SHIFTING PIPELINE ANALYSIS
General Approach
M.Munari
Engineering
Central Sumatra Gas Project
PT Perusahaan Gas Negara (Persero)
Bla-Bla-Bla
This paper is to describe the pipeline shifting where shifting the existing laid not exactly route per design on the seabed or trenching. The case exists due to some factors such:
1. Receiving GPS (Geographic Positioning Station) on the barge is poor.
2. Design route not same with trenching design.
3. No fairly coordination on the site
4. Not proper trenching (above, bottom, width)
5. Barge works under extreme conditions
Purpose
This paper is describing a situation of shifting pipeline procedure without cutting off at end the pipeline.
The pipeline that lay on wrong route shall lift 4 meter of the touchdown and shall shift 4 meter maximum of initial point.
Potential Factors
The below are list of some potential factors to be considered:
• Easy to be done
• Lifetime of working is short
• Risk to damage
• Constraints not free (fixed)
• Stress at each ends increase
• Tend to create the torque
• More cheaply cost than other methods
• Un-conventional Method
• Highly Percentage system mode of failure (SMOF)
Disadvantages
• No Recommend Standardizations
• Un-conventional Method
• No assurance
• Risk to damage
• Constraints not free (fixed)
• Stress at each ends increase
• Tend to create the torque
• Highly Percentage system mode of failure (SMOF)
Advantages
• Easy to be done
• More cheaply cost than others
Design Basis
The pipeline installed with refers to DnV 2000 Standardization (OF-S101).
A. Designed Pipeline Data
Outside Diameter (OD) : 0.7112 meter
Thickness (t) : 0.0127 meter
Inside Diameter (ID) : 0.6858 meter
Grade : API 5L X 65
Density (s) : 7850 Kg/m3
Yield Strength (S) : 65000 Psi (448 N/mm2)
Tensile Strength (T) : 77042.41 Psi (531 N/mm2)
S/T Ratio : 0.84
Modulus of Elasticity (E) : 1.94 x 105 N/mm2
: 29000000 Psi
Linear Coefficient Tensile Strength (t) : 2.97 x 10-4 mm/mmoC
Procedure Working
Step by Step
• Set up barge on location
• Diver inspection (to observe backfill materials on the shifting location, pipe position in relation to trenching)
• Inserting sling around pipe at lifting points (4 points with interval 20 meters) with diver, if necessary using air jet compressor.
• Lowering wire from davits to joint onto sling
• Lifting pipe to y-axis direction with 4 davits (refer to Lifting Schedule) up to max. 4 meter (interval lifting 0.5 meter)
• Shifting pipe to x-axis direction with no lifting (interval 1 meter, max distance 4 meters). Barge shall move by foot-print of anchoring system.
• Lowering pipe y-axis direction with 4 davits (refer to Lifting Schedule) up to max. 4 meter (interval lowering 0.5 meter) on to trenching.
• Post-shifting survey to make sure that pipeline already on right position.
• Report