TECHNICIAN DEVELOPMENT PROGRAM

Instrument Technician JOB GRADE A

MAINTENANCE TRAINING MANUAL

KNOWLEDGE MODULE

I-A-KM-04_Module 4_Instrument Fitting Skills

Student Version
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Instrument Technician
Instrument Fitting Skills Module JG A

Module 4: Instrument Fitting Skills

Table of Contents
Introduction............................................................................................................ 3
Terminal Objective .................................................................................................. 3
1.0 Cables.....................................................................................................4
1.1 Lesson Objective .......................................................................................... 4
1.2 Introduction ................................................................................................. 4
1.3 Components................................................................................................. 4
1.4 Sizes ........................................................................................................... 5
1.5 Wire Ratings ................................................................................................ 6
1.6 Terminations ................................................................................................ 6
1.7 Summary ....................................................................................................10
1.8 Knowledge Reinforcement and Self Check......................................................11
2.0 Methods of Running Cable ...................................................................13
2.1 Lesson Objective .........................................................................................13
2.2 Introduction ................................................................................................13
2.3 Conduit.......................................................................................................13
2.4 Cable Trays.................................................................................................16
2.5 Summary ....................................................................................................17
2.6 Knowledge Reinforcement and Self Check......................................................18
3.0 Tubing ..................................................................................................21
3.1 Lesson Objective .........................................................................................21
3.2 Introduction ................................................................................................21
3.3 Layout ........................................................................................................21
3.4 Construction................................................................................................22
3.5 Summary ....................................................................................................32
3.6 Knowledge Reinforcement and Self Check......................................................33
4.0 Task Details: Select and Install Proper Fittings and Bend Tubing ........35
4.1 Lesson Objective .........................................................................................35
4.2 Safety and Environmental.............................................................................35
4.3 Reference Material.......................................................................................35
4.4 Tools and Materials......................................................................................36
4.5 Select and Install Proper Fittings and Bend Instrument Tubing Procedure.........36

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4.6 Related Tasks..............................................................................................37

4.7 Knowledge Reinforcement and Self Check......................................................38
5.0 Document Revision History ..................................................................40

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Introduction
Cabling and tubing systems are used extensively in plants as they perform vital functions.
Cabling carries:
o AC/DC power
o Signals to and from instrument loops
Tubing carries:
o Process fluids, steam, water, and hydraulic fluids
o Pneumatic control signals, lubricating oil, and compressed air
o Connects instruments to process piping
The words piping and tubing are sometimes used interchangeably. However, they are not
the same. Tubing is normally more flexible than pipe and has thinner walls. The diameter
of tubing is measured on the outside (OD), while the diameter of pipe is measured on the
inside (ID). As an Instrument Technician, you will identify the type of tubing needed for
an installation, and you will install tubing.

Terminal Objective

Given: Knowledge module, maintenance procedures and policies,

vendor manuals, and associated equipment drawings;
You will be able to: Recognize and describe various cables and fittings for
instruments;
Standard: With 85% pass in a knowledge assessment.

Enabling Objectives
Using the documentation listed in the terminal objective, you will be able to:
Identify and describe instrument cable types and terminating connectors.
Describe the types of termination for different applications.
Describe how to select the correct cable and crimping tool and explain their use.
Describe different methods of running cable.
Describe cable glands.
Describe the fitting components of tubing.
Describe how to select and bend tubing using the standard tube bender.
Describe the steps required to complete the task of selecting and installing proper
fittings, and bend instrument tubing.

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1.0 Cables
1.1 Lesson Objective
After completing this lesson, you will be able to:
Identify and describe instrument cable types and terminating connectors.
Describe types of terminations for different applications.
Describe how to select the correct cable and crimping tool and explain their use.

1.2 Introduction
It is important that you are able to identify the common types of Low Voltage cables that
carry the AC/DC power and signals in the instrumentation loops. It is also important that
you can identify the methods of termination for these cable types.
Instrumentation control wiring links the field sensing, controlling, and operating devices
that form an electronic instrumentation control system. The type and size of
instrumentation control wiring must be matched to a specific job. Multi-conductor cables
may be grouped in pairs with as many as 50 or more pairs.

1.3 Components
Instrumentation control wiring is available with one conductor or it may have multiple
conductors. These wires may also have shielding or earthing conductors. An outer layer,
called the jacket, protects the conductors.

1.3.1 Shields
Shields are provided on instrumentation control wiring to protect the electrical signals
travelling through the conductors from external electrical interference. Electrical
interference is also called electrical noise. Electrical noise may come from other electrical
equipment operating in the same area. Shields are usually made of aluminium foil bonded
to a plastic film.
If the wiring is not properly shielded, electrical noise may cause inaccurate control
signals, false indication, and improper operation of control devices.

