Press-fit and pre-fab are the future

First used in the 1980s, press-fit fittings have gained considerable market share in the UK HVAC industry, and are now accepted as being as reliable as traditional threaded or soldered joints. In fact, press-fit systems account for around 40% of fittings used in new building projects alone, and press-fit manufacturers are still reporting sizeable growth. Richard Barnes, Specification Manager at Crane Fluid Systems, looks into the possible reasons for this.

In the UK, threaded and soldered joints have traditionally been used to fabricate building services systems, but as technology has developed, so too have engineering possibilities. The advent of modern methods of construction saw the launch of a new type of jointing, press-fit, but it’s never really been the preferred choice for the majority of specifiers. However, a shift in attitudes is taking place.

The building services industry, like many others, is tasked with keeping time, costs, and health and safety risks to a minimum. Press-fit jointing answers all of these issues because joints can be made effortlessly and with speed, and there’s no need for hot welding, threading machines or even sealants. With these benefits, it’s no wonder that the majority, if not all, of UK building contractors are using press-fit.

Press-fit popularity

It is no coincidence that the growth in press-fit popularity mirrors the growing use of prefabrication within the HVAC industry. In fact, the prefab market has really championed the modern jointing method. The reasons are clear as both prefabrication and press-fit make installation simpler, faster and ultimately cheaper. There is an initial cost associated with both but the installed costs and other benefits more than make up for it.

Before the 21st century, our construction industry stuck to its tried and tested methods rather than switch to the newer methods which were widely used on the continent. This was probably down to the challenges of persuading people away from methods they are comfortable with using, and changing the culture on site. It’s also perhaps partly due to the fact that the decision to use pre-fab must be taken very early on in a project. The M&E design must be completed and signed off at the start, which contrasts with the previous norm for our industry, plus the building itself has to be designed with the pre-fabrication element in mind.

However, manufacturing building services pre-fab modules in a dedicated factory environment and later transporting the module for installation on site has so many advantages. A clean, organised factory, where all components are within easy reach and safety is closely monitored, leads to higher quality output in quicker time and at lower cost. BSRIA studies show that the efficiency of prefabrication leads to greater productivity than on-site installation.

In the last few years we’ve seen leading firms from Wolseley to Balfour Beatty, SES and NG Bailey investing heavily in facilities dedicated to off-site fabrication, and the method is gaining popularity within the trade as people start to see its advantages more clearly. But why is press-fit so suitable for pre-fab, and what are the wider benefits of this combination?

Key considerations

With efficiency of time and cost such key considerations in today’s building industry, the pre-fabrication of building services systems using press-fit jointing represents the ideal solution, since it offers both. When compared to traditional on-site fabrication using threaded or soldered joints, the total installed costs of off-site fabrication using press-fit are 10-20% lower – not to be sniffed at when you consider that on average 10% of a project’s total value might be formed by the building services.

Although press-fit valves and fittings themselves are generally priced a little higher than the conventional type, there are other savings to be found within the process. For example, wastage is far lower than when using traditional jointing methods, since the exact dimensions are known in advance, and there are no tolerances with press-fit which means that pipes can be cut accurately in advance. Environmental impact can also be lessened through keeping the use of raw materials to a minimum, and this can only be a good thing as it’s likely that future regulations will be even tighter in this area. Additionally, thanks to the lack of a requirement for hot welding, insurance premiums can be lowered since the risk of fire or injury is mitigated.

It’s not just speed that can be guaranteed, but quality can be improved too, thanks to the ideal conditions achievable in a factory environment – unlike on site, there are no issues with failing light levels or inclement weather. This improvement in quality is critical for the reliability, efficiency and cost effectiveness of the result. The increased reliability of a pre-fab building services solution created using a press-fit jointing system also means that there is a reduced risk of a delay to a project, and surprise costs can be avoided. For example, thanks to the failsafes built into the best valves and fittings, unpressed joints can be identified at an early stage, which reduces the risk of an expensive and time-consuming system leak being found during the commissioning process.

Health and safety

In terms of site management advantages, off-site fabrication can reduce the headache of tough health and safety requirements since controlled environments, such as factories, are inherently safer places to work than building sites. Materials handling and the need for hot welding are also reduced, mitigating risk to workers. Additionally, site traffic can be minimised, and this has the added benefit of reducing noise and inconvenience for the local community – an important factor considering the increasing pressure for companies to deliver on corporate and social responsibility promises.

So what is it that makes press-fit and pre-fab such perfect counterparts? One main reason is the accuracy that can be achieved. Any variations in the insertion depth of pipes into fittings and valves will add up over the length of a sizeable installation, but press-fit fittings don’t allow any variation. By using the press-fit system the pipes can be cut to size during the pre-fabrication process, safe in the knowledge that the exact dimensions and tolerances can be relied upon.

While it is possible to purchase valves and press-fit connectors separately, there are definite benefits in opting for a product with integrated press-fit functionality. By choosing valves which have had press-fit adaptors manufacturer-assembled and tested as one unit, you can dramatically reduce the number of components purchased as well as the joints required to be made on site.

This not only makes the procurement process quicker and easier, keeping costs down, but also significantly lowers the installation time, and reduces the risk of a leak. Look for integrated valves and fittings which have been redesigned with parallel threads for better thread engagement, rather than valves with tapered threads which don’t have the same resistance to bending forces or such reliability. It’s also a good idea to find out how rigorous the manufacturer’s testing process is – for example, have valves been bend and vibration-tested and is every single unit leak-tested before it leaves the factory?

We may not be so far down the road of pre-fabrication as they are on the continent, but it is likely that it will reach the same popularity in the UK, since the business case for it is so strong. The future of building services design must focus on repeatability and reliability, and pre-fabrication in conjunction with press-fit can help us to realise this vision. Thanks to its ability to increase productivity, address safety and ma
nagement issues, aid more sustainable practices, and reduce programme duration, the system represents a better future for M&E design and installation.

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