Automatic sprinklers – Background and Benefits - Business Sprinkler Alliance

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Aims and Objectives

The aim of this CPD is to provide some background on automatic sprinklers and to look at their benefits. It will also cover some details on regulation and guidance and then look at design considerations for a particular occupancy, which in this case is offices. The business sprinkler alliance BSA is an alliance of fire safety professionals working to protect UK plc against fire. The BSA aims to highlight the true cost of fire and believe that automatic fire sprinkler systems provide multiple benefits to the business community. It's an area that does not receive a lot of attention, but we believe it should.

 

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How do Sprinklers Work?

We will start our session by going back to basics and talking about how sprinklers work. A basic sprinkler system is typified by the same things. The water supply could be from the town’s mains or a pump and a tank; these supply pressurised water into a network of pipes. There are valves to control the flow of water and to allow for alarms to be raised. The sprinklers are at the end of the pipe network.

 

The choice of using town mains or a tank really depends on the amount of pressure and water that's available at a particular point. This is balanced against how much water you need for the fire hazard you're likely to face in a particular building.

 

The business end of a sprinkler system comes in the form of a sprinkler, it is a technically engineered and refined device. The key to its operation is the thermal element, this has a glass bulb containing a liquid and this element holds a plug in place which in turn holds back the water in the pipes.

 

In a fire event, temperatures will rise at the ceiling and the thermal element will heat up the liquid inside the thermal element expands and at a predetermined temperature the expansion of the liquid breaks the glass bulb. Without the glass bulb there is nothing holding the plug in place, so it clears from the water pathway and water flows through the sprinkler. The water strikes the deflector causing an umbrella pattern that you normally see falling from a sprinkler head. It's as simple as that they do not respond to smoke and there are no wires attached to it, it's all down to heat. This is why someone having a cigarette in a building or someone burning their toast will not cause the sprinkler system to go off.

 

Sprinklers need sufficient heat to operate with the colour of the liquid inside the thermal element signifying the temperature at which the sprinkler will operate. Red liquid indicates a sprinkler will operate at 68 degrees Celsius. This video shows differing sprinklers in operation.

 

Different Sprinklers, Different Output

The image in the top left is what we would call a spray sprinkler. You can see the cone pattern that's coming away from that sprinkler, the water is pushed down hitting the deflector and the spray is formed. The image top right is a conventional sprinkler, it is slightly different in the fact that the deflector is slightly curved. If you look closely and compare it to the first image you will see some of the water thrown upwards, while the majority is thrown downwards.

 

The images at the bottom of the picture are sprinklers that are typically used to tackle fires in storage buildings. The image on the bottom left is a storage sprinkler. This is basically a larger hole in the sprinkler itself allowing more water to flow through it generating a larger spray pattern. It needs more pressure to make it work but pushes out a larger volume of water.

 

Compare the water flow to the image above it. The image in the bottom right is what we call an early suppression fast response sprinkler. It is very much typified by a strong spray pattern and a defined amount of water pushed down towards the floor. If you look closely you will see a white line coming straight down under the head, you'll also notice an intensity of water on the floor under the head, and that's how it's designed. It's designed to knock a fire down and to suppress it.

 

Automatic Fire Sprinkler System Investment 

This video shows the comparison of a scenario with and without an Automatic Fire Sprinkler System. These two identical arrays each have 12 pallet loads of carton polystyrene plastic cups, separated by Cardboard dividers. The nature of any cartoned commodity is that the fire develops very quickly on the vertical surfaces. As the fire grows the heat release rate is increasing at an exponential rate. That will continue until all available fuel finds available oxygen to support the combustion process.

 

When the light grey smoke from burning Cardboard turns a darker black, that means the plastic cups were 2.5 times the heat content of the Cardboard are contributing to the fire. The two fires represent the tale of two properties in one case the property owner has invested in properly designed sprinkler protection and has implemented the necessary inspection, testing and maintenance practices to assure the sprinklers operate when needed.

 

In the other case the property owner is still considering making the discretionary investment, since sprinklers are not mandatory building requirements. The presence of a fire detection system, non-combustible building and local fire brigade have given them a sense of security.