1.3.2 Earthing
An earthing wire may be bare wire or insulated wire used to provide continuous contact
with a specified earthing terminal. Usually, insulated grounding wires are colour coded.
An earthing wire allows connections of all the instruments within a loop to a common
earthing system. Not all instrumentation systems are earthed. Always refer to the
installation details to determine whether an earthing wire is to be terminated to an
earthing terminal.
In most instrumentation systems, the earth wire is not connected on both ends of the
wire. This helps prevent unwanted earth loops in the system. If the earth is not to be
connected at one end of the wire being installed, do not remove the earthing wire. Fold
the wire back and tape to the cable. This is done in case the earth at the other end
develops a problem.

1.3.3 Jackets
A synthetic plastic jacket covers and insulates the components within the instrumentation
control wiring. Polyethylene and PVC are the most common materials used for wiring
jackets. Some jackets have a ripcord that allows the jacket to be peeled back without the
use of a knife or cable cutter. This reduces the possibility of nicking the conductor
insulation when preparing for termination.

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1.4 Sizes
Wire sizes are expressed in mm2. This system uses the square millimetres of the cross-
section of the wire to identify the different sizes of wire and cable.

Metric Wire Sizes

American Wire Gauge (AWG) Wire Sizes

The most common sizes of wire used for instrumentation control wiring and their typical
uses are listed below:
1 mm2 to 2 mm2 120 Volts AC supply
0.8 mm2 Low Voltage DC supply
0.5 mm2 to 0.8 mm2 Low Voltage DC signal
You need to know what size wire to use and the right wire rating for the job.

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1.5 Wire Ratings

An important step in design of electrical circuits is selection of the type of conductor to be
used. Letters labelled on the wire’s jacket tells how durable it is.
T Stands for thermoplastic type of insulation covering the wire.
H Stands for a heat resistance rating of 75°C.
HH Stands for a heat resistance rating of 90°C.
W Stands for moisture resistance.
N Stands for an additional nylon coating that makes the wire both oil and gasoline
resistant.
Some examples of wire ratings include THHN and THWN. THHN stands for thermoplastic
high heat-resistant nylon coated wire and THWN stands for thermoplastic heat and water
resistant nylon coated wire. Other common ratings include TW, THW, RHH, and XHHW.
THHN and THWN are built to handle many different conditions. Temperature is an
extremely important factor to consider in instrumentation control wiring. If ambient
temperature exceeds 30°C, the current load rating of the conductors must be reduced
accordingly. Whether you are using the National Electrical Code (NEC) or the
International Electrical Code (IEC) as your standard for determining your wire rating, be
sure to use the appropriate chart or table for the job.

1.6 Terminations
To make good wiring terminations you must follow a good procedure. Pay close attention
to detail and follow the manufactures’ recommendations. The correct match between
connectors and crimping tools is critical.

1.6.1 Crimp Connectors

Crimp connectors are compression-type connectors for connecting conductors to screw
terminals. Crimp connectors are used in low voltage circuits. Hand tools are used to
indent or crimp tube-like sleeves that hold one or more conductors.
Proper crimping action changes the size and shape of the connector and compresses the
conductor strands enough to provide good electrical conductivity.
Solid wires are often smaller than wires made up of many strands. Some crimp splice
caps require small solid wires be twisted together before being placed in the connector
and crimped. This will vary with the type of indentations your hand tool makes. The
manufacturer’s recommendations on the correct method of making the splice should be
followed.
In most crimp connectors, the crimp barrel receives the wire and it is crimped. The
crimping tool makes an indentation that looks like the letter V. The indention inside the
barrel improves the wire-to-terminal conductivity. The indentions also increase the
strength of the connection.
Most crimp connectors are also available with insulation, such as nylon or vinyl, covering
the barrel to reduce the possibility of shorting to adjacent terminals. The insulation is
colour-coded according to the connector’s wire range to reduce wire-to-connector
mismatch.

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The terminal “tongue” physically connects the wire to the termination point, such as a
terminal screw. The barrel is connected to the terminal tongue. Information about the
connector size and conductor range is usually stamped on the tongue by the
manufacturer. Tongue styles vary depending on termination requirements.
Standard connector styles are as follows:

Crimp Type Connectors

One disadvantage of crimp connectors is that special tools are required to make the joint.
The two main tools that are used to make a good connection between wire and
connector are stripping devices and crimping tools.

1.6.2 Cutting and Stripping Tools

For cutting cable and wire, scissor-action cutting tools are preferred. Cutting tools with
cutting jaws that butt against each other have a tendency to produce a flattened chisel
end of the wire. The problem becomes worse as the cutting edges become dull. This
chisel end of a wire end makes it difficult, or impossible, to insert the wire into the barrel
of a terminal. Scissor-action tools make a clean cut.
After cutting the wire, remove the cable jacket using strippers with an adjustable blade or
a die designed for particular size wires to avoid nicking or stretching the wire or wire
insulation in a multi-conductor cable.

