October 2016, Vol. 243, No. 10
Features
How Pipeline Isolation Tools Save Time and Money
Pipeline repairs are a necessary evil. Internal positional plugging devices are one way that modern pipeline operators isolate sections of pipe – safely and quickly – with zero effect on the steel’s integrity.
Before isolation pigs arrived on the scene, operators had to choose between purging or draining long sections of pipeline, or installing an intrusive full bore tap. These older tactics, while effective, also carry a full range of issues. Older methods are significantly less efficient than isolation tools when it comes to saving time and money while maintaining high standards of safety and integrity.
Pipe operators, in general, don’t want to shut down massive lengths of pipeline, which pretty much shuts down the whole operation for the duration of repairs. A bore-tapping device opens up the possibility of future integrity issues in the pipe. Projected integrity issues are something no one wants – from pipeline operators to residents living nearby. Additionally, bore tapping leaves behind a mess of fittings or holes.
Used singly, or in tandem, isolation tools are an effective and efficient method for many types of pipeline remediation. These types of pigs have been used for: anomaly repairs, valve maintenance and repair, reroutes, new delivery points, new pump station tie-ins, launch/receive trap maintenance, stuck pig removal (flow required), decommissionings, and abandonments.
The tools are bidirectional-capable, making trap repairs a quick and easy in-out endeavor. They can also be configured to be purgeable, and nitrogen can be used to propel them for applications where is it necessary to displace the product, such as a re-route.
Isolation tools are relatively simple to operate. They can be used to minimize risk and keep downtime low while maximizing efficiency. The result is a clean, productive flow line that banishes the ghosts of repairs, like leftover fittings or holes.
Isolation at Crossroads
Project managers at a newly constructed tank farm in Cushing, OK needed a new delivery point along an existing pipeline. Integral Pipeline Technologies deployed two 24-inch IsoTools to Cushing immediately. The tools would isolate the pipeline and allow tie-in of the new valves and delivery laterals.
The IsoTools were launched 300 feet apart in crude oil, and tracked to the tie-in location. The lead pig was parked 12 feet downstream of the tie-in location. Tool operators used the remote communication system to set the tools, and the pipeline was isolated within 36 minutes.
The control boxes were lock out/tag out (LOTO) so Integral could monitor the tools, but not operate them. Workers cut the pipeline on either side of an existing tee that was to be removed. Once the new pipe was tied in, the project operators returned the previously evacuated product into the line.
After LOTO was removed from the isolation tools, the internal bypasses were opened and the pressure across them was equalized. Both tools were unset, all LOTO was removed from the pipeline, and control was returned to operations. The tools were trapped individually and pulled without event.
The project was successful and the new asset was effectively tied in. By using isolation tools, the company saved time by not having to purge the system and eliminated potential future integrity problems associated with conventional intrusive plugging devices.
How Does it Work?
Isolation pigs are launched as any inline inspection tool would be, pumped at line rate to the target area, and parked by shutting down the pumps and closing valves upstream and downstream to bring the tools to a stop. After the tools are located, suitcase-sized communication boxes are placed on the ground above them.
One benefit of an isolation tool is that no excavation is required. The tool communicates through steel and ground to relay real-time data. The tool operator sets the tools and in under 45 minutes, a bubble-tight seal is formed that can hold up to 500 psi of pressure.
Tool operators use the isolation assurance test to ensure the safety and integrity of the tool’s operation. Pressure between the isolation tools is drained to zero. The evacuation point is closed and the null pressure between isolation tools is monitored for a set period of time. If the pressure remains at zero, the Isolation Assurance Test passes. Remaining product is removed from the pipeline and repairs can begin.
Once repairs are complete, internal bypasses in the tools can be used to flood the volume in-between. Alternately, the product that was removed can be reinjected into the line. The tools are released and pumped to the next target area. Isolation tools often allow for multiple performance sequences before needing to be removed from the pipeline.
Replacements in North Dakota
A single isolation tool was deployed to North Dakota to assist in a three-valve replacement project on Dec. 15, 2014.
Well production could not be interrupted. Draining or purging the line would create an outage that jeopardized shutting down the well, at great cost to the producer.
Flow restrictions and receive trap dimensions required the isolation tool to be configured with bi-directional capability to allow the pig to be “trapped” in the launcher. Using a standard pig launcher, the tool was pumped out using standardized product and operating pressure.
