New cold storage for Chilleweni

By: Charles van der Walt of MRE

Chilleweni Cold Storage was a greenfield project where the main objective was to build a new cold storage facility complete with central two-stage ammonia refrigeration plant to supply cooling to all the various cold rooms.

Intro DPS

Founded in 2004, Chilleweni’s family-run company focuses on providing storage and logistics services to a wide range of clients within the frozen food market. Their impressive new facility is situated in Gosforth Park in Germiston, Johannesburg.

Project scope

The cold rooms supplied for the cold storage facility were:

  • 3 x -22°C holding freezers
    1 x 5°C chiller
    1 x 10°C receiving and dispatch area

During the negotiations it was decided to remove the designated room for the blast freezers and incorporate five blast freezing sections inside the one holding freezer, by boxing off a section at the bottom of the racking with a plenum for a fan and canvas on the sides to direct the cold air over the pallets.

 

Refrigeration project

MRE was appointed as the refrigeration contractor in March 2018 after the tender phase was completed and adjudicated. The project was commissioned in September 2018.

The plant room equipment included:

  • 1 x low-stage Mycom screw compressor;
  • 1 x low-stage Mycom reciprocating compressor;
  • 1 x swing Mycom screw compressor; 
  • 1 x high-stage Mycom screw compressor; 
  • -32°C accumulator vessel with 2 x hermetic ammonia pumps;
  • -5°C accumulator vessel with 2 x hermetic ammonia pumps;
  • Liquid receiver;
  • Hansen air purger;
  • 2 x Evapco evaporative condensers;
  • Sondex plate heat exchangers;
  • Evaporators by HC Heat Exchangers;
  • PLC for monitoring and control by Carel;
  • 2 x Southern Pumps glycol pumps; and
  • 2x Southern Pumps compressor head cooling pumps.

Plant design philosophy

The refrigeration plant was designed with operating efficiency and longevity as the primary design considerations.
This has resulted in the following operating principles being incorporated in the design:

  • Ammonia as a refrigerant.
  • Two-stage refrigeration with pumped recirculation for the highest practical efficiency. A coefficient of performances (COPs) of 4.4 can be achieved on the compressors.
  • Screw compressors with water-cooled oil cooling.
  • Variable frequency drive (VFD) for the screw compressors as well as the reciprocating compressor to ensure close matching of the operating compressor capacity to the system heat load.
  • VFD for the condenser fans.
  • Freezer evaporators mounted in pods for quick effective defrosting.
  • Glycol underfloor heating for the holding freezers.

Refrigeration plant details

The refrigeration plant has a low-stage operating capacity of 875kWR and high-stage operating capacity of 1 410kWR.

There are two low stage duty compressors, one high stage duty compressor and a swing compressor as standby.

The accumulator vessels have been designed to allow for future expansion of the refrigeration plant.

One ammonia to glycol plate heat exchanger is used to cool down the glycol which is then pumped to the HEVAC&R system installed by others.

One water to glycol plate heat exchanger is used to heat up the glycol which is then pumped through tubes underneath the freezers for underfloor heating. The water is heated by the shell and tube heat exchangers of the compressor oil cooling.

Two new Evapco induced draft condensers were installed with closed coupled mono-block type circulating pumps that circulate water over the galvanised coil. A closed loop cooling circuit for the compressor oil is also installed in each unit. Each condenser has a divider plate between the four fans to be able to switch off two fans when not needed so as to avoid short cycling the air.

A condensate collection tank is used to collect all the water from the evaporators when defrosting, which is then pumped to one Evapco condenser. The water treatment of these condensers was specially adjusted to accommodate this condensate water.

  • Heat rejection rate: 1 111.4kW (each)
  • Condensing temperature: 33°C
  • Wet bulb temperature: 21°C

A monitoring system from Carel Controls called the BOSS system was used. All the PLC equipment used to control the plantroom as well as all the valve stations for the cold rooms are wired via building management systems (BMS) cards.

Additional PLC units have been installed to accommodate evenly spaced temperature probes installed in all three holding freezers as well as the chill store and the five blast freezers.

The monitoring system is set up to send a report of all the various temperatures to the client every day. The BOSS system is also accessible remotely to check system operations off site.

Efficient project management

It was immediately clear that the installation period of this project would be extremely tight, with the site handover expected to be on 1 March 2018 and the intended practical completion to be on 1 of August 2018, including all the building works and refrigeration.

Stuart Walls and his team from Capex were appointed as the principal agent of this project. They compiled a detailed programme that was closely monitored every day to ensure all the contractors were up to date with their individual responsibilities and programmes.

Design changes and customer preference delayed the delivery of the capital equipment of the refrigeration installation, but because of efficient project management from MRE’s team as well as effective communication and planning from Capex, they were able to meet the deadline set out.

It was mentioned by all the contractors and bystanders that the deadline was impossible, but it has once again been proven that with efficient project management and the necessary communication, anything is possible.

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