This case study explores the innovative use of advanced freezing technology in industrial maintenance, focusing on applications where traditional methods would be costly or disruptive. The study highlights how freezing pipe contents upstream of repair zones, using systems like Qwik-Freezer® and Accu-Freeze®, offers an economical and efficient alternative to draining entire systems.
The first case illustrates how the Qwik-Freezer® system enabled a power station to replace a critical valve without halting operations. The second case details how NASA used the Accu-Freeze® system to perform an emergency repair on the space shuttle Atlantis without delaying its mission. The third case examines the use of Accu-Freeze® in maintaining a nuclear submarine's piping system, demonstrating its reliability in high-stakes environments. The final case discusses how Oak Ridge National Laboratory utilised this technology to replace vital components in its cooling system without disrupting ongoing research.
This study showcases how advanced freezing techniques provide significant time, cost, and safety advantages across critical maintenance scenarios.
The Challenge of Pipework Maintenance
Repairing or replacing pipe sections or in-line components such as valves and instrumentation is a common challenge in industrial settings. Traditionally, this involves isolating and draining the relevant section of the pipework, which can result in significant product loss and production downtime.
An increasingly popular, economical alternative is to freeze the pipe contents upstream of the repair or replacement zone, thereby avoiding draining large product volumes. In some cases, freezing both sides of the repair site allows for simple material drainage between the freeze points.
Historically, plumbers have used canned spray systems for such tasks, but these are limited to pipes of around 50 mm (2 inches) in diameter. For larger pipes, more sophisticated solutions like the Qwik-Freezer® system, which uses solid carbon dioxide, can handle pipes up to 8 inches in diameter.
Advanced Freezing with Liquid Nitrogen
Recent developments in freeze technology using liquid nitrogen have led to advanced systems like the Accu-Freeze® product. This technology is now recognised as a fast and reliable method for temporarily isolating pipe sections, allowing for repairs and modifications without draining the entire system.
Liquid nitrogen technology can create ice plugs that can withstand pressures of up to 140 bar (2000 psi) and can be used on pipes up to 300 mm in diameter. The process involves wrapping copper tubing around the pipe section to be frozen, placing an insulating jacket over it, and injecting liquid nitrogen.
The automated system monitors the pipe's surface temperature and controls the flow of liquid nitrogen to maintain the desired temperature. This not only ensures a consistent freeze but also minimises liquid nitrogen consumption. Additionally, these systems can be controlled remotely, reducing operator risk in potentially hazardous environments.
Expanded Case Studies Highlighting the Effectiveness of Freezing Technology
Case Study 1: Compressor Station Water Valve Replacement Using Qwik-Freezer®
A new compressor installation at a power station was progressing smoothly until an unexpected issue arose. The design drawings had overlooked a critical interference: a cold-water valve extension handle clashed with the compressor's air inlet pipe. This posed a significant problem because the valve was the only isolating mechanism for the cooling water main header. Moving or adjusting this valve would require shutting down the entire cooling water system, which, in turn, would halt the power station’s operations, leading to substantial downtime and financial losses.
Faced with this dilemma, the engineering team considered several options. Conventional methods of addressing the issue would involve shutting down the system, draining the water, and then performing the necessary adjustments—a process that would be time-consuming and costly. Instead, they consulted with the technical team at Huntingdon Fusion Techniques HFT®, who recommended the Qwik-Freezer® system as an effective solution.
Within 24 hours, a complete Qwik-Freezer® kit was delivered to the site. The system was set up to freeze the pipe upstream of the valve, creating a solid ice plug that effectively isolated the section of the pipe where the valve was located. The freeze took approximately an hour to establish, after which the welded valve was safely ground out and replaced with a new one. The entire operation, including the valve's freezing, removal, and replacement, was completed in just two hours. This quick and efficient solution allowed the power station to continue operating without interruption, demonstrating the significant time and cost savings the Qwik-Freezer® system can provide in emergencies.