The isolation tool was tracked and parked about 50 feet downstream from the launch and worksite. After wireless communication with the tool was established, the tool set command was initiated. The pressure reading displayed 300 psi.
Upstream product was evacuated into a waiting tank trunk. Following confirmation that all remaining oil had been evacuated from the pipeline, a second reading showed a downstream pressure of 290 psi and an upstream pressure of zero. The construction crew was cleared to begin work.
After replacing the valves, the crude oil product was reintegrated into the pipeline and the pressure equalized. The isolation tool showed a pressure of 290 psi, both up-and-downstream. After the tool was unset, two downstream valves were opened to increase head pressure in order to push the bi-directional tool to the original launcher setup.
Traditional methods would have required lengthy drain down, purging several miles of pipe, or using an intrusive plugging device which would have left fittings on the line and causing possible future integrity issues. Using an isolation tool, the line was only down for nine hours. This includes launch, isolation, drain up, repairs, de-isolating, and returning the pig to trap.
Well production was not interrupted and the project was completed before the battery required remote trucking. The project was completed safely per outlined procedure to the relief of the company.
Different than Old Methods
Traditional methods of isolating a pipe have their value. Using nitrogen to displace product is a proven solution to facilitating repairs. However, purging is costly. Also, extensive outages where oil is not flowing can be a result.
Line stopping using a full-bore tapping device and an articulating seal is also an effective way of isolating a section of pipe. The downside is that fittings are left behind on the pipeline. These have the potential to leak while pipe “jewelry” can hinder future operations. A bore-tapping device invites the possibility of future integrity issues in the pipe, a no-no when integrity management for the safety of all should always be at the forefront of any operation.
Using isolation pig technology is an extremely effective method to minimize downtime and keep the asset operating. Additionally, no accessories are left behind.
Safety
Every pipeline operator is concerned about safety. OSHA is concerned about safety. And the welder in the hole is definitely concerned about safety.
Onshore Isolation tools are electro-mechanical devices. Basically, they involve a screw turned by electric robotic motors. There are no hydraulics to leak. Once it is set, it is impossible for the tool to go slack and lose its seal.
In addition, the system control boxes are fully LOTO capable, which eliminates the possibility of unsetting the tool or opening the bypass while open pipe activities ensue. Meanwhile, tool operators can still remotely monitor the pressure on both sides of the tools, the power reserves of the battery, and the internal temperature of the tools.
The Isotool with integral technology, for example, has been tested to 1,000 psi with a suggested holding capability of 500 psi. Power reserves are similarly regulated, and there are enough battery stores to perform double the requirements of a multi-set project. This methodology ensures that the technology is operating well below its ability and offers assurance that the project will be completed safely.
Onshore vs. Offshore
Historically, pipeline isolation tools have been used for offshore, high-pressure applications. Though extremely successful in offshore conditions, there are limitations that deter their common use for onshore pipelines. These high-pressure tools generally have a hard diameter that is close to the ID of the pipe, and they typically require heavier wall pipe due to their strength and holding capabilities.
Innovative isolation tools are now designed to perform better, with enhanced functionality in land-based assets. Some isolation tools can traverse a 10% restriction and navigate a 3-D bend. With a focus on lower pressure-holding ability, designers have ensured that there is less stress applied to the pipeline for more onshore system practical applications.
Fluid vs. Gas
Natural gas lines by default will always require greater pressure-holding capabilities. Isolation tools designed specifically for use in fluids removes many of the constraints a gas application would imply.
Parking a pig at an exact location requires comprehensive communication and an experienced and knowledgeable tracking team. This is achievable in a fluid medium, but due to compressibility, it becomes problematical to position a pig with any degree of accuracy in gas.
Conclusion
Pipeline isolation pigs have been around for over 30 years, but market acceptance has been hesitant, primarily due to the associated risks. The rapid advance of technology as a whole in the last 10 years has facilitated the development of these devices to provide enhanced assurances to pipeline operators.
The prolific progress of electronics, batteries, and communication systems has been applied to isolation tool technology, allowing such tools to be a substantially safer and more robust solution.
Author: Curtis Rogers is a pipeline professional with 17 years’ experience and lives in Edmonton.
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