HEAT EXCHANGE INSTITUTE, INC

A2.3 Liquid Level Control in Vertical Channel Down Heaters …………………………… 43 A2.4 False Liquid Level Indication...
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HEAT EXCHANGE INSTITUTE, INC. STANDARDS for CLOSED FEEDWATER HEATERS

NINTH EDITION Copyright 2015 by Heat Exchange Institute 1300 Sumner Avenue Cleveland, Ohio 44115

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Reproduction of any portion of this standard without written permission of the Heat Exchange Institute is strictly forbidden.

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CONTENTS Page FOREWORD ………………………………………………………………………………………………………………… vii 1. DEFINITIONS …………………………………………………………………………………………………………… 1

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.10 1.11 1.12 1.13 1.14 1.15 1.16

Closed Feedwater Heater …………………………………………………………………………………… 1 Heater Duty …………………………………………………………………………………………………… 1 Design Maximum Working Pressure ……………………………………………………………………… 1 Operating Pressure …………………………………………………………………………………………… 1 Terminal Temperature Difference (TTD) ………………………………………………………………… 1 Drain Subcooler Approach (DCA) ………………………………………………………………………… 1 Logarithmic Mean Temperature Difference (LMTD)…………………………………………………… 1 Pressure Loss ………………………………………………………………………………………………… 1 Heat Transfer Coefficient …………………………………………………………………………………… 1 Desuperheating Zone (DSH) ………………………………………………………………………………… 1 Condensing Zone ……………………………………………………………………………………………… 1 Drain Subcooling Zone (DC) ………………………………………………………………………………… 1 Drains ………………………………………………………………………………………………………… 1 Total Surface ………………………………………………………………………………………………… 1 Effective Surface ……………………………………………………………………………………………… 1 Integral Flash Chamber……………………………………………………………………………………… 1

2. FEEDWATER HEATER PERFORMANCE…………………………………………………………………………… 2 2.1 Heater Performance ………………………………………………………………………………………… 2 2.1.1 Minimum Data Required to be Supplied by the Purchaser ………………………………… 2 2.2 Thermal Resistance ………………………………………………………………………………………… 2 2.2.1 Tube Wall Resistance …………………………………………………………………………… 2 2.2.2 Fouling Resistance ……………………………………………………………………………… 3 2.3 Terminal Temperature Difference ………………………………………………………………………… 3 2.4 Drains Subcooling Zone Approach ………………………………………………………………………… 3 2.5 Tube Side Velocity …………………………………………………………………………………………… 3 2.6 Shell Side Pressure Loss …………………………………………………………………………………… 3 2.7 Tube Side Pressure Loss …………………………………………………………………………………… 3 2.8 Nozzle Sizes …………………………………………………………………………………………………… 7 2.9 Steam Nozzle Location and Steam Distribution Dome ………………………………………………… 7 2.9.1 Single Nozzle Heaters …………………………………………………………………………… 7 2.9.2 Multi-Nozzle Heaters …………………………………………………………………………… 8 2.10 Drain Nozzle ………………………………………………………………………………………………… 8 2.11 Control of Feedwater Heaters ……………………………………………………………………………… 10 2.11.1 General Control Considerations ………………………………………………………………… 10 2.11.2 Capacitance Requirements for Vertical Heaters ……………………………………………… 10 2.12 Overload and Abnormal Operating Modes ……………………………………………………………… 10 2.13 Vent Off-Take Piping ………………………………………………………………………………………… 10 2.14 Oxygen Content in a Deaerating Heater ………………………………………………………………… 11 3. MECHANICAL DESIGN STANDARDS……………………………………………………………………………… 11 3.1 Code Requirements …………………………………………………………………………………………… 11 3.1.1 Corrosion Allowance ……………………………………………………………………………… 11 3.2 Design Pressure ……………………………………………………………………………………………… 11 3.3 Design Temperature ………………………………………………………………………………………… 11 3.4 Hydrostatic Test ……………………………………………………………………………………………… 12 3.5 Nil Ductility Temperature …………………………………………………………………………………… 12 3.6 Tubes …………………………………………………………………………………………………………… 12 3.6.1 Tube Metal Temperature ………………………………………………………………………… 12 3.6.2 Tube Joint Temperature ………………………………………………………………………… 12 3.6.3 Tube Wall Thickness Limitations ……………………………………………………………… 12 3.6.4 Tube Length ……………………………………………………………………………………… 12 3.6.5 U-Tubes …………………………………………………………………………………………… 12 3.6.6 Stress Relieving U-Bends ……………………………………………………………………… 13 3.6.7 Tube Plugging …………………………………………………………………………………… 13 3.7 Tube Bundle …………………………………………………………………………………………………… 13 3.7.1 Tube Layout ……………………………………………………………………………………… 13 3.7.2 Baffles and Support Plates ……………………………………………………………………… 13 3.7.2.1 Tube Holes …………………………………………………………………………… 13 3.7.2.2 Spacing and Tube Vibration ……………………………………………………… 13

