braze training manual

HUSSMANN SUWANEE TORCH BRAZING MANUAL4/8/2023

TABLE OF CONTENTS

I. INSTRUCTIONS...............................................................................................................................

II. DEFINITION OF BRAZING............................................................................................................

III. GLOSSARY OF BRAZING TERMS...............................................................................................

IV. DIFFERENCES OF BRAZING, SOLDERING AND WELDING..................................................

V. BRAZING EQUIPMENT..................................................................................................................

VI. MAINTENANCE OF EQUIPMENT................................................................................................

VII. BRAZING SAFETY..........................................................................................................................

VIII. PROCEDURE FOR START UP AND SHUTDOWN OF THE BRAZING STATION..................

IX. THE SEVEN BASIC STEPS IN BRAZING.....................................................................................

GOOD FIT AND PROPER CLEARANCE.....................................................................................................CLEANLINESS OF PARTS........................................................................................................................FLUXING THE PARTS TO BE BRAZED....................................................................................................FIXTURING...........................................................................................................................................BRAZING THE ASSEMBLY.....................................................................................................................CLEANING AFTER BRAZING..................................................................................................................

X. REPAIR AND DISASSEMBLY OF JOINTS...................................................................................

XI. SUMMARY........................................................................................................................................

Quality Assurance of 1


I. Instructions

The purpose of this brazing instruction manual is to provide standard operating procedures and instructions for torch brazing. This manual covers the complete brazing process with the objective of maintaining the highest level of product quality and reliability, and can also be used as a reference of brazing principles, policies, equipment, special instructions and safety guidelines to assist Brazers, supervisors, engineers and management.

II. Definition of Brazing

Brazing is the joining of metals through the use of heat and a filler metal whose melting point is above 840 degrees Fahrenheit, but below the melting point of the metals being joined.

Some advantages of brazing:

1. Brazed joints are strong on non-ferrous metals and steels. The tensile strength of a properly made joint will often exceed that of the metals being joined.

2. Brazed joints are ductile... able to withstand considerable shock and vibration.

3. Brazed joints are generally easy and rapid to make, and operator skills readily acquired.

4. Brazing is ideally suited to the joining of dissimilar metals. Assemblies that combine ferrous and non-ferrous metals and metals with widely differing melting points may be joined easily.

5. Brazing is essentially a one operation process. There is seldom a need for grinding, filing or mechanical finishing after the joint is completed.

6. Brazing is performed at relatively low temperatures, reducing the possibility of warping, overheating or diluting the metals being joined.

7. Brazing is economical. The cost per joint compares favorably with joints made by other metal joining methods.



III. Glossary of Brazing Terms

1. ALLOY... A mixture or combination of filler metals such as copper, silver, zinc, plus other flow improving additives.

2. FERROUS... Having iron content.

3. NON-FERROUS... Having NO iron content.

4. PHOSPHORUS... A non-metallic element of the nitrogen family used in some brazing alloys.

5. MELT POINT... The temperature at which the low melting constituents of the alloy START to flow. At this point the alloy will appear to be mushy or plastic.

6. FLOW POINT... The temperature at which all the constituents of the alloy - in combination - flow freely and the entire alloy is fluid.

7. DUCTILE... The ability of material to withstand stresses of shock, vibration, thermal expansion and contraction without failure.

8. OXIDE... A combination of oxygen with another element (such as copper) which forms a coating or “scale" on the surface of the metal.

9. FLUX... A chemical substance applied to the surfaces of metals, to be brazed, to remove existing oxides and prevent the formation of oxides during the brazing process, while assisting the flow of alloys and promoting the bonding of the alloy to the metal.

10. TENSILE STRENGTH... The strength in tension in pounds per square inch that a metal or brazed joint can bear without failure.

11. CAPILLARY ACTION. . The force created by alloy surface tension which pulls and distributes the molten alloy between the metals being joined.

12. ORIFICE... A small hole, such as in a torch tip.

13. CONE... The inner flame, between the tip and the outer flame.

14. CLEARANCE... The gap between the materials being joined.

15. PURGING… The flowing of a non-oxygen neutral gas (typically nitrogen) across a brazing site to minimize the build-up of oxides in and around a around the joint.



