Truong Dinh Hieu-PVE I. DROPPED OBJECT AT PLATFORM The crane lift object such as: container, pipe reel, drill riser, basket and other. All object could be dropped and impacted pipeline.
Truong Dinh Hieu-PVE1. METHOD RICK ASSESSMENT Failure Frequency due to Dropped Object will be checked with DNV OS F101. i.e . Frequency of accidental loads as table blow:
Truong Dinh Hieu-PVE2 INPUT DATA Pipe data. Number of Lifts Per Year of Crane (if available). Water Depth at platform. Drawing of pipeline approach at platform. Breadth of dropped object (if available). Data of protection (ex. Gravel Cover depth, Gravel Diameter, Bearing Capacity Coefficients, Structure Protection Energy )
Truong Dinh Hieu-PVE3 METHODOLOGY1. Angel deviation of object2. Drop probability due to crane activity (flift) selected in table 93. Probability of dropped object landing within any one ring.4. The probability of hit to a pipeline or umbilical with within a certain ring, r..
Truong Dinh Hieu-PVE3 METHODOLOGY Ar = Area within the ring Lsp = Length of subsea line within the ring based on the figure of riser approach.5. The frequency of hit can be estimated based on the number of lifts, the drop frequency per lift and the probability of hit to the exposed sections of the subsea lines. For a certain ring around the drop point. Nlift = number of lifts assumed as table below Overall annual risk of any dropped object impacting on pipeline
Truong Dinh Hieu-PVE3 METHODOLOGY6. The shape of dropped objects will be different impacted the pipeline, that impact energies are different. The range and probabilities of impact energies is show in Table below:7. Accumulated Hit Frequency for different Impact Energy Levels(i.e each object category hit (impact) pipeline can be given different frequency probabilities.8. Total Energy Absorbed E other see table 8 DNV RP F107
Truong Dinh Hieu-PVE3 METHODOLOGY Impact Energies for given dent sizes. i.e the pipe deformation 5%,10%.. need energies is: Energy absorbed by the gravel dump and natural backfill: Dropped object is tubule object: For other than non-tubular objects, like containers.The bearing capacity coefficients can be chosen as Nq = 99 and Nγ = 137. The effective unit weight γ’ isassumed to be 11 kN/m3. sγ is a shape factor equal to 0.6, and L is the length of the impacting side,z = penetration depth, Ap = plugged area of the falling pipe , Energy absorbed by concrete coating X0 : assumed as concrete coating thickness With each pipe deformation need total energy Dent depth, % Energy Required, kJ absorbed ex. As table side: 5 63.62 10 90.50 15 125.31 20 166.54 25 213.30
Truong Dinh Hieu-PVE 3 METHODOLOGY9. Each energy absorbed must be calculated frequency of impact to make pipe deformation 5%, 10%.. Dent Depth Impact Frequency 5 4.95E-06 10 1.29E-06 15 1.12E-06 20 7.72E-07 25 5.57E-0610. Probability of Damage and Release based on dent diameter. i.e. Condition Probability see table below: Calculation Probability of Damage. Note : Damage due to D1 is not considered to give damage leading to failure. The failure frequency is obtained by adding the results for damage class D2 and D3. i.e.
Truong Dinh Hieu-PVE3 METHODOLOGY Calculation Probability of Release. Note : release due to R0 is not considered to give release as defined in section 4.2 DNV RP F107 . The failure frequency is obtained by adding the results for damage class D2 and D3. i.e. Failure Frequency due to Dropped Object will be checked with DNV OS F101. i.e.11. Question 1 : Method of protected if DAMAGE_RESULT is FAIL ??????? Protect Frame Concrete mattress Concrete Sleeper Lids
Truong Dinh Hieu-PVEII. DROPPED ANCHOR ALONG ROUTE Shipping activity could be required to cast anchor (cross/along pipeline route) Anchor can be impact directly on top of the pipeline or dropped vicinity the pipeline route can be drag http://www.youtube.com/watch?v=wwaVD2KqitM&feature=related http://www.youtube.com/watch?v=9gmZXzmGNg0&feature=related http://www.youtube.com/watch?v=okKGTPA-470&feature=related
Truong Dinh Hieu-PVEII. DROPPED ANCHOR ALONG ROUTE Dropped Anchor from Shipping Activity along Pipeline Route Anchor Impact Directed Anchor Vicinity Pipeline Pipeline Route (Anchor Dragging)
Truong Dinh Hieu-PVE1. ANCHOR IMPACTB. Methodology based old project. (NOTED)1) Impact energy m: mass of anchor at impact position. Vt : Terminal Velocity at impact position. Question 2: What is Terminal Velocity ? Terminal Velocity is found when the object is in balance with respect to gravitation forces, displaced volume and flow resistance. i.e. The object fall with a constant velocity. Following DNV RP F017, after approximately 50-100 meters, a sinking object will usually have reached its terminal velocity. A question this here as “what happen before 50 meter”. Terminal Velocity is defined as below method:• The object falling with low speeds and faster every second until object reaches a terminal velocity (due to drag force resisting and Buoyancy effects ).
Truong Dinh Hieu-PVE1. ANCHOR IMPACT Based on defined above and Newton II law the velocity can be:i.e. The velocity at all position can be calculated as: For dropped object scenarios, results of the risk assessment are not normally very sensitive to an absolutely “correct” capacity assessment. Therefore variety of impact energy is estimated within ± 20% will normally give acceptable variations in the resulting risk level. i.e. Ek = E. ± 20%2) Following DNV RP F107: x0: Penetration depth of object into coatingY: Crushing strength of the concreteb: Is the breadth of the impacting object,h: The depthD: Pipeline diameter
Truong Dinh Hieu-PVE1. ANCHOR IMPACTC. Discussion Question 3 :Which criteria using to check damage impact ? i.e. how many penetration depth of anchor into coating is damage /safety ? Note : a methodology will be added to check pipe deformation of anchor into pipe steel (dent depth). E assumed as =50%( or 60%) Ek Percent of Pipe deformation and pipe diameterwill calculated form E.q 3 (side) will be checked with5% i.e. if (δ/D <5% ,“Minor Damage”, “Major damage”)
Truong Dinh Hieu-PVE2. ANCHOR DRAGGINGA. Input Data Anchor data Weight anchor Fluke length Shank width Angle between fluke and shank Soil Data Fiction angle if sand Clay
Truong Dinh Hieu-PVE2. ANCHOR DRAGGINGB. Methodology Each type different anchor (fluke length, weight ) will be given anchor penetration into different soil layer based on figure below: The anchor drop vicinity pipeline route can be drag anchor, that will be avoid as propose burial pipeline. The minimum burial depth requirement to avoid anchor dragging CL : Clearance Proposed is assumed 0.5m
Truong Dinh Hieu-PVE2. ANCHOR DRAGGINGC. Discussion Based on analysis in methodology section, the burial depth is required all the route (Actual, the pipeline just burial in shore approach section). Question 4: The shore approach section will be buried to avoid effect wave, reduced concrete thickness , anchor drop/drag and trawl gear. Will other section be buried? Why not Cost buried What method to protect pipeline to avoid damage due to anchor drop/drag outside shore approach section?(ex. Have 10 ship line busy crossing route pipeline )