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CONTENTS (continued) 3.7.2.3 Support of U-Bends ………………………………………………………………… 13 3.7.2.4 Thickness …………………………………………………………………………… 13 3.7.2.5 Drain Subcooling Zone End Plate ………………………………………………… 13 3.7.2.6 Shrouds and Longitudinal Baffles ……………………………………………… 13 3.7.2.7 Impingement Baffles ……………………………………………………………… 13 3.8 Tubesheet ……………………………………………………………………………………………………… 13 3.8.1 Tubesheet Corner Radius ……………………………………………………………………… 14 3.8.2 Tube Hole Diameters and Tolerances ………………………………………………………… 14 3.8.3 Ligament Widths and Tolerances ……………………………………………………………… 15 3.9 Channel Covers ……………………………………………………………………………………………… 15 3.10 Heater Supports ……………………………………………………………………………………………… 15 3.11 Condenser Installation ……………………………………………………………………………………… 15 3.12 Welded Joint Construction ………………………………………………………………………………… 16 3.13 Connections-Nozzle Length ………………………………………………………………………………… 16 3.14 Nozzle Loads ………………………………………………………………………………………………… 16 3.14.1 Nomenclature …………………………………………………………………………………… 16 3.14.2 External Forces and Moments ………………………………………………………………… 16 3.14.3 Sample Problem ………………………………………………………………………………… 17 3.15 Tolerances……………………………………………………………………………………………………… 17 4. MATERIAL DESIGN STANDARDS…………………………………………………………………………………… 23 4.1 Materials ……………………………………………………………………………………………………… 23 4.2 Quality ………………………………………………………………………………………………………… 23 4.3 Specifications ………………………………………………………………………………………………… 23 5. DESIGN AND SPECIFICATION OF REPLACEMENT HEATERS/BUNDLES………………………………… 24 5.1 Replacement Heaters/Bundles ……………………………………………………………………………… 24 6. FEEDWATER HEATER PROTECTION……………………………………………………………………………… 25 6.1 Safety Requirements ………………………………………………………………………………………… 25 6.1.1 Tube Side Relief Valves ………………………………………………………………………… 25 6.1.2 Shell Side Relief Valves ………………………………………………………………………… 25 6.2 Flashback Protection ………………………………………………………………………………………… 25 6.3 Cleanliness and Corrosion Protection ……………………………………………………………………… 25 6.4 Venting and Draining ………………………………………………………………………………………… 26 7. INSTALLATIONS………………………………………………………………………………………………………… 26 8. CHANNEL TYPES………………………………………………………………………………………………………… 27 8.1 Full Diameter Access Channels …………………………………………………………………………… 27 8.1.1 Low Pressure, Full Access ……………………………………………………………………… 27 8.1.2 High Pressure, Full Access ……………………………………………………………………… 27 8.2 Manway Access Channels …………………………………………………………………………………… 28 8.2.1 Minimum Access Manway Sizes ……………………………………………………………… 28 8.2.1.1 Minimum Manway Sizes ………………………………………………………… 28 8.2.1.2 Pass Partition Cover Design and Type …………………………………………… 28 8.2.2 Low Pressure, Manway Access ………………………………………………………………… 29 8.2.3 High Pressure, Manway Access ………………………………………………………………… 30 9. TYPICAL FEEDWATER HEATER INTERNAL ARRANGEMENTS……………………………………………… 31 APPENDICES Appendix A A1 A2

GUIDELINES FOR INSTALLATION, OPERATION, AND MAINTENANCE OF FEEDWATER HEATERS ……………………………………………………………………………… 41 INSTALLATION OF CLOSED FEEDWATER HEATERS………………………………………… 41 A1.1 General Considerations ……………………………………………………………………… 41 A1.2 Installation Under Freezing Conditions …………………………………………………… 41 A1.3 Pre-Operational Cleaning and Flushing Operation ……………………………………… 41 A1.4 High Level Condensate Dump ……………………………………………………………… 41 A1.5 Accessories …………………………………………………………………………………… 41 CLOSED FEEDWATER HEATER OPERATION ………………………………………………… 42 A2.1 Initial Start-Up Precautions ………………………………………………………………… 42 A2.2 Liquid Level Control ………………………………………………………………………… 42

