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Nov 19, 2004 For the measurement of local velocities the application of
has predominantly proved itself. |
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Nov 19, 2004 (Image: Principle of measurement of an ultrasonic Doppler measuring sensor) Sensors and measuring instruments that are meant to detect the maximum velocity in a flow profile usually operate in sewage according to the ultrasonic Doppler principle. Doppler measurements are based on the reflexion from solid particles in the flow that are always present in the sewage. The sensor sends an ultrasonic signal at an angle β (Bild 4.4.2.2.3.1) upwards. By … |
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Nov 19, 2004 The measurement of maximum velocity in a flow profile presents a special case of the measurement of local velocities. By means of correct installation, calibration and setting, the sensors and measuring instruments designed for this take over from the user the task of looking for the region of the maximum velocity in open channels (Abschnitt 4.4.1.5). |
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Nov 19, 2004 The flow velocity measurement may relates to
velocity of flow. |
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Nov 19, 2004 Rehabilitation and Maintenance of Drains and Sewers Instruments with Combined Detectors for Measuring Combined Flow Depth and Velocity Either magnetic inductive (MID) or ultrasonic Doppler sensors are built into the detectors for determining the flow velocity. Neither of them directly measure the flow velocity required for the volume flow calculations but rather a local point velocity. The MID sensor measures a local velocity in a limited flow tube above the combined detector. The ultrasonic Doppler sensor provides the connected converter with a frequency signal from the sonic lobe … |
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Feb 16, 2011 Rehabilitation and Maintenance of Drains and Sewers Instruments with Combined Detectors for Measuring Combined Flow Depth and Velocity (Image: Determining the flow profile with the Pulse Doppler method) The measuring instruments described in the previous section with their velocity sensors can only detect a local velocity in the profile. Based on assumptions on the structure of the velocity profile, the median velocity is calculated on partly empirical relationships. New measuring instruments on the market that work in a similar manner to the ultrasonic Doppler measurements, also … |
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Nov 19, 2004 (Image: Streamline shaped detector with combined flow depth and flow velocity probe) It is becoming increasingly common for measurements of volume flow to utilise instruments with combined flow depth and velocity sensors in a single detector housing. This trend reflects the wishes of the user for compact and easy-to-install measuring systems that will work without any installations that have restricting effects on the cross section. The measuring … |
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Nov 19, 2004 Various transducers or measuring instruments are necessary in order to be able to acquire the required measuring information from the methods described above. These, according to DIN 19559-1 [DIN19559-1:1983] should be "robust and require little maintenance" and should measure "without additional impairment of the flow cross section with a high degree of flow constancy, uninfluenced by extreme environmental conditions, with a good degree of accuracy … |
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The solving of hydraulic problems requires that all the relevant information for determining the situation is collected and evaluated. A calculated determination of the dry and storm weather flows, with the addition of an inventory of bad connections and leaks, is insufficient in many cases for comprehensively describing the hydraulic loads on the sewers. The actual flow in a drain and sewer network, or part network, can deviate substantially from … |
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Feb 16, 2011 Water pressure testing, in all international standards and regulations on this subject, is seen as testing with a constant pressure head, that is, the water quantity that is added in order to maintain the required test pressure during the test period is measured (Tabelle 4.5.1.1.1). On the assumption that the water addition during the water pressure test disappears completely through a leak, it can be calculated with reference to the test length and … |
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Nov 19, 2004 The equation for the air pressure test is based on the idea that an air mass flow escapes through a leak in a defined time period and thus leads to a reduction of pressure in the pipe to be tested. This can be calculated with the assumption of an isentropic and adiabatic flow, that is, during the flow there is neither loss due to friction nor is there a heat exchange between the flowing medium and the surroundings [Stein95a]. In order to derive the … |
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Nov 19, 2004 The determination equation for vacuum testing is calculated analogously to the equation for air pressure testing. Because of the reversal of airflow in comparison to air pressure testing, there are alterations in the integral that describes the air velocity (Formel 4.5.1.1.3). (Formula: Calculation of the test time for vacuum testing) Because of the differing physical properties of the test media - water as incompressible, air as compressible medium - … |
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(Image: Principle depiction of the assumed damage situation.) In all methods of leaktightness testing, the instrumental control extends either to
In all testing methods, therefore, a defined test medium loss is permitted. Thus, the definition of the leaktightness … |
