Training the Carbon Dioxide Technicians
Opened by WR Refrigeration, the facility builds on the company’s previous in-house training center and now includes working examples of all the main types of CO2 systems likely to be met within the field. This includes examples of subcritical, cascade, and transcritical.
Based on a mini-supermarket format, it incorporates high- and low-temperature display cases and a walk-in cold room. It provides a working environment for engineers and technicians to gain both theoretical and hands-on experience of working with the latest CO2 systems, according to officials.
The academy has become the center for WR Refrigeration and parent company Huurre’s group-wide European CO2 training program, designed to equip its engineers to support the anticipated rollout of CO2 equipment by major United Kingdom (UK) and Continental end manufacturers.
According to reports, the academy will operate as a commercial training center in its own right, providing courses for other UK contractors carrying out work on CO2-based systems for end users.
UNDERWAYIt is anticipated that several hundred individuals 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.”
Located in the center of the UK at Minworth, England, just outside Birmingham, the academy will also be used to demonstrate working CO2 technology to end users evaluating alternative systems.
The installation comprises three systems in a cascade arrangement:
• A subcritical LT system.
• A pumped circulation CO2 secondary system, operating at chilled-food conditions.
• A cascade CO2 transcritical multicompressor pack system that is used to provide the condensing medium for the pumped circulation CO2 secondary system via plate heat exchangers. This system provides refrigeration to multideck display cases and a cold room.
The new transcritical CO2 plant adds an important new dimension to the facility, said Mullins, as transcritical is the latest CO2 technology. It uses a bespoke system, 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 subcritical 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.
JOINT VENTUREThe plant was developed as a result of Huurre Group’s joint venture with European CO2 specialist Enex srl. The creation of Huurre ECO earlier this year brought together the expertise of Enex in the field of CO2 cooling with Huurre’s resources and market strength, Mullins said.
The transcritical pack was designed and built in Italy by Huurre ECO and shipped to the UK for installation and commissioning by WR engineers. The entire installation is monitored with a control and alarm monitoring system accessible remotely, providing further opportunities to train technicians on system analysis and interrogation techniques. The training room overlooks the installation on a mezzanine floor and provides views over the plant and cases.
WR worked 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 CO2 systems. WR is also working with controls specialist RDM to help develop a new range of CO2 controls, which are being tested at the center.
KEY ISSUECO2 refrigeration systems have some unique design and operating characteristics that require handling by trained personnel, it was reported. 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, said Paul Arrowsmith, WR Refrigeration head of engineering.
“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.
“We also emphasize the importance of good working practices that are essential to ensure the system charge and oil remains in optimum condition.”
Training standards in the UK are governed primarily by industry lead body City & Guilds (C&G), 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 finalized.
Arrowsmith is a member of the City & Guilds’ steering group responsible for establishing the new national training framework for CO2 refrigeration.
In the absence of a national framework for CO2 competence, WR Refrigeration has worked with food retailer Wm Morrison to develop a comprehensive CO2 training program to support the rollout 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 an emphasis on safety throughout. All contractors undertaking work on Morrison’s CO2 systems are required to successfully complete the course.
To date, some 200 engineers have successfully completed the WR course. Successful candidates are issued a personalized 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 CO2-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 recently secured a contract with a global industrial company to design and replace its existing HFC plant with the CO2 systems. This includes a transcritical system for use on low-temperature applications.
The transcritical plant, with a capacity of 40 kW at -8°C SST, incorporates a number of features that exemplify the flexibility of transcritical systems now being in- stalled 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 40 bars. On WR’s system, however, the design pressure is 60 bars, enabling the plant in the event of power failure to withstand ambient temperatures of up to 23°C without venting.
Due to these higher pressures, the Vulcan Lokring system is used on pipe work, as the current range of copper fittings is only being approved to 40-45 bar by suppliers. Vulcan Lokring permits the use of copper tube on the suction and intermediate pressure services up to 75 bar, 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 a result of collaboration between Arrowsmith and Enex. Installation was by WR Refrigeration engineers, with input from specialist coded welders on stainless steel pipe work.
The pack is designed for use in the Birmingham facility, but the core design has been used by Enex and Huurre Group on hundreds of installations in mainland Europe and Scandinavia.
CONFIGURATIONThe LT system is comprised of one-half of a 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 a multideck chilled-food display case also providing load.
The transcritical plant load is provided by the heat exchangers on the pumped circulation vessel, the multideck chilled-food display case, and an evaporator.
Publication date: 11/15/2010