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'Potential of CO2 for end-users unlocked'

23 July 2010

The European CO2 Refrigeration Training Academy has been launched as a centre of excellence for training engineers and end users in carbon dioxide-based refrigeration technology

Opened by WR Refrigeration on July 28, 2010, the facility - unique in the UK - builds on the company’s previous in-house training centre and now includes working examples of all the main types of carbon dioxide systems likely to be met with in the field.

This includes examples of subcritical, cascade and transcritical carbon dioxide refrigeration systems, all under one roof.

Based on a mini-supermarket format, it incorporates high and low temperature display cases and a fully functioning walk-in cold room. It provides a realistic working environment for engineers to gain both theoretical and hands-on experience of working with the latest carbon dioxide systems.

The Academy becomes the centre for WR Refrigeration and parent company Huurre’s group-wide European CO2 training programme, designed to equip its engineers to support the anticipated forthcoming roll-out by major UK and Continental end users.

The Academy will operate as a commercial training centre in its own right, providing courses for other UK contractors carrying out work on carbon dioxide-based systems for end users. This is already happening.

The first training courses will take place in August, with a forward programme rapidly being booked up. It is anticipated that several hundred engineers will attend the Academy in the first year.
Patrick Mullins, WR Refrigeration Business Development and Marketing Director, said: “Interest in carbon dioxide has increased dramatically over the past year or so. It is an attractive alternative to HFC systems as it is environmentally friendly, safe and proven.

“The major obstacle to widespread adoption to date, however, has been the shortage of engineers trained in handling carbon dioxide. The CO2 Academy meets this need and unlocks the huge potential of carbon dioxide for end users.”

Strategically located in the centre of the UK at Minworth, just outside Birmingham, the Academy will also be used to demonstrate working carbon dioxide technology to end users evaluating alternative systems.

The installation comprises three systems in a cascade arrangement: a sub critical LT system, a pumped circulation CO2 secondary system, operating at chilled food conditions, and a cascade CO2 transcritical multi-compressor pack system. The latter is used to provide the condensing medium for the pumped circulation CO2 secondary system via plate heat exchangers.

This system provides refrigeration to 15m of multi-deck display cases and a 22 m3 cold room.
The new transcritical carbon dioxide plant adds an important new dimension to the facility, giving engineers hands-on experience of the latest CO2 technology.

The transcritical pack is a bespoke system for the Birmingham facility, based on a single temperature design for HT operation. However, the company’s transcritical packs can be equipped with a low temperature booster or parallel compression arrangement for use on low temperature applications.

The transcritical plant in Birmingham has been incorporated alongside the existing CO2 plant, acting partly as a cascade system to the pumped circulation and sub-critical direct expansion systems.

This enables engineers to be given experience of handling all three types of CO2 systems currently being installed within the commercial retail sector.

The plant was developed as a result of Huurre Group’s recent joint venture with leading European CO2 specialist Enex srl. The creation of Huurre ECO earlier this year brought together the expertise of Enex in the field of carbon dioxide cooling with Huurre’s resources and market strength, to create a new European force in carbon dioxide refrigeration.

The transcritical pack was designed and built in Italy by Huurre Eco and shipped to the UK for installation and commissioning in Birmingham by WR engineers.

The entire installation is monitored with a control and alarm monitoring system accessible remotely, providing further opportunities to train engineers on system analysis and interrogation techniques. The ten delegate training room overlooks the installation on a mezzanine floor and provides views over the plant and cases.

WR has worked closely with suppliers and customers in creating the Academy. Contributing partners include Marks & Spencer, whose display cases are used, and Searle, which supplied cooling equipment and expertise in the design of evaporator coils for the pumped circulation carbon dioxide systems.

WR is also working with controls specialist RDM to help develop a new range of carbon dioxide controls, which are being trialled at the centre.

Training in carbon dioxide refrigeration – key issues
Carbon dioxide refrigeration systems have some unique design and operating characteristics that require handling by trained personnel. The high operating pressures and unusual properties of CO2 as a refrigerant mean that safety is a paramount consideration.