Case Study 2: Emergency Repair on Space Shuttle at NASA
The space shuttle Atlantis was on the launch pad, ready to embark on mission ST-101, when a critical issue was detected during a final systems check. The power drive unit (PDU), a hydraulic power pump responsible for controlling the shuttle’s rear rudder or air brake, showed signs of malfunction. Given the vital role of the PDU in ensuring the shuttle's safe return, any failure during the mission could have catastrophic consequences.
The traditional method of repairing such a fault would require rolling the shuttle back to the vehicle assembly building, draining the hydraulic lines, and performing the necessary repairs. This process would have delayed the mission several weeks, leading to significant additional costs and rescheduling challenges.
In a brainstorming session, an engineer suggested using a freeze isolation technique to address the problem without moving the shuttle. By freezing the hydraulic lines feeding the PDU, repairs could be carried out without draining the entire system, keeping the shuttle on the launch pad and maintaining the mission schedule.
Given this approach's high stakes and unprecedented nature, extensive testing was necessary. The Accu-Freeze® system was selected for the task, given its ability to create reliable ice plugs under controlled conditions. Over three days, multiple trial freezes were conducted to ensure the procedure's feasibility and safety. The tests were successful, and the procedure was approved for use.
On the day of the repair, the operation was carried out in challenging conditions, including drenching rain. Despite these obstacles, the Accu-Freeze® system successfully froze the six 16 mm hydraulic lines simultaneously. The repairs were completed without incident, and the freeze was maintained for over 24 hours—well beyond the initial expectation. This innovative freezing technology allowed NASA to keep the mission on track, avoiding a costly and time-consuming delay.
Case Study 3: Nuclear Submarine Maintenance
Maintaining a nuclear submarine's complex systems often requires innovative solutions, mainly when working within the confined spaces and stringent safety protocols of a dry dock. During a scheduled maintenance period, sections of piping within a nuclear submarine needed to be replaced; given the sensitive nature of the work and the need to maintain the highest safety standards, traditional methods of isolating the relevant pipe sections were deemed impractical.
The engineering team decided to use a freeze isolation technique, recognising that this approach would minimise the need for draining and refilling systems, reduce downtime, and maintain the integrity of the submarine's sensitive systems. The Accu-Freeze® system was selected for this task due to its proven reliability in similar high-stakes environments.
The freeze isolation needed to be maintained for an extended period—two to three weeks—while repairs were completed. A remote temperature control system was employed to ensure the freeze remained stable over this extended period. This system allowed engineers to monitor and control the freeze from outside the submarine, minimising the exposure of personnel to potentially hazardous environments within the radiation zone.
Extensive pre-testing was conducted to ensure the system would perform reliably over the required timeframe. The freeze was successfully maintained for five weeks without any issues, allowing the maintenance work to be completed safely and effectively. This case demonstrates the Accu-Freeze® system’s capability to provide long-term freeze solutions in critical, high-risk environments.
Case Study 4: Critical Repair at Oak Ridge National Laboratory
At Oak Ridge National Laboratory, a facility known for its cutting-edge research, the air conditioning and ventilation systems rely on 200-mm-diameter carbon steel pipes circulating a coolant mixture of 30% ethylene glycol in water. After 40 years of service, one of the two main circulating pumps failed, and it was determined that both pumps, along with sections of the piping, needed to be replaced.
The engineering team had a choice: either drain the entire cooling system—a process that would be labour-intensive, time-consuming, and disruptive to ongoing research activities—or use a freeze isolation technique to facilitate the repairs. Given the tight timeline and the desire to minimise disruption, the team opted for the latter.
The Accu-Freeze® system was chosen for its ability to create a stable ice plug in large-diameter pipes under challenging conditions. The system was set up to freeze the relevant sections of the pipework, allowing the pumps to be replaced and the piping to be upgraded to stainless steel without draining the system. This approach saved time and resources and ensured the laboratory’s critical cooling systems were back online quickly, minimising the impact on ongoing research activities.