IV. DIFFERENCES OF BRAZING, SOLDERING AND WELDING

1. BRAZING... The joining of metals through the use of heat and a filler whose melting temperature is above 840 deg. F. but below the melting point of the metals being joined. Brazing uses the heat of the metals to melt the alloy and draws the alloy into the joint by capillary action.

2. SOLDERING... The process of bonding metals using heat and a filler metal at temperatures BELOW 800 deg. F. and below the melting point of the metals being joined. Soldering is basically the same process as brazing, but at lower temperatures.

3. WELDING... The process of joining metals using heat at temperatures ABOVE the melting points of the metals being joined. Welding actually fuses the metals together instead of bonding them.

V. BRAZING EQUIPMENT

1. Torch assembly consisting of a torch body, gas and oxygen control valves, mixing chamber, yoke and torch tips.

2. A pressure regulator and gauge for fuel gas. (red).

3. A pressure regulator and gauge for oxygen. (green).

4. Two hoses. RED for the fuel gas and GREEN for the oxygen.

5. Flux brush.

6. Rose bud and single torch tips.

7. Access to Nitrogen for purging

8. Heat sinks, typically made of wet clean cloth (where required).

9. Clean water and bucket with ladle

10. Tip cleaner.

11. Check valve to prevent the reverse flow of fuel gas or oxygen.

12. Safety equipment including:

A) Protective GlovesB) Kevlar sleevesC) Shaded Safety glasses

13.Oil / Grease Cleaning Solution

14. Reamer



15. Approved scouring pad (such as Scotch-Brite)

16. Wire Brush

17. Clean Cloth / Rags – one to clean and one to dry, rotated as necessary to adequately remove grease and/or oil from the areas to be brazed (others to act as heat sinks)

VI. MAINTENANCE OF EQUIPMENT

Brazers at each brazing station will check brazing equipment to assure that it is in good condition and working properly at the beginning of each shift.

1. Fuel gas and oxygen regulators and gauges can be checked by observing the readings on both gauges. The readings on both gauges will increase by turning the handles clockwise, and decrease by turning the handles counter clockwise.

2. Glass covers must be checked for cracks and damage and to assure legible readings on the dials.

3. Hoses and fittings must be checked for wear, leaks and damage. If leaks are suspected and not readily visible, a solution of soap and water may be applied. Even a small leak will produce bubbles in the

soapy water.

4. Check orifices and tips for clogging. Do not submerge them in water for cleaning. Worn or damaged tips should be replaced.

5. Flux brushes can be cleaned in clean water. Worn or damaged brushes should be replaced.

6. Use clean water, hot water works best for removing flux. When water becomes saturated with flux it will not remove flux effectively, so it should be changed regularly.

7. Brazers must replace any damaged, warped or ineffective heat sinks or heat shields.

8. Contact your supervisor for necessary repair of broken or defective equipment. NEVER BEGIN TO BRAZE WITH EQUIPMENT BELIEVED TO BE BROKEN OR NOT WORKING PROPERLY.



VII. BRAZING SAFETY

SAFETY IS EVERYONE’S FULL-TIME RESPONSIBILITY

1. Never use matches or a cigarette lighter to light a torch.Always use a striker.

2. Never use the torch to light anything on fire (paper, cigarettes).

3. Lighted torches are dangerous, be careful. Keep your torchin front of you and under control at all times. Never lay a lightedtorch down or hang it on other objects.

4. Know where the nearest fire extinguisher is in your area.

5. Check for gas or oxygen leaks regularly. Leaks that are notobvious can be detected with a solution of soapy water.

6. Do not overheat the joints; a splattering alloy is dangerous!Also, do not touch braze joints until they have cooled.Wear gloves and use tools such as pliers to handle parts.

7. Keep combustible materials from brazing areas. Never useoil or grease around a brazing area because they arecombustible, and always keep your brazing area clean.

8. Before disassembly or repair of a braze joint, alwaysrelieve all pressure from assemblies, coils or units.

9. Always wear shaded safety glasses. Use a number 5 shade for gas fluxbrazing.

10. Always wear Kevlar gloves and sleeves when brazing.

Brazing accidents happen when people get careless and proper procedures are not followed. Two common accidents in brazing occur when:

A) The fuel gas and oxygen become mixed in the hoses and regulators, and B) When cylinder storage bottles are not properly secured, allowing them to fall over.

