Many sites use air-operated double diaphragm pumps. Check the center shifting mechanism of the pumps and elastomeric gaskets for leakage. Such leaks can lead to substantial losses. Likewise, scan air-powered motors and mixers to determine if gaskets or shafts are leaking.
Individual solenoids and banks of solenoids need to be scanned. A solenoid can suffer external or internal leakage. An airborne scanning module can uncover external leaks. The auditor can use a stethoscope module to listen for an internal leak in solenoids that may be fully or partially stuck in open position.
Extensive use of air or inert gases leads to many air switches and shut-off valves at plants. Check the air switches for gasket-deterioration leaks and ball valves for packing leaks under their handles.
Many facilities operate waste-heat boilers fueled by chemical byproducts. Tubing and other plastic components, such as bowls of air filters, close to these boilers can become intensely hot, causing rupture points in tubing and gasket failure at filter-bowl seal points. For instance, a massive amount of nitrogen recently was discovered leaking from a filter bowl located a few feet above a waste boiler. There was so much ambient noise in the room from the boiler that the leak went unnoticed for years. The ultrasonic scan allowed its identification at least fifty feet from the leak site.
Keys to Success
Success of a leak survey depends upon three major elements: knowledge, planning and follow-through.
You must have a good understanding of the compressed air or gas system, including all subsystems and components. What are the sizes, types and ages of compressors? Have they been properly maintained? What about traps and drains? Are pressure gauges working and, if so, is pressure adequate for various areas of use? What are assigned pressures for these areas? Can you replace any compressed air applications with alternative less-energy-intensive methods? For example, instead of relying on compressed air for cooling, drying or cleanup, consider low-pressure blowers or fans.
Knowledge also can include familiarity with the ultrasound instrument and techniques of inspection. If staff aren’t too sure about the technology or how to use the instrument, take advantage of available training courses to increase competence and effectiveness.
Planning has a number of facets. You should develop or update a map of the compressed gas system and its various components. If no map exists, take digital photographs of each section using long-range and close-up views and carefully label them. Planning also includes scheduling the survey. Don’t try to do it all at once. Arrange assignments so they don’t negatively affect other maintenance responsibilities of the personnel on the leak team.
Before the survey begins, inspectors should walk through the various sections to review their route. This walk-through can help in a number of ways: it can identify potential safety issues; suggest changes needed to the planned route; pinpoint obvious leaks; and clarify what equipment such as flashlights, keys or specialized leak-inspection attachments to bring along.
Another important aspect of planning is setting up a leak tag/identification method (Figure 1). Tag every leak found. Use the tag number, along with a photograph of the leak, in your report — and assign a leak rate that can be used to demonstrate the economic and potential environmental impact of the leak.
Follow-through also is crucial. An un-repaired leak continues to cost the plant money both directly and by wasting the effort and cost of the survey. The shear volume of identified leaks can seem overwhelming to a maintenance department, especially one already hard-pressed to handle its regular work. So, establish a realistic method to ensure repair of all identified leaks. For instance, prioritize repairs so the most costly leaks or those that can affect production are done first, the next most important later, and so on. In addition, check the repair — sometimes it might cause another leak to appear elsewhere or the wrong component has been “repaired.”
Record-keeping is another important element of follow-through. Some companies provide software that can help. For instance, a freeware program offered by UE Systems combines data management and comprehensive compressed-gas-survey analysis. Users can review annualized and monthly data that include leak cost and greenhouse gas savings. Such data on economic and environmental impact allow generating a report that demonstrates the effectiveness of the survey and the related cost savings.
Stopping Leaking Cash
Leaks incur obvious extra costs in producing or purchasing compressed gases. They also pose hidden costs. Safety and environmental issues, equipment degradation caused by leaks and equipment inefficiencies can add up in many ways. A planned, comprehensive leak-survey program can provide savings that can improve plantwide productivity, competitiveness and profitability.
Bruce Gorelick is vice president of Enercheck Systems, Charlotte, N.C. Alan Bandes is vice president, marketing, for UE Systems, Inc., Elmsford, N.Y. E-mail them at firstname.lastname@example.org and email@example.com.