HEAT EXCHANGE INSTITUTE, INC.

1 IHEAT EXCHANGE INSTITUTE, forCLOSED FEEDWATER HEATERSNINTH EDITION Copyright 2015 byHeat EXCHANGE Institute1300 Sumner AvenueCleveland, Ohio 44115 Reproduction of any portion of this standard without written permission of the heat EXCHANGE Institute is strictly .. vii1. DEFINITIONS .. 1 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.

2 1 Desuperheating Zone (DSH) .. 1 Condensing Zone .. 1 Drain Subcooling Zone (DC) .. 1 Drains .. 1 Total Surface .. 1 Effective Surface .. 1 Integral Flash Chamber .. 12. FEEDWATER HEATER PERFORMANCE .. 2 Heater Performance .. 2 Minimum Data Required to be Supplied by the Purchaser .. 2 Thermal Resistance .. 2 Tube Wall Resistance .. 2 Fouling Resistance .. 3 Terminal Temperature Difference .. 3 Drains Subcooling Zone Approach .. 3 Tube Side Velocity .. 3 Shell Side Pressure Loss.

3 3 Tube Side Pressure Loss .. 3 Nozzle Sizes .. 7 Steam Nozzle Location and Steam Distribution Dome .. 7 Single Nozzle Heaters .. 7 Multi-Nozzle Heaters .. 8 Drain Nozzle .. 8 Control of Feedwater Heaters .. 10 General Control Considerations .. 10 Capacitance Requirements for Vertical Heaters .. 10 Overload and Abnormal Operating Modes .. 10 Vent Off-Take Piping .. 10 Oxygen Content in a Deaerating Heater .. 113. MECHANICAL DESIGN STANDARDS .. 11 Code Requirements .. 11 Corrosion Allowance .. 11 Design Pressure.

4 11 Design Temperature .. 11 Hydrostatic Test .. 12 Nil Ductility Temperature .. 12 Tubes .. 12 Tube Metal Temperature .. 12 Tube Joint Temperature .. 12 Tube Wall Thickness Limitations .. 12 Tube Length .. 12 U-Tubes .. 12 Stress Relieving U-Bends .. 13 Tube Plugging .. 13 Tube Bundle .. 13 Tube Layout .. 13 Baffles and Support Plates .. 13 Tube Holes .. 13 Spacing and Tube Vibration .. 13iii Support of U-Bends .. 13 Thickness .. 13 Drain Subcooling Zone End Plate.

5 13 Shrouds and Longitudinal Baffles .. 13 Impingement Baffles .. 13 Tubesheet .. 13 Tubesheet Corner Radius .. 14 Tube Hole Diameters and Tolerances .. 14 Ligament Widths and Tolerances .. 15 Channel Covers .. 15 Heater Supports .. 15 Condenser Installation .. 15 Welded Joint Construction .. 16 Connections-Nozzle Length .. 16 Nozzle Loads .. 16 Nomenclature .. 16 External Forces and Moments .. 16 Sample Problem .. 17 Tolerances .. 17 4. MATERIAL DESIGN STANDARDS.

6 23 Materials .. 23 Quality .. 23 Specifications .. 235. DESIGN AND SPECIFICATION OF REPLACEMENT HEATERS/BUNDLES .. 24 Replacement Heaters/Bundles .. 246. FEEDWATER HEATER PROTECTION .. 25 Safety Requirements .. 25 Tube Side Relief Valves .. 25 Shell Side Relief Valves .. 25 Flashback Protection .. 25 Cleanliness and Corrosion Protection .. 25 Venting and Draining .. 267. INSTALLATIONS .. 268. CHANNEL TYPES .. 27 Full Diameter Access Channels .. 27 Low Pressure, Full Access .. 27 High Pressure, Full Access.

7 27 Manway Access Channels .. 28 Minimum Access Manway Sizes .. 28 Minimum Manway Sizes .. 28 Pass Partition Cover Design and Type .. 28 Low Pressure, Manway Access .. 29 High Pressure, Manway Access .. 309. TYPICAL FEEDWATER HEATER INTERNAL ARRANGEMENTS .. 31 APPENDICESA ppendix A GUIDELINES FOR INSTALLATION, OPERATION, AND MAINTENANCE OF FEEDWATER HEATERS .. 41 A1 INSTALLATION OF CLOSED FEEDWATER HEATERS .. 41 General Considerations .. 41 Installation Under Freezing Conditions .. 41 Pre-Operational Cleaning and Flushing Operation .. 41 High Level Condensate Dump.

8 41 Accessories .. 41 A2 CLOSED FEEDWATER HEATER OPERATION .. 42 Initial Start-Up Precautions .. 42 Liquid Level Control .. 42ivCONTENTS (continued) Liquid Level Control in Vertical Channel Down Heaters .. 43 False Liquid Level Indication .. 44 Effect of Low Liquid Levels on External Drain System .. 44 Effect of Load Rejection on Shell Liquid Level .. 44 Effect of Failed Tubes on Heater Operation .. 44 Effect of Plugged Tubes .. 45 Start-Up Limitations .. 45 Shutdown Limitations .. 45 A3 MAINTENANCE OF FEEDWATER HEATERS .. 46 In-Plant Cleaning .. 46 Chemical Cleaning.

9 46 Stagnant or Entrapped Areas .. 46 Special Product Warnings (Safety) .. 46 Lay-Up Procedure for Non-Operating Heaters .. 46 Repair Procedures .. 47 Tube Leak Repairs .. 47 Pressure-Boundary Repairs .. 47 Spare Parts and Special Tools .. 47 Spare Parts .. 47 Special Tools .. 47 Inspection .. 47 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 Compatibility of Tube Materials.

10 49 B4 Specific Zone Designs .. 50 Desuperheating Zone .. 50 Dry Wall Safety Margins at DSZ Outlet .. 50 Condensing Zone .. 50 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.