Gases mixed within the hoses and regulators create an explosive mixture, which if ignited can cause an explosion that is extremely violent. The resulting injuries can come from both the flames and the disintegrating metal. Oxygen and fuel gas burn at 4,000 to 6,000 degrees F, so the burn injury is frequently severe.

For a fire to start you must have three things: Fuel, Oxygen and Ignition (or heat). No two will burn alone.



Reverse flow caused by unequal pressures will result in mixed gasses in hoses and regulators. Reverse flow can happen when:

A. The oxygen cylinder or line empties and the oxygen valve on the torch is open. Fuel gas can reverse flow into the oxygen hose and regulator. An oxygen storage cylinder should never be completely emptied, it should be considered empty when the pressure drops to approximately 50 psi.

B. The operator opens both torch valves and attempts to light both gases at once. If more oxygen is flowing than the tip allows, the system is back-pressured and oxygen can reverse flow into the fuel gas hose and regulator. Light the fuel gas first. The operator should only light both gases at once when universal pressure equipment is used. Even with universal pressure equipment, if the tip is obstructed, back-flow will result. If a torch tip is plugged, the higher pressure gas will always back up into the lower pressure line.

Check valves are designed to prevent the reverse flow of fuel gases and oxygen, but the operator needs to have a working knowledge of brazing equipment (valves, gauges, regulators) etc.) and it's proper usage to prevent accidents.

Fuel gas and oxygen cylinders (storage bottles) should always be handled with extreme care and be properly secured. The most common means to secure them is by chaining them in place. When a bottle falls over usually what happens is that the valve stem, it's weakest point, will break off. A ruptured bottle becomes a lethal projectile capable of going through concrete walls. If it should happen to ignite, it becomes a bomb.

ALWAYS chain cylinders to prevent their falling over.

ALWAYS vent or bleed off a small amount of gas or oxygen from a cylinder valve before attaching a regulator. This blows any dirt or dust off the cylinder valve. Dirt or dust in a regulator provides the fuel for ignition if gases should happen to be mixed in the regulator.

ALWAYS bleed off pressure from hoses and regulators when not in use. If reverse flow has occurred, this precaution safely bleeds off the mixed gases.

ALWAYS light the fuel gas first. This prevents back pressuring the fuel line with the higher pressure oxygen.

ALWAYS use the correct tip size and pressure. To much pressure on a small tip can cause reverse flow. To little pressure can cause the tip to sputter and pop and perhaps encourage backfire or flashback.

ALWAYS keep heat and flames away from combustibles.

NEVER use oxygen as a substitute for air to blow off your clothing. The clothing will absorb the oxygen. Then if a spark or other source of ignition touches the clothing, the three necessary ingredients for a fire are present. Combustible materials burn more vigorously in an oxygen enriched atmosphere.

NEVER handle regulators, valves, cylinders or other equipment with oily or greasy hands or gloves.

NEVER use oil on hose or regulator connections. Oil is a combustible material with an extremely low flash point. An oxygen regulator frequently has two of the three necessary ingredients for a fire. If the cylinder valve is opened quickly, the heat of re-compression creates an ignition temperature. Oxygen is present and if oil is also in the regulator, a combustion triangle is complete and a dangerous explosion can occur.

DO NOT use acetylene pressure above 15 psi.

DO NOT empty an oxygen cylinder below 50 psi.



DO NOT attempt to repair or substitute parts on brazing equipment. Have your supervisor contact maintenance. Frequently, special tools or techniques are needed to safely make repairs.

VIII. Recommended procedure for start up and shutdown of the brazing station.

SETTING UP THE BRAZING STATION

1. Turn on the fuel gas and oxygen. supply valves. If using a gas fluxer, open the inlet and outlet valves on the fluxer now. Turn the fuel gas regulator handle (clockwise) until a pressure of approximately 5 psi is on the gauge. (Our Fuel Gas is Preset)

2. Open both valves on the torch handle. These valves are used to turn the fuel gas and oxygen on and off, they are not metering devices and should not be used to adjust gas and oxygen flow. The regulators are for regulating flow.

