Proven methods to lower costs and boost safety in gas distribution operations
Gas distribution systems exist in a multitude of applications, including laboratories, test centers and industrial sites. A crucial element of proper system function is ensuring gases are transported safely, keeping critical processes in place.
However, with the complexity of most operations, selecting the proper components for gas distribution systems is often deprioritized because these systems are viewed as utilities rather than finely-tuned arrangements that require frequent attention. They operate in the background—much like a plant’s power grid—and, as a result, are often assumed to work well in all circumstances.
Additionally, in many cases, no single department within an organization is tasked with clear accountability of gas distribution systems because they span entire facilities. In many instances, other more pressing operational concerns take precedence. Proper attention to gas distribution systems offers a simple way to enhance safety and cost controls at a plant.
Gas distribution system basics. At its core, a gas distribution system comprises tubes, pipes and other components that move pressurized gas from its original source to where it will be used. That often involves:
- Providing an access point to a gas supply system
- Reducing the source pressure to a lower constant
- Enabling an uninterrupted supply of gases
- Handling reactive, toxic, corrosive or high-purity gases.
Operational issues within the system can present significant risks to employees and end-product quality because its gases are often under extreme pressure and/or high temperatures. Under these circumstances, escaping gases can injure employees even if the gas is nonhazardous.
In addition, keeping a gas in an over-pressurized system can damage downstream components and force facilities to engage in expensive repairs or replacements. Finally, gases can be hazardous, toxic or flammable, meaning an undetected leak can put workers at risk.
Even seemingly harmless gas leaks can cause issues for plant operators. Minor gas leaks can go unnoticed for lengthy periods of time, and the costs of such losses can add up. Unidentified leaks of a gas like nitrogen—typically $0.01 per standard cubic foot (sft3)—can result in tens of thousands of dollars in losses annually. Costs associated with leaks of more expensive gases (e.g., helium, which costs > $1/sft3) can add up much more quickly.
How subsystems play a role. Operators must build safe, efficient systems from the ground up, ensuring each subsystem works effectively with its counterparts. Collectively, the entire system’s primary function is to reduce the pressure from the source and maintain stable pressure throughout the gas’ journey. This is accomplished with four key subsystems:
- Source inlet: The source inlet (FIG. 1) connects the high-pressure gas source to the gas distribution system. The inlet must be built with appropriate cylinder connections, hoses, tubing and filters, as well as vent, purge and relief functions. Some gas panels may lack a standard source inlet; always verify componentry and that panels employ the correct cylinder connector. Some high-pressure and/or hazardous gases (including oxygen) also require the use of special application hoses.
FIG. 1. The source inlet is the first component in a gas distribution system, connecting the gas source with the system that will carry it throughout the plant.
2. Primary gas pressure control panel: This panel (FIG. 2) completes the first pressure reduction and ensures the source gas is delivered at the correct flowrate to the next stage of the system. Pressure reduction is accomplished with either a single-pressure regulator or through a dual-pressure regulator arrangement. Pinpointing correct inlet and delivery pressures is challenging. It is important to factor for variations among media, such as the pressure difference between bottled ammonia and bottled nitrogen. Meanwhile, many bottles using a two-stage pressure regulator may not require one. This can be a cost-saving opportunity.
FIG. 2. The primary gas pressure control panel reduces the initial pressure from the gas source and delivers it to the next stage of distribution by regulating its flowrate.
3. Automatic changeover panel: This panel (FIG. 3) switches one gas source to another to ensure an uninterrupted supply to critical points of use. Staggered setpoints of two-pressure regulators allow the system to continue operating as the primary gas source changes. Leveraging an automatic changeover panel can help minimize waste by ensuring the removal of as much gas from each bottle as possible. An automatic changeover system that removes the need for an operator from the changeover event can also save direct labor and reduce risk.
FIG. 3. The automatic changeover panel merges two different sources to ensure the gas supply to crucial points of use remains uninterrupted.
4. Point of use: The point of use (FIG. 4) provides the critical last stage of control. These subsystems, which typically have a pressure regulator, gauge and isolation valve, provide operators with a convenient and accurate method for adjusting pressure. Where a varying line pressure between the primary gas pressure control and point of use is acceptable, a single-stage pressure regulator may reduce cost and complexity.
FIG. 4. The point of use is the final control stage, which provides technicians with the ability to fine-tune pressure levels before use.
The five crucial steps to building a gas distribution system. There are five essential building blocks to an efficient and effective gas distribution system: choosing the right components, designing the subsystem thoughtfully, ensuring that the subsystems work seamlessly with each other, assembling and installing the system correctly, and ensuring the system is easy to maintain.
The first step is choosing the right components. Selecting poorly matched components may cause a system to malfunction, putting employees and other systems at risk. With a variety of general industrial fittings, valves, regulators and other components on the market, most operators will need guidance to determine which best fits their needs.
The second building block is designing the subsystem thoughtfully. When designers create a system from scratch, they must ensure all components work together effectively so the system is safe and efficient. A perfectly designed subsystem should not rely on threaded connections to prevent leaks. Additionally, the subsystems should allow technicians to operate and maintain them intuitively, including integrated gas panels with clearly marked components. Reducing a system’s complexity greatly lowers the chances of mistakes occurring.
Once the subsystems are designed, the next crucial step is making sure they all work seamlessly with each other to distribute the gas when and where it is needed. Whether the system is new or modified, engineers should make well-considered decisions about items like tube routing, component selection and more. Considering these systems in advance will mean the systems are safer and more efficient.
Once all the pieces are in place, technicians must assemble and install the system correctly to ensure its long-term safe operation. Poorly assembled systems and insufficient testing before use can threaten workers and other bystanders. Often, assembly mistakes are made by undertrained technicians and can result in leaks or improper system function. It may be necessary to conduct follow-up training on system use and maintenance.
The final building block of an effective gas distribution system is ease of maintenance, which can be enhanced by deploying integrated gas panels that are far easier to keep working than other options. Ideal gas panels feature front-side primary components that make access easier for technicians if filter changes or other maintenance tasks become necessary.
A simplified access to regulators can result in:
- Time savings of 30 min–2 hr, depending on conditions
- Thousands of dollars in savings at each maintenance interval.
Building an effective gas distribution system can be challenging, and complexities can stump even the most experienced operator. Partnering with a supplier that employs fluid system specialists with pressure control experience is key. These experts can help designers choose the proper subsystems for their specific application, as well as ensure each part of the subsystems is engineered, fully tested and standardized for ease of installation and maintenance. Additionally, an experienced supplier can make changes to its products to customize them to specific applications.
The bottom line. Before designing a gas distribution system, it makes sense to bring in third-party evaluators who can advise engineers on optimizing the system with upgraded components. Choose a company that has gas delivery expertise to ensure the system meets the most recent requirements as defined by governing bodies in the region.
While gas distribution systems can be underappreciated systems in a facility, they deserve a significant amount of attention. A well-functioning system is essential to keeping a plant safe, efficient and economical, so it is vital the correct actions are taken to ensure it is working optimally.
ABOUT THE AUTHOR
Jeff DeWitt is an Applications Engineer for Swagelok.
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