COMMISSIONING AND TESTING

Commissioning shall not commence until the pipeline or facility has been certified that it is ready for commissioning.

Pipeline commissioning and testing includes—

(a) the introduction of the fluid that is to be transported and, in the case of gas or HVPL, pressurization of the pipeline to a level sufficient for initial testing of receipt and delivery equipment and associated control systems;

(b) leak testing of pipework and equipment, and rectification;

(c) tests that can only be undertaken once process fluid is available (including initial fluid delivery sufficient to commission and test flow, pressure control and other equipment); and

(d) pressurization to the level required for commercial operation.

Accessed by Fyfe Pty Ltd on 18 Oct 2012 (Document currency not guaranteed when printed)

NOTE: Most pipeline licences require regulatory approval before process fluid is introduced to the pipeline, and some require an additional approval at completion, or approval for commercial operation. These requirements should be identified and fulfilled.

12.9.2 Pipeline purge and pressurization (gas pipelines)

A procedure shall be prepared to safely purge air or other contaminant from the pipeline and then fill the pipeline with the process fluid.

The purging procedure should consider the guidance of AGA Purging Principles and Practice (see Note 1). A key decision is whether to purge the pipeline with process fluid (gas) or whether to separate the process fluid from the pipeline contents using a slug of inert fluid.

Calculations relevant to the complexity of the pipeline or facility shall be undertaken to establish the process conditions for purge. For pipelines, the purge process should be simulated using appropriate software to establish the minimum velocity, the gas flow and pressure, the purge duration and, where used, the minimum volume of an inert gas slug required to separate the air and process fluid. These shall be documented in the procedure.

Temporary (or permanent) equipment used to control the process shall be capable of providing the control actions required, and shall be safe for the process temperatures and pressures to which it is exposed.

An inert slug, or another means of separation, shall be used when it is not possible to guarantee a continuous supply of gas throughout the purge period.

NOTES:

1 See AGA Operating Section Report Purging Principles and Practice, Catalogue No. XK0101, as amended.

2 Software developed as part of the AGA Purging Principles and Practice provides a more accurate method of predicting the purge process and time to complete, including calculating the minimum inert gas slug volume. This software should be used if available.

3 Where this software is not available, purge calculations may be undertaken using gas hydraulic transient software. These are capable of predicting the process, but because they are usually not developed to accurately predict interface mixing, they may not accurately predict the minimum inert gas volume to separate air and the purge fluid.

4 Use of inert gas is frequently not justified in high pressure pipelines. The decision on whether to use inert gas should consider the likelihood and consequences of a flammable mixture forming and igniting, and balance that risk against the hazards to personnel associated with the inert gas, especially where large volumes of inert gas are required. In pipelines with high MAOP being purged at near-atmospheric pressure an ignition within the pipe will usually not create unacceptable pressures or temperatures, and in any case such ignition has hypothetical likelihood.

Significant noise may be generated at the point(s) where air is released from the pipeline.

The impact of such noise on the community shall be assessed and managed.

Where hydrostatic test water is discharged from the pipeline using process fluid to propel it, special procedures shall be developed for water discharge and disposal and removal of residual water from the pipeline.

Once air has been fully purged from the pipeline, additional process fluid should be introduced to raise its pressure.

Pressurization should be undertaken in stages to raise the pipeline pressure—

(a) to the minimum level required for commissioning pipeline stations and confirm their leak tightness and, if required, to establish initial flows to gas users, sufficient for commissioning those facilities; and

(b) to that required for commercial operation.

Accessed by Fyfe Pty Ltd on 18 Oct 2012 (Document currency not guaranteed when printed)

NOTES:

1 Because commissioning may identify problems that require depressurization of a facility or a section of the pipeline to rectify the problem, it is good practice to maintain the pressure as low as practicable until the potential for depressurization has been eliminated.

2 Where there is a possibility that water remains in the pipeline, the pressure should be maintained at the lowest practicable value, and the highest practicable flow maintained until the water has been removed by evaporation. The low pressure gas has a significantly higher potential to absorb water than high pressure gas and, at low pressures, it is unlikely that gas hydrates will form in downstream pressure regulators.

12.9.3 Filling a liquid petroleum pipeline

A procedure shall be prepared to safely purge air or other contaminant from the pipeline and then fill the pipeline with the process fluid.

The procedure shall take into consideration the following:

(a) The compatibility of fluid remaining in the pipeline with that of the displacing fluid.

(b) The pipeline profile and the method by which the air and process fluid will be received and separated.

(c) The method by which a continuous column of process fluid is maintained in undulating terrain and, in locations where the elevation gradient exceeds the hydraulic gradient of the process fluid, at the fill rate.

