Tales from the Road: Ultrasonic Leak Detection Survey Experiences at Industrial Plants, Part 1

January 30th, 2015

Industrial plants often lose valuable energy through steam and compressed air leaks. These defects can cost plants a fortune over time and negatively impact overall plant efficiency. But there is technology that can be implemented to locate the source of such costly leaks and prevent new ones from occurring. Ultrasonic detection is a technique manufacturing plants can use to minimize compressed gas leaks and steam leaks.

At the Ultrasound World IX Conference in 2013, Vernon Guidry conducted a seminar on how his company, DuPont, has successfully implemented ultrasonic detection technology since 2006. Following an extensive array of surveys of steam and compressed gas systems at over 135 plants, DuPont identified significant opportunities for system defect correction and energy savings. Guidry’s presentation summarized these survey’s findings and highlighted key elements of steam and compressed gas best practices.

In the first installation of the two-part series, we will focus on compressed gas leaks – their detection, causes and costs.

Ultrasonic leak detection survey overview
The primary goal of DuPont’s compressed air leak detection surveys is to help its plants identify and correct defects that negatively impact energy use and cost. The company maintains a big-picture approach that addresses several items: those that relate to other aspects of energy associated with these systems, those that impact safety and sustainability and those that affect mechanical integrity and manufacturing reliability.

Then, DuPont passes on the training, knowledge, awareness and tools necessary for continued benefits and sustained best practice to the employees and managers at the plant. Guidry also placed additional emphasis on safety – a plant can have the best, fastest production rate in the country, but if people are getting hurt along the way, none of that production is justified.

The company uses ultrasonic tools to detect and correct a broad array of defects, including compressed gas systems, steam systems, vacuum systems, hydraulic systems and mechanical equipment and components. This versatility allows factories to assess and troubleshoot a variety of mechanical issues in site systems and equipment.

Guidry and his team use the Ultraprobe 2000 and Ultraprobe 9000 as their primary tools. Many plant managers who worked with DuPont expressed their surprise at the wide array of defects that a single ultrasonic probe can discover.

Leaks’ costs can be significant
Compressed gas is not free – within DuPont and a number of industrial plants, it is actually the most expensive utility. Compressed air leaks increase variable cost incrementally and create artificial demand. The primary cost component is the small, steady increase in compressor drive horsepower and the subsequent energy use. Other costs come from cooling, water use and dryer use.

Nitrogen leaks comprise a significant chunk of the money lost even though they are not as common as other types of gas leaks. Nitrogen accounts for 9 percent of compressed gas loss but 31 percent of savings opportunity.

Guidry noted that some leaks are more severe than others – as a result, not every leak will equate the cost of having his company make the repair. In fact, a number of compressed air leaks can be resolved by simply tightening small fittings and valves that could be loose. These add up, but with a little common sense and a thorough check will locate and negate these issues.

The 59 compressed gas surveys DuPont has completed since 2006 yielded about 28,900 cubic feet per minute of gas leaks, which totaled close to $4.7 million in savings. That grand total broke down to $1.36 million in wet or plant air savings, $1.47 million in instrument air, $1.47 million in nitrogen, with the remainder divided among other gases. In 2012, DuPont conducted five compressed gas leak surveys. They found $312,000 worth of gas leaks, or 2,600 cubic feet of gas per minute.

Compressed gas surveys
Leak surveys of compressed gas systems include compressed air, nitrogen, natural gas, and various others. These leaks are among the most common and the most expensive, as they can affect a range of plant equipment. Compressors and drives, intercoolers and aftercoolers, wet air receivers, driers and filters, piping, tubing and coalescers can all succumb to compressed gas leaks. In general, 90 to 94 percent of all compressed gas loss is the result of plant and instrument compressed air leaks.

During the survey itself, DuPont uses either the UP 2000 or 9000 – in most cases – to identify all of the leaks onsite. Each defect is marked with a yellow notification ID tag and written up on a survey spreadsheet for work order generation and cost avoidance evaluations. Then, the Site Energy Champion or Reliability Engineer will see the notification through to SAP for repairs. Once the repairs are made, the yellow ID tag is removed and the spreadsheet is updated.

Guidry emphasized the importance of training employees to carry out plant maintenance techniques. With the right instruction, employees can use ultrasound tools to detect even the smallest leaks in the loudest environments.

Gas leaks can also be safety, health and environmental hazards. If the gas is not vented properly it can limit visibility and hearing, and cause irritation, particularly if it is hot or corrosive.

As for the reasons for and sources of the defects, there are a number of culprits. Hose leaks, quick-disconnect fitting malfunctions, pipe and pipe thread leaks and valve packing leaks are the primary causes of plant or wet air leaks. For instrument air, regulator diaphragms, piping or tube fitting connections and valve actuators are all susceptible to leaks. Breathing air leaks can be caused by threaded fitting defects or filter canister O-ring malfunctions. For nitrogen leaks, small piping or Solenoid valve leaks are often to blame.

Leaks are not always equipment malfunctions. They can reflect misapplications or misuse of air blowers, or indicate that a piece of equipment was installed incorrectly in the first place. That’s why it is important to have the necessary training and expertise so human error can be minimized.

Guidry maintained that compressed gas leaks are easily identified and corrected with routine ultrasound leak detection surveys and the proper training and awareness.
Click here for Part 2

Suggested Ultraprobe Instruments for leak surveys: Ultraprobe 3000; Ultraprobe 9000: Ultraprobe 10,000; Ultraprobe 15,000


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