08 - Working with Tubing and Piping

Question 1

What are the the two different classifications of wall thicknesses for copper tubing?

Answer 1

Type K and L. Type K is a heavy wall. Type L is a medium wall. The more commonly used type is Type L.

Question 2

What is ACR Tubing?

Answer 2

Air conditioning and refrigeration tubing (ACR) is manufactured specifically for use in air conditioning and refrigeration systems. ACR tubing is usually charged and sealed with gaseous nitrogen. This keeps the tubing clean and dry until it is used. ACR tubing is designated by the actual outside diameter of the tubing.

Question 3

What are the sizing differences between ACR copper tubing and conventional plumbing copper?

Answer 3

ACR tubing is sized using OD, and regular copper tubing is sized using interior size. While the nominal size for both may be 1/2”, they will be sized differently.

Question 4

Where is soft ACR tubing used?

Answer 4

Soft ACR tubing is used in domestic and some commercial refrigeration and air conditioning work.

Question 5

What is annealing? How is it done?

Answer 5

Annealing is a process in which a substance is heated to a specific temperature range and then allowed to cool slowly. Annealing makes tubing soft and flexible for easy bending and flaring.
- Hold the tubing in a vise or insulated pliers
- Light an oxy acetylene torch to a blue flame
- Heat the area of tubing to be annealed to a dull cherry red
- Allow the tubing to air cool slowly

Question 6

What is hard drawn ACR tubing?

Answer 6

Type L or K hard drawn ACR tubing is used in commercial refrigeration and air conditioning applications. Sizes of hard-drawn ACR tubing range from 3/8” to over 6”. Being hard and stiff, hard drawn tubing needs few clamps or supports, particularly in larger diameters. Hard drawn tubing should not be bent; therefor, flared connections cannot be used. Use straight lengths and fittings of different angles to form the necessary tubing connections. Hard-drawn ACR tubing should be brazed, not soldered.

Question 7

What is the process for unrolling soft copper?

Answer 7

Hold the coil upright with one hand and hold the open end on a flat surface, begin unrolling. Because it is difficult to recoil tubing, unroll only as much tubing as needed. After cutting the tubing, replace the cap or plug to prevent contamination within the tubing.

Question 8

Where should solder be used?

Answer 8

Solder should be used only on water lines.

Question 9

What is stainless steel tubing good for, and where is it commonly seen?

Answer 9

Stainless steel tubing is strong and very resistant to corrosion.

It is often used in various food processing systems such as ice cream manufacturing, milk handling, and transportation of food items. It can also be used for specialized cooling coils.

Question 10

What is aluminum tubing commonly used for?

Answer 10

A common use of aluminum tubing is to form evaporators.

Question 11

What is the difference between nominal size and outside diameter for copper water tubing?

Answer 11

Nominal size is equal to 1/8” less than outside diameter.

Question 12

What is ABS pipe and what is it used for?

Answer 12

ABS is a black pipe used for drainage, waste, and vent piping, as it is resistant to deposit formation. ABS is for non-pressure applications where the operating temperature will not exceed 180F. Either solvent cementing or threading can be used to join ABS pipe.

Question 13

What is PVC pipe and what is it used for?

Answer 13

PVC plastic pipe is white. It is commonly used for cold water supply, drain lines, fresh air inlet, and some furnace exhaust applications. A safe temperature range for PVC pipe is from -100F to 175F. Solvent cementing, threading, or flanging can be used to join PVC.
Grades for PVC include schedule 40 and schedule 80. Schedule 80 has a thicker wall than schedule 40, making it more appropriate for higher pressure applications.

Question 14

What are the two most common types of steel pipe in HVACR?

Answer 14

Galvanized pipe and black pipe.
Galvanized pipe is treated with a zinc anticorrosion material. Galvanized pipe is a gray colored steel pipe. It is used primarily in water systems to prevent rust.
Black pipe is usually less expensive than galvanized pipe and is used for gas lines and applications that do not carry water.

Question 15

What is a flare?

Answer 15

A flare is an enlargement at the end of a piece of tubing by which the tubing is connected to a threaded fitting using a flare nut.

Question 16

What is a good way to prevent brittle copper tubing from splitting when being flared?

Answer 16

The copper can be annealed to soften it before attempting a flare.

Question 17

For what connections is solder supposed to be used in HVACR?

For what purpose are brazed connections supposed to be used?

Answer 17

Soldered connections are for water pipes and drains.

Brazing is for tubing that circulates refrigerant.

Question 18

What temperature distinguishes solder from brazing?

Answer 18

If the filler alloy melts below 840F, it is considered solder. If it is above 840F but below the melting point of the materials being joined, it is considered brazing.

Question 19

What should always be done before attempting a brazing procedure on a closed refrigeration circuit?