3. Light the torch, using a striker.

4. Turn the oxygen regulator handle until the desired (Neutral) torch flame is achieved. Note: To achieve the correct brazing flame, both fuel gas and oxygen will need to be adjusted at the regulators. Readings on the regulators will vary with different tip sizes and fuel gases.

SHUTDOWN OF THE BRAZING STATION

1. Turn off the fuel gas and oxygen supply valves.

2. Open both the gas and oxygen valves on the torch, this will relieve all pressure from the torch, hoses and regulators. Wait until both gauges read zero (0) and the pilot is out.

3. Turn both regulators off. (counter clockwise)

4. If using a gas fluxer, turn off the inlet and outlet valves on the gas fluxer now.

5. Close both the gas and oxygen valves on the torch.

6. Replace the torch on its hanger.



IX. THE SEVEN BASIC STEPS IN BRAZINGA properly brazed joint is obtained by use of a capillary action - which evenly pulls the alloy into the joint. A well designed joint will facilitate good brazing but will not guarantee a good joint unless procedures are followed.

The following basic steps are generally simple to perform and no one step is any more important than the others since it takes all to insure a quality joint. Proper brazing procedures must be followed and the Brazer needs to have an effective knowledge of these basic principles.

1. Good fit and proper clearance of joints.

2. Cleanliness of parts to be brazed.

3. Fluxing the parts to be brazed, where necessary.

4. Assembling and supporting the parts, (fixturing).

5. Applying the purging gas (nitrogen) across the area to be brazed

6. Evenly heating the assembly, applying and flowing the alloy, (brazing the assembly).

7. Cleaning after brazing.

IT IS THE BRAZER’S RESPONSIBILITY TO FOLLOW THESE SEVEN STEPS WITH EACH JOINT THAT IS BRAZED.

Good Fit and Proper Clearance

Some of the reasons for good fit and proper clearance are:

1. To obtain capillary action. Capillary action is the force that pulls or draws the molten brazing alloy into the joint.

2. Ease of assembly. Tubes should go together easily, but without being sloppy.

3. Strength of the joint. A proper fit will produce a strong joint able to withstand the stresses of pressure, thermal expansion and contraction and vibration without failure.

4. Ease of applying alloy.

5. Economy. A well fitted joint will enable the Brazer to produce a good braze joint in the least amount of time and without using more alloy than necessary.



STEPS TO FOLLOW CHECKING FIT AND CLEARANCE

1. Make sure the tube ends are square, to allow the tube to seat all the way around the base of the socket.

2. To insure that the tubing area is free of burrs a reamer and thorough use of an approved scouring pad (Scotch-Brite) should be used in and around the opening. Burrs could prevent the tube from seating properly, and could also be a problem in a refrigeration system if they break loose inside the assembly.

3. Connect the tubing ends to check the fit. The clearance between the inner and outer part should be .002 to .005 at room temperature and .001 to .005 at brazing temperature, depending upon what materials are being joined and what alloy is being used (see figure below ). An “ easy slip fit " will make a good joint if procedures are followed. Too much clearance reduces the effect of the capillary action and retards the flow of the alloy. Proper clearance with a thin film of alloy will produce a leak tight joint with high strength.

Any problems with the fit-up and clearances between parts should be reported to lead person or supervisor . DO NOT ATTEMPT TO BRAZE PARTS THAT DO NOT FIT PROPERLY.

EFFECTS OF EXPANSION ON CLEARANCE

Metals such as steel, brass and copper expand differently when they are heated during brazing. Copper expands more than brass or steel, and brass expands more than steel. Figures 2 and 3 show a brass tube inserted into a steel fitting. The steel does not expand as much as the brass when heated, therefore the clearance is smaller when both the brass and steel are at brazing temperatures.


PROPER CLEARANCE AT BRAZING TEMPERATURE SHOULD BE .001” TO .005”

Figure 1

CLEARANCE AT ROOM TEMPERATURE

CLEARANCE AT BRAZING TEMPERATURE



STEELBRASS

STEELBRASS

Figure 2 Figure 3


The reverse is also true. Figures 4 and 5 show that a tight fitting steel tube, inserted into a brass fitting at room temperature, will create a suitable gap at brazing temperatures.

