Over the past 10 years, particularly on mega-builds, there has been a dramatic increase in prefabrication construction techniques across the Middle East. However as the availability of resources declines and the size of projects and pressure to build faster increases as well, prefabrication is now the rule rather than the exception.  

In the past, off-site prefabrication was the preserve of equipment installations; however, more and more contractors are seeing its potential for HVAC and on-site installations as well. 

But is prefabrication solely for use on mega projects, or does it have a place in the more typical HVAC sectors? Without a doubt, there is plenty of opportunity for prefabrication in the majority of installations. 

In fact, within the piping sector alone, prefabrication is considered to be up to four times more productive than field fabrication. 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. 

To determine the optimal level of prefabrication for the job at hand, project managers have to take into account a number of key factors when performing 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 or not.  

However, once the estimators have finished their work, prefabrication is utilised to minimise the variability of field labour and maximise the predictability of the project schedule. Even greater cost-efficiencies exist for mid- to large-sized contractors who have their own prefabrication shops.

DIFFERENT DIMENSIONS 

Prefabricated PDI risers featuring grooved end pipes and couplings are lifted into position

For a large job, the issue of manoeuvring prefabricated building segments around the jobsite obviously presents extreme challenges. The logistics on a normal jobsite, even though the scope is smaller, present challenges that dictate the complexity of prefabrication that is done prior to delivery.  

There is a tipping point, however, when complex, three-dimensional prefabrication becomes impractical in terms of materials handling and logistics. Handling time of 3D prefabricated spools on site is estimated to be approximately 50 per cent higher than that of straight pipe.  

Two-dimensional prefabrication (where straight lengths of pipework are fitted with grooved elbows) provides advantages in many situations because the assembled lines handle similar to a straight length of pipe but provide the advantage of the prefabricated fitting. The uniqueness of project designs, site logistics and the contractors’ experience and capabilities all dictate optimal build strategy.  

There is always a trade-off between materials handling and offsite construction; however, with larger, more complex projects and greater safety concerns and shorter schedules, prefabrication becomes a must. Does this mean that prefabrication is only for the larger contractors?  

Traditionally, medium- to larger-sized contractors have benefited from prefabrication; however, with proper planning and a solid build strategy, smaller contractors can also achieve the same cost benefits. If used on the prefabrication of key spools that will create the greatest productivity impact in the field, the outsourcing of the fabrication of products to a third party can be cost efficient.  

Victaulic has found that contractors who utilise grooved-end pipe joining systems can increase their direct installation productivity by as much as 50 per cent simply by using two-dimensional fabrication – such as the fitting of elbows onto straight lengths of piping.    

TIME, QUALITY AND RISK

The goal of prefabrication is to reduce the risk inherent in the variability of field labour whilst producing the best possible product at an overall total installed cost advantage. Fabrication shops provide predictable productivity and thereby reduce exposure to variable labour risk. A subsequent benefit of reduced field man-hours is the reduced exposure to jobsite injuries.  

One of the primary causes of onsite accidents, materials handling, is also kept to a minimum. Fabrication shops provide a cleaner, more organised environment where tooling and efficient shop layouts allow pipe spools to be manoeuvred more safely and more quickly than on the jobsite.  In addition, the quality of prefabricated pipework is typically more consistent due to the planning, tooling and controlled working conditions.  

By minimising the interference of everything from weather to other trades on the jobsite and removing people from the jobsite more quickly, prefabrication reduces onsite risk and increases overall installation speed and quality.

When it comes to pipe-joining, the choice of method and strategy can have a big impact on the project schedule and total installed costs. By prefabricating, offsite contractors can make significant productivity and efficiency gains. Prefabrication has traditionally been done using welding, yet grooved-end mechanical pipe-joining has been shown to deliver even greater benefits

Prefabrication with Victaulic allows easy fabrication and transportation of duct risers

The grooved pipe-joining system lends itself to prefabrication, since pipes can be cut and grooved and valves fitted to pump assemblies offsite ready for final assembly in the field as needed. Working in such a way avoids the risk of loss or damage to components on the jobsite, whilst reduced materials handling lowers the potential for accidents.  

For example, during Kuwait University´s Khaldiya Campus HVAC piping system refurbishment, the decision to prefabricate pipe spools with Victaulic components meant material handling was kept to a minimum while greatly reducing the challenge of installing pipe in confined tunnels. Meanwhile at the Development of King Abdul Aziz Endowment (DOKAAE) in Mecca, using Victaulic systems enabled prefabrication, whilst flame-free assembly using grooved products not only sped up installation times but kept welding to a minimum, as local ambient temperatures rose over 50 degrees centigrade.

Errors are inevitable on any jobsite and even prefabrication is not a perfect science; a small number of errors in the positioning of tees or headers coming off of a pump can have significant impact on an installation schedule. To make the field management of such rework easier, using a mechanical joining system such as Victaulic grooved-end technology, where there is a union at every joint, allows simple field correction of any prefabrication alignment errors thus minimising scheduling disruptions onsite.  

THE ROLE OF BIM

To boost productivity beyond what is achievable on the jobsite, mechanical contractors are progressively adopting prefab techniques such as modeling, predesigning and prefabricating risers and racks that are installed in long corridors. Prefab is especially useful for the quick installation of piping, ductwork, electrical and drywall

The advantages of prefabrication are widely acknowledged throughout the industry and prefabricating using grooved pipe joining has proved to deliver additional benefits. Not surprisingly, organisations that many years ago latched on to prefabrication as a strategy to minimise risk, increase productivity and save time on the jobsite are now among the first to have embraced Building Information Modelling (BIM). 

It is a prime enabler for lean construction that can be relied upon to facilitate prefabrication: contractors can use the 100 per cent correct model to determine cut lengths of piping and start prefabricating assemblies with total confidence.  Just as prefabricating in ideal conditions off site delivers greater efficiency on site, so using BIM removes uncertainty and eliminates problems during construction and installation. The philosophy is the same: spend time at the earlier stages to reduce problems and time spent in the field where the risk is greatest. 

BIM confirms, for example, that prefabricated sections can be dropped in as required and that there are clear access routes for maintenance staff – or otherwise clearly shows if there are clashes, in a way that would not be possible with other methods.  

Just as CAD and prefabrication have revolutionised the design and construction functions and become the industry norm, so BIM is set to become standard practice for the efficient whole-life management of building projects.

SUMMARY

Piping often is not seen as a critical value-engineering element with respect to the full scope of a job, but it is an area where front-loading efficiencies and maximising productivity can produce significant savings in man-hours and ultimately help compress construction schedules.  

In fact, while piping system materials can account for as little as one per cent of total installed costs on a project, their installation time can eat up nearly 30 per cent of the entire project schedule. 

Therefore, when considering the significant schedule and cost advantages achieved by strategic prefabrication and use of the latest BIM techniques, one can begin to see why prefabrication has indeed come of age.

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Victaulic, a stalwart in its field

Victaulic, with more than 900 active global patents, has been the world’s leading producer of grooved mechanical couplings and pipe-joining systems. The company has 15 major manufacturing facilities and its solutions are at work in 115 countries across diverse business lines including oil and gas, chemical, mining, power generation, water and wastewater treatment, military and marine as well as commercial building and fire protection.

Victaulic mechanical pipe joining systems can be found in projects as diverse as the Alexandria Library, the Burj Khalifa and the Development of King Abdul Aziz Endowment (DOKAAE). Victaulic provides sustainable solutions and is a member of the UAE Green Building Council. The company is involved with BREEAM (BRE Environmental Assessment Method) and other international initiatives.