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Combination Crimping and Stripping Tool

A few important points to observe anytime you are stripping wire:

Avoid nicking, cutting, or scraping the wire. This will affect the wires capabilities to
transmit the voltage needed.
Cut the insulation so that no frayed pieces or threads extend past the point of cut-off.
Frayed pieces or threads of insulation indicate that the wrong tool was used or the
tool had dull cutter blades.
Strip the wire to the proper length required for the terminals being used. The
manufacturer will recommend a stripping length.
o Stripping the wire too far will interfere with the terminal screw.
o Stripping the wire too short will reduce the contact surface area.
If possible, do not twist, spread, or disturb the wire strands from their normal position
in the cable. Twisting or tightening the twist of the strands will eventually result in
wire damage.
Terminate stripped wire as soon as possible. The exposed strands can quickly become
bent and spread. This makes termination difficult.

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Good and Bad Crimped Connections

1.6.3 Crimping Tools

With a compression-type wire connector, an electrical connection between a wire and a

terminal is made by tightly compressing the crimp barrel with an ordinary pair of pliers.
However, a connection made this way would not be compressed to the required pressure
or in the correct location to ensure a good connection.

A simple plier-type crimping tool is the most common type used by instrument
technicians. These tools are similar in construction to ordinary mechanics pliers except
the jaws are specially shaped and the handles are longer, as shown below.

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Crimping Tool

1.7 Summary
In this lesson, you learned to identify and describe instrument cable types. You learned
about wire shields, earthing, and jackets. You also learned about wire size and rating.
Next, you learned about terminating connectors with an emphasis on crimp connectors.
Finally, you learned about the tools you will use.

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1.8 Knowledge Reinforcement and Self Check

1. Why is it important to use shields on instrumentation cables?

Ans:
If the wiring is not shielded properly, electrical noise may cause inaccurate control
signals, false indication, and improper operation of control devices.
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 1.0

2. What is a disadvantage of using crimp connectors?

A. Crimp connectors are costly

B. Connection is not dependable
C. Special tools are required
D. Crimp connectors are difficult to use
Ans: C
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 1.0

3. What is the most common size of wire used for low voltage DC supply in
Instrumentation applications?

A. 2.0 mm2
B. 1.8 mm2
C. 1.0 mm2
D. 0.8 mm2
Ans: D
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 1.0

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4. What could happen if you twist stranded wire before terminating?

Ans:
If possible, do not twist, spread, or disturb the wire strands from their normal
position in the cable because it could result in wire damage.
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 1.0

5. What does THHN indicate on cables?

A. Thermoplastic high heat-resistant nylon coated

B. Thermoplastic high humidity-resistant nylon coated
C. Temperature heat humidity-resistant nylon coated
D. Temperature high heat-resistant nylon coated
Ans: A
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 1.0

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2.0 Methods of Running Cable

2.1 Lesson Objective
After completing this lesson, you will be able to:
Describe different methods of running cable.
Describe cable glands.

2.2 Introduction
A raceway system is the path cables and wiring take throughout the plant. The primary
function of a raceway system is to provide a path for the installation of electrical
conductors used in instrumentation applications. It also provides a level of protection for
the conductors.
The selection of the proper raceway components depends on many factors, including:
Classification of the area in which the raceway is to be installed
Conductor application (power or control)
Voltage or current levels of the conductors
Physical and environmental exposure
Based on these and other factors, the selection of a raceway system may be made from a
variety of systems. These include conduit, cable tray, or a combination of these systems.

2.3 Conduit
Conduit, as applied in the instrumentation trade, is typically used to provide a conductor
carrier system. Conduit also provides protection for electrical conductors that transmit
both signal and power to and from electrical or electronic instrumentation devices in the
field and control room environments.
The type of conduit that you will most likely see is rigid metal conduit (RMC). Rigid metal
conduit has walls thick enough to allow the cutting of threads for connection. RMC
provides the best physical protection for conductors.
Aluminium rigid conduit is an alternative raceway in some corrosive environments;
however, it does not offer the level of physical protection that RMC provides. Whenever
joining aluminium conduit to fittings, an anti-oxidizing compound should be applied to the
aluminium threads. This compound guards against oxidation and seizing of the two parts
caused by the forming of oxidation. It also helps maintain an earthing path through the
connection.
In order for a conduit raceway system to maintain its physical protection properties, the
properties of the fittings installed must match the conduit properties. In addition to
couplings, conduit bodies are used extensively in the installation of RMC systems.

2.3.1 Conduit Bodies

Conduit bodies are components of a conduit system that provide access to the wiring
through a removable cover. Conduit bodies should never contain splices, taps, or devices
unless they comply with plant specific rules.
Type C conduit bodies as shown below may be used to provide a pull point in a long
conduit run or a conduit run that has numerous bends in it.

