Steam Trap Performance Assessment - PowerPoint by fzb12999

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									Steam Systems

Technology – Concept
      Steam System Background


      Primary industrial energy source
            process heating
            pressure control
            mechanical drive
            space heating
      Significant consumer of natural gas
                “Over 45% of all fuel burned by U.S. manufacturers is
                consumed to raise steam.” – DOE Best Practices




            $$$                  Great energy & cost
                                  savings potential!

US DOE – Industries of the Future Workshop Series
      Why Use Steam?


       Extremely Uniform Heating
       Absolute Temperature Limit on Heated Surfaces

       High Heat Delivery
       Fast Recovery from “Cold Spots”
       Heats Unusually Shaped Heat Exchangers Uniformly




US DOE – Industries of the Future Workshop Series
      Classes of Steam


       Low Pressure Heating Steam – 15 psig
            Used Mainly for Space Heating Systems and Single Effect
               Absorption Chillers
              Actual Code is More Restrictive
       Medium Pressure Steam: 15-150 psig
            Used in Hospitals, District Steam Systems, Some Industrial
               Heating
       High Pressure: Above 150 psig
            Strictly Industrial and Power Generating Applications

       Each Class has Piping and Valve Requirements
            Increase in Expense with Each Higher Class

US DOE – Industries of the Future Workshop Series
      Steam System Operation


      Generation
      Distribution
      End Use
      Condensate Recovery & Feed Water
         Systems




US DOE – Industries of the Future Workshop Series
      Generation




                                                    Boilers
                                                       Fire-tube or water-tube
                                                    Heat recovery
                                                     generators
                                                       Turbine exhaust
                                                       Furnace exhaust
                Typical Boiler




US DOE – Industries of the Future Workshop Series
      Generation



                                                     Water tube
                                                          fuel burned within combustion
                                                           chamber
                                                          combustion gas surrounds
                                                           water tubes within vessel



                                                     Fire tube
                                                          fuel burned in combustion
                                                           chamber
                                                          combustion gases flow
                                                           through tubes
                                                          water surrounds tubes



US DOE – Industries of the Future Workshop Series
      Generation



   Fire tube
        Scotch Marine – most
           popular
          Two, three, and four pass
           designs
          Constant pressure with
           wide load fluctuations
          Steam pressure limited to
           under 350 psig
          Preferred between 3,500
           to 35,000 lbs/hr (120 Bhp
           – 1,200 Bhp)




US DOE – Industries of the Future Workshop Series
      Generation



       Water tube
            Fuel burned within combustion
               chamber
              Combustion gas surrounds
               water tubes within vessel
              Low water content allows rapid
               steam production
              Capable of high pressure and
               superheated steam
              Preferred ranges are below
               3,500 lbs/hr (120 Bhp) and
                                                    Source: Cleaver Brooks
               above 35,000 lbs/hr (1,200 Bhp)



US DOE – Industries of the Future Workshop Series
      Generation



       Modular Boilers
            Array of smaller boilers meet
               load more effectively without
               cycling
              Improved combustion
               efficiency
              Reduced jacket losses
              Fin tube design less durable
              Piping and controls important
              Mostly for commercial
                                                    Source: ES Magazine March, 2001


               markets




US DOE – Industries of the Future Workshop Series
      Generation


       Heat recovery steam
         generators (HRSGs)
            Create steam using a heat
               exchanger in a hot gas flow
                •   Turbine exhaust
                •   Furnace exhaust
            Can produce superheated
               steam
              Can produce high pressure
               steam




US DOE – Industries of the Future Workshop Series
      Distribution & End Users


    Distribution Systems
         Distribution lines
         Pressure reduction
             •   Pressure reduction valve
             •   Backpressure turbine




                                                     End Use Components
                                                       Heat exchangers
                                                       Mechanical drives
                                                       Steam
                                                        sparging/injection
                                                        equipment

US DOE – Industries of the Future Workshop Series
      Recovery & Feed Water


       Condensate Recovery System
            Steam traps
            Collection tanks
            Flash steam recovery
            Pumps

       Feed Water System
            Deaerator
            Economizer




US DOE – Industries of the Future Workshop Series
      Steam System Schematic




US DOE – Industries of the Future Workshop Series
      Typical Applications


      Steam is not commonly used for space
         heating only
            hot water systems are less maintenance intensive
      Exceptions
            Hospitals – need steam for sterilizers
            Older district heating systems
            Industrial plants which require process steam




US DOE – Industries of the Future Workshop Series
      Efficient Steam Systems


      Proper performance yields
            Low operating costs
            Minimal downtime
            Reduced emissions
            Effective process control
      Effective maintenance is the best strategy!!




