Management process Twice as much work can be completed per
man hour, due to the controlled environment of off site prefabrication and the availability of specific tooling. In addition, twice the productive hours can be achieved due to better materials flow control and improved supervision, among other things. In order to determine the optimal level of
prefabrication for the job at hand, project managers have to consider a number of key factors when doing the cost analysis. These include the logistics of the site, the design of the piping system, the schedule of the build and whether the contractor has to outsource the prefabrication. However, once the estimators have finished
their work, prefabrication is used to minimise the variability of field labour and maximise the predictability of the project schedule.
Height risks
The proliferation of plastics in packaging materials and the increased use of cardboard cartons created entirely unprecedented challenges for fire protection sprinkler systems to overcome. These newer, lightweight storage materials allowed for storage racks to be built to greater heights and changed the dynamic of how storage spaces were designed. Taller storage racks create a ‘chimney effect’ when their
contents burn, changing the way fires grow and increasing the challenge for adequate sprinkler protection. In addition, plastic materials generate more heat when burned than previously used manufacturing materials, and this increases the hazard. Overall, fires in a rack storage environment
are characterised by extremely fast fire growth, high heat release rate and high plume velocity, and they have therefore challenged the standard sprinkler to its limit of effectiveness. In some cases, combustibles are stored on solid shelves in their rack arrangements, or the storage height and commodity fire challenge are beyond the effectiveness of ceiling based sprinkler systems. In these instances, in-rack sprinklers are needed to provide sufficient fire protection. To combat the issue of taller storage
racks, fire protection specialists have come to understand the relationship between storage height, available pressure, sprinkler orifice size and K-factor (nozzle discharge coefficient).
Consider the future
In construction, even high quality and reliable parts might require replacing at any point in time due to the continuous re imagining and development of technology, or due to
FOCUS
www.frmjournal.com MAY 2020
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