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CONTENTS (continued) A2.3 Liquid Level Control in Vertical Channel Down Heaters ……………………………… 43 A2.4 False Liquid Level Indication ……………………………………………………………… 44 A2.5 Effect of Low Liquid Levels on External Drain System ………………………………… 44 A2.6 Effect of Load Rejection on Shell Liquid Level …………………………………………… 44 A2.7 Effect of Failed Tubes on Heater Operation………………………………………………… 44 A2.8 Effect of Plugged Tubes……………………………………………………………………… 45 A2.9 Start-Up Limitations………………………………………………………………………… 45 A2.10 Shutdown Limitations………………………………………………………………………… 45 A3 MAINTENANCE OF FEEDWATER HEATERS …………………………………………………… 46 A3.1 In-Plant Cleaning……………………………………………………………………………… 46 A3.2 Chemical Cleaning…………………………………………………………………………… 46 A3.3 Stagnant or Entrapped Areas………………………………………………………………… 46 A3.4 Special Product Warnings (Safety)………………………………………………………… 46 A3.5 Lay-Up Procedure for Non-Operating Heaters…………………………………………… 46 A3.6 Repair Procedures……………………………………………………………………………… 47 A3.6.1 Tube Leak Repairs………………………………………………………………… 47 A3.6.2 Pressure-Boundary Repairs……………………………………………………… 47 A3.7 Spare Parts and Special Tools……………………………………………………………… 47 A3.7.1 Spare Parts…………………………………………………………………………… 47 A3.7.2 Special Tools………………………………………………………………………… 47 A3.8 Inspection……………………………………………………………………………………… 47 A3.9 Alterations or Repairs………………………………………………………………………… 47 Appendix B GENERAL FEEDWATER HEATER INFORMATION …………………………………………… 48 B1 Vertical Feedwater Heaters ………………………………………………………………… 48 B2 Cycling and Off Load Conditions …………………………………………………………… 48 B3 Material Compatibility in Operating Environments …………………………………… 48 B3.1 Compatibility of Tube Materials ………………………………………………… 49 B4 Specific Zone Designs………………………………………………………………………… 50 B4.1 Desuperheating Zone ……………………………………………………………… 50 B4.1.1 Dry Wall Safety Margins at DSZ Outlet…………………………… 50 B4.2 Condensing Zone…………………………………………………………………… 50 B4.3 Subcooling Zone……………………………………………………………………… 50 B5 Heaters Removed from Service……………………………………………………………… 51 B6 Manway Sizes for Hemispherical Heads…………………………………………………… 51 B7 Integral Flash Chamber Considerations …………………………………………………… 51 B8 Floating Pass Partitions ……………………………………………………………………… 52 B9 Emergency Liquid Bypass for Feedwater Heaters ……………………………………… 52 B10 High Pressure Closures: Gasketed vs. Welded Diaphragm ……………………………… 53 B11 Drains and Vents for Heaters………………………………………………………………… 53 Appendix C

REFERENCE DATA …………………………………………………………………………………… 56 C1 Metric Conversion Factors …………………………………………………………………… 56 C2 Areas of Circular Segments ………………………………………………………………… 60 C3 Modulus Of Elasticity E of Materials For Given Temperatures ………………………… 61 C4 Thermal Conductivity of Materials for Given Temperatures…………………………… 63 C5 Mechanical Characteristics of Tubing ……………………………………………………… 64 C6 Mechanical Characteristics of Steel Tubing ……………………………………………… 66 C7 Chart for Solving LMTD Formula ………………………………………………………… 67 C8.1 Closed Feedwater Heater Specification Sheet - English Units ………………………… 68 C8.2 Closed Feedwater Heater Specification Sheet - SI Units ………………………………… 69 C8.3 Closed Feedwater Heater Specification Sheet - MKH Units …………………………… 70

Appendix D TROUBLESHOOTING GUIDE……………………………………………………………………… 71 FIGURES Fig. No. 1 Fig. No. 2 Fig. No. 3a Fig. No. 3b Fig. No. 4 Fig. No. 5 Fig. No. 6a

Feedwater Specific Volume Ratios …………………………………………………………………… 4 Design Feedwater Velocity at 60°F …………………………………………………………………… 5 Density Correction Factor ……………………………………………………………………………… 6 Loss Correction Factor for Tube Configuration ……………………………………………………… 6 Steam Nozzle Location-Single Inlet …………………………………………………………………… 8 Steam Nozzle Location-Multiple Inlets ……………………………………………………………… 9 Tubesheet Formula Perimeter Calculation ………………………………………………………… 14 v

