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.