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Testing for Infiltration for Underground Sewer network.

A possibility little discussed in Germany up to now for leak tightness testing of sewers is the infiltration measurement. This method is standardized in the USA in the ASTM Standard C 1091-90 [ASTMC109190] for gravity pipes of vitrified clay and in Great Britain independent of the materials. With this type of leak tightness testing, leaks are methodically sanctioned which contradicts the requirements of the EN 752 [DINEN752f] for watertight sewers. For this reason, the acceptance of a corresponding test criterion of the European standards was declined. The testing in accordance with [ASTMC109190] is carried out on backfilled piping under the condition that the groundwater level is at least 2 feet (65 cm) above the crown of the pipe - measured in a section of the sewer or the middle of the test length. For this purpose, if necessary, the groundwater section must be interrupted for at least 24 hours. For sewers lying only partly in groundwater or with low groundwater pressures, then, according to [ASTMC109190], other methods of testing must be used whereby, however, the exact determination of the height of the groundwater presents a problem (Abschnitt 4.4.1). After the sealing of the section of the sewer with commercially available packers or test sealers, the actual infiltration measurement at a constant flow or infiltration quantity can begin. Here the infiltrating and flowing water is collected in a measuring device over an unspecified period of time. Alternatively, instead of a test seal, a very low overfall limit can be installed at the lowest part for measurement (Abschnitt 4.4.1). The pipe is judged to be leak tight when, over a length of 100 feet (30 m), the infiltration rate mentioned in ASTM C 1091 [ASTMC109190] as water addition is not exceeded. The corresponding, and still permitted, rate of infiltration is given in the British CEN draft [CENN69E] as 0.5 l/m of sewer length and per m of sewer diameter during a test period of 30 minutes.

In comparison, reference is made to the values [Taylo78] of a corresponding drainage project in Abu Dhabi. There a rate of infiltration of 1 l/(day x pipe length [km] x pipe nominal size [mm]) is still permitted. The testing equipment used in this case must measure the infiltrating water and display the volume flow. An apparatus for the non-man-accessible nominal size range is shown in (Image 4.6.2.10-1) and (Image 4.6.2.10-2).

Qatar Construction Standards of 2014 edition(QCS-2014-Section-8)

(c) Infiltration Test (i) the upper ends of the sewer and service connections shall be closed sufficiently to prevent the entry of water and pumping of groundwater shall be discontinued until the groundwater surface reaches its natural level before beginning the infiltration test the dewatering system shall be stopped, but not be removed until the infiltration test has been successfully completed or as otherwise permitted by the Engineer the infiltration shall not exceed 6 litres per millimetre diameter per kilometre per day of the portion of sewer being tested, including the length of service connection entering that section. (ii) the total length tested in one section shall not exceed 400 m in length. This length is dependent upon the type of deflection measuring equipment proposed by the Contractor if flexible pipes are used. (iii) no gravity pipeline will be accepted if the total infiltration exceeds the above mentioned limit and joints will not be accepted if during an internal inspection, any infiltration is visible

image Image 4.6.2.10-1: Socket testing device based on electrical resistance measurement for sewers DN 150 [FI-Hydro] image Image 4.6.2.10-2: Principle sketch of an infiltration measurement with the leakage measuring device with reference to [FI-Müller]