AS 2885.5 PDF
Australian New Zealand Standard AS / NZS Pipelines – Gas and Liquid Petroleum – Field Pressure Testing – Western Australia. AS – , Field Pressure Testing, Revision committed formed, Expected AS – , Safety Management Studies, With. AS/NZS Accessed by CITIC PACIFIC MINING PTY LTD on 03 Dec AS/NZS Australian/New Zealand Standard?.
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Where this has been done in practice, the occurrence of ruptures during field tests from manufacturing defects has almost disappeared.
AS Pipelines-Gas and liquid petroleum – Field pressure testing_图文_百度文库
Locations for temperature-measuring devices at the outer edge of the trench or in the undisturbed ground are preferred. This edition of the Standard provides a procedure for the evaluation of indication of leakages that are very small.
The application of correction charts in the field is not permitted. The Committee has always believed that it is important to set standards for measuring equipment and techniques, but in recent years the need to set objective criteria for the acceptability of large volume leak tests has been recognized. Except as provided in Clause 2. Experience indicates that exposed pipe temperatures tend to follow ambient rather than direct exposed sun temperatures due to shading, heat exchange and time lag effects.
Unaccountable pressure changes may be caused by one or more of the following: Both the equipment and the technique of assessing leaks from pressure change present a number of problems. Procedures for pressurizing the test section. It may also be used for testing other pipelines including pipelines designed to, or operated to, AS Where measurement of strain is used to check for yielding, strength testing of aboveground very short test sections may be performed without volumetric control.
Added volume required for maintenance of pressure on account of strain in the test section may be distinguished from added volume required because of a leak in the test section by the shape of the pressure decay curve. No allowance is made for changes in hole size due to elasticity of the steel at different pressures. This will vary according to the contracting practices of the owner of the pipeline. As the amount of air in the test section is determined by either the rising or the falling pressure method, the pressure response to dissolution of air can be estimated and allowance made for it in the determination of the acceptability of the leak test.
Reading of additional numbers is not profitable since they cannot be plotted, and grossly enlarged graph scales are not useful. Representative stress-strain curve information typical of the pipe.
The same sensitivity, i.
Although possible, it is generally impracticable to pre-sort a production run aa pipe according to mill test and material ws strengths in order to place the higher strength pipe at lower elevations.
The Standard warns that the traditional practice of cutting flattened strap samples from a number of pipes in the section as a means of investigating a premature end-point should be treated with great caution because a number of inaccurate steps are taken in series and the accuracy of the end result is low.
The type, specification and brand name of the pipe coating. For test sections with a small volume, a deadweight tester may not be required. This may be useful if elevation differences do not determine the length of test sections and is often required for submarine pipelines that cannot be subdivided. This is achieved by monitoring the pressure over an extended period, usually 24 h. Adequate warning signs shall be displayed along 288.55 test section.
The pressure strength is an important parameter used to calculate the MAOP of a pipeline. It is necessary to be able to detect leaks of L, 40 L or 20 L per 24 h against the background uncertainty of measurement of pressure and pipe wall temperature.
If the result is greater than 0. Operating temperature of the gas Leak testing may only be performed on a section that has previously been subjected to a satisfactory strength test.
SCOPE OF ACCREDITATION
All valves and equipment that are not suitable shall be isolated or removed. The method of disposal of the test liquid shall be considered in the selection of the test liquid, and relevant environment protection requirements shall be established.
No part of this work may be reproduced 2858.5 copied in any form or by any means, electronic or mechanical, including photocopying, without the written permission of the publisher.
Precautions shall be taken to protect the equipment against adverse effects such as weather and other threats. Where the test liquid in the test section may experience thermal expansion, provision shall be made for the relief of the resulting increase in pressure.
The accurate location of the test point. Where the section is small, so that the sensitivity of leak detection substantially overrides the uncertainty due to temperature changes or temperature measurement, high sensitivity is attained even without full thermal stability, the hold period is 3 hours and temperature measurements and correlation of temperature changes with pressure changes are not necessary.
The end-point used and the reason for its adoption.
The test program should also detail the division of the pipeline into test sections, and the physical and environmental characteristics of each section. At the end of the strength test hold period, any observed leaks are noted or repaired and the section is leak-tested. Between editions, amendments may be issued. The requirements are, wherever possible, based on an engineering assessment of what is significant and useful, rather than on what currently available equipment is the most accurate.
There may be a number of causes for temperature change, including seasonal and weather effects, water table movement and tides, and diurnal effects for shallow buried pipe with porous cover.
If, however, the strength test is carried out well beyond the minimum requirement, a lower level of accuracy is sufficient since uncertainty in the reading is of no consequence. During the hold period, visible parts of the test section shall be inspected for leaks. Care should be exercised when pressurizing to 0.
Where the test pressure is greater than either the mill test pressure or a previous test pressure, Paragraph A6. A significant improvement in accuracy results from their use. This Standard was prepared to provide a basis on which approving authorities could assess tests or testing programs.
The maximum section length can be increased, but not more than doubled, provided the leak test hold time is increased to 48 h.
Serious instrument error is most likely to be the result of an error in volume measurement, since instruments for pressure measurement are easily verified against a pressure gauge or recorder and errors of the magnitude required to az a premature end-point would be immediately apparent.
An understanding of the uncertainty of the assessment of whether the test section is leaking or not is an integral element of the assessment of the test.
The time taken for stabilization to occur depends on the temperature of the test liquid at the time of filling, specific heat capacity 22885.5 the test liquid, pipe diameter, burial depth, undisturbed ground temperature and the thermal conductivity of the backfill and ground, which can be affected by ground water.
The highest degree of certainty approaching absolute certainty is achieved when the factor is at least 1. Unless significant lengths of the test section have been pressured well above the SMYS pressure see Paragraph E5a premature end-point is likely to indicate substantial quantities of under-strength pipe in the test section.