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C Type Conduit Fitting

The letter L represents elbow. A Type L conduit body is used as a pulling point for
conduit that requires a 90° change in direction. There are configurations with removable
covers located on the back (Type LB), or on the sides (Type LL or LR).

LL, LB, and LR Type Conduit Fittings

A Type T conduit body is used to provide a junction point for three intersecting conduits.
There are configurations with removable covers on the back (Type TB), or on the side
(Type T).

TB, T, and X Type Conduit Fittings

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2.3.2 Bushings
An insulating bushing is made of non-metal material or has an insulated insert. Insulating
bushings are installed on the threaded end of conduit. The purpose is to protect the
conductors from being damaged by the sharp edges of the threaded conduit end.

Insulating Bushing

2.3.3 Cable Gland Bushings

Cables terminate in a number of different locations. It is always important to protect both
the cable entering a device and the device itself from the environment. The primary way
to provide this protection is with cable glands. The primary purpose of a cable gland is:
Mechanical rigidity of the cable entering a device
Continuity of the protective conductor system such as conduit or a cable tray
A seal to the devices being used

Cable Glands

Cable glands are available in materials and design to suit any environment, size, or
variety of cable. There are many types of cable glands. Choose the correct type and size
to fit the job. Failure to do so could result in an unsafe condition.

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It is important to make sure that there is enough room outside of the terminated devices
to assemble the gland over the cable correctly. Also, make sure that there is enough
room inside the device to correctly terminate the cables, without causing damage to
either the device or the cables.

Cable Gland Example

2.4 Cable Trays

Cable trays are rigid structures used to support wire and cable. Most cable trays are
either metal or fibreglass. Cable trays have fittings to provide a means of changing
direction or dimension of the different types of cable trays. Some of the different types of
fittings are:
Straight run
Inside vertical bent
Outside vertical bend
Left hand reducer
Horizontal tee
Horizontal cross
Horizontal bend
The following picture shows the application of these types of fittings. There are many
combinations of fittings that can be used to route cable to the needed locations.

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Cable Tray Fittings

2.5 Summary
In this lesson, you learned about running cable. You learned that cable could be run
through conduit, and cable trays. You learned about conduit bodies, bushings, and cable
gland bushings. In the next lesson, you will learn about tubing.

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2.6 Knowledge Reinforcement and Self Check

1. Why is conduit used for running cable used in instrumentation?

Ans:
Conduit, as applied in the instrumentation trade, is typically used to provide a
conductor carrier system. Conduit also provides protection for electrical conductors
that transmit both signal and power to and from electrical or electronic
instrumentation devices in the field and control room environments.
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 2.0

2. What is the primary purpose of cable glands?

Ans:
The primary purpose of a cable gland is:
o Mechanical rigidity of the cable entering a device
o Continuity of the protective conductor system (conduit, cable tray)
o A seal to the devices being used
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 2.0

3. Most cable trays are made of what materials?

A. Rubber or wood
B. Plastic or rubber
C. Metal or fibreglass
D. Wood or plastic
Ans: C
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 2.0

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4. What are three common types of conduit fitting?

A. T, L, C
B. W, D, P
C. A, V, Q
D. H, M, G
Ans: A
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 2.0

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5. Match the conduit fittings with the correct type below:

Answer Symbol
Letter

Answer
Description
Number
E LB
F LL
B T
G C
D LR
A X
C TB

Ref: I-A-KM-04_Instrument Fitting Skills Lesson 2.0

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3.0 Tubing
3.1 Lesson Objective
After completing this lesson, you will be able to:
Describe the fitting components of tubing.
Describe how to select and bend tubing using the standard tube bender.

3.2 Introduction
The words piping and tubing are sometimes used interchangeably. However, they are not
the same. Tubing is normally more flexible than piping and has thinner walls. The
diameter of tubing is measured on the outside (OD), while the diameter of pipe is
measured on the inside (ID). As an Instrument Technician, you will identify the type of
tubing needed for an installation and you will install tubing. The three major tasks are:
Layout
Construction
Installation
This lesson will provide you with the steps that are required for layout and construction.
Tubing installation is beyond the scope of your current technician level.

3.3 Layout
The first step in the construction of any tubing job is the layout. You must consider many
potential obstructions to make sure that the system is built properly. Maintenance and
operation should be your primary concern when deciding the route of a tubing system.
A visual observation of the system is the most important element when planning this type
of job. This walk-through will reveal any possible problems that may hinder the
installation of the tubing. The main things to look for are:
Obstructions
Preferred routing
Proximity to hazardous elements
Bends and connections
Venting and draining requirements

3.3.1 Obstructions
During a walk-through prior to constructing tubing system note should be taken
regarding the entire length of the system. Items to consider are other pipes or tubing,
valves, structural beams, stationary and rotating equipment.

