Steam Theory 1. Basics of Steam What is Steam? Principal Applications for Steam Types of Steam Flash Steam How to Read a Steam Table 2. Steam Heating Heating with Steam Steam Heating Mechanism Overall Heat Transfer Coefficient What is Vacuum Steam? Tracing the Causes of Heat Maintenance Issues 3. Basics of Steam Traps What is a Steam Trap? The History of Steam Traps #1 The History of Steam Traps #2 How Mechanical Traps Work: A Look at their Mechanism and Merits How Disc Traps Work: A Look at their Mechanism and Merits How Bimetal-Type Thermostatic Steam Traps Work: A Look at their Mechanisms and Merits 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 Compare Two Fixed Orifice Venturi Products to a Variable Orifice Free Float Steam Trap 5. Steam Trap Problems Is My Trap Leaking Live Steam? Temperature Control Trap Precautions Trap Installation Orientation Trap Back Pressure Double Trapping Group Trapping Steam Locking Air Binding My Steam Trap Is Good - Why Doesn't It Work? 6. Steam Trap Management Introduction to Steam Trap Management Steam Trap Losses - what it costs you A Guide to Steam Trap Testing Implement a Sustainable Steam Trap Management Program Impact Plant Performance by Improving the Steam System 7. Water Hammer 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 Identifying Water Hammer Using a Thermal Camera Mitigation of Water Hammer in Vertical Flashing Condensate Transport Piping Stop Knocking Your Condensate Return Steam Trap Management: Do Something; Anything. Please! 8. Risk Mitigation Steam System Optimization and Risk Mitigation Risk Based Methodology for Industrial Steam Systems Why Bad Things Happen to Good Steam Equipment Beware of the Dangers of Cold Traps Steam System Winterization: How to Protect Your Plant 9. Steam Quality Wet Steam vs. Dry Steam: The Importance of the Steam Dryness Fraction Separators and their Role in the Steam System Clean & Pure Steam Temperature Problems Caused by Air Removing Air from Steam Equipment Air Vents for Steam Steam Quality Considerations 10. Steam Distribution Best Practices for Condensate Removal on Steam Lines Installation Tips for Steam Traps on Steam Mains Erosion in Steam and Condensate Piping Corrosion in Steam and Condensate Piping Allocate New Plant Focus to Steam System Design—Part 1 11. Condensate Recovery Introduction to Condensate Recovery Returning Condensate and When to Use Condensate Pumps Condensate Recovery: Vented vs. Pressurized Systems Condensate Recovery Piping What is Stall? Methods of Preventing Stall Cavitation in Condensate Pumps Steam Heat Exchangers are Underworked and Over-Surfaced Allocate New Plant Focus to Steam System Design—Part 2 Optimize Reboiler Performance via Effective Condensate Drainage Vent Away Condensate Pump Frustrations in a Flash 12. 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 Waste Heat Recovery Boiler Energy Saving Tips Steam Line Energy Saving Tips Steam-Using Equipment Energy Saving Tips Preventing Steam Leaks Handle Steam More Intelligently Optimize the Entire Steam System Use Available Data to Lower System Cost 13. Compressed Air / Gas Removing Condensate from Compressed Air Preventing Clogging of Air Traps Air Compressor Energy Saving Tips Improving Compressed Air Quality and Countermeasures Against Leaks 14. Other Valves Types of Manual Valves Bypass Valves Check Valve Installation and Benefits Pressure Reducing Valves for Steam Check Valve Installation and Benefits Contents: A check valve is a type of valve that allows fluids to flow in one direction but closes automatically to prevent flow in the opposite direction (backflow). Check valves are used in a wide variety of locations, but the focus of the discussion in this tutorial will be the installation of check valves at the steam trap outlet side. Questions are often asked about the need and purpose of check valves, such as: Is it always necessary to install a check valve downstream of a steam trap? Does installation of a check valve prevent water hammer? Let’s discuss these two points. Is it always necessary to install a check valve downstream of a steam trap? Check valves are necessary if there is a risk of condensate backflow. For example, when a trap discharges into a common condensate collection line, there is the potential risk of backflow from condensate discharged from other traps, so as a rule a check valve should be installed. Preventing this backflow is important because it can not only diminish process heating efficiency, but can also damage steam traps. In contrast, when there is a single downward sloping pipe that is not submerged at any point, there is almost no possibility of backflow, so a check valve is not necessary. Single Dedicated Line If the trap is gravity drained through a downward sloping dedicated line that releases to atmosphere without being submerged at any point, there is usually no risk of backflow, so there is no need to install a check valve. Note: Depending on piping configuration after the steam trap, back flow can also occur in open lines if equipment goes to vacuum or if there is positive pressure from a too small vent or pipe rise which can cause unwanted return line pressure. In such cases, installing a check valve may help prevent back flow. Common Collection Line If the trap outlet piping is connected to a common condensate collection line, condensate discharged from equipment in operation may backflow into equipment that is out of service unless there is a check valve installed at the trap's outlet. Illustration C: No check valves at trap outlets If a check valve is installed, even if the trap outlet piping is connected to a common collection line, the condensate discharged from equipment in operation will not backflow into equipment that is out of service. Illustration D: Traps with check valves Does installation of a check valve prevent water hammer? There are various mechanisms that generate water hammer. A principal cause of water hammer in condensate recovery lines is condensate flowing back down in vertical rises. The installation of a check valve at each of these locations is very effective in preventing water hammer due to backflow. Water hammer caused by condensate backflow in vertical rises of condensate recovery lines Illustration E: No check valve on vertical riser If the condensate discharge piping on a pump with intermittent operation (e.g. TLV PowerTrap® series or motorized pump with ON-OFF control) has a long horizontal run followed by a vertical rise, any condensate that falls back down the vertical rise becomes backflow that may collide with newly discharged condensate, resulting in water hammer. Similarly, in situations where a PowerTrap® discharges high temperature condensate, the combination of flash steam and backflow could be another possible cause for water hammer. In such cases, water hammer may be prevented by installing a check valve at critical locations within the system (e.g. the beginning of a vertical rise). Illustration F: Check valve on vertical riser Additional Info Check valves can also help prevent water hammer caused by a pulsating flow of low temperature condensate in condensate transport piping. For more information on water hammer, please visit the water hammer tutorial. Check Valve Restrictions When high pressure hot condensate is discharged through a steam trap to lower pressure, flash steam is generated. If this flash steam then flows into a return line that contains sub-cooled condensate at a much lower temperature, an instant collapse (condensing) of the flash steam will occur as it gives off its latent heat to the condensate, and water hammer may result. Installation of a check valve is generally not effective in this situation. Check valves prevent backflow, but not back pressure. It is not possible to discharge low pressure condensate into a higher pressure line. Even if a check valve is installed after a steam trap, condensate will not flow if the pressure upstream of the trap is lower than the downstream (return) side. Additionally, it should be noted that if a check valve is installed at the outlet of a trap operating under an extremely large operating differential pressure, the check valve itself becomes a point of resistance (i.e., the check valve has a pressure drop as well), which means that it is necessary to calculate pressure drop very carefully. Bypass Valves Pressure Reducing Valves for Steam Also on TLV.com Spring Loaded Disc-type Check Valves Steam and Condensate Training Seminars Engineering Calculator Steam Bulletin: Archive - Email Magazine