Where liquid (water) is to be displaced, it should be physically separated from the hydrocarbon liquid with spheres or batching pigs, unless the interface length can be managed by maintenance of an appropriate velocity.

Consideration should be given to the risk of corrosion from residual water that may accumulate at pipeline low points.

Where air is to be displaced from a pipeline, the liquid hydrocarbon should be physically separated from the air with spheres or batching pigs. If possible, the flashpoint of the initial hydrocarbon liquid should be not less than 61°C, to prevent the formation of explosive gas/air mixtures.

NOTES:

1 The risks of introducing lower flashpoint hydrocarbon liquid should be considered and managed.

2 Physical separation using a batching pig is recommended. This can be improved by using a slug of inert liquid or high flashpoint hydrocarbon in front of the pig to improve separation.

3 The use of an immiscible fluid like water may introduce contamination risks, and the risk of corrosion to the pipe invert where trace quantities may exist for long periods after the initial filling.

When the pipeline has not been designed to allow pigging, alternative procedures shall be developed and approved.

12.9.4 Filling a high vapour pressure liquid (HVPL) pipeline 12.9.4.1 General

Special procedures shall be developed for filling a pipeline that transports an HVPL. These shall reflect the thermodynamic properties of the fluid, temperature effects at the fill point and, as the pressure is raised, at leaks or release points. The potential for unplanned fluid release to pool at the point of release, rather than dispersing as expected of a lighter-than-air gas, shall be taken into consideration.

NOTE: Process simulation should be undertaken to develop a thorough understanding of the fluid behaviour during this operation and to develop control methods.

Accessed by Fyfe Pty Ltd on 18 Oct 2012 (Document currency not guaranteed when printed)

Because special processes are required for depressurizing an HVPL pipeline and pipeline station, an HVPL pipeline should not be pressurized above its dewpoint unless the equipment for safely managing this process is available, and personnel are trained in its use.

12.9.4.2 Single component HVPL

Where the HVPL consists of a single component hydrocarbon or CO2, the pipeline should be purged in the gas phase in accordance with Clause 12.9.2, and then pressurized in accordance with this clause.

To the extent practicable, pipeline facilities and stations should be commissioned and tested in the gas phase.

Fluid should be introduced at a controlled rate to raise the pressure to the dewpoint, and then continue to be added until the contents are fully liquid.

12.9.4.3 Multi-component HVPL

Where the HVPL is a mixture of hydrocarbon components, there is a potential for the component to separate during the purge and pressurization phases. This may result in initial deliveries from the pipeline being off-specification. Where this is not acceptable, the pipeline should be filled first with water or a suitable low vapour pressure hydrocarbon liquid, and then the liquid displaced by the liquid phase HVPL.

Suitable spheres or pigs should separate the two liquids.

The pressure shall be maintained at or above the bubble point of the HVPL to maintain it in its liquid phase.

12.9.5 Commissioning pressure control and metering equipment

A commissioning procedure shall be developed to align vendor recommendations with the application-specific details of the installation, including set point and allowable tolerance.

Records shall be produced to demonstrate compliance of commissioned equipment with design parameters.

Safety-critical equipment, which may be used for pipeline pressure control, leak detection or mass balance calculations, shall be fully commissioned prior to handover of the pipeline for routine operation.

NOTE: Metering equipment used for fiscal or custody transfer may require external verification or the presence of witnesses from parties involved in the transactions.

12.9.6 Commissioning SCADA equipment

The functional capability of logic controllers shall be confirmed at a factory acceptance test and reviewed in pre-commissioning for compliance with system design intent.

Demonstration of appropriate responses to simulated system inputs shall occur at the factory acceptance test. Confirmation of these responses shall be demonstrated at site acceptance test.

Any changes to the SCADA equipment or software from the original design shall be managed through the approved change management system and be subject to factory acceptance or site acceptance testing prior to commissioning.

NOTE: Commissioning of logic controllers and communications to SCADA should be undertaken to confirm site conditions and data are accurately and consistently represented remotely.

Functional testing of remote commands should also be undertaken.

Accessed by Fyfe Pty Ltd on 18 Oct 2012 (Document currency not guaranteed when printed)

12.9.7 Commissioning cathodic protection (CP) systems

Commissioning of cathodic protection systems shall be carried out in accordance with the requirements of AS/NZS 2832.1.

NOTES:

1 AS/NZS 2832.1 describes a preference to apply CP at the earliest possible time during construction, although it may be necessary to provide a temporary system prior to the installation and commissioning of a permanent system.

2 Liaison with the pipeline’s regulator to confirm testing and licensing requirements prior to commissioning is recommended.