Fall2011 jalowiec


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Steam Systems Basics, Challenges and Troubleshooting

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Fall2011 jalowiec

  1. 1. Steam Systems Basics, Challenges and Troubleshooting John Cilyo Senior Account Executive Spirax Sarco Inc. For Steve Jalowiec, PE, CHFM
  2. 2. Steam Systems & Chaos Theory In mathematics, chaos theory describes the behavior of certain dynamic systems – that is, systems whose states evolve with time – that may exhibit dynamics that are highly sensitive to initial conditions (popularly referred to as the butterfly effect). As a result of this sensitivity, which manifests itself as an exponential growth of perturbations in the initial conditions, the behavior of chaotic systems appears to be random. This happens even though these systems are deterministic, meaning that their future dynamics are fully defined by their initial conditions with no random elements involved. This behavior is known as deterministic chaos, or simply chaos .
  3. 3. Steam Systems & the 2 nd Law Second Law of Thermodynamics • The entropy of an isolated system not in equilibrium will tend to increase over time , approaching a maximum value at equilibrium. • In a simple manner, the second law states "energy systems have a tendency to increase their entropy rather than decrease it." This can also be stated as "heat can spontaneously flow from a highertemperature region to a lower-temperature region, but not the other way around." (Heat can flow from cold to hot, but not spontaneously —- for example, when a refrigerator expends electrical power.) • A way of thinking about the second law for non-scientists is to consider entropy as a measure of disorder . So, for example, a broken cup has less order (more entropy) than an intact one, and it is more difficult to repair a broken cup (reducing its entropy) than to break an intact one (increasing its entropy). Likewise, solid crystals, the most organized form of matter, have very low entropy values; and gases, which are very disorganized, have high entropy values.
  4. 4. Basic Steam System
  5. 5. Another view of a Steam System Loads Radiators, Sterilizers Heat Exchangers, etc Steam Header Steam Traps BOILER Condensate Return Piping (Treated) Make up water Deaerator Condensate Return Tank
  6. 6. Steam System Basics • Boiler Design • Water Tube, smaller steam space, need to be run closer to • • design pressure • Fire Tube, large steam chest, can be run a lower than design pressure. Definitions • "Carryover" means that you have a problem with the TDS (total dissolved solids). You need to properly define the PPM values needed. Fire tube boilers have a normal TDS of 3000 ppm, while water tube designs need 2000 ppm. Everyone uses the 3000 ppm value regardless of boiler type and that is their first mistake. • "Priming" is a mechanical condition caused by too great of a takeoff velocity (50 to 100fpm).This is corrected mechanically. Testing • With the boiler running, take a condensate sample from a drip pocket on the main header. If you see a high TDS value (say 2000 PPM), you have a carryover issue. If your value is 5 ppm or is immeasurable, you have priming. Remember, steam has no TDS!
  7. 7. Steam systems have many end uses in hospitals; radiators, heat exchangers, humidification but probably none as critical as Steam Sterilizers
  8. 8. Your Objectives (Challenges) • Deliver good quality steam to heating, humidification and process equipment. • Operate the system safely. • Get maximum efficiency from heating equipment - energy $$$ • Maintain the system at a reasonable cost.
  9. 9. Steam Has Another Objective In Mind! (Challenges) • Condenses anywhere and everywhere it can. • Happily fills the system with air, in the worst possible locations. • Carries entrained water, gases, chemicals and dirt into every nook and cranny. • Will slow down and stop flowing as soon as differential pressure is lost.
  10. 10. Your Mission Is To Stay Ahead of Potential Problems (Challenges) • • • • • • • Test/maintain steam traps routinely. Clean strainers! Clean and maintain regulators/control valves Routine maintenance of condensate pumps. Keep an ear open for excess pipe-line waterhammer & correct the root-cause. Watch for repeat instances of valve wire-draw & correct root-cause (wet steam, valve sizing) Recognize that water hammer in heat exchangers and heating coils is correctable.
  11. 11. Challenges No problem – right? All it takes is money and manpower! Anyone here have enough of both? But there is help: • Boiler Water Treatment Company • Steam Specialty Companies • Steam Consultants • Some of these can help for free, some will cost.
