Know these basics of gas panel design to choose the right system
The purpose of the gas control panel
The gas control panel is the primary pressure control point in a gas distribution system. It is located near the gas/liquid source (one or more cylinders or bottles) and reduces the gas pressure of the cylinder(s) to deliver it at the proper pressure and flow rate to the point of use, such as a laboratory, process equipment or analyzer. A properly functioning gas distribution system requires a properly sized and selected pressure regulator. Primary gas control uses two methods to reduce pressure: a single-stage pressure regulator or a two-stage pressure regulator.
Two critical factors affect gas pressure regulation: pressure drop and supply pressure effect.
Pressure drop indicates the difference in delivery pressure between zero flow conditions and the maximum flow capacity of a regulator. Supply pressure effect indicates the changing delivery pressure as supply pressure decreases when a cylinder becomes empty. Single-stage and two-stage regulators differ in their pressure drop characteristics and response to changing supply pressure.
Single-stage pressure regulator
A single-stage pressure regulator reduces cylinder gas pressure within a specific range in one step. A single-stage regulator shows minimum droop as flow rates vary, but demonstrates a relatively large supply pressure effect. A single-stage regulator is typically used in applications where there's little inlet pressure variation, constant outlet pressure is not critical, or periodic readjustment of delivery pressure does not present a problem.
Two-stage pressure regulator
A two-stage gas pressure regulator reduces cylinder gas pressure in two steps. A two-stage regulator exhibits significant pressure drop but minimal supply pressure effects. A two-stage regulator provides a constant supply pressure without the need for periodic adjustment. Two-stage regulators are used in applications that require constant outlet pressure over the life of a gas cylinder.
Variations in gas panel design
A good panel design allows for easy installation and maintenance. The panel design starts with a standard backplate that is matched to the width of standard gas cylinders. A standard size allows multiple panels to be installed without varying the spacing. With a standard backplate, each panel can be easily configured for the specific requirements of the gas distribution system.
Optional components that can be incorporated into the design include vent and safety components for safe operation, gas pressure indicators before and after the regulator, and color-coded regulators and valves for easy identification. With a standardized backplate, all components on the panel can be easily disconnected for maintenance or upgrade, if needed.
Gas panel design considerations
Not every company has the privilege of having an in-house engineering team for gas distribution systems. Most companies lack in-house engineering resources and rely on the expertise and experience of local suppliers. While the function of a gas control panel may seem relatively simple, a thorough understanding of the purpose of the gas distribution system and the planned or existing infrastructure is required to properly design the gas panel.
The type of gas, end-use application(s) and available component options influence the design of each gas panel. An experienced fluid systems engineer will consider all of these factors to calculate the proper gas pressure and flow rate and determine the optimal gas control panel design.
Calculate the correct gas pressure and amperage
There is a wide range of commonly used gases in industrial applications, including nitrogen, oxygen, carbon dioxide, argon, propane, propylene, hydrogen, helium and acetylene. The semiconductor industry uses dozens of less common gases, such as bromine, phosphorus trifluoride and titanium tetrachloride. To support effective and consistent application, these gases must be reliably delivered at constant pressures and flow rates.
Calculating the proper delivery pressure and flow strength can be difficult. This is where the expertise of an experienced fluid systems engineer comes in handy, calculating the required pressure and amperage based on the type of gas and application. These calculations determine the size of the pressure regulator used on the gas control panel, and whether a single-stage or two-stage pressure regulator is needed. In many cases, calculations show that a single-stage regulator is sufficient, reducing the cost of the panel and simplifying long-term maintenance.
Ensure safe operation
Safe operation is a requirement for any gas distribution system. The gas control panel components selected must have been evaluated to meet the pressure and temperature requirements of the process. Pressure control components such as safety valves and pressure regulators must be sized to manage the full range of possible gas pressures and flows to ensure safe operation of the system.
Operational differences between components are also a consideration. For example, a multi-rotation needle valve and a quarter-turn ball valve may have similar ratings, although each valve is best suited for specific purposes. A multi-rotation needle valve allows for small increases in pressure. A ball valve can change pressure rapidly and lead to a pressure spike. An experienced fluid systems engineer will specify the valve that allows the safest operation.
Certain gases can be harmful to the environment and/or workers located near the gas distribution system in the event of leakage. The risk of leakage can be reduced by using compression fittings instead of threaded fittings. Industry and local regulations can determine where and when different fittings are acceptable and ensure that the gas control panel is designed to comply.
Catastrophic leaks or ruptures in a well-designed gas distribution system are rare. But in the event of a significant downstream leak, a restriction orifice strategically placed close to the gas source limits the leak and provides an additional level of protection for workers and the environment.
Anticipate future process changes
Process conditions are likely to change, and smart fluid systems engineers should design the gas control panel to anticipate these changes. Sizing pressure controls to accommodate a wide range of pressure and flow parameters gives the system flexibility to meet future processing requirements without the need to change components on the gas control panel. Again, design experience is crucial. Specifying gas panel components for too wide a range of parameters can compromise the panel's ability to deliver the required pressure and flow for the originally specified process.
Swagelok's experience in the design of gas distribution systems
Well-designed gas control panels are critical to the safe distribution of high-pressure gas to end process applications at the required pressures and flow rates. Organizations with limited or no experience in gas distribution system design benefit greatly from the services Swagelok offers. Our Field Services Engineers will perform an in-depth assessment of your gas distribution needs and use the results of the analysis to design a gas control panel to meet your specific needs. In addition to gas panels, we are equally adept at designing and manufacturing all other relevant subsystems to provide a complete gas distribution system.
We have been supporting the fluid handling needs of industries in the Netherlands for over fifty years, and during that time we have developed design practices that deliver gas distribution systems that are intuitive and safe to operate, easy to maintain and minimize the potential for leaks. Swagelok gas panels are highly configurable, with features or modifications based on process requirements. Swagelok gas delivery panels are delivered fully assembled and tested, and all gas distribution systems are covered by our limited lifetime warranty.
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We design, manufacture and test Gas distribution systems for customers, here in Waddinxveen
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