Significance of Atypical Features

Signficance of Atypical Features | Print Version

Impregnation issues are associated with the bunching up of the inner liner(s) and are unacceptable.

Inversion issues

• Stopped inversions due to premature cure are clearly catastrophic failures.
• Circumferential fins, unless slight, are unacceptable due to the possibility of deposition upstream. Because they are associated with the thickening of the pipe wall, such fins can be ground-off.
• Longitudinal fins, even moderate in nature, are not detrimental to the structural or hydraulic performance of the liner.

Seams and patch repair issues

• Stained seams are often due to water passing through in small quantities and impurities filtering out. Unless significant resin loss has resulted, stained seams are a question of aesthetics.
• Leaking seams are unacceptable. It is important that the liner is impregnated under adequate vacuum and at the correct nip roller gap. This will normally, with conventional catalyst cocktails, ensure a low porosity and result in sound seams. If the leaks are not too extensive, then a grout packer may be used to correct this issue.
• Leaking patch repairs through which groundwater can leak are unacceptable. It is possible that after grinding away the patch, a grout packer may be used to correct this issue.

Coating-related issues

• Bubbles on liners can be removed if they are unacceptable aesthetically. If they are caused by ingress of groundwater then some means may be needed to prevent further ingress.
• Spots and other Stains (e.g., on seams) are associated with leaks of water through small holes in the coating. The cause of the holes is discussed in the spots section.
• Uneven finishes on liners are typified by surface irregularities and although appear unsightly when viewed along the pipe on CCTV, do not detract from the structural or hydraulic performance of the liner. Air pockets behind liners are only of significance under high external head.

Inward folding of the lining are a potentially serious problem, but can in favorable circumstances be overcome by inverting a dry liner through the problem liner and circulating hot water. This should soften the liner sufficiently so that it can be reshaped. Do not apply a high head until hot or the liner may crack.

Damage to the surface of liners can be caused by a range of factors. The coating can be ripped and gouged by sharp objects used for rope end/soft end fittings. Alternatively, damage can be caused to the coating by dragging the liner over rough surfaces. In any case, if such damage results in water leaks, then it is unacceptable and should be repaired.