Most consumers do not stop to think about the complexities that go into the production of everyday necessities. But industrial professionals involved in the making of plastics, gasoline, and all manner of other petrochemicals know these products are the result of critical, complicated processes, often involving the use of a variety of volatile and unstable chemicals.
It is critically important that all systems responsible for containing and transporting process gases like hydrogen fluoride, hydrogen sulfide, and other harmful substances operate free of leaks. When these sorts of chemicals do escape a critical system – commonly referred to as a fugitive emission – the health and safety of both employees and the broader community is placed at risk.
So, how can plants maintain leak-free systems? It comes down to their operational teams and how well trained they are in understanding and proactively addressing fugitive emission leaks.
Reliable performance begins at installation
One good rule of thumb when it comes to maintaining leak-free performance in any refinery fluid system is this: Improper component installation, rather than individual component failure, is most often the source of leaks or performance issues.
Installation errors can take many forms, and they often intersect with flaws in system design. Operators and employees should be properly trained on certain fundamentals of assembly, installation, and system design to ensure long-term resistance to leaks and optimized process safety from the initial construction and start-up of the system. This is especially important in systems handling hazardous process gases. Training opportunities to defend against fugitive emissions and other fluid system leaks are available. Elsewhere, prefabricated, custom assemblies are another option to ensure quality, performance, and fluid system safety.
A few common installation and design flaws commonly found in the field include:
Tube routing and bending. A well-designed system minimizes the number of individual connection points and bends – and therefore the number of potential leak points (see Figure 1). Good design and tube bending also allow for some flexibility during installation, better enabling installers to make high-quality, leak-resistant connections. Reducing the number of individual connection points also helps reduce the amount of maintenance time needed in the future.
Improper tube fitting assembly. Connecting tubes and fittings might seem like a rote process, but it is highly important for the proper operation of any fluid system. Not deburring a tube properly before making a connection, for example, can cause leaks later. Under-tightening or overtightening fittings are other common errors.
Tube support. Fluid systems are often subjected to repeated vibrations, impulses, and other operational stresses that may lead to leaks. Therefore, tubes, fittings, and connections should be properly prepared to handle these variables. Good system design helps to limit the negative effects of these common system stressors by including tube supports that restrict the movement of tubing and fluid components.
Intermixing products from different manufacturers. Product incompatibility between components made by different manufacturers can be an issue, leading to unpredictable performance in some instances. In the most critical applications, choosing all components from a single supplier eliminates the risk associated with product intermix.
Tubing materials. Certain industrial refining process liquids and gases require systems that are highly corrosion resistant. Material choice is important here. While standard 316 stainless steel is suitable for a variety of system media, fluid system components made from alloys C-276, 625, 2507, or 400 may offer superior performance against corrosion, helping to improve component life cycles and reduce overall cost for the system. Specialized alloys are more expensive upfront, but they may be a worthwhile investment to maintain assured operational refinery safety.
Proactive maintenance for long-term performance
After installation is complete and the system is up and running, proactive maintenance plans are crucial – and often are just as important as initial setup.
When it comes to inspection and performing required repairs, accessibility is often the first challenge maintenance technicians face. Critical components can exist in confined, hard-to-reach spaces. Reaching those trouble spots for proper inspection sometimes requires system downtime – a tradeoff that operators may sometimes not consider worthwhile, especially if there is no apparent leak or other issue currently occurring.
However, proactive maintenance is essential, especially where hazardous materials and fugitive emissions are concerned. While this intervention may come at a cost, it is insignificant compared to the costs that could be incurred in the event of a safety incident.
Still, leaks can occur even when the most robust proactive maintenance and inspection measures are taken. And when leaks do occur, it is important to be prepared. The right refinery leak-detection equipment and supplies should be readily available for technicians, who can use a variety of products and methods for manual leak detection, including the following:
Visual testing. For liquid systems, visual checks are the simplest form of leak detection, typically indicated by visible drips or surface wetting.
Bubble testing. This is a simple, cost-effective, and common test for installed gas systems, performed either using a thin film surfactant (as shown in Figure 2 on a hydraulic system) or submergence in a water bath. A variety of surfactants are available. Visible bubbles using either of these methods indicate the presence of a leak but do not measure the quantity, which will need to be measured using alternate methods.
Pressure change testing. This method involves pressurizing an isolated line at a prescribed pressure for a set duration. Leakage results in a measurable, gradual pressure drop.
Airborne ultrasonic testing. This test is used on gas systems and uses an airborne ultrasonic measurement device to locate the presence of a leak. In pressurized systems, this test approximates the rate of leakage. It can also be used on nonpressurized systems by using an additional inboard, sound-generating device.
Mass spectrometry testing. A mass spectrometer can be used on gas systems to detect the presence of trace amounts of leaked gas and quantify the leakage. Outboard testing is used for pressurized systems, while inboard testing is used on vacuum systems.
Keeping teams engaged and empowered
Preventing hazardous material leaks and fugitive emissions depends on a team that is well-versed in tubing, tube fittings, comprehensive fluid system knowledge, and proactive maintenance. It is one thing to know the best practices. It is another to create a culture in which all employees are empowered to make important decisions regarding plant safety.
In refineries that have abundant hazardous process gases, any person who sees a dangerous situation – especially those working hands-on with the system – should have the authority to halt production. Those decisions can come at a cost, of course, but remember that a safety incident related to a hazardous gas leak can lead to massive downtime and much worse.
Employees who are armed with the right knowledge and are engaged with the organization’s commitment to safety can make a major difference for overall plant productivity and safety. Consulting a training provider to ensure employees are fully up to speed, engaged, and empowered can be a highly worthwhile investment for any refining plant.
Ken Backus is a senior field engineer for Swagelok. He can be contacted at 281-744-3644.