310101c Tube Bending and Tube Joining

Objectives

• Identify the different types and sizes of tube and tube fittings.

• Identify common tools and techniques used in tube joining.

• Identify common tools and techniques used in tube bending.

• Calculate tube bending lengths for various tube configurations and angles.

• Identify hazards associated with tube fitting selection and installation.

Definition and Uses of Tubing

• A tube, or tubing, is a long hollow cylinder used for:

  • Moving fluids (liquids or gases).

  • Protecting electrical or optical cables and wires.

  • Serving as construction material.

• Common tube types:

  1. Mechanical tube

  2. Pressure tube

  3. General purpose tube

Mechanical Tube

• Comes in many shapes and sizes.

• Does not support any internal process pressures.

• Primarily used for construction and protection purposes.

Pressure Tube

• Usage:

  • Carries process fluids and gases.

  • Connects measuring instruments (termed as impulse lines).

• Common materials:

  1. Copper

  2. Steel

  3. Thermoplastic

Copper Tube Standards

• Applications: Used mainly for plumbing and HVAC systems.

• ASTM (American Society of Testing Materials) specifies that copper tubes be manufactured to 99% purity.

• Types of copper tube (by lettering and color):

  • Type K (Green)

  • Type L (Blue)

  • Type M (Red)

  • DWV (Yellow)

  • ACR (Blue)

  • OXY/MED (Green for K, Blue for L). Different types serve various applications.

Tube Sizes and Specifications (Table 1)

• Type K: Domestic water service, fire protection.

• Type L: Similar uses as Type K with slightly different applications.

• Type M: Light duty applications.

• Each type has specified nominal lengths and sizes.

Tube Sizing

• Size is determined by the outside diameter (OD).

• Temper:

  • Drawn temper = hard or rigid.

  • Annealed temper = soft and flexible, achieved via slow cooling or heating.

Tube Fittings

1. Flare fittings:

   • Consists of a nut, sleeve, and body with a flared end.

   • Requires a flaring tool for preparation.

2. Flareless fittings:

   • Contains a ferrule that bites into the tubing to create a seal.

   • Susceptible to leaks over time.

3. Mechanical grip fittings:

   • Two ferrule design; the back ferrule grips the tubing and the front ferrule creates an additional seal.

4. Push-in fittings:

   • Utilizes an O-ring to grip and seal the tubing.

Tightening Tube Fittings

• Hand-tighten the fitting nut before turning it an additional 1 ¼ turn (up to 1” fitting).

• Ensure proper torque and tubing positioning using a gap gauge (NO GO Gauge).

Solder and Soldering Techniques

• Solder is a metal alloy that joins metallic surfaces by melting.

• Melting point typically ranges between 90 to 450 °C; above that is termed brazing.

• Tin/lead solders (soft solders) have tin concentrations affecting solder strength.

  • Common alloys: 50/50 and 60/40 Tin/lead.

• Soldering equipment includes a small propane torch and soldering alloy.

Flux in Soldering

• Flux acts as a cleaning agent, removing oxidation that occurs during heating.

• It enables solder to bond effectively to metals by preventing oxidation from reforming.

Producing a Good Solder Joint (Six Steps)

1. Cut tube to desired length & deburr.

2. Clean tube ends and apply flux.

3. Clean fittings and apply flux.

4. Assemble and support components.

5. Heat uniformly and solder.

6. Allow to cool slowly; remove excess flux and test.

Capillary Action

• Capillary action is the liquid's ability to rise in narrow spaces

  • Driven by intermolecular forces between liquids and solids.

  • Works against gravity due to surface tension and adhesion forces.