A Safe and Reliable System
The safety of the people who live and work near our gas lines and facilities is of the utmost importance. We are committed to designing, maintaining and operating a safe and reliable natural gas system.
Whether it's through our damage prevention efforts, or our gas line integrity programs, safety is at the core of everything we do.
Safe Design and Installation
We design our natural gas lines and facilities to national standards. All gas lines are coated with protective covering such as epoxy and polyethylene before installation. This provides the first line of protection against corrosion. We also design and install cathodic protection systems to prevent corrosion.
Grading and Trenching
We carefully prepare the surface right-of-way area before gas line installation begins. Topsoil is stripped off the trench construction zone using soil preservation techniques. The topsoil sits in piles on the right-of-way until construction ends. We then use a trencher or other suitable excavation equipment to dig the trench, which is approximately one metre deep.
Once complete, we replace the topsoil and restore the terrain to its original state.
Stringing, Bending & Welding
Segments of pipe are shipped to the construction site. These segments, called joints, are about 16 metres in length. We lay them end-to-end on pipe stands alongside the trench. Sometimes we bend a pipe joint using hydraulic equipment to form the pipe to the lay of the land.
We weld each joint together to form one continuous gas line. Certified welders do all the welding according to strict TransGas weld procedures. Welding also follows industry specifications and national standards.
After each weld has passed radiographic inspection, the weld seam is coated with a sleeve. The sleeve, similar to polyethylene coating, protects the pipe.
Lowering-In and Backfilling
Construction workers use sidebooms to lower the gas line into the trench. If a trench bottom may damage the pipe, a layer of sand is placed at the bottom of the trench to protect the gas line and its coating.
The gas line is then backfilled using as much original dirt as possible. If the original material contains larger rocks, it may not be used as backfill. Rocks cannot be placed directly on a gas line as they may damage the coating or the steel pipe.
If using the original material isn't possible, we apply an extra protective coating called rock shield to the gas line surface. This is done before backfilling.
All TransGas natural gas lines are designed and installed to have at least one metre of ground cover.
Crossings and Tie-ins
At roads, railways and waterways, we use specific techniques to minimize surface damage and enhance safety. We drill a hole underneath these crossings and then pull the gas line through the hole. One method of drilling is using a direction drill unit (directional drilling). Once complete, we weld this section of pipe to the rest of the gas line. This technique minimizes any adverse effects to the road, railway or waterway.
For added protection, we use thicker-walled pipe to allow the gas line to withstand any extra weight at these locations. At least 1.5 metres of cover exists under roadways and two metres under railways and waterways.
Following installation of the gas line system, we begin pressure testing operations. This helps our engineers make sure the natural gas line is safe and ready for operation. Under normal circumstances, the gas line is filled with water and raised to a higher pressure than the maximum operating pressure.
All testing is done according to national standards and provincial and federal regulations. It is also approved by a professional engineer.
With help from our Environment & Sustainability team, we restore the right-of-way for the entire length of the natural gas line. Our goal is always to return the terrain to as close to the original condition as possible. We replace the topsoil that was originally removed and seed it where appropriate.
Prevention, Detection and Mitigation
We are committed to the safe and reliable operation of our gas lines and facilities. We take steps to ensure that every kilometre of our natural gas system is monitored and protected. Significant steps are also taken to prevent the chance of any leaks on the system.
Our gas line integrity program focuses on prevention, detection and mitigation.
We protect our gas lines and facilities from conditions that may lead to integrity concerns.
Every year, we perform a variety of tests and inspections throughout different parts of the province. We also have processes in place to prevent external damage to our facilities.
Our detection and monitoring activities identify any defects that may lead to integrity concerns. This includes leak surveys and both aerial and ground visual inspections of gas line right-of-ways.
We implement risk-reduction controls, which may include repairs, replacement or monitoring.
Risk control is prioritized in the following areas:
- Facilities near populated areas
- Gas lines and facilities where inspection programs indicate a possible concern
- Where the effectiveness of cathodic protection on gas lines is low or coatings are damaged or deteriorated
Using tools such as ROSEN 'smart pigs', which can check for cracking and long seam defects, is one of the ways we mitigate risk to our system.
We use in-line inspection (ILI) tools to inspect hundreds of kilometres of gas lines every year.
The natural gas line inspection gauges we use are referred to as ‘pigs.’ We place electronic pigs inside our gas lines to gauge wall thickness, the size of any potential defect or dent, geometry and metal loss. This information is associated with a specific location using a global positioning system (GPS).
Our employees gather data and work with experts to analyze and diagnose any potential gas line anomalies. We mitigate risk by developing plans to address and/or repair irregularities on each inspected gas line. We also conduct inspections at compressor stations and other transmission assets.
Stress Corrosion Cracking
Stress corrosion cracking (SCC) is damage caused by the following:
- stress in the pipe steel
- a corrosive environment around the gas line
- susceptible gas line material
Under specific conditions, a hairline crack on the outside of a gas line can compromise the structure of the line and progress into many cracks. These cracks may eventually grow through the entire wall of the gas line. TransGas monitors its system for this type of damage and, if detected, immediately fixes the affected section of the gas line.
Cathodic protection uses an electric current to prevent metal loss on a natural gas transmission line. Every month, we monitor the voltage readings to ensure our gas lines are not being damaged by corrosion.
TransGas regularly performs transmission leak survey and encroachment patrols. We conduct walking, all terrain vehicle (ATV), airplane and helicopter surveys of our facilities. The purpose is to inspect, identify and report activities, or leaks, that may affect the safety or integrity of our system.
Our personnel investigate any findings discovered through these activities.
Gas Line Crossings and Encroachments
We take precautions to remove any third-party contact with the gas line.
TransGas coordinates any activity that encroaches on our natural gas lines. Crossings work permits are issued based on specific risk-based decisions.
We also track encroachments to mitigate threats and to identify any required actions.