Answer 19

Refrigerant recovery procedures and practices should always be followed to avoid the risk of creating phosgene gas. This is a by product of some refrigerants when they are exposed to an open flame or extreme heat, and it is extremely dangerous, even in trace amounts.

Question 20

What is Oxyacetylene?

What are the benefits of using it?

Answer 20

Oxyacetylene describes a torch configuration that mixes pure oxygen and acetylene.

Oxyacetylene can create more heat than a traditional torch. The hotter flame will bring the joint to brazing temperature quickly. Since materials transfer heat at a fixed maximum rate, the hotter flame actually reduces the amount of heat transferred from the copper tubing because the flame does not need to be held to the joint as long.

Question 21

Describe the three different types of oxyacetylene torch flames

Answer 21

Carburizing flame has too much acetylene. The outer flame ends in a ragged orange-red flame. There will appear to be two separate inner cones in the flame: a small white cone and a longer light blue cone. A carburizing flame also generates a lot of smoke.

Oxidizing flame has more oxygen than a neutral flame. The inner cone of an oxidizing flame is small, sharply pointed, and white. An oxidizing flame also hisses as it burns. The louder the flame hisses, the more oxidizing it is.

Neutral flame is the most efficient flame is brazing. It has just the right mixture of oxygen and acetylene. A neutral flame is recognized by its single, bullet-shaped bluish-white inner cone and an outer flame with a bit of reddish-purple at the tip. A neutral flame burns relatively quietly and does not generate smoke.

Question 22

What is capillary action?

Answer 22

Capillary action is the movement of a liquid substance between two solid substances due to the molecular adhesive forces between the solids overcoming the liquid’s cohesive forces.

Question 23

When should Tin-lead or 95/5 tin-antimony solder be chosen for a given application?

Answer 23

Tin-lead solder is appropriate for moderate pressure and temperatures.

For higher pressure or greater joint strength, as well as very low temperatures, a 95/5 tin-antimony solder should be used.

Question 24

What is flux?

Answer 24

Flux is a paste, powder, or liquid that prevents oxide from forming on the surfaces to be soldered and aids solder flow.

Question 25

What are the two most common filler rod materials used for brazing?

Answer 25

Alloys containing 5% to 60% sliver and copper and copper alloys that contain some phosphorus.

Question 26

What is purging?

Why is it important?

Answer 26

Purging is the process of removing unwanted airs, vapors, dirt, and moisture from a system by flushing them into the atmosphere with a compressed gas, usually nitrogen.

Any oxygen inside tubing may promote the formation of oxide on the interior surface. Also, any oil inside the tubing or part may be vaporized by the heat of a torch, which could explode if ignited.

Question 27

What is Swaging?

What is it useful for?

Answer 27

Swaging is the mechanical enlarging of one end of tubing to allow another piece of tubing of the same diameter to be inserted into the enlarged tubing for a soldered or brazed connection.

It is an effective practice to reduce the use of costly fittings. It is also more convenient to solder or braze one joint than to make two flared connections.

Question 28

What should the length of a swage be?

Answer 28

Equal to the outside diameter of the tubing.

Question 29

What is a street fitting?

Answer 29

A street fitting is an angled fitting that is male on one end and female on the other.

Question 30

What is solvent welding?

Answer 30

Solvent welding is the joining of two components of the same material using a solvent that temporarily dissolves the surface polymers at room temperature, allowing the polymer chains to become entangled

Question 31

Why is soft ACR tubing considered soft?

Answer 31

Because it has been annealed

Question 32

What is the recommended flow rate to use for nitrogen when brazing ACR tubing?

Why is it important?

Answer 32

1 to 2 psi.

This prevent oxygen from contaminating the weld and weakening its strength.

Question 33

What is the maximum temperature Oxy/Acetylene is able to heat to?

Answer 33

6000F.

Question 34

What is the procedure for brazing a joint?

