Contents
Gas
Gas is one of the four fundamental states of matter. It is the state where particles are the most energetic and spread out. Unlike liquids and solids, gas has no fixed shape or volume.
What Is Gas in the Context of Compressors?
Gas is a working medium intentionally pressurized and stored to power pneumatic systems. In specialized industrial applications, the term “gas” is used to distinguish pure gases from standard compressed air.
Different types of gases are primarily used in compressors:
- Inert gases: These are gases with nonreactive properties, such as nitrogen, argon and helium. They are ideal in laser cutting and other applications seeking to prevent oxidation and other chemical reactions.
- Reactive and process gases: These gases, which include oxygen, hydrogen and carbon dioxide, are used in industrial processes like steel manufacturing for their specific chemical properties. Reactive gases require specialized compressors.
The type of gas medium determines the compressor type needed for an application. When choosing a compressor, consider safety, reactivity, material compatibility and purity requirements.
FAQs
Compressibility is one of the primary properties of a gas. Because gas molecules are far apart, they can be compressed to reduce their volume. The distinct characteristics a gas takes when forced into a smaller volume include:
- High pressure: When a gas is compressed, the molecules collide with the walls more frequently, causing a pressure increase. Volume is inversely related to pressure.
- Increased density: Compressed gas maintains its mass, but the volume decreases, resulting in increased density.
- Elevated temperature: Compressing a gas rapidly increases its temperature because the energy added to the system forces the molecules to move faster. In contrast, the temperature drops when a compressed gas expands quickly.
The primary contaminants include solid particles such as rust and dust, water in vapor and liquid form and oil from the compressor. Industries use different equipment to ensure a contamination-free system:
- Aftercoolers: They cool the hot gas leaving the compressor to remove moisture.
- Air dryers: Desiccant dryers absorb water from gases for dry applications, while refrigerated dryers cool the gas to condense and remove water.
- Filters: They remove solid particles and oil aerosols from the gas.
- Condensate management: These products efficiently and safely collect, drain and dispose of the liquid waste.
PDP is the dew point of a gas under pressure, while dew point is the temperature at which water vapor suspended in a gas begins to condense into liquid water at a specific pressure. A lower PDP indicates drier gas, which is essential in preventing corrosion and moisture contamination, especially in sensitive use cases.
Compressing oxygen in a standard oil-lubricated compressor can cause the oil to auto-ignite, leading to an explosion. Therefore, oxygen requires specialized, oil-free air compressors.
Hot compressed gas from the compressor holds a lot of water and can degrade seals and lubricants. As the gas cools downstream, this moisture condenses into liquid water, creating conditions for rust to form. To address this problem, use aftercoolers and dryers.
The mechanical performance of most standard pneumatic systems will be nearly identical. Nitrogen is slightly less dense than air, drier and more inert, reducing internal corrosion and extending component life.
This is a sign of compressed gas that is not dried properly. The air was cooled below its PDP within your system, causing the water vapor it was carrying to condense into liquid, which is damaging to tools and valves.
On-site gas generation is generally more cost-effective for users with consistent, high-volume demands. It eliminates cylinder rental fees, delivery costs and logistical challenges of managing inventory, providing a lower cost per unit of gas over the long term.
Additional Resources
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