The issue of sleeves for buried pipelines
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Regarding the burial depth of pipelines, the Code for Design of Oil Depots stipulates that where pipelines pass under railways or roads, culverts or sleeves should be used; the top of such sleeves shall be at least 0.8 m above the railway track surface and at least 0.6 m above the road surface. If a casing is to be used for buried pipelines, what type of pipeline should the casing be? My process pipeline is made of seamless steel pipes with a diameter of DN250, dimensions of Φ273x7.0, and it is buried at a depth of nearly 2 meters. What specifications and standards should be applied to the casing pipes?
Using threaded steel pipes made of Q235B is sufficient; there is no need for pipes of a higher grade.
Spirally welded steel pipes made of Q235B will suffice; the sleeve should be two sizes larger than the pipe diameter.
The casing shall be made of welded pipe, with a diameter at least one size larger.
Two larger sizes of spiral-welded steel pipes will suffice; however, in the case of cathodic protection, since the pipe is electrified, insulating supports need to be placed between the sleeve and the pipe
Refer to the American standards API PR 1102 and API PR 1102-2014 Steel Pipelines Crossing Railroad Highways, which specify the dimensional requirements for the sleeves used to cross railways as well as the associated process pipelines: \"The inner diameter of the sleeve should be large enough to accommodate the transport pipeline, provide adequate insulation for maintaining cathodic protection, and prevent external loads from being transmitted from the sleeve to the transport pipeline.\" The nominal diameter of the sleeve should be at least two sizes larger than that of the delivery pipe. ”