Can the thin-walled gas PE pipe be pulled?

in the trenchless construction of gas pipelines, tubing (horizontal directional drilling) has become the first choice for urban old areas or busy traffic sections because it does not need to break the road and has high efficiency. But many engineers will ask: "Can thin-walled gas PE pipes be used for tubing?" After all, the word "thin wall" always makes people worry that the strength is not enough, and they are afraid of breaking or deformation. In fact, the answer is not simply "yes" or "no". It must be dismantled step by step according to the material characteristics, wall thickness standards and construction requirements of PE pipes.

First of all, two concepts must be clarified: what is "tubing" and what is "thin-walled gas PE pipe". Pipe pulling is a trenchless technology in which a directional drilling rig drills a guide hole underground, then uses a hole reamer to expand the hole diameter, and finally pulls the pipe from the hole into the hole to the hole. The core is the process of "pulling" - the pipe has to withstand tensile, bending stress and soil friction. The "thin wall" of the PE pipe for gas is not randomly thinned, but follows the provisions of GB 15558.1 "Buried Polyethylene (PE) Pipeline System for Gas, Part 1: Pipe Materials": The wall thickness is determined by the nominal pressure (PN) and pipe diameter (dn), such as the PE pipe of DN110 and PN1.0, the standard wall thickness is 6.6mm. The wall thickness of DN160 and PN1.0 is 7.7mm. - these "thin walls" are compliance designs that meet the requirements of gas pressure, not "thin pipes" that cut corners.

The compliance of the thin wall gas PE pipe, can it be pulled? The key depends on three factors:

First, whether the material performance is up to standard. The PE pipe itself has good flexibility (elongation at break 350%) and impact resistance, which is the basis for pulling the pipe - when pulling the pipe, the pipe should be bent through the guide hole, and the flexibility is not enough to break; In terms of tensile strength, the minimum fracture tensile force of PE80 grade pipe is about 12MPa, and PE100 grade can reach 16MPa. As long as the tensile force during construction is controlled within the allowable range (usually 1/3 of the fracture tensile force), it will not be damaged.

Second, whether the wall thickness meets the construction stress requirements. The design of the standard wall thickness not only considers the internal pressure of gas transportation, but also reserves the external force redundancy during construction. For example, the tensile force when pulling a pipe mainly comes from two parts: the weight of the pipe itself (the smaller the pipe diameter, the lighter the weight, and the smaller the tensile force) and the soil friction force (the more fully reamed the hole, the smaller the friction force). Small-diameter thin-walled pipes (such as dn63-dn160) are very feasible as long as the wall thickness meets the PN requirements due to light weight and small tensile force; large-diameter thin-walled pipes (such as dn200 or more) need to calculate the allowable tensile force - if the wall thickness is too thin (such as lower than the standard minimum wall thickness), the wall may be deformed or even cracked due to excessive tensile force when pulling the pipe.

Third, whether the construction follows the specifications. Even if the pipe is in compliance, improper construction will also cause problems. For example, before pulling the pipe, do the tensile force calculation (tensile force = the unit weight length of the pipe + the weight of the soil friction coefficient pipe), and use the tensile force meter to monitor in real time to avoid overstretching; the guide hole should be as straight as possible, with a curvature radius of 50 times the pipe diameter (such as DN160 pipe, the curvature radius is at least 8 meters) to reduce bending stress; the diameter of the reaming hole should be 20% -30% larger than the pipe diameter (such as DN160 pipe, reaming to 190-208mm) to reduce the friction when retracting; the retracting speed should be uniform (0.5-1 meters per minute) to avoid sudden force.

also clarifies a misunderstanding: not all "thin walls" can be pulled, but "compliance thin walls" can be pulled. If you use a "fake thin-walled pipe" that cuts corners (for example, the wall thickness of the DN160 pipe is only 5mm, which is far lower than the standard 7.7mm), even if the pipe diameter is small, it will break due to insufficient strength when pulling the pipe - this situation is not "thin-walled can't be pulled", but "unqualified pipe can't be used".

Summarize: compliance thin-walled gas PE pipe, as long as the material meets the standards, the wall thickness meets the standards, and the construction specifications, it can be safely completed. The key is not to equate "thin-walled" with "unsafe", but to use the national standard (GB 15558.1, GB 50251) and calculation as the basis. After all, the core of pipe pulling is "pipe compliance + construction specifications", not "the thicker the wall thickness, the better" - if the thick-walled pipe is not constructed properly, there will be problems; as long as the thin-walled pipe is in compliance, it can be competent to pull the pipe.

Finally, remind: before construction, be sure to check the pipe test report (wall thickness, raw material grade, fracture tension), confirm that it meets the requirements before starting work; do not use unqualified thin-walled pipes to save costs, otherwise the cost of later air leakage pipeline maintenance will far exceed the money saved in the early stage.