3.3.2 Preferred Routing

Tubing systems should always be laid out so that they do not affect future expansion or
maintenance. Stairs, platforms, ladders, aisles, and minimum headroom allowances
should always be considered.
When considering routing, another primary concern should be the type of connections
that will be provided for the system. You should select fittings that will provide ease of
maintenance such as repair and replacement of parts, as well as choosing the correct
fittings based on ratings for the type of service that the system would be used in.

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Tubing should also be installed in a way that does not interfere with the maintenance and
disassembly of any adjacent equipment. Tubing congestion around pumps and other
equipment that require frequent maintenance should be avoided. Tubing should not be
run above pumps when possible, as this will interfere with the removal of the pump for
maintenance.

3.3.3 Proximity to Hazardous Elements

The environment surrounding a tubing run is yet another important consideration. If the
surrounding systems carry a fluid that is corrosive or harmful to the materials of the
tubing system that is being designed, consideration needs to be made to limit the hazard
from potential leakage.
Many instrument field devices such as pressure devices, level devices, and others must
often be vented to the atmosphere or blown down into the surrounding environment to
field calibrate or maintain them. During the walk-through, be sure that you are not
designing a system that will endanger others later when maintenance is required.

3.3.4 Bends and Connections

Whenever a piece of tubing is bent, it may be weakened. At the bend itself, the inside
wall is thickened and the outside wall is thinned. Connections also weaken a tubing run,
increase cost, and lengthen construction time. The tubing must be cut and connectors
must be used to continue the run. If a system must be routed with any angles, bends are
preferred over fittings. The time and cost incurred by a bend is cheaper than with a
fitting. Bends also reduce the possibility of leaks through the mechanical failure of a
fitting.
When bending tubing you should always remember there are limitations on tubing and by
not exceeding these limitation you will have less of a chance of damaging the tubing.
This limitation is called the ideal bend radius. For a guide remember that this radius is
defined as a bend with a radius that is two and a half times the outside diameter of the
tubing.
When fittings are necessary, minimize the use of reducing unions, bushings, or union
elbows. These fittings should only be used when called for in the design of the system
but never used only to make the tubing fit into a constricted area.

3.3.5 Venting and Drainage Requirements

In tubing systems, air or vapour tends to collect in high spots and liquids collect in low
spots. In order to avoid the maintenance problems involved with trapped fluids, vent lines
are installed on high spots and drain lines are installed on low spots. Careful attention
should be taken so that none of these traps are overlooked. To minimize the number of
vent and drain lines required, the tubing should be sloped. The amount of slope depends
on the system requirements.
All of these items should be reviewed and considered before the construction of any
tubing system. In the next section, you will learn about the steps needed to properly
construct a tubing system.

3.4 Construction
This section will show you how to properly construct a tubing system. Any tubing system
construction job has four major parts:
Proper size, type and fitting selection
Measuring and bending
Cutting
Installing fittings

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3.4.1 Proper Size and Type

It is important to use the proper size and type of tubing for specific applications. The
engineering specifications, piping specifications, installation detail drawings, and other
information for a project usually tell you what size and type of tubing to use. However,
you must be able to identify and verify the size and type of the tubing once you know the
requirements. Tubing is selected for specific applications according to a number of
different factors, such as pressure and temperature conditions, corrosiveness of the
environment, vibration in the system, system flow requirements, and compatibility with
the process fluids.

General Sizing
Tubing is generally sized according to its outside diameter (OD) and wall thickness. The
common way to identify tubing size is by a metric designation of diameter nominal (DN).
Although the sizes are not exact, common tubing sizes are 1/4 inch, 3/8 inch and 1/2
inch. Whenever you start a tubing job, it is important to make sure that you have the
right material.

Tubing Types
Tubing is made from a wide variety of materials including different types of metals and
plastics. Each material has certain characteristics that make is a better choice for a
specific job.
Plastic tubing is less expensive than metal tubing, easier to install, and easier to bend and
reshape. However, it has limitations regarding its strength, compatibility to certain
process fluids, and ability to withstand certain temperatures and pressures.
Metal tubing comes in two types, welded and seamless. Welded tubing is made by rolling
flat strips of metal and then forming the metal into a tube. The seam is then welded.
While the welded seam may not be visible on the outside of the tubing, it can usually be
seen on the inside. Seamless metal tubing is made by extruding.

Copper Tubing
Copper is one of the most widely used metals for making tubing. Copper is easily
identified by its colour when new. Copper is often used in instrumentation pneumatic
systems because it resists rust that could contaminate the air running through the tubing.
It is lighter and easier to use than stainless steel and it can be easily bent to form bends.
Copper tubing holds up well in most environments and is strong enough to handle loads
that would rupture plastic tubing. It is usually used in systems where the temperature
and pressure conditions are not extreme. The primary disadvantages are that copper
tubing can be more expensive than other types and it may not be suitable for systems
that are extremely corrosive.

