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 Steam Locking Contents: Have your steam-heated processes ever experienced unexplainable temperature drops even though the system appears to be working properly? The reason could be a condition known as "steam locking" (when caused by steam) or "air binding" (when caused by air or a non-condensable gas such as carbon dioxide). While countermeasures for these two problems might differ, their mechanism is the same: steam or non-condensable gas such as air enters the trap in front of condensate and shuts the trap valve, impeding condensate discharge. This article will focus on steam locking. For information about air binding, please read: Air Binding What Causes Steam Locking? Steam locking is typically not caused by the steam traps themselves because these are designed to close when steam enters them. Rather, it is the configuration of the equipment or piping around the trap that typically causes the problem. Steam locking should not be left unresolved because problems can worsen over time. Since it can be a difficult problem to pinpoint, it is important to understand typical setups that can lead to the problem. Steam Locking Issues at Outlet of Cylinder Dryers Temperature problems with steam-heated equipment can sometimes occur due to steam locking, which can cause condensate to pool into equipment. Steam locking is likely to occur in either of the following two situations: Equipment configuration causes steam to be mixed in with condensate upon discharge Piping configuration causes steam to move ahead of condensate into a trap If the steam locking is caused by a steam-condensate mixture entering the trap, then a steam trap with an optional "lock release" valve or needle valve should be used to install a bypass line that will allow for a small amount of steam to flow downstream of the trap. If the steam locking is caused by piping configuration, then the piping must be corrected to allow condensate to naturally flow into the trap in front of steam. Steam Locking Caused by Equipment Configuration When equipment configuration causes steam locking, one solution is to first discharge the steam-condensate mixture into a receiver such as a flash tank before discharging condensate through a steam trap. The separated steam should then be returned to the heat exchanger for reuse. However, this setup can be difficult with certain types of equipment such as rotating dryers that use a siphon pipe or internal scoops to discharge condensate. If reusing steam is not an option, then a different countermeasure is required. Siphoning of Steam-Condensate Mixture When using a siphon pipe, steam pressure is used to forcibly discharge condensate out of the equipment, sometimes causing steam to be mixed in with the condensate. Using a Lock Release Valve or Needle Valve Another countermeasure is the use of a lock release valve or needle valve to allow steam to be released to the downstream side of the trap, fixing the steam locking problem. Since lock release valves and needle valves can control the release of steam, steam loss is minimized. Lock Release Valve A lock release valve uses the automatic venting feature of a steam trap (such as an X-element) to forcibly open the valve and release steam to the outlet side of the trap, fixing the steam locking problem. Needle Valve A needle valve releases steam to the outlet side of the trap either internally, if the trap has a built-in venting feature (see above), or externally by using a bypass line (see below). External Bypass Line An external bypass line can be installed to allow for steam to bypass the trap, fixing the steam locking. Steam Locking Caused by Piping Configuration Steam traps should not be installed at the top of vertical sections of piping because this can lead to steam locking. Issue of Steam Locking in a Trap Piping configuration can cause steam to be "locked" within a trap and impede condensate discharge. How does piping configuration cause steam locking? You might not expect steam locking to occur if the hydraulic head pressure is large enough to overcome the steam locking. However, head pressure cannot resolve this type of problem because of the following two points: The pressure within a trap and within inlet piping leading to the trap are virtually same Condensate is discharged only when the valve is open Condensate and steam at the inlet side of a trap experience the same inlet pressure because traps are designed to discharge condensate with minimal steam loss. So steam, which has a lower density than condensate, will logically rise above the condensate when there is a vertical rise and enter the trap before the condensate, causing the valve to shut. Providing extra pressure to forcibly discharge condensate will not resolve the problem because the valve remains shut by steam. A "steam locked" trap will eventually be able to discharge condensate again when the "locked" steam has condensed. In the meantime, however, it may cause condensate back-up in piping and equipment. If the problem is not resolved, it can then reoccur at every following discharge cycle. Vertical Rise Causing Steam Locking What about flow at the trap outlet? It might seem peculiar that steam locking only occurs from vertical sections on the inlet side of a trap, and not the outlet. Flash steam at the outlet side of a trap will indeed rise to the top of vertical sections of piping. However, since no other traps follow, nothing remains to stop the steam from flowing out of the piping. This also applies to lines connected to an open or closed vessel used to collect condensate because these already require a negative pressure differential to function, allowing for smooth flow of condensate and flash steam. Steam Flow at Trap Outlet The pressure differential at the outlet of a steam trap should allow for unrestricted flow of both steam and condensate. Other Issues With Piping Steam locking problems from piping configuration are not limited to vertical sections of piping, but can also happen with other piping configurations. For example, piping set at an incline or bent because of lack of support can also lead to steam locking. Bend in Piping That Causes Steam Locking The bend in this piping causes steam to be trapped, delaying condensate discharge. Even if piping is installed parallel to the ground, long stretches of narrow piping before a trap can cause steam locking if the piping diameter isn't sufficiently large enough to allow condensate to move in front of the steam. Narrow Piping That Causes Steam Locking The narrow piping causes steam to be trapped within the steam trap, delaying condensate discharge. Additional Note "Air binding" is a problem that is similar to "steam locking", but caused by air. It can occur in both steam traps and compressed air/other gas systems, and typically requires a balance line to be resolved. More information on this problem is available in the next article. Also, "group trapping" can lead to problems similar to those caused by "steam locking". For more information on "group trapping", please read: Group Trapping Group Trapping Air Binding Also on TLV.com Free Float® Steam Traps for Process Use Free Float® Steam Traps for Steam Mains and Tracer Lines Steam and Condensate Training Seminars Engineering Calculator