The amount of clearance that should be allowed for expansion and contraction depends on the nature and sizes of the metals being joined and the configuration of the joint itself. Although there are many variables involved, if you keep in mind that different metals expand at different rates when heated, common sense and a little experimentation will quickly put you on the right track.

Cleanliness of Parts

REASONS FOR PROPER CLEANING

1. Capillary action will work only when the surfaces of metal are clean. All contamination (oil, grease, rust, scale, oxides etc.) must be removed. Failure to do so will result in an unsatisfactory braze joint.

2. Contaminated surfaces prevent brazing alloy from flowing into the joint, causing voids and inclusions in the brazed area.

3. Oil and grease will carbonize when heated, forming a film over which filler metal will not flow and brazing filler metals will not bond to a rusty surface.

STEPS AND METHODS TO FOLLOW WHEN CLEANING PARTS

1. Dirt, oil and grease must be removed before scale, rust and oxides. This is to be done using a soapy solution on a clean towel to wipe our the area to be brazed and then the part should be either rinsed with clean water or wiped with a wet towel soaked in clean (non-soapy) water.


A FORCE FIT AT ROOM TEMPERATURE ..........

STEEL STEEL

BRASSBRASS

BECOMES A SUITABLE GAP AT BRAZING TEMPERATURES

Figure 4 Figure 5


2. After dirt, oil and grease have been removed, finish the cleaning process by thoroughly using an approved scouring pad (Scotch-Brite) or wire brush to insure that all rust, scale, oxides or paint are removed. After loosening the contaminants, remove all residue or loosened particles. Do not allow loosened particles to enter inside the parts being cleaned; contamination of the refrigeration system will result. After the parts have been cleaned they must be completely dry and used as soon as possible to prevent recontamination.

Fluxing The Parts To Be Brazed

Flux is a chemical compound applied to the joint surfaces before brazing. Flux on the joint area will shield the surfaces from the air, preventing oxides from forming. Flux will also dissolve and absorb oxides that form during heating or that were not completely removed during the cleaning process. FLUX IS NOT FOR CLEANING PARTS; parts need to be cleaned PRIOR to fluxing. It is applied to promote the flow and bonding of the alloy to the metals throughout the joint being brazed.

On copper to copper joints, the phosphorus in the phos-copper alloy is the flux, so paste flux is NOT necessary. A flux is necessary when joining dissimilar metals such as copper to brass or copper to steel, and when using an alloy with no phosphorus content.

CARE OF FLUX

Flux must be kept clean. Dirty flux will cause inclusions or voids in the braze joint. Ensure that the tubing is clean prior to applying the flux and clean flux brushes periodically with clean water.

Most paste flux is shipped in concentrated form and must be diluted with clean water before being used. The amount of flux or type of flux needed changes with wall thickness, diameter, and the heating time required.

Flux must be applied in the proper amount. Too much flux increases the risk of it entering the refrigeration system and it also prevents the alloy from properly entering the joint. Use of too little flux will quickly be used up and the bare metal will become saturated with oxides resulting in a weak joint and possible leaks.

APPLYING FLUX

Use only approved flux; the right flux for the job.

Apply flux using a brush. Never dip parts in flux. If the parts are dipped into the flux, the flux will be inside the tubing. FLUX MUST BE KEPT OUT OF THE REFRIGERATION SYSTEM. Flux will cause parts such as strainers, capillary tubes and distributors to become plugged and inoperative. Flux will also damage valves, driers and compressors. Flux inside the refrigeration system will cause corrosion, contamination and ultimate failure of the unit.

Flux must stick to the surfaces of the metals to allow the alloy to bond to the metals being brazed and it must be applied smoothly. A flux that " balls up " or " beads up " is an indication that oil or grease is on the metal; re-clean the parts and re- flux them before brazing.



FLUX ACTS AS A TEMPERATURE INDICATOR

Flux can act as a temperature indicator letting the Brazer know that the base metal is just about hot enough to melt the brazing filler metal.

TEMPERATURE FLUX APPEARANCE

212 deg. F Water boils off.

600 deg. F Flux becomes white and slightly puffy and starts to work.

800 deg. F Flux lies against the surface and has a milky appearance.