Stainless Steel Tubing

Stainless steel is a steel alloy that is stiffer and stronger than copper tubing. It is used to
handle many types of corrosive fluids. It performs well in high-pressure and high
temperature applications.
Even though stainless steel tubing is more expensive than some other tubing materials, it
is used quite a bit in instrumentation installations due to its resistance to corrosion, high-
pressure failure, and high temperature failure.

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3.4.2 Tubing Connection Fittings

Tubing is connected to other components with tubing fittings to make a tubing system.
Tubing fittings are used to connect tubing-to-tubing, tubing to piping, tubing to a valve,
or tubing to a bulkhead. The sizes and types of fittings to be used for a job are usually
decided by engineering specifications or installation details. Most fittings are sized by the
outside diameter of the tubing to be used.
Fittings should be chosen to match the application for which they are being installed.
Pressure, temperature, and process characteristics must be considered when selecting
tubing fittings. You should never connect tubing of one material to a fitting of a different
material, except in the case of plastic tubing.
The most common type of tubing fittings used in instrument work are compression
fittings.

Compression Fittings
Compression fittings are reliable and easy to install. Compression fittings can usually be
disconnected and reconnected without damaging the tubing or fitting. Compression
fittings come in a variety of designs, sizes, and materials to fit different tubing jobs.
When using compression fittings, the end of the tubing is not flared. The tubing is fitted
with a compression ring, or ferrule, that pinches the tubing as the nut is tightened on the
body of the fitting. Compression fittings can have one or two ferrules for each joint. The
ferrule of the fitting must be harder than the tubing to allow the swaging effect to take
place. The picture below shows the parts of a compression fitting.

Compression Fitting

Compression fittings can be used for connections on plastic tubing. Fittings used for
plastic tubing may differ slightly in design from those used on metal tubing. The fittings
may have nylon ferrules rather than metal ferrules to prevent damage to the tubing as
the ferrule is compressed. Most compression fittings used for plastic tubing have a tube
support insert as shown below.

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Poly Tube Support Insert

3.4.3 Types of Tubing Fittings

There are numerous types of fittings used to change direction of tubing runs and provide
branch connections. There are also fittings to connect tubing-to-tubing, tubing to piping,
and tubing to instruments.

Male and Female Fittings

The term male fitting refers to fittings that have outside threads, which connect tubing to
a component with a female, or internal, thread.
The term female fitting refers to fittings that have internal threads, which connect tubing
to a component with male, or outside, threads.

Male and Female Fittings

Tee Fittings
Tee fittings are a commonly used type of branch fitting. They are available in a variety of
designs and sizes. All tee fittings are designed to branch tubing at a 90° angle.

Tee Fitting

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Elbow Fittings
Elbow fittings are curved fittings that connect tubing-to-tubing or piping to tubing at
different angles. An elbow fitting is commonly referred to as an ell. The most common
angles are 45° and 90°.

Elbow Fitting

Union Fittings
Union fittings connect two pieces of tubing or tubing and piping without branching off.
Unions can be connected and disconnected without disturbing the position of the tubing.

Union Fitting

Cross Fittings
Cross fittings have two branch outlets, providing four outlets that are spaced 90° from
each other. Cross fittings come in a variety of sizes and designs. They may have all equal
sized outlets or they may have different sizes to accommodate the connecting of smaller
or larger sized tubing in a system.

Cross Fitting

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Reducer Fittings
Reducer fittings are designed to change a run of tubing to a larger or smaller size. This is
usually done to increase flow pressure or to reduce the volume of flow in a tubing
system. A reducer may be a separate fitting or may be built-in part of another fitting like
a tee, cross, adapter, or connector.

Reducer Fitting and Reducer Fitting in an Elbow Fitting

3.4.4 Measuring and Bending

Tubing usually comes in straight lengths. Tubing must be bent to fit into the raceway
scheme. Accurate measurement and bending of the tubing will ensure that the tubing is
in the shape and size needed.
You may pre-measure a set of bends needed for a system to make sure that you have
enough material to do the job. As you begin to make the bends, always measure again.
Measuring the distances after each bend will always produce a higher level of accuracy. A
method to remember is:
1. Measure
2. Bend
3. Measure
4. Bend
A good run of tubing will eliminate as many connections as possible.

Measuring
The centreline of the tube should be the basis for all tube measurements. Always
measure from the centreline of the tubing, except for the first bend. The first bend is
measured from the end of the tube. On most benders, the edge of the radius block is at
the centreline of the tube

Tubing Centreline

When measuring, do not use the end of the measuring tape as a starting point. The end
of a measuring tape tends to be damaged over time and can lead to measurement
inaccuracies. Start at the one inch mark to make sure you have an accurate
measurement and subtract one inch from the total accordingly.

