Rand Refrigerated Logistics new $35 million cold storage distribution centre runs an ammonia system. Adaptable in Adelaide A new cold storage distribution centre in South Australia s capital has been designed with adaptability in mind so as to accommodate approximately 6,000 pallets now, and an even greater number in the future. As Sean McGowan reports, meeting a dynamic system load profile is behind the successful design. Rand Refrigerated Logistics is a leading national refrigerated transport, cold storage and distribution services provider with cold storage distribution centres located across Australia. In April 2013, work commenced on the construction of a new $35 million cold storage distribution centre in Direk, near Port Adelaide, for the company s fresh produce arm, Harris Refrigerated Logistics. The project was developed by EPC Pacific then sold at the completion of the development to Cromwell Property Trust. The development is contained within the Vicinity industrial estate. The 10,500 sq m cold storage facility comprises an office and administration area, along with a 5,000 sq m dedicated chiller area, a 1,440 sq m dedicated freezer area and over 1000 sq m of dual-temperature zone that can operate either as a chiller or freezer. The total refrigerated space is 7,500 sq m, and has been designed to allow expansion up to 10,000 sq m in the future. Additionally, the facility also features expansive warehousing and cross-dock facilities, as well as a truck wash-down area. 18 ECOLIBRIUM JUNE 2014
ADOPTING AMMONIA Energy and sustainability targets were to be in line with industry best practice. Naturally, this meant using a refrigerant with low global warming potential (GWP) and ozone depletion potential (ODP) to reduce the environmental impact should a refrigerant leak occur. There was also strong desire to future-proof the system in response to the phase-out of high-gwp and high-odp refrigerants. For this reason, ammonia became the refrigerant of choice. The project was well-suited to the use of ammonia due to the site location, system load characteristics and the desired room temperatures, Quast says. Fully automatic operation was required, with inbuilt fault detection and warning systems, including remote monitoring and diagnostic capabilities Oomiak was engaged to design and install the refrigeration services for the new facility, built by Vaughan Constructions. According to Ben Quast, M.AIRAH, mechanical engineer with Oomiak, the project brief was to design, install and commission a fixed refrigeration system to service the distribution centre s entire refrigeration load. Refrigeration loads were a combination of freezer and chiller duty product storage rooms, Quast says. The refrigeration system had to provide cooling to these rooms to achieve the required temperature, with the capability to adjust temperature ranges to suit a variety of product. Fully automatic operation was required, with inbuilt fault detection and warning systems, including remote monitoring and diagnostic capabilities. Ammonia has a zero GWP and ODP, which is highly desirable given the industry s increased awareness of the adverse impacts that the accidental leakage of high-gwp and ODP refrigerant has on the environment. Ammonia also has the greatest cycle efficiency of known refrigerants due to requiring the smallest amount of compressor displacement per kilowatt of refrigeration. Quast says this reduced compressor displacement allows for reduced compressor sizes and a reduction in electrical input per kw of refrigeration, in comparison to other refrigerants. Ammonia also has a large latent heat of vapourisation, along with excellent heat transfer properties that allow for smaller heat exchangers. Ultimately, this translates to a reduction in the size of both condensers and evaporators. JUNE 2014 ECOLIBRIUM 19
When the detection system senses a low-level ammonia leak, site-wide alarms will be raised to alert personnel Of course, adopting ammonia also carries with it some significant safety risks, due to its toxic nature to people, as well as its flammability. Oomiak was able to mitigate both these risks through the use of an automatic detection and warning system. The central refrigeration plant room under construction. When the detection system senses a lowlevel ammonia leak, site-wide alarms will be raised to alert personnel, says Quast.