  12. 12. Steam System Challenges • Remember Steam Systems are dynamic systems • Never Steady State • Loads coming on and off • • • • Sterilizers Heating coils Steam Absorption Chillers Manual Building Heat (Old fashion radiators) • System Sizing • Sized for steady state or instantaneous loads (sterilizers)
  13. 13. Steam System Troubleshooting Myths • My boilers never carry over, prime, etc. • The water level is always steady in the gauge glass. • I don’t need trap maintenance, failed traps will become apparent on their own. (The water hammer will tell me about a bad trap.) • Boiler water treatment is a scam. • Boiler blow-down wastes energy and water.
  14. 14. Steam System Troubleshooting Steam System Chemistry • Feed Water Quality • Softener • Deaerator – Dissolved O2 and non-condensable gases • Chemical Treatment • Totaled Dissolved Solids (TDS) • Blow down • Continuous Surface • Bottom Blow Down
  15. 15. Typical Steam System Chemistry (May vary with chemical supplier and boiler manufacturer) Test pH Sulfite % So2 (Higher in lay-up) Typical Limits Low/Hi Softener Feedwater Boiler Condensate Return See chart > 8.5 30/60 XX Alkalinity P 200/400 Alkalinity M Deaerator 8.3 – 9.4 XX XX 250/500 Silica Monitor trends < 150 mg/L XX XX Conductivity 3000/3500 XX XX Calcium < 0.3/FW XX Iron Copper Primary Treatment Chem. Dissolved O2 XX XX XX < 0.1/FW XX XX < 0.05/FW XX XX Per mfg 7 ppb XX XX
  16. 16. Typical Boiler Water Treatment Test Report (partial) Status Polytreat Sulfite Alkalinity Silica TL-200 as SO3 P M Conductivity Calcium Iron Copper pH Boiler 2 Lead 18.5 110 370 510 - 77.6 2886(N) - Boiler 3 Open - - - - - - - - 6.0 129 0.17 8.60 45 0.05 0.03 0.03 MR1 cond. - - - - - Kitchen Dish. - - - - - - Softener 2 Pwr. Plnt. cond. condensate Sub base. large Feedwater Recommended Low/ High Limits 3.6 __10__ 20 _30_ 60 8.35 _200 _ 400 _250 _ 500 2.2 72 0.26 0.10 0.03 _8.0_ 8.5 Record __3000__ 3500 _< .3_ FW _< .1_ FW _< .05_ FW Courtesy of Barclay Water Management, Inc.
  17. 17. Steam System Troubleshooting • Water Level Control • Sight glass levels are not reliable • Variable feed versus on/off • Steam Flow Metering & Data • Data is invaluable for system troubleshooting “ You cannot manage what you cannot measure” Lord Kelvin
  18. 18. Why is proper condensate drainage important?
  19. 19. Water hammer! Result of a drip trap being removed, that was draining a 100 psig line, before a valve
  20. 20. Steam System Troubleshooting • Steam Traps • Properly located • Drip Legs properly sized • Trap Selection and sizing • Steam Trap Testing &
  21. 21. Steam System Troubleshooting • • • • • • • • Steam Traps Main Header Main header drip legs are full size Other drip legs are properly sized Drips located 300’ or less and any change of elevation Drip stations located ahead of automatic valves Steam traps are properly sized Steam traps are working and maintained Missing insulation • heat goes to cold • another consequence of the 2nd law thermodynamics!
  22. 22. Ineffective vs Proper Drain Points Steam Flow Condensate Correct   Cross Section Full Diameter Pocket Steam Trap Set Incorrect Steam Flow Cross Section Steam Trap Set
  23. 23. Steam System Troubleshooting Steam Trap Testing • • • • Visual * Temperature ** Ultrasonic *** Continuous monitoring systems **** • conductivity
  24. 24. Steam System Troubleshooting • Belts & suspenders • Steam separators & filters Dry Steam Wet Steam Condensate Outlet
  25. 25. Steam Conditioning Dry Steam saves energy Example: Process requires 4,645,000 Btu’s / hr Available: 30 psig steam @ 274oF @ 100% Dry (saturated) steam supplies 929 Btu / lb. ∴ process requires 5,000 lb/hr. @ 90% Dryness Fraction, steam supplies 836 Btu/lb. ∴ process now requires 5556 lb /hr. A 11% Increase @ 80% Dryness Fraction, steam supplies 743 Btu/lb ∴ process now requires 6251 lb /hr. A 25% increase
  26. 26. Steam System Troubleshooting • Condensate equipment operating properly • Pumps • Flash tanks • Loads • Varying loads • Instantaneous loads - Sterilizers
  27. 27. Steam System Troubleshooting Now what do I do If you suddenly have problems • What has changed? • Go back to basics • Start at the boiler plant and work your way out into • the system Left Hand Analysis
  28. 28. Courtesy of Walt Graham Thermo Diagnostics, Co, LLC
  29. 29. Now what do I do • • • • • Steam Trap Repairs Steam Trap Survey & Assessment Steam Trap Maintenance Program Boiler Water Treatment Modification Steam Conditioning Equipment • Separators • Filters • Repair damaged insulation • Steam Metering (for troubleshooting)
  30. 30. Thank you! • Questions or Comments • Special Thanks to – John Cilyo, Spirax Sarco – William Wethey, Barclay Water Management • Contact Information – – – – Steve Jalowiec, PE, CHFM Waterbury Hospital, 64 Robbins Street, Waterbury CT Work 203-573-7197 Cell 203-228-3480