- Steam Theory
- 1. Basics of Steam
- 2. Steam Heating
- 3. Basics of Steam Traps
- 4. Steam Trap Selection
- Steam Trap Selection: How Application Affects Selection
- Steam Trap Selection: Understanding Specifications
- Steam Trap Selection: Safety Factor and Life Cycle Cost
- Traps and Orifices Part 1
- Traps and Orifices Part 2
- Casting vs. Forging
- Applications of Different Types of Steam Traps
- Don't Get Steamed : Selecting Steam Trap Design
- Understanding Steam Traps
- 5. Steam Trap Problems
- 6. Steam Trap Management
- 7. Water Hammer / Risk Mitigation
- Water Hammer: What is it?
- Water Hammer: The Mechanism
- Water Hammer: Cause and Location
- Water Hammer: In Steam Distribution Lines
- Water Hammer: In Equipment
- Water Hammer: In Condensate Transport Piping
- Water Hammer: Conclusion
- Mitigation of Water Hammer in Vertical Flashing Condensate Transport Piping
- Stop Knocking Your Condensate Return
- Steam Trap Management: Do Something; Anything. Please!
- Steam System Optimization and Risk Mitigation
- Risk Based Methodology for Industrial Steam Systems
- 8. Steam Quality
- 9. Steam Distribution
- 10. Condensate Recovery
- 11. Energy Efficiency
- Tips to improve steam plant efficiency
- Advice on Winter Preparation for Steam Systems
- Insulating Traps
- Steam Compressors
- Why Save Energy?
- Management Strategies for Conserving Energy
- Recovering Steam Clouds and Waste Heat
- Handle Steam More Intelligently
- Optimize the Entire Steam System
- Use Available Data to Lower System Cost
- 12. Compressed Air / Gas
- 13. Other Valves
What is Vacuum Steam?
Vacuum steam is the general term used for saturated steam at temperatures below 100°C.
As briefly discussed in Principal Applications for Steam, both positive pressure steam and vacuum steam can be used in heating processes. The following article will discuss the properties of vacuum steam and its advantages over heating with hot water.
The higher the pressure, the higher the temperature of saturated steam. At regular atmospheric pressure, saturated steam is roughly 100°C. Saturated steam generated from boilers, however, is generally much higher in temperature because it is generated at higher pressures. This steam (positive pressure steam) is therefore frequently used in industry for heating processes requiring temperatures above 100°C.
Alternatively, producing saturated steam for heating processes below 100°C is also possible. Such steam is often referred to as vacuum steam because it requires pressures below regular atmospheric pressure. Vacuum steam is generally generated at higher pressures after which pressure is reduced by using equipment such as an inlet control valve. A vacuum pump is also usually used to help achieve lower pressures at start-up and enable the smooth release of condensate.
Use of vacuum steam requires careful temperature and pressure reading. To determine steam temperature, referring to a steam table such as the one above is recommended. For example, through this steam table, we can see that if a process requires saturated steam at temperatures of 60°C or 90°C, saturated steam pressures should be set to 19.946kPa and 70.182kPa, respectively.
Vacuum Steam vs. Hot Water
Heating with vacuum steam offers the same advantages as heating with steam at temperatures of 100°C or higher:
|Rapid even heating through latent heat transfer||Improved product quality and productivity|
|Pressure can control temperature||Temperature can be quickly and precisely established|
|High heat transfer coefficient||Smaller required heat transfer surface area, enabling reduced initial equipment outlay|
|Overall Heat Transfer Coefficient||What is a Steam Trap?|