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Wind loads act in particular on piping installed above ground outdoors and can cause additional lateral forces, moments and support loads.
Wind acts on every line outdoors. It governs where a large area meets little weight or where the line is high up: large diameters and heavily insulated lines, gas and flare lines, pipe racks, and lines running up columns and towers.
The wind force acts transverse to the pipe axis and horizontally – in a direction in which many lines are not restrained at all. A support that only carries weight offers the wind nothing but friction.
The wind force on a pipe is the product of three quantities:
F = q · cf · A
The velocity pressure q follows from the wind speed as ½ · ρ · v², with an air density ρ of about 1.25 kg/m³. The force coefficient cf describes the influence of shape, and A is the projected area: outside diameter including insulation times length. For piping the load is usually given per metre, that is q · cf · D.
An example: a wind speed of 40 m/s gives q = ½ · 1.25 · 40² = 1000 N/m². With an assumed force coefficient of 0.7 and a diameter of 0.4 m including insulation, 1000 · 0.7 · 0.4 = 280 N act on each metre of pipe.
In Europe, EN 1991-1-4 with the respective national annex provides the velocity pressure – depending on the wind zone of the site, the terrain category and the height above ground. The German national annex divides the country into four wind zones. ASME B31.3 refers to ASCE 7 for wind loads.
The force coefficient of a circular cylinder depends on Reynolds number and surface roughness and is therefore not a fixed number. Where many pipes lie side by side on a rack, they partly shield one another. Project specifications normally contain a simplified approach for this.
Wind is an occasional load. It is applied in separate load cases for the governing horizontal directions, each with both signs, and combined with the sustained loads. The comparison is made with the increased allowable value for occasional loads. Under ASME B31.3, wind is not applied simultaneously with earthquake.
For the stresses in the pipe, wind rarely governs. The other results matter more: the lateral forces on guides and steelwork, the additional loads on nozzles and the lateral displacement of the line.
Wind load is rarely calculated wrongly but often applied incompletely.
What Entracon offers here is on the matching page.
See what we offer| Quantity | Meaning | Source |
|---|---|---|
| Velocity pressure q | Dynamic pressure of the wind at the height considered | Wind code with wind zone, terrain and height |
| Force coefficient cf | Influence of the shape of the circular cylinder | Wind code or project specification |
| Reference area A | Outside diameter including insulation times length | Piping data |
| Direction | Governing horizontal wind directions | Plant layout |
It is one of the loads on every line outdoors. It governs mainly for large diameters, light lines and great heights. For small lines in a pipe rack a blanket allowance according to the project specification is often sufficient.
As a rule, no. ASME B31.3 does not require the two to be considered as acting concurrently. Each load is checked on its own; the more unfavourable one governs.
Guides and lateral stops transfer it into the steelwork. A plain resting support does so only through friction, which should not be relied on. The lateral loads go to the structural engineer as part of the support loads.
One short conversation usually settles more than three quotations. Call or write — you will reach an engineer directly.
Start typing – for example “balancer”, “SAP” or “pipe stress”.
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