1100 deg. F Flux is completely clear and active. Looks like water. A bright surface is visible. At this point, test the temperature by touching the filler metal to the base metal. If the filler metal melts, the assembly is at the proper temperature for brazing.

1600 deg. F Flux is totally spent.



Fixturing

Assemblies brazed in the sub-assembly areas must be brazed in the proper fixtures. A fixture may be dedicated to one assembly or it may be a universal fixture, (one in which several different assemblies are made). Fixtures can become worn or damaged over time, so piece parts and final assemblies must be checked against drawings and/or methods sheets and NOT to the fixture. If fixtures are not available or parts will not fit, notify your supervisor or inspector. All assemblies built off-line and later installed on the unit should fit smoothly and not forced into position.

In final assembly, fixtures are usually not needed, but if they are needed, they should be available and used to ensure proper alignment of the tubing.

Parts and sub-assemblies must be carefully aligned and adequately supported during the brazing process so that the joints are straight to ensure a sound joint.

Parts must not be moved after brazing until the alloy sets or the joint will crack and a leak will develop.

Parts may be held together with gravity, provided they remain in correct alignment during heating and cooling.

Valves must be isolated or protected from heat during brazing to prevent damage to seats or seals. This can be accomplished with the use of a heat sink. There are a variety of styles of heat sinks, such as a performed block, inflammable putty or a wet shop cloth. A wet shop cloth or rag is the most commonly used. The area to be protected should be wrapped with the wet cloth, with the wrapping concentrated on the end nearest to the joint to be brazed. If brazing a one-piece sight glass, wrap both sides of the connections but Do Not place the wet rag over the glass. This will cause the glass to crack.

Heat sinks and heat shields must be used when called for. Defective, warped, broken or ineffective ones must be replaced. The proper size and design heat sinks and heat shields must be used for the corresponding size and design of the tube. Heat sinks and heat shields must remain in place for a minimum of 30 seconds.

Adequate nitrogen flow must be provided at all brazing stations to insure internal cleanliness. Nitrogen flowing through tubing during brazing displaces oxygen thereby preventing the formation of oxides on the inside of tubes and assemblies. There are other gases that can be used but nitrogen is one of the best from a safety standpoint because it is non-combustible. It is also one of the least expensive gases to use. Ideally the purge gas supply will be attached to the fixture in such a way that simply placing the parts in the fixture makes the connection to the assembly.

Ensure the prescribed nitrogen purge is operable. Report any problems to your supervisor.

Selecting the correct extension arm and tip size is as important as adjusting the torch. You need to consider whether to use a single or double extension and what size tip to use on it. Both singles and doubles are used with the double probably being the most popular in production use. However, a single tip is best when you need to keep the heat more closely concentrated, as in brazing a tee joint where the parts do not overlap. You are not relying on capillary action, but physically depositing the alloy at the joint. If too large an area is heated, the alloy will run away from the joint. We use two types of tips in our brazing processes. A Rosebud Tip with multiple flames used on larger copper and a #10 tip single flame used on smaller copper.

A tip that is too small will cause you to take excessive time to reach brazing temperature. A tip that is too large wastes fuel and oxygen and you can quickly overheat, causing burns and excessive oxidation. You can get more or less heat by changing tip sizes, and adjusting the oxygen and gas regulators to the manufactures recommended settings for the size tip you are using.



Brazing The Assembly

Some metals heat rapidly and some slowly. A heavy section of metal takes longer to heat than a light or thin one. Also some metals, such as copper, conduct heat better than other metals, such as steel. Therefore, when unequal thickness’ or masses are being joined, care must be taken not to over heat the light or thin one or under heat the heavy one. When joining a good conductor to a poor conductor, more heat will have to be applied to the good conductor.

For correct brazing, the correct oxygen and gas mixture must be used. Adjust the torch by turning the fuel gas regulator handle clockwise until fuel is flowing from the torch tip. Light the torch with the pilot or striker, then adjust the oxygen regulator slowly until a neutral flame has been established. Adjusting both the fuel and oxygen will be necessary to achieve the correct flame.

A light blue neutral flame contains the proper mixture of oxygen and gas for brazing copper to copper and copper to brass joints. (see figure.7).

