CPCPGS3051A - PURGE CONSUMER PIPING
CONSTRUCTION, PLUMBING AND SERVICE
INTEGRATED FRAMEWORK
TRAINING PACKAGE
CPC08
CPCPGS3051A
PURGE CONSUMER PIPING
LEARNING GUIDE
ACKNOWLEDGEMENTS
National Plumbing Services Training Advisory Group
Plumbing Industry Commission Victoria
© Commonwealth of Australia 2015
Construction and Property Services Industry Skills Council
PO Box 151
Belconnen ACT 2616
Tel: 02 6253 0002
This work is copyright, but permission is given to trainers and teachers to make copies and contextualise the resources for use within their own training organisation or in a workplace where training is being conducted. This permission does not extend to making copies for use outside the immediate training environment for which they are made, or the making of copies for hire or resale to third parties.
This work was first published in 2004 with the assistance of funding provided by the Commonwealth Government through the Australian National Training Authority (ANTA). The2015 publication has been updated to reflect changes to the national units of competency.
The views expressed in this work do not necessarily represent the views of the Commonwealth of Australia or CPSISC. In addition, the Commonwealth of Australia and CPSISC do not give warranty or accept any legal liability in relation to the content of this work.
The website addresses and other contact information provided in this publication were compiled in good faith and were correct at the time of printing.
The updating of these resources was completed by:
National Plumbing and Services Training Advisory Group, with funding and support provided by the Construction and Property Services Industry Skills Council (CPSISC):
This guide was developed in consultation with representatives of the Plumbing Industry by NPSTAG and CPSISC to support the implementation of the CPC08 Construction, Plumbing and Services Training Package.
Contents
What is this resource about?......
How do I use this resource?......
Flexible Delivery......
What do I have to do?......
Purge consumer piping......
Unit Descriptor......
Element......
Performance Criteria......
How will I be assessed?......
Are there any pre-requisites?......
What other resources will I need?......
Texts......
Web sites......
Video or audio cassettes......
Safety......
Workplace environment and safety......
Introduction......
Purge or purging
Environmental concerns......
Gases used for purging......
Replacing fuel gas with inert gas or air......
Replacing inert gas or air with fuel gas......
Before purging......
Preparing to purge large volume gas installations
Quality assurance......
Work notices......
Pre-installation......
Preparing to purge using natural gas......
Preparing to purge using nitrogen......
Safety, tools and equipment......
Purging a service pipe......
Purging a sub-meter......
Determine purge requirements......
Selecting the purge medium......
Precautions......
Purging a small volume gas installation......
Determine purge requirements......
Purging through an appliance fitted with an open burner......
Purging through an appliance fitted with a flame safeguard device......
Electronic flame safeguard device fitted
Thermo-electric or bi-metallic device fitted
Electrical safety bonding or bridging......
Purging a large volume gas installation......
Using the equipment to purge......
Purging the meter......
Purging the installation......
Gas sample test methods......
Detergent in water method......
Gas detector method......
Purging consumer piping of fuel gas......
Determine purge requirements......
Replacing air or natural gas using nitrogen......
Introduction......
Volume of nitrogen required......
Purging with nitrogen......
Nitrogen set pressures......
Preparation for purge commences......
Carry out and test purge operation......
Testing for completion of purge......
Clean up......
Worksheet
Practical application......
Assessment checklist......
Worksheet......
© Commonwealth of Australia 2015 1
CPCPGS3051A - PURGE CONSUMER PIPING
What is this resource about?
CPCPGS3051A – Purge consumer piping. This resource will help you gain the skills and knowledge necessary to demonstrate competence in this unit.
How do I use this resource?
