The characterisation is carried out on the one hand via the type of defect with the help of the code additions A to N or Z listed in the table, and on the other hand via the type of orientation [EN13508-2:2011]:

• Type of orientation (if applicable)

  • in a longitudinal direction; mostly in parallel to the pipe axis (code specification A)

  • circumferential; mostly at the circumference of the pipe (code specification B)

  • complex (code specification C)

  • …

Important:

It is recommended to limit the use of the main code “defective repair” to methods of repair in rehabilitated sewer sections and as a repeated description following the code for point repair (BCA). Furthermore, it does not apply to replaced pipes. If the given type of defect can be categorised as “part of the wall is missing (A)”, "repair in order to seal a hole is defective (B)” or “hole in the repair material (F)”, it might be required …

Among the following possible causes of types of defect categorised under the main code of “defective repair” there exist, for example:

• selection of an inappropriate repair method

• selection of an inappropriate rehabilitation material

• insufficient preparation of the spot to be repaired (e.g. cleaning, removal of deposits, preparation of the surface, etc.)

• improper execution of the repair method

The possible consequences of a defective repair are almost identical to those mentioned in “lining
observations”:

• Reduction of the hydraulic performance capacity

• Increased operating expenditure

• Risk of congestion

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

• Increased expenses for a repeated repair

In EN 13508-2, the type of defect categorised as “Weld Failure” is applied to all welded seams in pipelines without limitations [EN13508-2:2011].

Defective welds in factory-made linings (composite materials) or linings created in the context of rehabilitation measures belong to the main code group “Lining Observations (BAK)” [DWAM149-2:2013].

The defect is characterised according to EN 13508-2 depending on the orientation of the
defective welded seam:

• Longitudinal – Failure that is mostly parallel to the pipe axis (code specification A)

• Circumferential – Failure that is basically around the circumference of the pipe (code specification B)

• Helical (code specification C)

A quantification of the defect is not required. However, concerning defects in the longitudinal direction, the exact position must be recorded. In addition, the following requirement must be met: “For circumferential and helical failures record the start and finish points.” [EN13508-2:2011]

The following list represents possible causes of weld failure:

• Non-professional execution of the welded seam

• Material defects

• Temperature effects

• Errors in …

The possible consequences of weld failures in a pipeline can be:

• reduction of the hydraulic performance capacity,

• increased operating expenditure,

• cracks (BAB),

• break (BAC),

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

Important:

In the following, some examples for descriptions of defects categorised by means of the main codes “Soil visible” or “Void visible” are illustrated inclusive of their corresponding coding according to [EN13508-2:2011]. The circumferential location, where either the soil or void appears to be visible, is to be recorded.

(Table: Pipe break – Missing wall segment and soil visible)

(Table: Pipe break – Missing wall segment and cavity visible)

Important:

The types of defect classified as “Soil visible” and “Void visible” cannot be traced back to a single cause. That is why, as already mentioned, the two main codes must never be used on their own, but always in combination with the main code of another type of defect as a secondary piece of information.

Possible consequences of defect are:

• infiltration (BBF) / exfiltration (BBG) (leakages)
• ingress of soil material (BBD)
• stability hazard (pipe fracture / collapse) (BAC)
• breaking into the open
• increased operating expenditure.

(Image: Road collapse due to damaged sewer pipe) (Image: Road collapse due to a damaged sewer) (Image: Road collapse du to a damaged sewer in South America)

According to Stützel et al. [Stütz2004], pipe joints should meet the following requirements in order to prevent root ingrowth:

• Appropriate counter-pressure of the sealant by using mechanically effective sealants with a high structural safety against external pressure loads

• Repelling geometry of the pipe joint (e.g. use of socket and spigot joints with a lower tendency of gap formation)

• The anti-stick surface structure of the pipes in order to avoid …