessels shall be located so that: · They do not affect, and are not affected by, other nearby underground structures (e.g. foundations, pipelines, sewers); · They are not subjected to loads from vehicles; · They are not affected by other hazards such as power cables and cathodically protected pipelines. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Typical Layout of LPG storage vessels L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Safe distances for mounded LPG pressure Storage vessels L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Foundation Types L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Foundation Types…. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Mechanical Design Aspects L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Design Codes & Standards • ASME Sec VIII or PD 5500. • EEMUA (Engineering Equipment & Materials Users Association) Publication No.190:00 • OISD (Oil Industry Safety Directorate) - 150 : Design & safety requirements for LPG mounded storage facility L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Material of Construction Components MOC Shell and Heads SA 516 Gr. 60 / 70 (Impact tested) SA 537 Cl1 Nozzles necks SA 333 Gr. 6 Nozzle flanges SA 350 LF2 External studs / nuts SA 320 Gr. L7 / SA 194 Gr. 4 Pipe fitting SA 420 Gr. WPL6 Gaskets SS 304 SPWD L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Weight of Mound • Weight of empty vessel (metal weight) • Weight of stored liquid • Weight of hydrotest water • Internal design pressure • Internal vacuum • Hydrotest pressure • Weight of Mound q q0 cos , 2Qe q0 R Qe = Weight of mound per unit length L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Mound Load on Vessel L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Distribution of Bed Reaction & Mound Pressure L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Pressure Exerted by Mound • Pressure by mound on domed ends p =C.gs.h C = Soil pressure coefficients, h = Depth below top of mound C depends on slope of mound and movements of domed ends For mound slope of 30o and end movements 0.02 m: Cneutral = 0.3, Cactive = 0.2, Cpassive = 1.7 • Axial frictional loads Soil friction exerted when the vessel expands or contracts due to temperature or pressure Friction coefficient of 1.0 may be considered L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Pressure due to uneven support • Pressure due to uneven support Two cases of uneven distribution of soil reaction considered • 1) Settlement of mid point wrt two end points 2) Settlement of ends wrt mid point Soil reaction pressure 1) Radially inward soil pressure follows cosine distribution. 2) Bed angle depends upon preparation of soil bed below vessel. For properly prepared sand bed, bed angle is 120o 3) For hydrotest condition, bed angle of 60o-90o may be taken L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Pressure due to uneven support • Pressure due to uneven support 1) Horizontal Force = Horz. Seismic coefficient weight (loads a, b, f). 2) Vertical Force = Vert. Seismic coefficient weight. (Weight is increased proportionally.) L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Load Combination Operating condition Hydrotest condition X X Weight of the liquid in the vessel. X X Internal Pressure. X X Loads Design Cases Empty condition with vacuum Dead weight of the vessel. X Internal Vacuum. X Loads due to the mound X X Loads due to uneven support by the foundation X X Loads due to variation of the vessels length X X Loads due to earthquake X X X Loads due to an external explosion X X X L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis • Detail stress analysis using FEM Software Packages • Integrated model of vessel, domed end and stiffeners • All Possible load combinations (12 load cases) are considered for stress analysis. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Stress Analysis L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Settlements in Sand Bed Sagging Type (Settlement at Mid Span) Hogging Type (Settlement at Ends) L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Design Guidelines L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Design Guidelines • The vessels should be installed at least 0.6 m above the highest ground water level in a sand foundation of at least 1 m thickness in order to obtain proper bedding. • The foundation of the bullet shall be constructed such that for the operational lifetime of the bullet, its longitudinal slope shall be in 1 : 200 minimum and 1 : 50 maximum. • The thickness of the mound shall be 1 meter minimum. • Longitudinal weld seams shall be avoided in the bottom 120 deg. • The ratio of distance between internal stiffeners to bullet diameter is in the order of 1 : 2. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Design Guidelines….. • Minimum 2 no. manholes shall be provided, one at each end of the bullet. • All plates, welds, HAZ shall be impact tested . Impact test temperature shall be determined as per design code. • PWHT shall be carried out for the complete bullet. • Radiography shall be full. • There are two methods of arranging nozzles : 1) All nozzles except manholes and large size nozzles (liquid inlet) shall be grouped and shall be installed on a dome and not directly on the shell. L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Design Guidelines….. 2) All nozzles except manholes and large size nozzles (liquid inlet) shall be grouped on the shell. Rectangular box shall be provided around the grouped nozzles, manholes and large size nozzles . This construction is called BOX TYPE CONSTRUCTION. • Settlement of soil bearing foundation : 1) Immediate settlement shall be limited to 50 mm. 2) Long-term settlement shall be limited to 25 mm. • Min. Factor of safety for foundation design is 2.0 L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Corrosion Protection L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Corrosion Protection • Mound & Foundation are potentially Corrosive Environment External Coating: glass fibre reinforced bitumen coating/epoxy /urethane based coating • Internal Coating: for refinery services: bottom 90o is coated if water/H2S ingression in LPG • Cathodic Protection: Impressed Current System: NACE RP - 0169 L&T-CHIYODA LIMITED Safety Aspects L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Protection system for situations in which filling/delivery rates are based on alarms and corrective actions are manually implemented L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Suggested Alarm Priorities SUGGESTED ALARM PRIORITIES Priority Alarm Record Low High Suggested Action Emergency PIA/HH PIA/LL X X X X Stop Supply Stop Offtake LA/HH X X Stop Supply LIA/HH LIA/H LIA/L LIA/LL X X X X HZ X X Stop Supply and Offtake XA X X Call-out Instrument Maintenance X Stop Supply Re-route Supply Re-route Offtake Stop Offtake X X X L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Protection system for situations in which filling/delivery rates are high and corrective actions are automatically implemented L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Suggested Alarm Priorities SUGGESTED ALARM PRIORITIES Priority Alarm Record Low High Emergency X X Suggested Action PIZA/HH PIZA/LL X X PIA/H PIA/L X X LZA/HH X LIA/H LIA/L LISA/LL X X X HZ X X Stop Supply and Offtake XA X X Call-out Instrument Maintenance X X Trip Supply Valve Trip Offtake Valve Re-route Supply Re-route Offtake X X X Trip Supply Valve Re-route Supply Re-route Offtake Trip Pump X L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Photographs L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Photographs L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT Thank You L&T-CHIYODA LIMITED EQUIPMENT ENGG. DEPARTMENT