This resource is divided into four main sections:
- A learning unit, which contains background information on CPCPGS3051A – Purge consumer piping
- Worksheets, which prepare you for the practical application
- Practical application, which allows you to experience purge consumer piping
- Assessment materials, which help you demonstrate competency
To complete this unit of competence you will need to:
- read the information contained in the learning unit
- complete the worksheets as instructed
- have your answers checked by your trainer or supervisor
- work with your trainer or supervisor to practise purging consumer piping
- read the assessment checklist together with the assessment sheets
- complete the assessment.
Learning Resources are not intended to be the only source of information nor are they intended to be an exhaustive form of instruction.
Flexible Delivery
The Trainer or Supervisor may adapt and deliver this Learning Resource to suit people from diverse backgrounds to meet equity principles and conform to Legislative policies.
What do I have to do?
To demonstrate competence in this unit you will be required to show the level of skills and knowledge for each of the elements involved in CPCPGS3051A – Purge consumer piping. The elements are:
- prepare for purge
- determine purge requirements
- carry out and test purge operation
- clean up.
If you are unsure of the meaning of these elements you should read the performance criteria on the following page.
CPCPGS3051A / Purge consumer pipingUnit Descriptor / This unit of competency specifies the outcomes required to purge consumer gas piping systems.
Element / Performance Criteria
Elements describe the essential outcomes of a unit of competency. / Performance criteria describe the performance needed to demonstrate achievement of the element. Where bold italicised text is used, further information is detailed in the required skills and knowledge section and the range statement. Assessment of performance is to be consistent with the evidence guide.
1Prepare for purging / 1.1Design drawing and specification are obtained
1.2Work health and safety (WHS) and environmental requirements associated with purging consumer gas piping systems are adhered to throughout the work
1.3Quality assurance requirements for company operations are identified and adhered to
1.4Work is planned in conjunction with others involved in or affected by the work
1.5Appropriate tools and equipment for the conduct of purging, including personal protective equipment, are identified, selected and checked for serviceability
1.6Work area and materials are prepared to support efficient purging of consumer gas piping system
2Identify purge requirements / 2.1Installation is checked to ensure compliance with standards and relevant specifications
2.2Volume of piping system is determined from design drawing and standards, and calculations are recorded in format required by job specification
2.3Method of purging is selected in compliance with standards and authorities' requirements
2.4Purge medium is selected in compliance with standards, and calculations of the purge medium volume are recorded in format required by job specification
3Carry out and test purge operation / 3.1Outlet point for purge gas is located and purge site is checked for ignition sources
3.2Purge is carried out according to standards or statutory and regulatory authorities’ requirements and sustainability principles and concepts
3.3Completion of purge is verified by test equipment, or by recognised and approved workplace testing procedures
4Clean up / 4.1Work area is cleared and materials disposed of, reused or recycled according to legislation, regulations, codes of practice, and job specification
4.2Tools and equipment are cleaned, checked, maintained and stored according to manufacturer recommendations and workplace procedures
4.3Informationis accessed and documentation completed according to installation requirements
Required knowledge / Required knowledge for this unit is:
- characteristics of materials used in the purging process
- effect of heat on the materials used during the purging and testing process
- electrical safety and requisite precautions
- how to access relevant information, including codes and technical standards
- job safety analysis (JSA) and safe work method statements (SWMS)
- procedures for purging gas piping systems, including isolation processes and procedures
- properties of gas, gas safety, combustion principles, ignition principles, pressure and flow rates
- relevant statutory requirements related to purging gas piping systems
- SI system of measurements
- workplace and equipment safety requirements
An up to date version of the ‘Unit Descriptor’ may be located on the Australian Government web site training.gov.au
How will I be assessed?
Your trainer or supervisor will decide with you how you will be assessed. Your assessment activity may include completion of the student worksheet and practical task selected by your trainer or supervisor. Your assessment should allow you to demonstrate all the skills and knowledge required to purge consumer piping.
This unit may be assessed in conjunction with other units of competence. Your trainer or supervisor will tell you if you are to be assessed this way.
Are there any pre-requisites?
