Installation Guide

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Although soldering and brazing

operations are inherently simple, the

deletion or misapplication of a single

part of the process may mean the

difference between a good joint and a

failure.

THE JOINING PROCESS

Regardless of the process, solder-

ing or brazing, the same basic steps

should be followed, with the only

differences being the fluxes, filler

metals and amount of heat used. The

following joining process outlines the

basic requirements for consistently

making a high-quality soldered or

brazed joint:

 measuring and cutting

 reaming

 cleaning

 fluxing

 assembly and support

 heating

 applying the filler metal

 cooling and cleaning

Measuring and Cutting

Accurately measure the length of

each tube segment. Inaccuracy can

compromise joint quality. If the tube is

too short, it will not reach all the way

into the cup of the fitting and a proper

INTRODUCTION

The basic theory and technique of

soldering and brazing are the same for

all diameters of copper tube. The only

variables are the filler metal and the

amount of time and heat required to

complete a given joint. The American

Welding Society defines soldering as

a joining process which takes place

below 840°F and brazing as a process

that takes place above 840°F but

below the melting point of the base

metals. In actual practice for copper

systems, most soldering is done at

temperatures from about 350°F to

600°F, while most brazing is done at

temperatures ranging from 1100°F to

1500°F.

The choice between soldering or

brazing generally depends on the

operating conditions of the system and

the requirements of the governing

construction codes. Solder joints are

generally used where the service

temperature does not exceed 250°F,

while brazed joints can be used where

greater joint strength is required or

where system temperatures are as

high as 350°F.

Although brazed joints offer higher

joint strength in general, the annealing

of the tube and fitting which results

from the higher heat used in the

brazing process can cause the rated

pressure of the system to be less than

that of a soldered joint. This fact

should be considered in choosing

which joining process to use.

Although soldering and brazing are

the most common methods of joining

copper tube and fittings, they are

often the least understood. It is this

lack of understanding that can

develop into poor installation tech-

niques and lead to poor or faulty

joints. Investigations into the common

causes of joint failures revealed

several factors contributing to faulty

joints, including:

 Improper joint preparation

 prior to soldering.

 Lack of proper support and/or

 hanging during soldering

 or brazing.

 Improper heat control and 

 heat distribution through

 the entire joining process.

 Improper application of solder

 or brazing filler metal to

 the joint.

 Inadequate amount of filler 

 metal applied to the joint.

 Sudden shock cooling and/or

 wiping the molten filler metal

 following soldering or brazing.

 Pre-tinning of joints prior to 

 assembly and soldering.

Copper Development Association

260 Madison Avenue, New York NY 10016

Soldering and Brazing

Copper Tube

and Fittings

APPLICATION

DATA SHEET

COPPER • BRASS • BRONZE

Summary of content (8 pages)

PAGE 1
APPLICATION DATA SHEET COPPER • BRASS • BRONZE Soldering and Brazing Copper Tube and Fittings INTRODUCTION The basic theory and technique of soldering and brazing are the same for all diameters of copper tube. The only variables are the filler metal and the amount of time and heat required to complete a given joint.
PAGE 2
joint cannot be made. If the tube segment is too long, system strain may be introduced which could affect service life. Cut the tube to the measured length. Cutting can be accomplished in a number of different ways to produce a satisfactory squared end. The tube can be cut with a disc-type tube cutter (Figure 1), a hacksaw, an abrasive wheel, or a stationary or portable bandsaw. Care must be taken to ensure the tube is not deformed while being cut.
PAGE 3
Use care in applying flux. Careless workmanship can cause problems long after the system has been installed. If excessive amounts of flux are used, the flux residue can cause corrosion. In extreme cases, such flux corrosion could perforate the wall of the tube, fitting or both. Assembly and Support Insert tube end into fitting cup, making sure that the tube is seated against the base of the fitting cup . A slight twisting motion ensures even coverage by the flux.
PAGE 4
Heat is generally applied using an air-fuel torch (Figure 9). Such torches use acetylene or an LP gas. Electric resistance soldering tools can also be used (Figure 10). They employ heating electrodes and should be considered when an open flame is a concern. Applying Solder For joints in the horizontal position, start applying the solder metal slightly off-center at the bottom of the joint (Figure 12, position a, and Figure 9).
PAGE 5
Table 2: Filler Metals for Brazing Principal Elements, percent AWS Classification1 1. 2. Zinc(Zn) Cadmium(Cd) Temperature, ºF Silver(Ag) Phosphorus(P) Tin(Sn) Copper(Cu) Solidus Liquidus BCup-2 — 7.00-7.5 — — — Remainder 1310 1460 BCup-3 4.8-5.2 5.8-6.2 — — — Remainder 1190 1495 BCup-4 5.8-6.2 7.0-7.5 — — — Remainder 1190 1325 BCup-5 14.5-15.5 4.8-5.
PAGE 6
Figure 13. Melting Temperature Ranges (a) Melting and Brazing Ranges 120 psi) are shown in Table 3. These pressure ratings should be used only when the correct capillary space has been maintained. FLUXES The fluxes used for brazing copper joints are different in composition from soldering fluxes. The two types cannot be used interchangeably. Brazing fluxes are water based; whereas, most soldering fluxes are petroleum based.
PAGE 7
Table 3: Pressure-Temperature Ratings for Copper Tube Joints Joining Material(4) Service Temperature, O F Maximum Working Gage Pressure (psi), for Standard Water Tube Sizes (1) Fitting Type Alloy Sb5 95-5 Tin-Antimony Solder Alloy HB Joining materials melting at or above 1100º F(6) 5 through 8 1 /4 through 2 Pressure(2) DWV (3) Pressure(2) 150 DWV (3) Pressure(2) 200 DWV (3) Pressure(2) 250 DWV (3) Saturated Steam Pressure Pressure(2) 100 DWV (3) Pressure(2) 150 DWV (3) Pressure(2) 200 DWV (3) Pres
PAGE 8
Figure 14. Brazing Flux Recommendations joined. If tube or fitting start to oxidize during heating, there is too little flux. If the filler metal does not enter the joint and tends to flow over the outside of either member of the joint, it indicates that one member is overheated or the other is underheated. COPPER BRASS WROUGHT WROUGHT BCuP BCuP COPPER CAST BCuP BRASS CAST COPPER BCuP CAST BRASS BAg Testing Test all completed assemblies for joint integrity.