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A Boiler: The Explosive Potential of a Bomb
Acoustic Emission Examination of Metal Pressure Vessels
Anatomy of a Catastrophic Boiler Accident
Austenitic Stainless Steel
Basic Weld Inspection - Part 1
Basic Weld Inspection - Part 2
Black Liquor Recovery Boilers - An Introduction
Boiler Efficiency and Steam Quality: The Challenge of Creating Quality Steam Using Existing Boiler Efficiencies
Boiler Logs Can Reduce Accidents
Boiler/Burner Combustion Air Supply Requirements and Maintenance
Carbon Monoxide Poisoning Preventable With Complete Inspection
Combustion Air Requirements:The Forgotten Element In Boiler Rooms
Creep and Creep Failures
Description of Construction and Inspection Procedure for Steam Locomotive and Fire Tube Boilers
Ensuring Safe Operation Of Vessels With Quick-Opening Closures
Environmental Heat Exchangers
Factors Affecting Inservice Cracking of Weld Zone in Corrosive Service
Failure Avoidance in Welded Fabrication
Finite Element Analysis of Pressure Vessels
Fuel Ash Corrosion
Fuel Firing Apparatus - Natural Gas
Grain Boundaries
Heat Treatment - What Is It?
How to Destroy a Boiler -- Part 1
How to Destroy a Boiler -- Part 2
How to Destroy a Boiler -- Part 3
Identifying Pressure Vessel Nozzle Problems
Inspection, Repair, and Alteration of Yankee Dryers
Inspection, What Better Place to Begin
Laminations Led to Incident
Lay-up of Heating Boilers
Liquid Penetrant Examination
Low Voltage Short Circuiting-GMAW
Low Water Cut-Off Technology
Low-Water Cutoff: A Maintenance Must
Magnetic Particle Examination
Maintaining Proper Boiler Inspections Through Proper Relationships
Microstructural Degradation
Miracle Fluid?
Organizing A Vessel, Tank, and Piping Inspection Program
Paper Machine Failure Investigation: Inspection Requirements Should Be Changed For Dryer Can
Pipe Support Performance as It Applies to Power Plant Safety and Reliability
Polymer Use for Boilers and Pressure Vessels
Pressure Vessel Fatigue
Pressure Vessels: Analyzing Change
Preventing Corrosion Under Insulation
Preventing Steam/Condensate System Accidents
Proper Boiler Care Makes Good Business Sense:Safety Precautions for Drycleaning Businesses
Putting a Stop to Steam Kettle Failure
Quick Actuating Closures
Quick-Actuating Door Failures
Real-Time Radioscopic Examination
Recommendations For A Safe Boiler Room
Recovering Boiler Systems After A Flood
Rendering Plants Require Safety
Repair or Alteration of Pressure Vessels
Residential Water Heater Safety
School Boiler Maintenance Programs: How Safe Are The Children?
Secondary Low-Water Fuel Cutoff Probe: Is It as Safe as You Think?
Short-Term High Temperature Failures
Specification of Rupture Disk Burst Pressure
Steam Traps Affect Boiler Plant Efficiency
Steps to Safety: Guide for Restarting Boilers After Summer Lay-Up
Stress Corrosion Cracking of Steel in Liquefied Ammonia Service - A Recapitulation
Suggested Daily Boiler Log Program
Suggested Maintenance Log Program
System Design, Specifications, Operation, and Inspection of Deaerators
Tack Welding
Temperature And Pressure Relief Valves Often Overlooked
Temperature Considerations for Pressure Relief Valve Application
The Authorized Inspector's Responsibility for Dimensional Inspection
The Effects of Erosion-Corrosion on Power Plant Piping
The Forgotten Boiler That Suddenly Isn't
The Trend of Boiler/Pressure Vessel Incidents: On the Decline?
The Use of Pressure Vessels for Human Occupancy in Clinical Hyberbaric Medicine
Thermally Induced Stress Cycling (Thermal Shock) in Firetube Boilers
Top Ten Boiler and Combustion Safety Issues to Avoid
Typical Improper Repairs of Safety Valves
Wasted Superheat Converted to Hot, Sanitary Water
Water Maintenance Essential to Prevent Boiler Scaling
Water Still Flashes to Steam at 212
Welding Consideration for Pressure Relief Valves
Welding Symbols: A Useful System or Undecipherable Hieroglyphics?
What is the Best Welding Process?
What Should You Do Before Starting Boilers After Summer Lay-Up?
Why? A Question for All Inspectors