A brilliant blue, reducing flame with a small light blue cone or feather contains the proper mixture of oxygen and gas for brazing steel. However you must be careful not to use excessive oxygen. Too much oxygen causes excessive oxidation and overheating and results in the formation of black scale. (see figures 8 & 9).


NEUTRAL FLAME REDUCING FLAME OXIDIZING FLAME

LIGHT BLUEINNER CONE

Best type ofbrazing flamefor brazingnon-steeljoints.

BRILLIANT BLUEINNER CONE

Best type ofbrazing flamefor largesteel joints.

SMALLER THANREDUCING ORNEUTRAL FLAME

Do not use!

Figure 6 Figure 7 Figure 8


THE BRAZING PROCESS

Start the brazing process by first heating the inserted member, 1/2" to 1" from the outside member. (see figure. below) Except when steel is inserted into a copper fitting. The copper fitting or outside member must be heated first.

The outer flame (not the inner cone) must heat the parts to be brazed. The inner cone must be kept 3/4" to 1" from the parts being brazed.

Copper and brass are good heat conductors and steel is a poor one, so more heat must be applied to the copper or brass.

If the tubing is small enough for both the inside and outside part to be surrounded by the flame, both may be heated at the same time, but in all cases both parts should be brought up to brazing temperature as evenly as possible.

Use a rolling or sweeping motion with the torch to keep both parts at brazing temperature and evenly heated (see figures 10 & 11). This will prevent hot spots and over or under heating and will allow the capillary action to occur.


Figure 9 Figure 10

Figure 11Figure 12


BRAZING TEMPERATURES

The Brazer must keep in mind that both parts being joined must be heated as uniformly as possible, so they reach brazing temperature at about the same time. The best insurance against uneven heating is to keep a watchful eye on either the flux or the part being brazed.

When flux becomes clear and active and looks like water (about 1100 deg. F) a bright shiny surface is visible underneath. This is about the right time to start applying alloy. Different alloys melt at different temperatures, but the alloy should be applied while the flux is active.

Molten brazing filler metal tends to flow toward areas of higher temperature, so care needs to be taken to deposit the filler metal immediately at the joint.

When copper turns a dull red, brazing temperature has been reached. If copper is cherry red it is overheated.

When brass turns dark red, brazing temperature has been reached. When brass is bright red, it is overheated and ready to melt.

When steel just starts to turn dark red, brazing temperature has been reached.

APPLYING THE ALLOY

The alloy must be kept clean (bright and shiny). Store alloy in original packaging. Dirty or corroded alloy will cause inclusions or voids in the joint, resulting in a defective joint. Alloy should be cleaned by wiping with a damp cloth.

Start applying alloy only after brazing temperature has been reached. If the alloy sticks to the metal and does not melt when applied, brazing temperature has not been reached.



On smaller diameter tubes, the alloy can be applied at the joint at one point and moved around the joint with the heat of the torch. ( see figure. 13 ).

On larger diameter tubes it will be necessary to add alloy at two or more places. When applying the alloy, the alloy should not extend past the outside of the part, so that the alloy does not flow outside the joint. The end of the alloy rod should touch the metal, not the side of the rod. ( see figure. 14 ).


Figure 13



Figure 14


Use enough alloy to make a good joint, BUT ONLY THE ALLOY IN THE JOINT, BETWEEN THE PARTS MAKES A GOOD JOINT. Alloy on the outside of the joint is a waste of alloy. It gives the joint a poor appearance and weakens an otherwise strong joint.

When the alloy begins to flow, do not stop adding it until the joint is full. Pull the alloy into and around the joint by the heat of the torch. ALLOY WILL FLOW WHERE THE HEAT IS APPLIED. Once the alloy starts to flow, continue moving the torch back and forth and around the joint, keeping both the inside and outside part evenly heated. This will ensure the proper capillary action.

Follow the flame with the alloy and let the heat of the copper melt the alloy not the flame of the torch.


Figure 15


All the proper procedures must be followed or capillary action -will not be achieved. If the joint has been made properly, the alloy will be at the bottom of the inside tube, between the inside tube and the outside all the way around the joint (see figure. 16). The bell of the fitting should be full of alloy, but not overflowing.

Figure 16 shows the proper insertion, inside tube seated in the socket, and the heat was applied to the entire joint area. Once the alloy was melted with the heat of the tube, capillary action draws the alloy into the entire joint.