Prior to commencing CPCPGS3051A – Purge consumer pipingyou must have successfully completed the following pre-requisite:
- CPCPCM2043A Carry out WHS requirements
It is also recommended that prior to commencing CPCPGS3051A – Purge consumer piping you should have successfully completed the following competencies:
- CPCPGS3056A – Install gas piping systems
- CPCPGS3058A – Install and commission ‘Type A’ gas appliance.
Project work may also group pre-requisite and or co-requisite competencies together to carry out such projects. It is recommended that the following competencies are grouped with this unit of competency:
- CPCPGS3056A – Install gas piping systems
- CPCPGS3058A – Install and commission ‘Type A’ gas appliance.
What other resources will I need?
To assist you the following resources have been suggested and should be available to you to do this competency:
Texts
- AS/NZS5601 - Gas Installations Relevant Version.
- State or Territory regulations may override this Learning Guide.
Web sites
Video or audio cassettes
Safety
Workplace health and safety (WHS) requirements need to be observed in accordance with legislation. You need to know the WHS laws governing your job. Revision of CPCPCM2043A - Carry out WHS requirements, before commencing this unit is advisable
In any work situation you can reduce the risk of injury to yourself and others by using appropriate personal protective equipment (PPE). The types of PPE that you will need include:
- overalls – used for the protection of the installer when working in different conditions
- boots – it is recommended that soft soled footwear is worn while working on roofs, as deep grooved footwear pick up small stones and debris that might damage or scratch the roof sheets
- safety glasses or goggles to protect the eyes from injury when cutting the sheets with a power saw
- ear plugs or muffs to protect the installer’s hearing from excessive noise
- dust masks or respirators to protect the user from breathing in dust or fine particles when cutting the sheets with a power saw
- gloves, for the protection of the installer’s hands when working with different types of pipes, tools and equipment.
Workplace environment and safety
Handling of materials / Manual lifting and handling techniques must always be followed according to WHS requirements. You should move materials into position by hand where possible. Excessive manual handling should be avoided and cranes and other mechanical lifting devices should be employed when necessary.Introduction
In this unit you will look at how to purge consumer piping utilising a variety of purging mediums and methods. Purging is defined in (relevant version)AS/NZS5601 - Gas Installations as follows.
Purge or purging
With respect to consumer piping means:
- replacing the air in consumer piping with gas or inert gas
- removing the gas from consumer piping by replacing the gas with either air or an inert gas.
Note
The purpose of purging is to prevent the presence in the piping of an explosive mixture of fuel gas and air.
It is important that all purging operations are performed safely and that the relevant requirements of (relevant version) AS/NZS5601 - Gas Installations are met.
Only persons with adequate training and experience should carry out purging operations.
Layout of pipework from main to meterPurging is necessary to prevent the occurrence of an air or gas mixture that might cause an explosion in consumer piping, in an appliance, or in a confined space.
Purging needs to be carried out in the following areas:
- a service pipe (normally the function of the authority)
- a sub-meter
- a small volume installation with gas (volume up to 0.03 m3)
through an appliance fitted with an open burner
through an appliance fitted with a flame safeguard device
- a large volume gas installation (volume exceeding 0.03 m3)
- consumer piping of fuel gas.
Purging must be undertaken before commencing work and after completion of work. This is to avoid the possibility of an explosive air or gas mixture existing or forming in consumer piping, appliances or confined spaces.
Fuel requires oxygen to burn, without oxygen it is impossible for any fuel to burn. This would mean that if a sealed container were completely full with a fuel gas then it would be impossible to ignite the gas even from inside the container.
We have three sealed containers which have been filled with air, fuel gas and a mixture of fuel gas and air. Each container has an ignition source placed at the side. The ignition source is a push button piezo igniter. What will happen if the buttons of the piezo igniters are pushed?
Examples of the three conditionsNothing will happen in number one, because there is only air and no fuel. Nothing will happen in number two, because there is only fuel and no air. But in three if the ratio is correct then there will be an explosion.
