# Calculation of the pipe wall thickness for strength

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initial data Liquid Water Estimatedwall temperature +5^{о}С material: AISI 304 Subsea pipeline An increase to the wall thickness Operating gain pipe outer diameter of 133 mm or more *C*_{21} =3 *mm*. The estimated thickness of the pipe wall t_{c} = p_{0}D_{a}/(2σφ) +*c*_{1}+c_{2}= 0,913·133/(2·173.73·1)+0.45=0,8 mm where

p_{0} – design pressure in the conduit, MPa,

p_{0} = (p_{i} – p_{g min}) + Δ p=1,0-0,087=0,913 MPa,

p_{i} =1,0 MPa – the internal operating pressure of the pipeline;

p_{g min} – minimum external hydrostatic pressure in the pipeline, MPa;

Δ p – additional pressure is calculated taking into account the pressure medium breakaway transported in the pipeline and / or water hammer pressure in the pipe, MPa.

p_{g min}= ρ_{w} · g · (d_{min} – h_{w} / 2) · 10^{–6}=999,99 · 9,81 · 8.9 · 10^{–6}=3,27 м=0,087 MPa;

where ρ_{w} =999.99 kg/m^{3}, density of the water;

g =9,81 m/c^{2} – acceleration of gravity;

d_{min} =8.9 m - the minimum level of quiet water along the pipeline route, taking into account the tidal conditions and surges with the provision 10^{–2} 1/year;

h_{w} =0 m, the estimated wave height on the projected area of the pipeline;

D_{a} =133 mm - outer diameter of pipe.

Allowable stress σ must be made equal to the lower of:

σ = min (R_{y}/n_{y }, R_{T}/n_{T}),

where R_{y}=205 MPa - the minimum value of the yield strength of the metal pipe;

R_{T}=510 MPa the minimum value of the tensile strength of the metal pipe;

n_{y}=1,18 - safety factor of yield strength;

n_{T}=1,75 safety factor for tensile strength.

σ = min(205/1,18 , 510/1,75)

σ = min(173,73 , 291,43);

φ – safety factor, determined according to the method of manufacturing a pipe, a safety factor of φ is taken equal to 1.0 for seamless pipes.*c*_{1} =0 mm, – corrosion allowance for subsea pipelines made of stainless steels and alloys;

c_{2} =0,45 mm – gain compensating manufacturing tolerances for manufacturing pipes, mm.

Calculated taking into account the thickness of the wall of increases t_{c} + C_{21} =0,8+3=3,8 mm

The wall thickness of the pipe diameter 133 mm accepted 4 mm.

literature

1.РД 10-249-98 "Нормы расчета на прочность стационарных котлов и трубопроводов пара и горячей воды"

2.Правила классификации и постройки морских подводных трубопроводов Российского морского регистра судоходства от 28.02.12.

Chief technical designеr Priymak Victor

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