LESSONS FROM THE CONSULTANT Ben Quast, M.AIRAH, mechanical engineer with Oomiak This project was my first involvement in a large-scale refrigeration plant installation on a Greenfield site, so there were a number of lessons I personally took away from the project and experience, says Quast, who conducted an AIRAH site visit to the facility last month. 1. Understand the specification Having a full understanding of the specification can save a lot of headaches at the conclusion of a project. 2. Build a strong communication link with the builder This ensures the ongoing requirements of both parties are met throughout the project. 3. Ask questions Rather than making an assumption, ensure that all parties understand what is to be provided, implemented and agreed upon. This can be applied to many aspects of professional life. If the atmospheric ammonia concentration continues to increase and is detected to be approaching the lower explosive limit (LEL), a signal is sent to the fire indicator panel to alert local fire authorities. All refrigeration equipment, apart from intrinsically safe items, is also shut down. TWO-STAGE In order to serve the freezer and chiller load requirements of the facility, a two-stage refrigeration system was implemented. The low-stage compresses ammonia from -32 C to -4 C, and the high-stage compresses it further from -4 C to +33 C. This two-stage compression allows the compressor ratio of each compressor to remain low to further increase operational efficiency. To supplement the low-stage and highstage compressors, a non-operating stand-by swing compressor has also been provided. This can operate at either duty to provide compressor redundancy. This swing compressor allows for zero plant downtime during maintenance of duty compressors, and can provide system cooling in the event a problem with one of the other machines is encountered.
According to Quast, the use of screw compressors here offered lower capital cost on a system of this size because a single, large-capacity compressor can accommodate the entire low-stage and high-stage loads. By using a single machine, we benefit from a smaller equipment footprint, which allows for a reduction in plant room size, he says. Screw compressors also have the advantage of lower ongoing maintenance costs due to reduced frequency of maintenance when compared to other compressor types. The refrigeration system at the new Direk facility comprises of three compressor sets, one condenser, three penthouse evaporators and 10 under-ceiling evaporators. It serves a freezer design load of 265kW at -25 C, and a designed refrigeration load of the chiller area of 688kW at temperatures range from +3 C to +15 C. The dual-temperature zone has a design freezer load of 147kW and a design chiller load of 80kW. This results in a total maximum freezer capacity of 412kW and a total maximum chiller capacity of 768kW. PROJECT AT A GLANCE The Personnel Client: Rand Refrigerated Logistics Consultant: Beca Developer: EPC Pacific Owner: Cromwell Property Trust Project manager/builder: Vaughan Constructions Refrigeration contractor: Oomiak HVAC Equipment Compressors: Mycom Condensers: Evapco Evaporators: Cabero PLC/drives: Schneider Valves: Danfoss Owners: Mirvac Property Trust and Keppel REIT Structural engineer: Arup AIRAH members tour the plant room as part of the recent AIRAH site visit event. Quast says allowance has been made in the plant design to expand the freezer capacity in the future by 320kW. This will ultimately result in a total freezer design load of 732kW. Adjustable room temperatures and highly variable room loads needed an adaptable refrigeration solution, he says. Distribution centre room loads are dynamic in that product throughput, temperature of entering product, external air temperature and facility door movements all vary greatly depending on the time of the day and season, providing a dynamic system load profile. This refrigeration system was designed with the adaptability to ensure that operating conditions are maintained at design settings, even with a changing load, without forgoing efficient operation. CENTRAL PERKS Centralising the refrigeration plant has also provided a number of significant benefits to the overall efficiency of the system. For instance, by centralising it, larger motors with higher motor efficiencies have been able to be used. Coupling these larger motors with a variable-speed drive (VSD) has allowed full-load compressor efficiency to be achieved at part-load conditions, further consolidating the energy savings derived from the higher motor efficiency. A centralised plant also allows for ease of implementation of the system redundancy, says Quast. In this case, a common non-operating stand-by compressor has been installed that is capable of serving the entire high-stage or low-stage. Along with the mandatory automatic refrigerant leak detection system and alarms, Oomiak has implemented a range of automatic control measures to optimise the plant s operational efficiency under changing conditions. These include floating the condensing pressure, compressor capacity control via speed control, automatic scheduled defrosts and evaporator fan speed control. Complete system control is achieved using a central programmable logic controller (PLC). According to Quast, some examples of the controlled aspects of the plant include speed control of condenser fans, evaporator fans and compressors; and level control of the surge vessels via modulating control valve and level transducer. Automatic feed control via solenoid valve at each coil also ensures cooling is supplied to the coils only when required. A significant amount of space has also been allocated in the plant room for additional major equipment in the event of future expansion, including room for an extra low-stage compressor, high-stage compressor and evaporative condenser. The pipe installation was also tailored to suit future needs. Pipe sizes were selected to specifically accommodate the increased future load as well as provide valved connection points in strategic locations. Rand Refrigeration Logistics took occupancy of the facility in December 2013. 22 ECOLIBRIUM JUNE 2014