API 632 : 1ED 88

Section 1 - General
1.1 Scope
1.2 Definition of terms
1.3 Referenced publications
Section 2 - Winterization problem areas
2.1 General
2.2 Reasons for winterization
2.3 General design data requirements
2.4 Heat losses
2.5 General problem areas
2.6 Process categories
2.7 Safety margins
Section 3 - Methods of winterization
3.1 Airflow and air temperature control systems
3.2 Cocurrent flow
3.3 Bare tubes or reduced fin density
3.4 Varying the active heat transfer surface
3.5 Serpentine coils
3.6 Indirect cooling
3.7 Duty separation
3.8 Combinations
3.9 Instrumentation
Section 4 - Critical process temperatures
4.1 Pour points of hydrocarbon liquid mixtures
4.2 Freezing points of hydrocarbons and other organic
      liquid pure compounds
4.3 Water solutions of organic compounds
4.4 Ammonium bisulfide
4.5 High-pressure gases
4.6 References
Section 5 - Tube wall temperature calculations
5.1 General
5.2 Nomenclature
5.3 Calculations
5.4 References
Section 6 - Heat losses
6.1 General
6.2 Louver leakage
6.3 Surface heat loss
Section 7 - Guidelines for sizing air ducts
7.1 General
7.2 Design methods
Section 8 - Mechanical equipment
8.1 General
8.2 Design temperatures
8.3 Design temperature range
8.4 Typical characteristics and operating ranges for
      standard mechanical equipment
8.5 Auxiliary heating equipment
Section 9 - Start-up and shutdown procedures
9.1 General
9.2 Start-up procedures
9.3 Shutdown procedures
Appendix A - Sample economic comparison of indirect
             (tempered-water) versus direct air cooling
             for systems requiring winterization
Appendix B - Calculation of minimum tube wall
             temperature
Appendix C - Sample calculation of heat losses
Figures
1 System A: Airflow control with automatically
      controlled variable-pitch fans
2 System A: Airflow control with automatically
      controlled outlet louvers and fixed-pitch fans
3 System B: Induced draft with noncontained internal
      air recirculation
4 System B: Forced draft with noncontained internal
      air recirculation
5 System C: Typical forced-draft air-cooled heat
      exchanger with contained internal air
      recirculation
6 System D: Typical forced-draft air-cooled heat
      exchanger with external air recirculation
7 Freezing points of phenol-water solutions
8 Freezing points of ethanolamine-water solutions
9 Freezing points of glycerol-water solutions
10 Dissociation constant of ammonium bisulfide
      (NH4HS)
11 Hydrate pressure-temperature equilibria
A-1 Tempered-water system
Tables
1 Safety margins for different process categories
2 Freezing points of frequently encountered liquid
      pure compounds
A-1A Description of indirect and direct air cooling
      systems (customary units)
A-1B Description of indirect and direct air cooling
      systems (SI units)
A-2 Comparison of costs of indirect and direct air
      cooling systems
B-1A Values for rm referred to the total outside area
      for a tube with an outside diameter of 1 inch and
      aluminium fins
B-1B Values for rm referred to the total outside area
      for a tube with an outside diameter of 25.4
      millimeters and aluminium fins 15.9 millimeters
      high and 0.4 millimeters thick (SI units)

Recommends design features and other considerations to give satisfactory operation of air cooled heat exchangers with low temperature inlet air. Coverage includes: reasons for winterization; general design data requirements; general problem areas; airflow and air temperature control systems; bare tubes or reduced fin density; varying the active heat transfer surface; pour points of hydrocarbon liquid mixtures; freezing points of hydrocarbons and other organic liquid pure compounds; high pressure gases; water solutions of organic compounds; typical characteristics and operating ranges for standard mechanical equipment; auxiliary heating equipment. Also gives detailed tables, diagrams and appendices.