PROJECT: Kings College London

Project Outline:

During the construction phase of any modern building the availability of craneage is rarely an issue as there is usually a resident crane on site which can be used to facilitate the siting of large roof top plant. Placement of cold water chillers on roof tops has become a popular option with building service consultants as the removal of heat from the condenser to atmosphere negates the need for a cooling tower. When a cold water chiller is constructed the first thing to be fitted to the chassis is the compressor followed by the evaporator / condenser assembly. In general, due to size constraints, the foot print of a water chiller is kept to a minimum which means that the unit is packaged as tightly as possible. This is fine for new installations; however, in the event of a compressor failure this can create huge challenges for the repair team. This indeed was the case for one of the 200kW chillers located on the 8th floor roof at King’s College London Institute of Psychiatry on the Denmark Hill campus. The compressor in question weighed 758kg, the problem was further compounded by access restrictions imposed by adjacent buildings.

King’s College London put the compressor repair task out to competitive tender, Artic Building Service Ltd was successful and was duly awarded the contract to replace the compressor and re-commission the cold water chiller. A thorough site survey was performed in order to compile a Risk Assessment and Method Statement, and included the sizing of a suitable crane to lift the old compressor down prior to lifting the new compressor onto the roof plant area. The choice of crane was critical due to the space constriction and the jib height required to clear communications antennas located next to the chiller. As a busy educational site in constant use the consequences of errors on our behalf could lead to catastrophic consequences for the university.

Work commenced on the 16th of October with the removal of the R407C refrigerant, isolation and disconnection of pipework and electrical connections. The broken compressor was winched out then craned down onto a waiting lorry below to be sent back to Daikin for reconditioning. The new compressor was lifted onto the roof plant area, winched into position then reconnected to the existing pipework and all electrical connections made. The system was re-charged with refrigerant, and following a successful pressure test was commissioned back into service on the 19th October.

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