SOME DON'TS OF BRAZING

Do not melt the alloy with the heat of the torch! Always melt the alloy with the heat of the metal.

Do not use the " Heat and Dab " method, which is applying a small amount of alloy then pulling back. Apply the alloy in smooth strokes and use enough alloy to do the job.

Do not use “Tack Brazing". Tack Brazing is depositing a small amount of alloy around the top of the joint, without achieving capillary action. The joint will eventually crack and leak.

Do not heat only one tube. Be sure to heat both tubes EVENLY when applying solder alloy.


Figure 16


DON'TS OF BRAZING, CONT.

Figure 17 is an illustration of the male tube being at brazing temperature while the female tube is still cool. The effect is that the alloy migrates toward the heat source.

Figure 18 shows what happens when the torch and the braze alloy are applied at the same time. The total joint area was not heated properly and the heat never reached the male tube to allow capillary action.

Do not overheat because the material could be weakened and time and alloy will be wasted. When joints are overheated, alloy will flush to the inside or outside of the joint and flux becomes more difficult to remove.

If lumps of alloy are on the joint, it is an indication that proper procedures were not followed. Some possibilities are:


Figure 17

Figure 18


1. The metal was not clean.

2. Under or over heating.

3. Alloy melted with the heat of the torch, rather than the heat of the metal.

4. Excessive clearance. Alloy flushes out leaving a gap at the top and a lump at the bottom.

5. Excessive use of alloy.

Cleaning After Brazing

ALL assemblies must be cleaned after brazing.

The joint MUST be thoroughly cleaned of flux and should be free of scale and oxidation. This cleaning is required EVEN IF THE JOINT WILL BE COVERED BY INSULATION. Flux will cause corrosion and eventual joint failure.

Flux can be removed using clean water, hot water works best, and using a brush or hand mop if necessary. Flux must be removed completely from the top, sides and bottom of joints. The flux must be removed so that it cannot be seen or felt. Flux is still there if the joint is sticky to the touch (BE SURE THE JOINT IS COOL BEFORE TOUCHING IT).

Caution must be used when cooling and cleaning brass and steel assemblies such as distributors or valves. NO HOT BRAZED PARTS SHOULD BE DUNKED IN WATER. RAPID COOLING IMMEDIATELY AFTER BRAZING CAN CAUSE CRACKS IN BRASS AND STEEL BODIES. Brass and steel must be allowed to cool before cleaning. Clean brass and steel when they are warm (not hot).

When removing flux, caution must be used not to get water in sub-assemblies, coils or tubing. Moisture will cause serious problems in the refrigeration system.

Some of these problems are:

1) Extra time for evacuation. (pump down).

2) Ice will form inside the system plugging strainers, capillaries and distributors causing improper system operation.

3) Shorten the life of the compressor.



X. Repair and Disassembly of Joints

ALWAYS relieve all pressure in the assembly. NEVER attempt to repair or disassemble with pressure in coils, assemblies or units. Make sure the system is vented and open.

Flux can be applied to the joint to be disassembled to act as a temperature indicator and to prevent oxidation.

Heat uniformly until the joint is free. Remove the parts with tools to avoid being burned.

Clean joints after cooling and repeat the brazing process.

Use nitrogen, to insure internal cleanliness and heat sinks and heat shields, where necessary to protect valves and surrounding components.

Make the repair by adding flux, if necessary, re-heating the joint, adding and flowing the alloy into the joint.

Always use the same alloy that was first used to make the joint. Failure to do so can result in a defective joint that will fail in a short period of time.

After the repair has been made, remove any flux left on the tube surface.



XI. Summary

The importance of a quality braze joint cannot be over emphasized in the refrigeration industry. Brazing is utilized to join the component parts in the refrigeration system into a closed circuit. Since the closed circuit contains high pressure refrigerant, every braze joint must have good penetration around the entire joint, be leak free and pressure secure.

The allowable leak standard for Hussmann is (1/10) one-tenth of one ounce of refrigerant per year (or one ounce of leakage in a ten year period). This size leak is so small that it would take 15 to 20 minutes for a bubble to form under water.

Practicing the seven basic steps of brazing, outlined in this manual, are important to maintaining our quality goal.
