The pressure change is calculated according to the isochoric equation-of-state by applying the formula:. Symbols cf. The counter-pressure at the pressure maintaining device must be set to the line pressure when beginning with the measurements and must not be changed during the measurement period.
Any temperature dependencies must be taken into account. The pressure drop is calculated with the formula:. Gas quality Subsequent pressure increase in gas lines Gas service lines for operating pressures up to 4 bar - Construction Installation of gas lines with operating pressures of up to 4 bar with pressure pipes and ductile castiron pipe fittings Installation of gas lines with operating pressures above 4 bar to 16 bar with pressure pipes and ductile cast-iron pipe fittings Steel gas pipelines for operating pressures up to 4 bar - Pipes and fittings Steel gas pipelines for operating pressures above 4 bar to 16 bar - Construction Construction of steel gas pipelines for operating pressures above 16 bar Work on gas pipeline networks with an operating pressure up to 4 bar.
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Report this Document. Flag for inappropriate content. Download now. Related titles. Carousel Previous Carousel Next. Dharan et al. Springer, Jump to Page. Search inside document. If there is no deviation, becomes The change in volume of the tested pipeline section can be determined with the following state equiation.
The pressure change is calculated according to the isochoric equation-of-state by applying the formula: Symbols cf. Teesing BV. Ramadan Rashad. Salah Alawneh. Manish Sharma. BN RD. Raja Faheem Khalid. Omar Tocmo. Gdfsndh Gfdvhjzd.
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These cookies do not store any personal information. Skip to content PDF Portland. Search for:. This website uses cookies to improve your experience. In place of air also other suitable gaseous test media may be used; hereafter, only air will be mentioned.
In place of operating gas also mixtures consisting of operating gas and inert gas may be used; hereafter, only operating gas will be mentioned. Special measures must be taken for lower temperatures.
Sufficient time must be allowed for the temperature of the water filled into the pipeline and its surroundings to even out. Already when applying the test pressure the ratio between the amount of water that has been filled in and the subsequent increase in pressure may point to insufficient venting or the presence of major leaks.
For the checking of air freeness confer to pressure testing methods B 1 or B 2. If, when carrying out pressure testing with operating gas, higher pressure nitrogen is added, for example, the test pressure in the pipeline or system may rise to a level which is above that of the working pressure of the feeding line or system.
Furthermore, Section 2. As an example, Fig. For the setting and measuring of test pressures, master pressure gauges of at least class 0. Other necessary measuring devices and their respective requirements are dealt with in the Sections on test methods B 1, B 2, B 3, and C 3. The purpose of visual testing of a pipeline or system is to visually assess its tightness, and, if the testing pressure significantly exceeds maximum allowable operating pressure, also its strength when exposed to the testing pressure.
For all visual test methods, the pipeline or system to be tested must be exposed; in particular pipe joints, fittings, valves, pressure vessels, etc. The test pressure, however, must at least be 1. After filling and venting cf. Section 2. During this time, the pipeline or component assemblies of the system must be inspected for tightness in particular at the joints and where parts have been installed flanges, sockets, valves etc.
After having reduced the pressure to the lowest possible level holding time 30 minutes , which at the high point must still be at least 2 bar, and after having increased the test pressure a second time, the pressure is held again for at least 90 minutes.
Where these rules stipulate minimum values, the exact test pressure must be defined before beginning with the test. The pipeline joints to be tested must be free from grease or coatings. It is recommended to repeat the test with foaming agent after having lowered the test pressure to approximately 2 bar. During the increasing of pressure and after an appropriate holding time, all pipeline joints, valves, flanges and similar items must be tested for tightness with a foaming agent.
Any joints to be tested must be free from grease and coatings. That is why these methods are in particular suitable for buried pipelines which do not provide the accessibility needed for visual tests. The pressure test proper only begins when the temperatures of the test medium and adjoining soil or atmosphere have balanced out. The exact test pressure must be determined before beginning with the test. If the tests are carried out in seasons during which frost might occur, any exposed sections of the pipeline must be protected against freezing.
In order to confine temperature fluctuations to a minimum, the pipe trench must be filled out as best as possible. If possible, vales and mechanical joints should be easily accessible. To conduct the test, a special test rig is required such as a construction site trailer which is equipped with the following measuring equipment:.
All pressures occurring during the course of testing must be recorded with a recording manometer. For the measuring of the temperature at the wall of the pipe it is as a rule sufficient to place one thermometer at every 2.
However, regardless of the length of the test section at least three thermometers should be used. After filling and purging cf. All values measured during this period should be recorded. It is recommended to ascertain that the line is air- free before beginning with the test. As far as the pipe wall temperatures in the buried portion of the tested section are concerned, it is normally sufficient to read the thermometer every 6 hours. All other measured values should be recorded every hour.
After the holding period is over, the absence of air in the pipeline must be double-checked purge test. Only the amount of water drained at the very end of the test and the corresponding reduction in pressure must be used as the basis for evaluation. The amount of water which has actually been drained is compared with the calculated amount by applying the formula below:.
The calculated amount of water and amount of water actually drained may deviate from one another due to minor air entrapments, pipe grades, wall thickness and diameter tolerances. If there are different wall thicknesses and pipe radii, formula 2 should be inserted correspondingly into formula 3. In the majority of cases the measuring tolerances of this method results in changes in volume, which in their summation do not cancel each other out and which can be converted by inserting all tolerances into the corresponding calculation formulae.
To determine the allowable hourly change in volume therefore, the simplified formula given below must be applied which will yield a sufficiently accurate result:.
The line is then repressurized until the test pressure is reached. As a rule, this pressure must be maintained for 24 hours. The measuring time may be reduced if the metrological conditions and the pressure over time correspond to the changes in temperatures, i.
During this period all measured values must be recorded. For this purpose, the pressure should be lowered at least twice. Regarding the measuring apparatus, the evaluation of the test and the control check to ensure that the lines are free of air, Section 3. The test pressure must be 1. These test methods are applied on pipelines which are if possible completely buried.
While the measurements are being carried out, the pressure in the pipeline should be recorded by a recording manometer. The measuring devices used must be a Class 1 recording manometer as well as Class 0. As reference value for temperature equalization after the injection of air, a duration of one hour can be assumed for 1 bar in test pressure, unless the equalization period can be curtailed by suitable measures such as a compressor with cooling system.
The potential influence of the measuring line on the measuring results should be kept to a minimum. The following only applies to pressure measuring method B 3. In order to ensure that a variation in pressure can be identified within an reasonable period of time, the length of the pipe sections to be tested should, if possible, not exceed the standard values stated below:.
DN Length km.
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