This is a particular concern given the proximity of working retail refrigeration systems to the general public. It is therefore essential to ensure that the highest standards of engineering, installation and maintenance are applied and maintained at all times.

Paul Arrowsmith, WR Refrigeration, Head of Engineering, said: “The key is to ensure that engineers are aware of the special properties of CO2 as a refrigerant, which make it behave differently from the refrigerant they are used to handling, and the techniques required to handle it safely in order to avoid hazards.”

He added: “We also emphasise the importance of good working practices that are essential to ensure the system charge and oil remains in optimum condition.”

Training framework
Training standards in the UK are governed primarily by industry lead body City & Guilds, with the main refrigerant competence/assessment course for engineers being C&G 2079. This covers standard fluorinated refrigerants. Work is underway to develop a national competence qualification for CO2, but this has not yet been finalised.

WR Refrigeration’s Paul Arrowsmith is a member of the City & Guilds’ steering group responsible for establishing the new national training framework for carbon dioxide refrigeration.

In the absence of a national framework for CO2 competence, WR Refrigeration has worked closely with major food retailer Wm Morrison to develop a comprehensive carbon dioxide training programme to support the roll-out of CO2 refrigeration in the company’s stores across the UK.

The syllabus involves a two-day course, covering both theoretical and practical aspects, with a strong emphasis on safety throughout. All contractors undertaking work on Morrison’s carbon dioxide systems are required to successfully complete the course.

To date, some 200 engineers have successfully completed the WR course. Successful candidates are issued with a personalised plastic credit card certificate of registration, which they must show on request to prove competence in working with carbon dioxide systems.

A register of engineers who have successfully completed the course is maintained by WR Refrigeration as a reference for Wm Morrison’s PLC.

WR Refrigeration is working with several other major end users to help them implement plans to introduce carbon-dioxide-based refrigeration in their stores. It has installed a number of CO2 systems already in the UK, and has a growing number of systems of other suppliers and installers under maintenance.

WR Refrigeration has recently secured a seven figure contract with a leading global industrial company to design and replace its existing HFC plant with state-of-the-art CO2 systems. This includes a transcritical system for use on low temperature applications.

The transcritical CO2 refrigeration system
The transcritical plant, with a capacity of 40kW at -8oC SST, incorporates a number of features that exemplify the flexibility of transcritical systems now being installed in many retail applications:

 The pack has a “standstill unit” this is an independent system that protects the CO2 charge in the event of power failure, and can also be used for extended duration maintenance work.

 Where a “standstill unit” is employed, design pressures typically for the intermediate and low pressure side of the system would be 40bars. On WR’s system, however, the design pressure is 60bars, enabling the plant in the event of power failure to withstand ambient temperatures of up to 23oC without venting;

 Due to these higher pressures, the Vulcan Lokring system is used on pipework, as the current range of copper fittings is only being approved to 40-45bar by suppliers. Vulcan Lokring permits the use of copper tube on the suction and intermediate pressure services up to 75bar, if appropriate pipe wall thicknesses are used;

 Mechanical back-up valves are also used for the two key primary control valves;

 Control panels incorporate an RDM system in parallel with the primary Danfoss control system.
The design is result of collaboration between WR Refrigeration’s Paul Arrowsmith and Enex. Installation was by WR Refrigeration engineers, with input from specialist coded welders on stainless steel pipe work.

The pack is a one off, designed for use in the Birmingnam facility, but the core design has been used by Enex and Huurre Group on hundreds of installations in mainland Europe and Scandinavia.
Configuration of the refrigeration system

The LT system comprises of a half glass door frozen food display case and a frozen food cold room. Load can be applied by a variable electric heater.

The LT plant is cascaded off the pumped circulation CO2 system, providing load to the system. In addition, there is 15m of multi deck chilled food display case also providing load. The transcritical plant load is provided by the heat exchangers on the pumped circulation vessel, 6m of multi deck chilled food display case and an evaporator.

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