Quasi-static catenary solution for offshore pipe-laying — computes bottom (horizontal) tension and top (barge) tension from water depth, submerged pipe weight and departure angle.
LAY PARAMETERS
Derive weight from pipe data▸
Pipe geometry
Coatings (outer diameter after each layer)
set equal to pipe OD to skip
kg/m³ density
set equal to previous OD to skip
kg/m³ density
Densities
steel kg/m³
contents kg/m³
seawater kg/m³
Bottom tension
—kN
— t
Top tension
—kN
— t
Suspended length
—m
arc length, TDP → lay point
Sag-bend radius
—m
min. radius, R = H / w
DERIVED VALUES
Horizontal reach (touchdown → lay point)—
Vertical tension component at lay point—
Catenary parameter, a = H / w—
Top / bottom tension ratio—
Model: quasi-static, frictionless catenary from the touchdown point (TDP) to the lay point at the stinger tip.
Bottom tension is the horizontal tension component, constant along the free span.
Top tension = bottom tension ÷ cos(departure angle). This ignores stinger roller friction, dynamic (vessel motion) loads,
and residual lay tension held by the tensioners — treat results as a first-pass estimate, not a final engineering check.