Answer 34

Before starting, ensure all refrigerant has been recovered from the system. All air should be purged, and nitrogen should be flowing to prevent oxygen introduction into the joint. Also ensure all sensitive components are protected from heat, including Schrader cores.
1. Ream or deburr the inside of the tubing. Ensure no metal shavings fall into the tubing
2. The parts to be brazed must be carefully cleaned and accurately fitted. Use a stainless steel wire brush or fine-grade sand cloth to clean the exterior of the tubing from the end to just beyond the point where the edge of the fitting will be. Do not use emery cloth, as any of its grit that accidentally enters the system can cause damage.
3. Clean the internal surfaces of the tubing and the fitting with an abrasive, such as a stainless steel wire brush or stainless steel wool rolled on a rod.
4. Degrease the parts and clean the joints thoroughly.
5. Apply the flux recommended for the brazing alloy. Generally it is best to apply a thin but thorough coating of flux. This should cover from the end of the tubing to just beyond where the edge of the fitting will be.
- Assemble the torch set, and verify all connections are leak free.
- Set the pressures for your torch, use a chart to determine the most accurate setting. Standard is 7 for acetylene and 11 for oxygen. Light the torch and achieve a neutral flame
6. Fit the joints closely and support them securely so they will not move during brazing.
7. Heat the tubing first. Keep the torch moving constantly in a figure eight motion, never hold the flame in one spot. It should be moved around the entire brazing area. Using a torch tip that is larger than the tip used for soldering allows a soft flame and a large quantity of heat without excessive pressure. A good feather on the inner cone of the flame is good. Keep the joint surrounded by the flame during the entire operation, with the tip of the flame’s inner cone just touching the surface of the metal. This heats the metal efficiently and prevents air from getting to the joint.
8. Flux behavior is a good indication of the temperature of the joint as the heating progresses. At 212F the flux will turn somewhat puffy and white. At 600, it will bubble and turn white. At 800F the flux lies flat on the surface and has a milky appearance. At 1,100F It will turn into a clear liquid and be just short of brazing temperature. During the brazing of a copper base metal, the flame starts to show a green shade as the brazing temperature is reached.
9. Apply the filler rod to the seam between the tubing and fitting at approximately a 30 to 45 angle. Pushing the rod at this angle helps draw the brazing material into the seam. Keep the flame away from the brazing material. If the filler rod does not melt quickly, withdraw the rod and continue heating the joint. If the filler rod melts, gradually move both the flame and brazing rod around the entire joint, with the rod following the flame.
10. Stop feeding brazing material and remove the flame from the joint when there is an unbroken circle of brazing material around the joint.
11. Allow the finished joint to cool naturally. Shock cooling with water may stress or crack the joint.
12. Clean the joint thoroughly using warm water and a brush. be sure all flux has been removed. Flux left on the metals may corrode them or temporarily stop a leak that will only show up later.
13. Visually inspect the brazed joint to see if there are any places where the alloy did not adhere. It is better to watch for poor adhesion (dark cup shaped areas) as you braze the joint. Then, any corrections can be made during the brazing operation, while the parts are still hot.

Question 35

What is the procedure for creating a good soldered joint?

Answer 35

1. Ensure the tubing and fittings being connected are dry, and clean of contaminants or oil.
2. Ream or deburr the inside of the tubing while making sure no pieces enter the tubing.
3. Clean the exterior of the tubing that will be soldered with emery cloth, and abrasive pad, or a wire brush. Repeat the same process for the inside of the fittings with a round wire brush.
4. Apply flux to the completely cover the outside of the tubing where the parts will be in contact. The coating should extend slightly past where the fittings connect, and should be thin but thorough.
5. Assemble the tubing and fitting together, and remove any excess flux with a clean, dry cloth.
6. Heat the tubing and fitting by directing the torch flame at the tubing, two to three inches back from the fitting. The inner cone of the flame should be touching the tubing. Ensure all sides are heated evenly. Heat the pipe from the bottom, as the heat will rise and transfer to the rest of the pipe much faster. The joint between the fitting and the tubing should be heated last.
7. Once the flux has melted and boiled away, and the copper has a slightly dull appearance, redirect the flame to the center of the fitting, away from the joint. If the solder does not quickly melt, withdraw it and start the process over. Feed the solder around the circumference of the joint to completely fill the joint. Capillary action should draw the solder in to the joint. The solder joint is completely filled when a ring of solder is visible all around the tubing where it enters the fitting.
8. Shut off the torch and wait a couple of minutes before wiping the joint with flux then a damp rag.

Question 36

What is the procedure for flaring a copper joint?

Answer 36

1. Make the end of the tubing straight and square, de-bur the inside of the pipe.
2. Place the flare nut on the tubing with the open threaded end facing toward the end of the tubing where the flare will be made.
3. Insert the tubing into the flaring block so that the flaring end extends above the surface of the block approximately 1/16” or to manufacturer specifications.
4. Tighten the flaring block’s clamp so the tubing cannot move.
5. Put a drop of refrigerant oil on the flaring cone where it will contact the tubing.
6. Mount the yoke onto the flaring block.
7. Turn the flare handle clockwise to tighten the flaring cone against the tubing end one-half turn and back it off one-quarter turn.
8. Advance the flaring cone by turning the flare handle clockwise three-quarters of a turn and again backing it off one-quarter turn.
9. Repeat the forward and backward pattern until the flare is fully formed. Do not tighten the flare handle too much. This would thin the wall of the tubing at the flare and weaken it.
10. Back off the flaring cone by turning the flare handle counterclockwise.
11. Remove the yoke from the block, and open the block.
12. Seal the fitting with a drop of nylog on the seat and the threads