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Feb 16, 2011 The preparatory measures for leaktightness testing apply generally for all the test methods described in Abschnitt 4.5.1.1. They will be described in the following on the basis of the ATV-M 143 Part 6 [ATVM143-6:1998]. The employer must make comprehensive plan documentation available for carrying out the leaktightness testing. From these, the following information must be recognised, among others:
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Nov 19, 2004 According to [ATVM143-6:1998], all the equipment in the Federal Republic of Germany must correspond to the VDE and DIN regulations as well as the accident prevention regulations. The sealing elements utilised must be robust, and used in accordance with the area of application. They must be permanently marked by the manufacturer with a type label on which the following is clearly legible:
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Feb 16, 2011 The classical method of leaktightness testing provides for pressure testing with water as the test medium (Abschnitt 4.5.1.1). It is specified for the leaktightness testing of newly laid drains and sewers that are operated as gravity pipes, for the countries of the EU in EN 1610 [DINEN1610:1979] within the scope of the construction acceptance and indirectly in EN 752-5 [DINEN752-5:1997] also for the acceptance of rehabilitated sewers. The test itself … |
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Feb 16, 2011 Over the past few years, the testing with air pressure as a test medium has become more and more common in the Federal Republic of Germany (see, among others [ÖNormB2503] [SIA190] [SFS3113E] [ASTMC109190] [ASTMC82890] [FI-Cherna] [ASTMC92485] [NASSCO89b] [Taylo78] [VAVP50]). This has the following advantages over water pressure testing [FI-Hydro] :
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Nov 19, 2004 Air testing with negative pressure (vacuum testing) has up to now been subject to the same restrictions of the ATV-M 139 [ATVA139b] mentioned above in the Federal Republic of Germany as testing with compressed air and was thus not implemented. In contrast to the last named test method, it has the following additional advantages [Doutl83] :
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The principle and general sequence of a leaktightness test with the measures to be taken to carry this out are shown in Bild 4.5.1.2 and Bild 4.5.1.2. These measures will be discussed in the example of the section of the sewer method of leaktightness testing. The closing of the section of the sewer or the testing volume at both ends is carried out by means of sealing elements in which there are integrated connections for compressed air for inflating … |
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In the leak testing of parts of sections of the sewer, the method used is analogous to the leaktightness testing of whole sections of the sewer (Abschnitt 4.5.1.2) whereby the sealing elements, for example, are connected by a chain and are pulled, either manually, or by means of a cable into the required positions (Bild 4.5.1.3) (Bild 4.5.1.3). This system can also be applied for the leaktightness testing of laterals (Bild 4.5.1.3). The leakage criteria … |
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(Image: Leakage testing of a pipe joint - test criteria to ATV-M 143 Part and EN 1610) With the testing of sockets with water as a test medium according to EN 1610 [DINEN1610:1979], the test requirements correspond to those of the sections of the sewer or parts of sections but with a test pressure of 0.5 bar at the pipe crown (Bild 4.5.1.4.1). In this case, the water addition quantities that are required to keep the pressure constant are measured. … |
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Nov 22, 2004 As regards the testing of sockets of newly laid or rehabilitated drains and sewers with air pressure, there is stated in EN 1610 [DINEN1610:1979] that principally the basics of leaktightness testing of a section of the sewer or parts of sections must be considered whereby the leakage criteria are to be worked out individually (Bild 4.5.1.4.2.1). Because the test volume of the socket test apparatus in comparison to the testing of parts of sections … |
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Feb 16, 2011 In the testing of sockets according to ATV-M 143 Part 6 [ATVM143-6:1998], the following limiting conditions must be adhered to (Bild 4.5.1.4.2.2) : Test pressure: p = 100 mbar Perm. Pressure difference: Δp = 15 mbar Settling time: ts = 15 s The required test times are given by equation Bild 4.5.1.4.2.2 : (Formula: Calculation of the test time for leaktightness testing of pipe joints to ATV-M 143 part 6) (Image: Leakage testing of a pipe joint - test criteria … |
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(Image: Schematic depiction of the test space with a socket test) As can be seen from the determination equations given in Abschnitt 4.5.1.1, the test volume is a linear component in the calculation of the required test time. In leaktightness testing by means of a compressible medium under pressure, such as air, the pressure decay is not only dependent on the geometrical dimensions of the leak position, but primarily on the air volume within the test … |
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In the testing of existing or rehabilitated drains and sewers, the testing of sections of the sewer is only possible in exceptional cases as this is made difficult or impossible, as a rule, due to the numerous building connections. An alternative to the section method of leaktightness testing (Abschnitt 4.5.1.3) is the possibility of testing individual pipe joints (testing of sockets) with water as well as with air as the test medium. Basically the … |
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