US DOE – Industries of the Future Workshop Series
      Why make a change?



            Great energy & cost savings potential!

                                      Save energy (20% or more)
                                      Reduce downtime

              $$$                     Eliminate maintenance crises
                                      Improve process control
                                      Minimize safety hazards




US DOE – Industries of the Future Workshop Series
      Why make a change?



                INEFFICIENT STEAM SYSTEM




US DOE – Industries of the Future Workshop Series
      Why make a change?



                  EFFICIENT STEAM SYSTEM




US DOE – Industries of the Future Workshop Series
Technology – Common System
Improvements
      Benchmarking


       Profile your existing system
              Separating process boiler load from seasonal heating
              Steam System Assessment Tool (US DOE)
       Calculating the cost of steam ($/ thousand lbs)
              Fuel
              Water
              Chemicals


                                    Rough estimate:
       Total Steam Cost ($/MMBtu) = Fuel Cost ($/MMBtu) x 130%


       DOE steam cost estimating resource:
         http://www.oit.doe.gov/bestpractices/steam/pdfs/tech_brief_true_cost.pdf



US DOE – Industries of the Future Workshop Series
      Common Problem Areas

        Incorrect air/fuel ratio  combustion inefficiency
        Lack of insulation
        Insufficient trap maintenance
        Steam leaks
        No heat recovery
        Insufficient water treatment/blowdown issues
        Frequent boiler cycling
        Water hammer
        Poor record keeping
             Gas usage
             Steam production

US DOE – Industries of the Future Workshop Series
      Air/Fuel Ratio – Combustion Efficiency


       In theory . . .



     AIR (O2 & N2)
                              PERFECT                 EXHAUST
                             COMBUSTION             (CO2, H2O & N2)
       FUEL (C2H)




US DOE – Industries of the Future Workshop Series
      Air/Fuel Ratio – Combustion Efficiency

       In the real world . . .
      Excess air introduced to prevent incomplete combustion



     AIR (O2 && N )                                  EXCESS O2
      AIR (O2 N2)2
                                Combustion
                                                      EXHAUST
         FUEL (C2H)                                 (CO2, H2O & N2)


       Left over oxygen carries heat away from boiler

US DOE – Industries of the Future Workshop Series
      Steam System Exercises – Air/Fuel Ratio


      Optimum combustion air = increased efficiency
            Too much air = excess heat loss in stack
            Too little air = wasted fuel
      Worksheet example (use boiler chart on next slide):




US DOE – Industries of the Future Workshop Series
      Steam System Exercises – Air/Fuel Ratio




                 Net Stack Temp = Stack temp reading – ambient air temp



US DOE – Industries of the Future Workshop Series
      Insulation


       Lack of insulation  unnecessary heat loss
       Wet insulation  heat loss




      Condensate return lines need insulation too.
      3E Plus available at www.pipeinsulation.org
  *Based on 8,000 hours of operation, 85% efficient boiler, mineral fiber insulation with
  all purpose jacket

US DOE – Industries of the Future Workshop Series
      Insulation


       What about insulating valves?
       Removable insulation is available




    Savings  energy savings (btu/hr)  hours  fuel cost



US DOE – Industries of the Future Workshop Series
                                      Steam traps


                                       Expect 15% to 30% failure every 3 to 5 years
GO TOSupplemental Steam Trap Info




                                       Easily tested using ultrasonic equipment
                                       Steam trap example problem




                      US DOE – Industries of the Future Workshop Series
      Steam Leaks


       Easy to find
       Hard to fix
                                              Steam Leak Rates Through Holes (lbm/hr)

        Orifice                                              Steam Pressure (psig)
       Diameter
       (inches)    2      5     10     15         25        50        75        100     125    150    200    250    300
         1/32     0.31   0.49   0.7    0.85      1.14      1.86       2.58       3.3    4.02   4.74   6.17   7.61   4.05
         1/16     1.25   1.97   2.8     3.4       4.6      7.4        10.3      13.2    16.1   18.9   24.7   30.4   36.2
         3/32     2.81   4.44   6.3     7.7      10.3      16.7       15.4      29.7    36.2   42.6   55.6   68.5   81.5
         1/8       4.5    7.9   11.2   13.7      18.3      29.8       41.3      52.8    64.3   75.8     99    122   145
         5/32      7.8   12.3   17.4   21.3      28.5      46.5       64.5      82.5     100    118    154    190   226
         3/16     11.2   17.7   25.1   30.7      41.1       67         93       119      145    170    222    274   326
         7/32     15.3   24.2   34.2   41.9      55.9      91.2       126       162      197    232    303    373   443
         1/4       20    31.6   44.6   54.7      73.1      119        165       211      257    303    395    487   579
         9/32     25.2   39.9   56.5   69.2      92.5      151        209       267      325    384    500    617   733
         5/16     31.2   49.3   69.7   85.4      114       186        258       330      402    474    617    761   905
        11/32     37.7   59.6   84.4   103       138       225        312       399      486    573    747    921   1095
         3/8      44.9    71    100    123       164       268        371       475      578    682    889   1096   1303
        13/32     52.7   83.3   118    144       193       314        436       557      679    800   1043   1286   1529
         7/16     61.1   96.6   137    167       224       365        506       647      787    928   1210   1492   1774
        15/32     70.2   111    157    192       257       419        580       742      904   1065   1389   1713   2037
         1/2      79.8   126    179    219       292       476        660       844     1028   1212   1580   1949   2317