NoteThe flammability limits for natural gas are 5% to 14% and for propane 2.5% to 9.5%
Consider a 100 mm copper pipeline, which is filled with air, the contents of the line would be regarded as safe. If this same 100 mm copper pipe were filled completely with fuel gas, it would also be considered safe. If the pipe had a mixture of fuel gas and air then this could be considered a dangerous situation.
Purging the pipeline so it is either full of air or fuel gas or inert gas will prevent this potentially dangerous situation.
NoteAn inert gas means: a non-explosive gas, such as nitrogen.
Note
As defined in (relevant version) AS/NZS5601 - Gas Installations, Purging is carried out to avoid the possibility of an explosive air or gas mixture existing or forming in consumer piping, appliances or confined spaces.
Requirements for when purging must take place are in(relevant version)AS/NZS5601 - Gas Installations.
Definition:
- small volume gas installations = volume up to 0.03 m3
- large volume gas installations = volume more than 0.03 m3.
All consumer piping wherever possible, should be purged to a well ventilated area. Because of the lower capacity of small volume gas installations, the amount of gas dispersed during purging is not regarded as a problem.
For example, small volume gas installations may be purged at a cooking appliance inside the building. Small volume gas installations are the type found in most domestic houses.
Large volume gas installations should be purged to the outside atmosphere. The purge outlet should be at least 6 m away from any ignition source and well clear of any opening to the building.
Two methods used to purge large volume gas installations are:
- purge stack
- purge bucket.
Other purging methods may be acceptable. Persons likely to carry out purging on a regular basis may consider obtaining IGE/UP/1A, Soundness testing and direct purging of small low pressure Industrial and commercial natural gas installations. The document was published in 1998 by the Institution of Gas Engineers (UK).
Environmental concerns
Because of concerns regarding the environmental impact of methane in the atmosphere, the volume of vented gas should be kept to a minimum.
Gases used for purging
There are a number of gas mediums that can be used to purge consumer piping, and submetres:
- nitrogen
- carbon dioxide
- air
- fuel gas.
For the purpose of purging, these gases have different characteristics and different uses.
Replacing fuel gas with inert gas or air
The gases nitrogen, carbon dioxide and air are used to replace fuel gas in a pipeline. This would be done where consumer piping is to be opened for alteration, repair or extension. The section involved should be turned off from the supply at a convenient point and the piping vented to the atmosphere.
Nitrogen and carbon dioxide are both inert gases, with nitrogen being the preferred inert gas and carbon dioxide being an acceptable alternative.
Replacing inert gas or air with fuel gas
After the installation of a new gas pipeline or after the alteration of an existing line it is necessary to fill the line with fuel gas. This would mean removing air or an inert gas from the line and replacing it with a fuel gas. The fuel gas could be natural gas, liquefied petroleum gas or other gas depending on the gas being supplied.
Showing flow of gases through new and existing installationsWorksheet
Now go to the Worksheet and answer Questions 1 – 6.
Plan work activities
When you are purging consumer piping, you must remember your company’s WHS and quality assurance responsibilities and those that may apply in the workplace because of the nature of the work.
It is important to ensure that all purging operations are performed safely and that the relevant requirements of(relevant version)AS/NZS5601 - Gas Installations are met.
Before purging
The following precautions are to be taken before purging commences:
- do not commence any purging operation until a purge area has been defined, made safe and cleared of all ignition sources, eg. naked flames, pilot lights, electrical switchgear, etc
- do not allow smoking in or near the purge area
- purging must be planned to occur when it does not affect or interfere with others on the site
- a suitable outlet point for the purge gas should be located
- a purging area should be defined before the purging operation can commence. The area must be made safe and cleared of all sources of ignition, eg naked flames, pilot lights, electrical switchgear.
On small volume gas installations when purging air from the line to replace with fuel gas: