Displaced joints are differentiated on the basis of the type of displacement:

• longitudinal (code specification A) – the pipes are displaced parallel to the line of the sewer;

• radial (code specification B) – the pipes are displaced in a direction at right angles to the line of the sewer;

• angular (code specification C) – the axes of the pipes are not parallel.

The defect is quantified subject to its characterisation. For a displacement in a longitudinal direction, subsequently also called axial displacement, the dimension of the displacement is to be specified in mm (distance between the end of the spigot and the inside of the socket of the adjacent pipe in millimetres (≥ 10 mm according to EN 13508-2)). Longitudinal displacements of less than 10 mm shall not be recorded.

In the case of a radial displacement

Positional deviations are only permissible within the tolerances specified by the client, standards, guidelines, and worksheets. Such tolerances are / have been available for e.g.:

• changes in lengths due to temperature effects (DIN 19543)

• displacements of axes (DIN 1986-1)

• angular deflections (DIN EN 476)

• deviations perpendicular to the axis direction or gravitational effect (DIN 19543)

The corresponding tolerances apply for newly installed piping. …

In addition to the damage characterisations according to DIN EN 13508-2, the terms U-bends must be considered in this context.

According to DWA-M 149-2, U-bends consist of a series of several displacements at an angle. These displacements – as far as visible – shall stated individually. In the first description, the starting point of the U-bend is to be additionally designated as the start of the section, while the end of the U-bend shall be identified …

Possible causes of positional deviations are:

• hydrogeological changes
• change in the external forces (change in loads)
• settlements
• changes in the bedding as a consequence of infiltration (BBF) / exfiltration (BBG) (leakages) in conjunction with ingress of soil material (BBD)
• defective pipe bedding
• mining subsidence [Hollm85] [Meißn76] [Schil81]
• seismic events

The effects of positional deviations onto sewers depend on the type of pipe – rigid or flexible – and the type of pipe joint – rigid, tension-proof, or articulated.

Depending on its magnitude, the movement that is linked to positional deviations can, in particular, cause the following consequences of damage:

Important:

According to EN 13508-2, the main code “Lining Observations” differs from all other already mentioned main codes by the fact that this code is not set within the category of "defects". Instead, the lining of the pipeline is observed to have a “feature”. Although, de facto, many types of observations / features represent types of defect and their consequences without a doubt [EN13508-2:2011].

(Image: Lining observations (BAK) - crack (I)) (…

Following [EN13508-2:2011], the defect is supposed to be characterised regarding the nature of the observation with the aid of the code specifications A to N or Z, listed in the table.

The table below further specifies the quantification of the respective finding.

(Table: Selection chart for the characterisation of the description of damage categorised as “Lining observations (BAK)” in accordance with DWA-M 149-2 and DIN EN 13508-2)

Here are some examples of findings regarding the inner lining with the corresponding codes according to [EN13508-2:2011].

(Image: Detection of the inner lining - bulge in the inner lining) (Image: Lining observations – Radial wrinkling in a Troliner (studded HD-PE liner)) (Image: Lining observations – Wrinkling in a longitudinal direction and a reduced cross section for an improperly laid hose liner)

Possible causes for the lining observations listed in [EN13508-2:2011] are, for example:

The possible consequences of defect categorised as lining observations are:

• reduction of the hydraulic performance capacity

• increased operating expenditure

• risk of congestion

• infiltration (BBF) / exfiltration (BBG) (leakages)

• increased expenditure in the renewed rehabilitation of the already rehabilitated sewer section

According to [EN13508-2:2011], a “defective repair” (main code BAL) is defined as follows: “A repair has been carried out on the drain or sewer which now has a defect”. When this code is used, the point repair code BCB is also required. In the case that the repair is carried out through localised lining (BCB B), the code BAK should be used.