Environmental Heat Exchangers

Francis Brown
National Board Staff Engineer

Winter 1996  

Category: Operations 


Summary: The following article is a part of National Board Classic Series and it was published in the National Board BULLETIN. (4 printed pages)



An environmental heat exchanger, as defined by the ASME Code, is a single-chamber pressure vessel that exchanges energy with the surrounding atmosphere. The heat exchanger consists of one or two headers and a number of tubes separating the working fluid from the atmosphere. The tubes may or may not be finned. The heat exchanger is a single-chamber vessel because none of the components is designed to be operated independently of the other components. A typical heat exchanger is shown in Figure 1.


Presently, a number of methods are used to complete the Manufacturers' Data Reports (MDRs) for environmental heat exchangers. Some heat exchangers are documented on U-1A data report forms and some are documented on U-1 report forms. The information included in the data report varies from manufacturer to manufacturer. Often, data reports must be returned for revision because of insufficient information.

Therefore, the National Board is offering the following guidelines to assist manufacturers with the completion of the data reports for this type of heat exchanger. Either the U-1 or the U-1A report form may be used for documentation of a single-chamber vessel, but it may be easier to complete the U-1 form for this type of heat exchanger. The U-1 form is used in the following example.

For this example, the headers are rectangular in cross section, are designed to the requirements of Appendix 13, and the opposite walls have the same thickness. An exploded view of a header is shown in Figure 2.



Typical header dimensions are shown in Figure 3.


The majority of the items on the U-1 form are completed in the normal manner. Only those items affected by the heat-exchanger configuration are discussed below.

    • The vessel is identified in Item 4 of a U-1 data report form as a heat exchanger.
    • The headers are described as shells in Item 6, as shown in Table 1. "Headers" is entered under "Shell" to indicate that the components described in Item 6 are not standard shell courses.
    • The significant cross-sectional dimensions (inside) of the headers are listed for the vessel diameter, as shown in Table 1. The remaining part of Item 6 is completed as needed. The longitudinal and circumferential joint efficiencies are determined from 13-4, 13-5, UW-12, and UG-23(c). In this example, corner welds were used to fabricate the headers.
    • The ends in the headers are documented as flat heads, as shown in Table 2. The asterisk indicates that the significant head dimensions are shown in "Remarks."
    • Items 9, 10, and 11 are completed in the normal fashion.
    • Item 12 is not completed because this vessel is not a tube-in-shell heat exchanger, and the part was described in Item 6.
    • The tubes connecting the headers are described in Item 13.
    • All penetrations in the headers are described in Item 19. The threaded openings in the "plug sheet" are treated as nozzles.
    • The head dimensions and the length of the tubes are added to "Remarks" (see below) to complete the description of the heat exchanger.




6. Shell (a) No. of Course(s): 1 each (b) Overall length (ft. & in.): 5 ft. 0 in.


No. Diameter, in. Length (ft. & in.) Spec/Grade or Type Nom. Corr.
1 3-5/8 x 10-1/2 5 ft. 0 in. SA-516 GR 70 See Remarks
1 3-5/8 x 10-1/2 5 ft. 0 in. SA-516 GR 70 See Remarks





7. Heads: (a)    SA-516 Gr70, NONE      (b)    SA-516 Gr70, NONE

(Mat'l Spec. No., Grade or Type) H.T. Time & Temp. (Mat'l Spec. No., Grade or Type) H.T. Time & Temp.



(Top, Bottom, Ends)
Thickness Radius Elliptical
Apex Angle
Hemispherical Radius Flat
Side to Pressure Category A
Min. Corr. Crown Knuckle Convex Concave Type Full,Spot,None Eff.
(a) ENDS 0.625






(b) ENDS 0.625








22. Remarks: Item 6: Tubesheet and plug sheet thickness: 1.25 in.; top and bottom wrapper thickness: 1.00 in.
      * Item 7 - Head dims.: 3-5/8 x 10-1/2 in.
      Item 13 - Tube length: 20 ft.







Editor's note: Some ASME Boiler and Pressure Vessel Code requirements may have changed because of advances in material technology and/or actual experience. The reader is cautioned to refer to the latest edition of the ASME Boiler and Pressure Vessel Code for current requirements.

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