John Fleming writes about the development of the Australian Pipelines and Gas Association PE Code of Practice.
The rapid development of the three LNG plants and the massive field infrastructure which supported them must count as one of the largest projects ever undertaken in Australia. As well as placing heavy demands on both physical and people resources, they also stretched our technological skills into unknown territory.
Pivotal to the supply of the prodigious amounts of coal seam gas (CSG) needed to feed the Curtis Island LNG plants was polyethylene (PE) pipe. Around 20,000 kilometres of pipe has been installed over four years – a world first.
This article will explore the development of the APGA PE Code of Practice, the changes made in Versions 1.1, 2, 3, and the ongoing development which will lead to Version 4 in 2016. 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.
The use of PE pipe in the gas industry is certainly no new phenomenon, dating back to the 1970s, where its use was confined to gas reticulation below ground. However, PE pipe had never been used in the diameters or in the places required by the CSG projects.
Industry was placed in a situation where the Australian Standards for city based distribution networks were inappropriate for rural and semi-rural areas. Likewise, pipeline standard AS2885 was not appropriate as it focused on steel pipelines.
The industry saw a need for a Code of Practice to improve the following:
- Safety – between 2006 and 2011, safety became an issue particularly with respect to pressure testing. There was a urgent need to standardise safe pressure testing procedures;
- The design factors in accordance with AS4130/AS4655, which were formulated for the gas distribution systems, were seen as excessive for remote rural gathering system designs; and
- To create a common design and construction standard, producers, designers and contractors all had different guidelines resulting in confusion, potential unsafe practices and cost inefficiencies.
Additionally, new construction techniques were proposed including new butt fusion welding techniques, PE pipe coiling and installation techniques, such as plough-in.
Following significant consultation within the CSG industry, it was agreed that APGA would oversee development of a Code of Practice, funded by industry, to specifically focus on the upstream CSG industry and covering both gas and water pipelines. A number of committees were established, supported by the APGA board, in particular then-president Peter Cox, and with the enthusiastic encouragement of chief executive Cheryl Cartwright.
It was decided to follow the structure of AS2885 as this Standard was well known in the industry. The chapters would be largely the same, but the contents could be very different.
Some new problems soon arose such as the impracticability of hydraulic testing in areas where water was in scarce supply, so the challenge was how to make pneumatic testing safe. Pipelines under cropping farmland would face hazards due to ploughing and also hydrostatic head could lead to problems when running water pipelines through hilly areas. Each of these hazards, as well as many others, had to be considered and dealt with.
The issue of pneumatic testing was considered at length and, in the end, the simple rule of “if no-one’s there, then no one gets hurt” prevailed. Considerable effort was put into exclusion zones to be imposed during pneumatic testing.
From the start the Chief Inspector, Petroleum and Gas, Stephen Matheson gave his support to the project. To meet realistic time frames, sub-committees dealing with specific chapters were formed, fully supported by industry representatives. The Plastic Industry Pipes Association (PIPA) were invited to join and provided invaluable assistance, both in the expertise of their members and the use of their existing documents.
There was a real imperative to have the Code available as soon as possible as work was already underway in the field. 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. 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 Chief Inspector agreed to call up the Code as a preferred standard in the Queensland Petroleum and Gas (Production and Safety) Act 2004. As a preferred standard, the Code had to be complied with or another action taken which would result in a risk equal or less than that achieved by compliance. In other words, “follow the Code or do something equally safe”.
As the construction of the pipelines continues, applications of PE were changing and demands increasing. These demands included larger diameter pipes which inevitably led to increased wall thickness and, of course, greater weight. The requirement for welding these heavier pipes brought with it more reliance on mechanical handling and much longer cool down times. Large automated welding machines, previously proven on smaller 315mm diameter pipelines, made an entrance and various techniques to reduce cool down times were being trialled as the Code was under further review.
“Around 20,000 kilometres of pipe has been installed over four years – a world first.”
The improvement of the Code continued with advances in HDD methods. It included a thorough review of the whole pressure testing process. Pressure excursions above the maximum allowable operating pressure were also addressed, as well as specific guidance on external loads, HDD and other drilling methods. The section on squeeze-off was expanded to include other flow-stopping devices. These changes were included in Version 2 of the Code, which was again called up in Queensland legislation in 2012.
Version 3, which was completed in June 2014 and is the current version, made some further changes to the Code, many of which arose from extensive field experience. More information was given about Safety Management Studies, details of which were contained in a new appendix. The difference between MAOP and Design Pressure was addressed as was flange and gasket management. There were further improvements in safe distance calculations and further information provided regarding maintenance, modification and emergency response. Information on sidewall fusion and “Golden Welds” and changes to minimum separation distances were also included.
Version 3 is the current approved version. It is available free to APGA members and for a fee to others.
Version 4 is currently under development and includes more changes arising from field experience, planned with a possible completion date of mid-late 2016. One of the major areas being examined is the use of factor f3 called the “risk factor” in calculating the design factor C and thus the MAOP. This factor changed the MAOP for a given diameter and wall thickness pipe depending on whether it was laid in a rural or a rural residential area. The real outcome being that in the more hazardous areas, installers were required to increase wall thickness for the same diameter pipe.
It has been determined that this increase in wall thickness provides virtually no defence against the common types of impact damage which pipelines can suffer, including damage from ploughing, deep ripping or the ubiquitous star picket. A current proposal being developed and subject to risk assessment is to replace f3 with a series of procedural and physical controls intended to prevent external and integrity threats occurring in the first place.
In the period 2016-2017, a series of companion papers will be issued to provide additional technical information and may be used by the wider resources industry which uses similar PE networks for gas or water handling.
There is an expectation in APGA that non-destructive testing of PE welds will one day become a reality and reach a maturity to enable it to be referenced in the Code.
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 and, given the corrosive nature of the gas, PE pipe is ideal for this application.
The journey with PE pipe has been technically challenging but has led to a well-structured industry dedicated to continuous improvement. Lessons learned during the CSG development will continue to be applied and will be of benefit to other industries and jurisdictions wishing to use this product.
“As the construction of the pipelines continues, applications of PE were changing and demands increasing.”
John Fleming has been in the gas industry for more than 50 years in scientific, engineering and Government positions. He was Chief Inspector, Petroleum and Gas in Queensland for more than 20 years and, in retirement, operates a small consultancy business, Gas Advisory Services.
John was the foundation technical editor of the APGA Code of Practice for Upstream Polyethylene Gathering Networks and now serves on the steering Committee for the Code.
Note that the Australian Pipelines Industry Association (APIA) changed its name to Australian Pipelines and Gas Association (APGA) in 2014. In this article, to avoid confusion, the later acronym is used throughout.