Prepared by:

R. HallCopper Development Association

A. Kireta, Jr.Copper Development Association

Contents

Introduction 610

Copper andCopper Alloys 610

Cutting and SizingPipe and Tubing 612

Surface Preparationand Cleaning 616

Fluxes and FluxingOperations 618

Assembly 619

Application ofHeat and BrazingFiller Metals 619

Postbraze Cleaning 620

Inspection 620

Bibliography 621

CHAPTER 35

Photograph courtesy of Lucas-Milhaupt, a Handy & Harman Company

PIPE AND TUBING

AWS BRAZING HANDBOOK 609

INTRODUCTION

610 CHAPTER 35—PIPE AND TUBING AWS BRAZING HANDBOOK

It is unknown exactly when human beings firstmade use of metal tubular goods to convey materialsfrom one location to another. Remnants of copperpipe show that metal was used to convey water asearly as 3000 B.C. in the great Egyptian pyramid builtfor the Pharaoh Cheops.1 By the time of the RomanEmpire, the use of metals to convey water and othermaterials was certainly well established. At this time,too, tubular members were probably first joined tovarious alloys.

Basic joining methods have changed little sincethen, and for the most part, they are still manualoperations. However, the demands and service con-ditions of today’s technology have created the needfor a wide variety of materials, the development ofnew alloy filler metals, as well as advanced joiningtechniques.

Brazed joints are economical and can easily bemade by skilled personnel with the proper equipmentand materials. Brazed joints can readily be made inaluminum alloys, copper and copper alloys, steel,stainless steel, and most other metals. Most pipe andtubing materials that can be soldered can also bebrazed, and when service conditions are too severefor soldered joints, brazed joints can very often beused satisfactorily.

A wide variety of brazing filler metals and fluxesare available, and most are readily applicable to pipeand tubing. A brazing filler metal for use with tubingor piping material should be chosen from the tablespresented in the chapters addressing the various met-als. In situations in which joint clearances cannot beheld to close tolerance, the brazing filler metalshould have a melting range wide enough to be easilyworkable and be fluid enough to flow readily intothe capillary space with good wetting action.

1. Copper Development Association (CDA), 2004, The CopperTube Handbook, New York, Copper Development Association, p. 6.

COPPER AND COPPER ALLOYS

Copper tube is used extensively in heating, cool-ing, plumbing, and other applications, as can beobserved in Table 35.1. Copper tube is durable, eco-nomical, lightweight, corrosion resistant, safe,readily formable, and easy to join. Leak-tight jointscan be produced in copper tube with brazing fillermetals having liquidus temperatures of 1100°F(593.3°C) to 1500°F (815.6°C). The brazing fillermetals most commonly used are the BCuP series andthe BAg series. The fluxes most commonly used areAWS FB-3A or AWS FB3-C.2, 3, 4

Most brazed joints in pipe and tubing do not needas much depth of socket insertion (overlap) as do sol-dered joints. A depth of tube insertion three times thethickness of the tube ordinarily results in a joint thatis as strong as or stronger than the base metal. This isillustrated by the test results shown in Figure 35.1. Itshould be noted that attempts to draw brazing fillermetal to the base of a socket designed for solderingoften result in serious overheating.

2. Copper Development Association (CDA), 2004, The CopperTube Handbook, New York, Copper Development Association,pp. 6; 49.3. American Welding Society, 1992, Fluxes for Brazing andBraze Welding, AWS A5.31-92(R), Miami: American WeldingSociety.4. At the time of the preparation of this chapter, the referencedstandards were valid. If a standard is cited without a date ofpublication, it is understood that the latest edition of the docu-ment referred to applies. If a standard is cited with the date ofpublication, the citation refers to that edition only, and it isunderstood that any future revisions or amendments to the codeor standard are not included; however, as standards undergo fre-quent revision, the reader is encouraged to consult the most recentedition.

PIPE AND TUBINGCHAPTER 35