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Hand Bending
In order to make sure you accurately bend tubing, following this checklist will help you
get good results from each bend.
1. Measure and mark exactly. Make sure that the bend mark goes all the way around
the tubing.
2. Always try to bend in the same direction.
3. When bending tubing the distance around a curved bend is always less than a sharp
bend such as a 90°. Remember that tubing gain always occurs to the right side of
the bender die.

Swagelok Tubing Bender

4. Swing the short handle up so it is above the bender die.

5. Open the tube latch.
6. Place the tube in the groove of the bender die.
7. Close the tube latch over the tube just enough to hold the tube in place.
8. Carefully lower, the short handle until the roll dies rest gently on the tube while
keeping the link straight and parallel to the long handle.

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Back of Bender

9. Align the zero on the roll support with the zero on the bender die.

Aligning Tubing in Bender

10. Align the bend mark with the mark on the roll support that corresponds to the bend
angle.
11. Push the tub latch securely into place.
12. Slowly push the short handle down until the 0 on the roll support reaches the
desired degree on the bender die, taking spring back into consideration.
13. After completing the bend, swing the short handle up and away from the tube.
14. Pull the tube latch off the tube and remove the tube from the bender die.

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15. Double check bend angle with triangle or level.

16. Check measurement length with tape or ruler.

Spring Back
All tubing will exhibit spring back after a bend has been completed. The amount of spring
back depends on the bend angle, bend radius, tubing material, and wall thickness.
Experience will help you predict the amount of spring back. Usually you can expect 1° to
3° of spring back.

Bench Bending
There are several types and sizes of table or bench mounted tubing benders that are
used to bend tubing of medium and heavy wall thicknesses. These benders are often
used for tubing that is ¾ inch or larger. They are also used when a large number of
bends are being made. Most table and bench mounted benders work similarly to a hand
bender.

3.4.5 Cutting
When you cut tubing, you must leave a clean edge. If the edge has burrs, it must be
cleaned. Using a sharp cutting blade that is not damaged will minimize deburring
required. Always maintain tools properly to prevent damage from occurring to tubing
while cutting.
There are many ways that tubing can be cut, but the primary ways are by the use of a:
Tubing cutter
Hacksaw

Tubing Cutter
The tubing cutter method is used for thin walled metal tubing that is made of copper,
brass, aluminium, or steel. Tubing cutters come in several sizes. Some models have
rollers that are tightened to force the tubing against the cutting wheel. Other models
have a sliding cutting wheel that is forced against the tubing.

Tubing Cutter

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The process for using this tool is the same if you are cutting very small tubing or very
large tubing as long as it fits in the cutter.
1. Open the tubing cutter and place the tubing on the rollers.
2. Tighten the handle until the tube cutting wheels come in contact with the tube.
3. Rotate the cutter around the tube while maintaining a continuous light force of the
cutting wheel on the tube by rotating the handle about a quarter turn each
revolution.
4. Repeat until the tube is cut through.
5. DE burr the tubing using the appropriate tool.
Always use a tubing reamer to clean burrs from tubing. The tubing reamer is small
enough to be carried in your pocket.

Tubing Reamer

Hacksaw
There are times when using a tubing cutter is not practical. In that situation, you should
use a hacksaw. When using a hacksaw to cut tubing, use a guide to assure that your cuts
are perpendicular to the tube.
To minimize residual burrs, a hacksaw blade of at least 24 teeth per 25mm is needed.
Hacksaw blades are labelled with how many teeth per inch the blade has.

Hacksaw Blades

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3.5 Summary
In this lesson, you learned many of the principles of tubing. Even though you will not be
laying out or installing tubing at this technician level, you need a basic understanding of
how tubing is installed.
The first step in the construction of any tubing job is the layout.
As you are planning layouts, you must consider obstructions, preferred routing, proximity
to hazardous elements, bends and connections, and venting and draining requirements.
Every tubing system construction job consists of selecting the proper size and type of
tubing as well as fitting selection. Next, in order for the installation to be successful you
must correctly measure, cut, and bend the tubing. You can use a tubing cutter or a
hacksaw to cut the tubing then use the tubing reamer to clean the burrs from the cut.
These principles will help you understand the principles used in tubing lay

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3.6 Knowledge Reinforcement and Self Check

1. Why is tubing used in most instrumentation jobs?

Ans:
Tubing is normally considered more flexible than piping and has thinner walls. Since
tubing is not as hard as piping, it is easier to bend.
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 3.0

2. For a hacksaw blade that will be used for cutting tubing, how many teeth should the
blade have per 25mm?

A. 6
B. 12
C. 18
D. 24
Ans: D
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 3.0

3. Why should you avoid using the end of the measuring tape as a starting point when
measuring tubing?

Ans:
When measuring, do not use the end of the measuring tape as a starting point. The
end of a measuring tape tends to be damaged over time and can lead to
measurement inaccuracies. Start at the one inch mark to make sure you have an
accurate measurement and subtract one inch accordingly.
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 3.0

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4. What method should be used to ensure accuracy when constructing tubing runs?

