REFRIGERANTS 1. Classify the System
Determine the PED category of each component and the complete system, based on refrigerant type, maximum allowable pressure (PS), and volume or pipe size
Required for Category II, III, or IV systems, they will review your technical documentation and may need to witness strength testing
Include system drawings, pressure ratings,
the design complies with the essential safety requirements, typically by following relevant harmonised or designated standards
4. Test at the correct pressure; some tests must be witnessed depending on the category
Apply CE or UKCA mark and issue a Declaration of Conformity.
Hazard categories and how systems are assessed
Individual components in the system and the complete system have a hazard category. This is determined from the type of component (piping, vessel, pressure accessory or safety accessory), the refrigerant, maximum allowable pressure (PS) and size. In essence things which are bigger and/or have greater PS and/or run on a more dangerous refrigerant have a higher hazard category.
hazard categories. Note the following: SEP – sound engineering practice. Items and systems do not need to meet the PED’s essential safety requirements and are not CE or UKCA marked
Category I tems and systems must meet the essential safety requirements, are CE or UKCA
Categories II, III and IV must meet the essential safety requirements, are CE or UKCA marked and
more onerous the higher the hazard category. For example, for systems which are hazard category
witness all strength testing. The hazard category of the complete system is simply the highest individual hazard category, ignoring safety accessories such as PRVs which are always category IV. Installing contractors need to be aware of the system hazard category but also the category of all the joints on the system (pipe to pipe and pipe to component):
Joints which are SEP or category I can be brazed by brazers with an industry standard brazing qual-
tested at 1.1 x PS.
Joints which are Category II or higher must be
at 1.43 x PS (or 1.1 x PS with 10% non-destructive testing).
Most joints are SEP or category I, but larger R744
erants (e.g. A2Ls) have joints which are category II or higher.
Risk analysis and essential safety requirements
A risk analysis must be carried out, identifying hazards associated with pressure and showing how they are eliminated or reduced, and what protection methods are used. The essential safety requirements listed in the PED form the basis of this risk analysis. Most of the risks relevant to RACHP systems are met through compliance with harmonised standards.
The most important elements of the risk analysis
cover: Determination of PS Selection of appropriate over-pressure protection The use of components and assemblies which are rated for the relevant PS and, where required, are CE or UKCA marked in accordance with the PED
The design of interconnecting pipe work – includ- ing the pipe OD and thickness, its routing and support
Mounting of components, assemblies and pipe work to minimise vibration
The brazing or welding of connections, either pipe to pipe or pipe to component
Strength testing of the installed pipework Protection of personnel from hot surfaces and PRV vents.
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Demonstrating compliance Compliance with the PED is usually demonstrated documentation). These primarily comprise:
General description of the system Design information, including PS and hazard
category for the individual items of pressure equipment and for the whole system
(thickness) is adequate
The risk analysis Pipe layout drawing as installed
sumables) and declarations of conformity for the items of pressure equipment in the system
procedures
tests carried out
O&M manual Draft declaration of conformity and CE plate for the completed system
for category II, III and IV systems several weeks before the system is to be pressure tested.
you: Check brazers/welders have the appropriate
That all items are rated for your system PS (or higher) and that the over pressure protection prevents the system exceeding PS
that all items meet the requirements of the PED)
That you own and have read the relevant stand- ards
That you pressure test the system safely and to the correct pressure.
Summary The PED is a legal requirement in the UK under the PE(S)R. It is there to ensure pressure systems are safe and in the 23 years since its introduction has led to more consistent design and improved installation practices. The result is safe, more reliable systems with reduced leakage, and of course, compliance with the law. In this short article it is not possible to provide all the information you need to install PED compliant systems and to demonstrate compliance - contact
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