The release of Version 2 of the APIA Code of Practice for Upstream Polyethylene Gathering Networks – Coal Seam Gas Industry once again has given prominence to the increasing use of polyethylene pipe in the petroleum and gas industries, particularly its extensive use for the carriage of both water and gas in coal seam gas projects. It would be no exaggeration to assert that the viability of these projects would have been questionable in the absence of polyethylene pipe.
This article will explore the development of the code, the changes made in Versions 1.1 and 2 and the ongoing development, which will lead to Version 3 some time in 2015. It will also address other related issues where polyethylene (PE) has found a role and some issues yet to be resolved. As the code is called up in Queensland legislation where the vast majority of the pipe is being laid, this article focuses on the Queensland experience.
PE in the gas industry
The use of PE pipe in the gas industry is certainly no new phenomenon. The author remembers the introduction of PE pipe into the gas reticulation system of Gas and Fuel Corporation of Victoria which would have commenced in the early-1970s, replacing the experimental polyvinyl chloride (PVC), which had also been tried about the same time. From the earliest days its use was confined to gas reticulation below ground with above ground piping retained as the traditional copper or steel. This was done due to the susceptibility of the yellow PE pipe to ultra violet degradation, but more importantly, from a safety perspective, to the ability of copper or steel pipe to better resist excessive heating and prevent gas being released into a fire, which the fire brigade agreed was a good idea.
PE quickly became the preferred pipe material for gas distribution and was even inserted into old leaking cast iron gas mains where the decreased diameter was compensated for by the lower wall roughness so that flow rates could be maintained or even increased. In addition, pipe diameters were gradually increased with PE soon taking over larger gas mains until all but high pressure pipes were included in the PE inventory. The pipe diameters used were, relative to today, quite modest with most distribution pipelines being less than
300 mm and pressures used being normally up to a maximum of 500 kilopascals (kPa).
This state of affairs continued for many decades and it was only the demands of the coal seam gas (CSG) industry that was responsible for the changes we see today, with pipe diameters in excess of 600 mm coming into use and the pressures up to 1,000 kPa being on the table. The gas distribution standards were not suitable for use in the CSG environment as they were largely focused on urban area issues and there was no equivalent to the eminent AS 2885 which could be accessed for reference.
Development of the PE Code of Practice
APIA stepped into the breach with a proposal that a code of practice be developed to specifically focus on the upstream CSG industry and give guidance to industry as to safe working practices and a number of committees were established, supported by the APIA board, in particular Peter Cox and with the enthusiastic encouragement of Chief Executive Cheryl Cartwright. The structure unashamedly followed some of the principles of AS 2885 which had served the steel pipe industry so well.
In Version 1.0, released in April 2011, some areas such as squeeze-off techniques and requirements for horizontal directional drilling (HDD) were not included as the issues were still being considered. There were other issues as the code, which was advisory only at this stage, was being implemented and feedback from the field was recommending improvement. Version 1.1 was issued in October 2011 with changes which included allowance for a fit for purpose design as well as the prescribed method in Version 1. Squeeze-off was also included as a shut-off method.
But there was another major event that occurred shortly after the release of Version 1.1 – the code was called up as a preferred standard in the Queensland Petroleum and Gas (Production and Safety) Act 2004. This gave the code new importance as it now really set a standard, which was enforceable by law. The term “˜preferred standard’ meant that, in the terms of the regulation, the code had to be complied with another action taken which would result in a risk equal or less than that achieved by compliance.
The second version
The improvement of the code continued as further work was done on HDD and more field experience was received. The issue of the safety aspects of pneumatic testing of pipelines had been of concern and it was believed that there was the need to thoroughly review the whole pressure testing process. Other areas where progress was needed included a consideration of pressure excursions above the maximum allowable operating pressure, specific guidance on external loads HDD and other drilling methods. The section on squeeze-off was expanded to include other flow stopping devices. These significant changes were included in Version 2 of the code, which was again called up in Queensland legislation and is the current approved version. It is available free to APIA members and for a small fee to others.
It is recommended that anyone contemplating a PE project in the CSG arena thoroughly read Version 2 as many of the changes introduced are profound.
Latest developments
Work on the code will continue as technology matures and Version 3 is already undergoing early development, with new considerations including:
- Minimum and preferred spacing in the trench. Depth of burial requirements;
- Identify any PE material which can exceed the capability of PE100;
- General improvements to pressure testing section;
- Guidelines for use of PE above ground;
- Expand guidelines for PE pipes for water service up to 80 degrees Celsius;
- Enhanced sections on PE hot tapping and side wall fusion; and,
- Exclusion zones review.
There is opportunity for anyone with useful ideas to put them before the steering committee for consideration. The person to contact is Shane Becker at Shane.Becker@originenergy.com.au
Another recent and very welcome innovation has been the development by SkillsTech, in partnership with Polymer Fusion Technology, of an industry-supported High Density Polyethylene (HDPE /PE100) Centre of Excellence at the Acacia Ridge Training Centre in Queensland. This centre is equipped with the latest PE welding and other equipment thanks to the support from manufacturers Iplex Pipelines and Georg Fischer. A course called Certificate III in Polymer Processing is currently being offered at SkillsTech Australia.
One other area which is quietly becoming a small but significant user of PE pipe is the biogas industry, not really a single industry as such, but a wide variety of industries treating waste product to generate a combustible gas which, in many cases, is used for useful purposes including power generation and boilers. These industries include food production, council landfills, animal farms, abattoirs and the like. The gas generated, called biogas, typically contains about 50 per cent methane with the remainder being carbon dioxide and some nitrogen. There are also other compounds present in varying quantities such as hydrogen sulphide (H2S), which is toxic at low concentrations. Currently there are some differing opinions as to the use of PE pipe above ground in these industrial situations where typically, the pressures are extremely low, or even less than atmospheric pressure when being collected for use.
The rapid development in the use of PE, particularly in larger diameters, did not happen by accident and it stands as a testament to the diligent work and enthusiasm of so many industry specialists.
For more information on the HDPE /PE100 Centre of Excellence at the Acacia Ridge in Queensland contact Commercial Plumbing Officer Elizabeth Schelbach on (07) 3224 0384 or email commericalplumbing.skillstech@tafe.qld.edu.au