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Pipeline Challenges Limits of Leak-Tight Pipeline Isolation Capabilities

Written By pipeline-engineer.com on Saturday, October 3, 2020 | 12:48:00 AM

(PGJ) Maintaining the integrity of piping and pipeline infrastructure continues to be of vital importance to owners and operators, particularly as a higher number of pipelines move into their fourth and fifth decade of operation, far beyond their original design life.

Despite this, and due to continued integrity management programs and regular inspection, these pipelines continue to operate safely. As part of an integrity management program, pipeline and piping systems require inspection, maintenance, and repair to ensure efficient and safe operation. 
Any interruption to the product flow can be costly for the operator and to the end user in terms of loss of production and potential application of penalty clauses for loss of supply.  
Loss of integrity or malfunction generating a leak to the atmosphere adds major safety consequences and environmental hazards to the loss of production and inventory costs. There are also downstream consequences of prolonged loss of supply to the clients and end users. 
To meet ever-increasing safety standards as the industry strives to continually reduce incidents, the repair and maintenance of aging process pipework and pipeline infrastructure has become increasingly important.  

STATS was contracted to provide leak-tight pipeline isolation services on three pressurized steam lines as part of a larger restoration project at a major refinery in the Middle East. 
Unlike the first project, this scope presented many challenges that would push the limits of current isolation technology and require further research and development to provide an engineered solution capable of isolating each of the high-temperature steam lines. 
The purpose of the restoration project was to rebuild sections of the refinery following a fire that caused damage and limited refinery production capacity. The steam lines to be isolated included a 30-by-30-inch (762-by-762-mm), 24-by-6-inch (610-by-152-mm) and 36-by-10-inch (914-by-254-mm) with temperature ranging from 374° F to 718° F (190° C to 381° C) and pressures from 58 psi to 609 psi (4 bar to 42 bar).

Because the pipework was not piggable, the only viable option was to deploy the isolation plugs at locations through a branched fitting (either by welded split tee or mechanical clamp). The clamps with equal-sized branches allowed hot tapping to be conducted to provide access for STATS branch-installed self-energized plugging (BISEP) tool to be deployed into the live steam lines.  

An additional challenge to the project was that the steam pipework was situated 66 feet (20 meters) off the ground, which required scaffolding to be erected at each location. However, space was limited due to surrounding pipework, which added further difficulties. A detailed risk assessment was conducted for each of the steam lines and isolation locations.  


The specialist rubber seal was selected for the project due to its performance during testing. Prior to the live deployment, final tests were conducted at the refinery using a 10-inch steam loop. This provided final confirmation that the rubber compound would perform as required at the temperature, pressure and flow conditions of the live pipelines. 

STATS isolation methodology for the high-temperature steam lines was to use the U-bends in the system as the location for the isolation. 

This allowed deployment of a modified BISEP with a single high-temperature seal into the steam line to create a heat barrier. 

The seals on the BISEP were each independently tested, and the annulus void between the seals was vented to create a leak-tight double block and bleed isolation. With the fully tested and constantly monitored BISEP isolating the steam line, an isolation certificate was issued to the client allowing breaking of containment activities to safely take place.  

The client had requested that the split tee fittings were removed from the pipeline after the workscope was completed, so STATS methodology involved using the company’s inline isolation tool to enable the fittings to be cut and removed from the pipeline.