      The table can also be used to determine steam losses through
                    steam traps that have failed open.
US DOE – Industries of the Future Workshop Series
      Heat recovery options


                                                    Vent Condensers

 Economizer/
 Recuperator




  Blowdown Heat
     Recovery

US DOE – Industries of the Future Workshop Series
      Economizers and Recuperators


       Recuperators
            Recover heat to
               combustion air
              Require steady
               boiler loading


       Economizers
            Recover heat to
               boiler feed water
              Require continuous
               feed water flow                      Boiler Recuperator



US DOE – Industries of the Future Workshop Series
      Boiler Recuperator


      Boiler efficiency indirectly proportional to stack temp
      Causes of excess stack temps:
              Excess air
              Fouled waterside surfaces
              Fouled fireside surfaces
              Overfiring
              Insufficient heat transfer surface
              High steam pressure
      Only insufficient heat transfer surface or high pressure justify a
      recuperator:
              Excess air - adjust air/fuel ratio
              Fouled surfaces - can be detected by visual inspection
              Overfiring
              Flue temp must be at least 50°F over the minimum allowable

US DOE – Industries of the Future Workshop Series
      Boiler Recuperator


      Boiler conditions:
              450°F stack temperature
              80° inlet air
              4% O2 in stack
              Current natural gas consumption: 67,286 MMBtu/year
              Current natural gas cost: $5.90/MMBtu
      To find the potential savings from a recuperator:
              Net stack temp: 450° - 80° = 370°
              Net stack temp w/recuperator: 280°F
              New efficiency – current efficiency = efficiency gain
              83.0% - 80.7% = 2.3%



                                                                       continued

US DOE – Industries of the Future Workshop Series
      Boiler Recuperator


      …continued
      Energy Savings:
              = current use x (1- (old efficiency/new efficiency))
              = 67,286 MMBtu x (1 – (0.807 / 0.830))
              = 1,865 MMBtu/yr
      Cost savings:
              = energy savings x energy cost
              = 1,865 MMBtu/yr x $5.90/MMBtu
              = $11,000/yr




US DOE – Industries of the Future Workshop Series
      Vent Condensers




      Recover flash steam or fugitive steam
           Condensate tanks
           Deaerators



US DOE – Industries of the Future Workshop Series
            Blowdown Heat Recovery


                                                                               Requires continuous mid-




                                                     Vent
                             Feed
                                                                                drum blow down
            Boiler           Water                               Condensate
                                                                   Return
                                                                               Intermittent mud-drum blow
                                             Deaerator
                                                                                down can be accommodated
                blow down
                Mud-drum
blow down
 Mid-drum




                                     Flash
                                     Steam
                                                                               Approximate Savings:
                              Flash
                            Separator
                                                                         % energy savings  blowdown %  0.4
                            Down




                                                    Preheated
                            Blow




                                                    feed water

                                       Heat
                                     Exchanger
                                          Make up
                                           Water




US DOE – Industries of the Future Workshop Series
      Water treatment/blowdown issues


       Typical steam system
                           Blowdown <10% feed water

       Systems with high quality water treatment
                           Blowdown <5% feed water

       Reducing blowdown saves
            Energy
            Water costs
            Chemical costs

US DOE – Industries of the Future Workshop Series
      Boiler Short Cycling


      Boiler cycle:
            Pre-purge – fan removes combustible gases from boiler
            Firing interval
            Post-purge – gases removed again
            Idle period
      Problem: heat is removed during purges




US DOE – Industries of the Future Workshop Series
      Boiler Short Cycling


      Short cycling…
            Occurs when an oversized boiler quickly satisfies heat
               demands
              Boiler shuts down until next demand
      Causes:
            Boiler oversized for expansions that never happened
            Energy conservation measures have reduced heat
               demand
              Space heating based on design-basis temperature
               conditions
              Space heating sized for quick recovery from night
               setbacks




US DOE – Industries of the Future Workshop Series
      Boiler Short Cycling


            Illustration of a typical boiler short-cycling:




      Green areas represent energy that will be wasted while the boiler is not firing
      but the fan is in pre-purge or post-purge phase.
US DOE – Industries of the Future Workshop Series
      Boiler Short Cycling


             Illustration of an improved boiler cycle:




                              Note the reduction in wasted energy
                              from eliminating short-cycling.