A. Measure, bend, measure, bend

B. Measure, cut, measure, cut
C. Measure, bend, cut, measure, bend, cut
D. Bend, cut, bend, cut
Ans: A
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 3.0

5. Which of the following is a preferred tool to use for cutting tubing?

A. Knife
B. Band saw
C. Tubing cutter
D. Cutting torch
Ans: C
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 3.0

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4.0 Task Details: Select and Install Proper Fittings and Bend
Tubing
4.1 Lesson Objective
After completing this task detail, you will be able to describe the steps required to
complete the task of selecting and installing proper fittings, and bend instrument tubing.

4.2 Safety and Environmental

1. Never operate equipment outside of design or environmental limits.
2. Always move to a safe, controlled condition, and seek assistance when a situation is
not understood.
3. Always operate with safety devices in service.
4. Always follow all approved work practices and procedures and act to stop unsafe
conditions and actions.
5. Always produce a product that meets or exceeds your customers’ requirements.
6. Never contaminate or compromise a dedicated system.
7. Always report environmental and safety compliance information accurately and on
time.
8. Always address abnormal conditions and clarify and understand procedures before
proceeding.
9. Always follow written procedures for high risk or unusual situations.
10. Always involve people with expertise and first-hand knowledge in decisions,
improvements, and changes.

4.3 Reference Material

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4.4 Tools and Materials

Tape measure
Permanent marker
Tubing benders
Tubing cutters
Tube deburring tool
Tubing

4.5 Select and Install Proper Fittings and Bend Instrument Tubing
Procedure

4.5.1 Procedure Review

1. Select the proper size and type of tubing.

2. Select the proper fittings.
3. Measure the bends for the system to determine how much tubing is needed.
Hand Bending Tubing
4. Measure and mark the tubing exactly. Make sure that the bend mark goes all the
way around the tubing.
5. Always try to bend in the same direction.
6. When bending tubing the distance around a curved bend is always less than a sharp
bend such as a 90°. Remember that tubing gain always occurs to the right side of
the bender die.
7. Swing the short handle up so it is above the bender die.
8. Open the tube latch.
9. Place the tube in the groove of the bender die.
10. Close the tube latch over the tube just enough to hold the tube in place.
11. Carefully lower, the short handle until the roll dies rest gently on the tube while
keeping the link straight and parallel to the long handle.
12. Align the zero on the roll support with the zero on the bender die.
13. Align the bend mark with the mark on the roll support that corresponds to the bend
angle.
14. Push the tube latch securely into place.
15. Slowly push the short handle down until the 0 on the roll support reaches the
desired degree on the bender die, taking spring back into consideration.
16. After completing the bend, swing the short handle up and away from the tube.
17. Pull the tube latch off the tube and remove the tube from the bender die.
18. Double check bend angle with triangle or level.
19. Check measurement length with tape or ruler.

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Cutting Tubing
20. Open the tubing cutter and place the tubing on the rollers.
21. Tighten the handle until the tube cutting wheels come in contact with the tube.
22. Rotate the cutter around the tube while maintaining a continuous light force of the
cutting wheel on the tube by rotating the handle about a quarter turn each
revolution.
23. Repeat until the tube is cut through.
24. DE burr the tubing using the appropriate tool.

4.6 Related Tasks

Describe the steps required to replace a pressure transmitter.
Describe the steps required to overhaul a fisher control valve

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4.7 Knowledge Reinforcement and Self Check

1. What is the first step in the construction of a tubing run?
Ans:
The first step in the construction of any tubing job is the layout. You must consider
many potential obstructions to make sure that the system is built properly.
Maintenance and operation should be your primary concern when deciding the
route of a tubing system.
Ref: I-A-KM-04_Instrument Fitting Skills 4.0

2. What is the difference between pipe and tubing?

A. Tubing is longer than pipe

B. The material it is made from
C. Pipe is better for steam tracing
D. The way the diameter is measured
Ans: D
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 4.0

3. If a piece of tubing is not long enough to reach the other end of the run, which type
of fitting should be used to attach another joint of tubing?

A. Coupling
B. Connector
C. Union
D. Adapter
Ans: C
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 4.0

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4. When you place the tubing in the benders, with the end you measured from on the
left side, which mark on the benders should line up with the mark on the tubing for
a 90° bend?

A. 0
B. 45
C. R
D. L
Ans: D
Ref: I-A-KM-04_Instrument Fitting Skills Lesson 4.0

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5.0 Document Revision History

MOC
Rev No Change Description Date Initial
No
0 Initial Release 19MAY2015 SCHEM

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