Maintenance and reliability engineers, corrosion specialists and inspectors of fixed equipment at refineries, petrochemical and LNG plants are all aware of the financial penalties and potential dangers associated with critical heat exchanger tube failures.
These failures and related emergency shutdowns cost these industries millions of dollars per day and billions of dollars per year worldwide.
In 1985, CTI Industries developed a technology that extends the service life of new or damaged heat exchanger tubes: the Full Length Tube Liners™
Liners show projecting from air-finned cooler tube ends prior to hydraulic expansion.
CTI Full Length Tube Liners are thinwalled tubes that are hydraulically expanded inside heat exchanger tubes. They can be fabricated from a number of different erosion-/corrosion-resistant alloys and custom sized to allow a proper fit into existing parent tubes. CTI works with plant metallurgists to select a material that will resolve their specific corrosion problems.
The installation process begins by inserting liners into previously cleaned parent tubes with their ends protruding from the tubes (and header boxes on airfinned coolers). A hydraulic expansion chuck is connected to CTI's pneumatic- powered hydraulic liner pump and is attached to one end of the liner. An airbleed hydraulic chuck is affixed to the opposite end. The liners are filled with water and pressurized by the pump until full length expansion and a contact fit with the tube IDs is achieved. When the hydraulic expansion process is completed, liner ends are cut and trimmed flush to the tube ends, then roller expanded at the tube ends at both tubesheets.
Although this technology was first developed by CTI nearly 35 years ago to repair existing damaged tubes, in 2006 BP's Carson, California, refinery was the first plant in the U.S. to have CTI Full Length Tube Liners installed into new carbon steel tubes in two of their air-finned coolers.
The major factors that prompted BP's metallurgists and team of reliability engineers to utilize this technology were the historical problems experienced with these units in previous years, including:
- Excessive corrosion rate of the parent tubes in a very short time period.
- In-service tube failures leading to unscheduled shutdowns.
- Undersized water wash and unequal water wash distribution.
- Nondesaltable (phantom) chlorides.
- Chemical inhibition program could not manage the corrosion issues.
Rather than wait for these failures and related production losses to occur, the decision was made by BP to take a proactive approach and hire CTI Industries to install 389 liners, manufactured from C276 material, into each of the two bundles in-situ.
The installation of 778 Full Length Tube Liners was successfully achieved alongside BP engineers and maintenance personnel. CTI field crew completed the project ahead of schedule, enabling the refinery to return the exchangers to service ahead of schedule.
Since that time, major oil companies across the globe have utilized this technology to increase reliability and extend the service life of their heat exchanger tubes through proactive planning. CTI has installed over 50,000 liners in more than 200 different heat exchangers in over 20 countries in the past 15 years.
Working in tandem with the design engineering and inspection groups can result in a useful preventative maintenance program, which starts by closely monitoring the heat exchanger tubes during scheduled turnarounds, including NDT and hydro/pressure testing, measuring IDs with tube gauges, and documenting the external and internal conditions. Liner installations can be performed on select tubes from NDT results, individual passes or entire bundles.
Depending on the type of exchanger and the application, customers can select alloys such as 316 Stainless Steel, Alloy 825 or C276, to name a few. Benefits of installing CTI Full-Length Tube Liners include:
- Increased reliability, with liner material selected to combat specific corrosion mechanisms.
- Greater fouling resistance in comparison to carbon steel tubes.
- Eliminating unexpected tube leaks between scheduled turnarounds.
For more information, visit www. cti-ind.com or call (800) 446-0060.