US DOE – Industries of the Future Workshop Series
      Replacement and alternative technologies


      Backpressure Turbines
            Replace pressure reducing valves
            Produce electrical power by reducing steam
             pressure
            Require
                • >5,000 lbs/hr steam flow
                • >100 psig pressure drop across turbine




US DOE – Industries of the Future Workshop Series
      IAC implementation trends and analysis




US DOE – Industries of the Future Workshop Series
      Application of New Technologies/Concepts


       Combustion analysis testing equipment
       Removable valve insulation
       Trap analysis with ultrasonic equipment
       Steam flow metering
       Gas sub-metering
       Continuous blow down and conductivity metering
       Exhaust stack economizers
       Modular boiler systems
       Direct contact water heaters



US DOE – Industries of the Future Workshop Series
Technology - Next Steps
      How to start


       Steps in evaluating your system
       Best Practices
       Monitoring needs
       Implementation


          TREAT STEAM LIKE A FOURTH UTILITY!




US DOE – Industries of the Future Workshop Series
      Steps in evaluating your system


       Utility bill analysis
       Steam trap inventory
       Combustion testing
       Ensure all insulation is in good shape
       Optimize boiler blowdown
       Monitor boiler cycling during periods of low demand
       Check for applications for new technologies




US DOE – Industries of the Future Workshop Series
                         Natural Gas Utility Profile

                  30,000


                                                                               Heating Load
                  25,000
Gas Use (MMBtu)




                  20,000
                                  Process
                  15,000           Load

                  10,000



                   5,000



                     -
                            Jun     Jul   Aug   Sep    Oct   Nov   Dec   Jan   Feb   Mar   Apr   May




            US DOE – Industries of the Future Workshop Series
      Best Practices


       Combustion testing (quarterly)
       Steam trap testing (annually)
            Inventory / maintenance history
       Steam leak reporting mechanism for all staff
       Insulation standards formalized


      Benchmarking



US DOE – Industries of the Future Workshop Series
      Monitoring needs


       Monitor and track boiler system data
            Daily Natural Gas Usage (meter on each boiler)
            Daily Steam Production (meter on boiler water feed)
            Daily Water Usage (meter on make-up water feed)
            Chemical Costs (compare to water usage)
       Boiler cycles
       Stack temperature




US DOE – Industries of the Future Workshop Series
      Implementation of Improvements


        Improving system performance
              Assessing the entire system (supply and demand)
              Identifying opportunities
              Quantifying benefits and costs
              Implementing most feasible projects
        Implementation requires participation
              Production staff
              Maintenance staff
              Management staff


US DOE – Industries of the Future Workshop Series
      ISO 14000


       Formalized method for identifying and documenting
        process improvements
       Can be used for benchmarking
       Proper use can lead to significantly reduced energy
        costs
       All program goals are set by company




US DOE – Industries of the Future Workshop Series
                                        Assessing your current system


                                         In house assessment
                                            Tools available from US DOE Steam Challenge Program
GO TO Assessment Resources Listing




                                             Tools available from US DOE Steam Challenge Program

                                        US DOE Industrial Assessment Centers
                                        Energy Resources Center @ UIC
                                        Private energy service companies
                                        Steam equipment manufacturers




                       US DOE – Industries of the Future Workshop Series
       Assessment Resources


        Energy Resources Center @ UIC www.erc.uic.edu - can provide
           expertise in industrial steam systems, also will perform energy
           assessments for industrial clients.
          Industrial Assessment Centers http://www.oit.doe.gov/iac/ - will provide
           energy assessments (including steam systems) free of charge to
           qualified industrial clients.
          US DOE Steam Challenge Program
           http://www.oit.doe.gov/bestpractices/steam/ - provides a wide range of
           technical assistance materials, tools, and services to the industrial
           market.
          National Association of Energy Service Companies
           http://www.naesco.org/ - trade organization of companies that will
           perform energy audits and finance improvements.
          “Steam System Survey Guide”
           http://www.oit.doe.gov/bestpractices/steam/pdfs/steam_survey_guide.p
           df - guide to assessing industrial steam systems.
          Rutgers IAC “Self Assessment Guide”
           http://iac.rutgers.edu/manuals/selfassessment.pdf - guide to assessing
BACK       industrial plants for energy efficiency.

 US DOE – Industries of the Future Workshop Series

								
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