CONTENTS (continued) Fig. No. 6b Fig. No. 7 Fig. No. 8 Fig. No. 9 Fig. No. 10 Fig. No. 11a Fig. No. 11b Fig. No. 12 Fig. No. 13 Fig. No. 14 Fig. No. 15 Fig. No. 16 Fig. No. 17 Fig. No. 18a Fig. No. 18b Fig. No. 19 Fig. No. 20 Fig. No. 21 Fig. No. 22 Fig. No. 23 Fig. No. 24 Fig. No. 25 Fig. No. 26 Fig. No. 27 Fig. No. 28 Fig. No. 29 Fig. No. 30 Fig. No. 31 Fig. No. 32 Fig. No. 33 Fig. No. 34 Fig. No. 35 Fig. No. 36 Fig. No. 37 Fig. No. 38 Fig. No. 39 Fig. No. 40 Fig. No. 41 Fig. No. 42 TABLES TABLE I TABLE II TABLE III TABLE IV TABLE V TABLE VI TABLE VII

Wall Thickness/I.D. Ratio for Integral Tubesheets ………………………………………………… 14 Nozzle Load Nomenclature …………………………………………………………………………… 16 Allowable Nozzle Loads (a)……………………………………………………………………………… 18 Allowable Nozzle Loads (()…………………………………………………………………………… 19 Allowable Nozzle Loads (D)…………………………………………………………………………… 20 Standard Tolerances for Nozzles and Support Locations - English Units ……………………… 21 Standard Tolerances for Nozzles and Support Locations - SI Units……………………………… 22 Horizontal Installation ………………………………………………………………………………… 26 Horizontal In Condenser Neck Installation ………………………………………………………… 26 Vertical Channel Up Installation ……………………………………………………………………… 26 Vertical Channel Down Installation ………………………………………………………………… 26 Welded Type Pass Partition Cover Design …………………………………………………………… 27 Gasketed Channel Cover Pass Partition Design …………………………………………………… 27 High Pressure, Full Access Channel ………………………………………………………………… 27 High Pressure, Full Access Channel ………………………………………………………………… 27 Typical Full Access Bolted Pass Partition Cover …………………………………………………… 28 Hemispherical Head Channel Design-LP …………………………………………………………… 29 Elliptical Head Channel Design-LP ………………………………………………………………… 29 Hemispherical Head Channel Design-HP …………………………………………………………… 30 Combination Tubesheet Channel Type Design-HP ………………………………………………… 30 Modified Hemispherical Head Design-HP …………………………………………………………… 30 Straight Condensing Feedwater Heater - Horizontal Mounting…………………………………… 31 2-Zone Feedwater Heater - Horizontal Mounting…………………………………………………… 32 2-Zone Feedwater Heater - Horizontal Mounting…………………………………………………… 33 3-Zone Feedwater Heater - Horizontal Mounting…………………………………………………… 34 Straight Condensing Feedwater Heater - Vertical Channel Down Mounting…………………… 35 2-Zone Feedwater Heater - Vertical Channel Down Mounting …………………………………… 36 3-Zone Feedwater Heater - Vertical Channel Down Mounting …………………………………… 37 Straight Condensing Feedwater Heater -Vertical Channel Up Mounting ……………………… 38 2-Zone Feedwater Heater -Vertical Channel Up Mounting ……………………………………… 39 3-Zone Feedwater Heater -Vertical Channel Up Mounting ……………………………………… 40 Bolt Tightening Sequence ……………………………………………………………………………… 42 Liquid Level Test………………………………………………………………………………………… 43 Liquid Level Controls for Typical Vertical Channel Down Heater………………………………… 43 Liquid Level Controls for Typical Horizontal Heater……………………………………………… 45 Free Surface Area for Shell Liquid Level Control…………………………………………………… 49 Integral Flash Chamber………………………………………………………………………………… 52 Emergency By-pass to Prevent Water Damage……………………………………………………… 53 Recommended Schematic Piping Arrangement for Feedwater Heaters ………………………… 54

Maximum Tube Side Velocity…………………………………………………………………………… 3 Maximum Metal Temperatures for Tube Materials ………………………………………………… 12 Maximum Temperature of Expanded Tube Joints………………………………………………… 12 Design Minimum Tube Wall Thickness……………………………………………………………… 12 Tube Hole Diameters and Tolerances for Tubesheets……………………………………………… 14 Tubesheet Drilling Tolerances………………………………………………………………………… 15 Steam Flow Multiplier………………………………………………………………………………… 51

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