 

As the sprinkler over one array or property begins to gain control over the fire, there is minimal fire water and smoke damage and operations will be largely unaffected. This fire will not even make the nightly news. At the other property a disaster is unfolding ceiling temperatures are now exceeding 540 degrees Celsius and the overhead steel begins to lose its strength.

 

Cost of Automatic Fire Sprinkler Systems

One thing that people often ask about is the cost of sprinklers. Typically, it depends very much on the style of building that you're building and the sprinkler system design. Each sprinkler head typically covers and protects an area on the ground of about 10 square meters. Heads are arranged to achieve this level of coverage across the floor. Typically, the installation of a sprinkler head is valued at about 180 pounds per sprinkler head to install and includes the pipework and fittings. You also need to consider the water supply looking at spawn’s price book the water supply is priced at between 60,000 to 80,000 pounds this would be for a pump and tank system.

 

For a typical 4 to 5000 square metre building the price for sprinklers including water supply is around 35 to 40 pounds per square metre. In terms of the cost of installation of the sprinklers those figures can vary depending on building height and complexity of arrangement. One area that has caught a lot of attention recently, is the installation of sprinklers into domestic homes and flats. Typical costs reported in the market for a two to three bedroom flat or apartments is between one and a half thousand and two and a half thousand pounds per flat.

 

Regulations: Sprinkler Guidance

Sprinklers have a position within building regulations and guidance throughout the UK and in the next section we will explore them. Building regulations have a life safety focus. The guidance on sprinklers are related to a building's use, compartment sizes, and building heights. There is a similar approach amongst the devolved powers the guidance on building regulations is contained within the approved documents in England and Wales.

 

The technical booklets in Northern Ireland and building standards and the technical handbooks in Scotland. You will have to read the document carefully to pick out the guidance that offers options on the use of sprinklers. The table in this slide gives an overview of when this occurs in England. The guidance for sprinklers has three components. It is based on the use of the building, sometimes referred to as a purpose group.

 

The potential size of compartments and the potential height at which people will be within the building. So, as an example there is guidance for sprinklers in blocks of flats which have a story about 30 metres in England, or roughly 10 stories. There is similar guidance for officers with a story about 30 metres, some are surprised to learn that hotels and student accommodation blocks which have stories above 30 meters do not have the same guidance. There is no guidance for sprinklers in single storey industrial buildings in England. There is guidance for the provision of sprinklers in warehouses in England and Wales when they exceed 20,000 square meters, or having a building height of 18 metres or more. To put that into context that would be the equivalent of a six storey building that covers an area of just under three Wembley football pitches.

 

Do people really understand the singular focus on life safety with our building regulations? According to research carried out by YouGov, 69% of businesses thought that current building regulations in the UK protect their premises against the devastating effects of fire. So, there is a misunderstanding in the business community over what building regulations are there to do.

 

The recent fire which destroyed a self-storage unit in south London highlighted this point clearly. The building did not have sprinklers and met building regulation guidance. The people who stored their goods within their premises claimed that their property should have been protected, meaning safe from fire. The premises owner highlighted that they complied with building regulations, which meant that people would be safe in the event of a fire. An obvious gap. You may ask how the guidance on sprinklers compares to other countries?

 

When it applies to warehouses UK regulation lags behind our nearest European neighbours. Interestingly England, Wales Scotland have some of the largest compartment sizes that can be built without guidance for sprinklers in those properties. This is 3 times the size of those allowed by our nearest neighbours, which have been said based on the capabilities of their fire services to contain such fires. Our fire services have similar equipment and tactics.

 

Is fire under control?

These fire statistics show a general trend of fires decreasing overtime, but we are still looking at over 1,000 industrial and warehouse fires in England every year. Fire has not gone away. Neither has the impact of these fires.

 

While people claim fire is under control the opposite is true in terms of the cost of fire and its impact. Insurance trends show the cost of fire is rising all the time. So, when we talk about sprinklers if you have a fire, they can be effective in containing the fire reducing it to a smaller area and the consequent damage.

 

Benefits of Automatic Fire Sprinkler Systems

So how can sprinklers help? You've seen the sprinkler video but what's it like in real life situations? A recent five year study of Fire and Rescue service data across the UK highlighted some remarkable results. It showed that in real fire events where automatic fire sprinkler systems were present, they had a 94% operational reliability. In other words, 94 times out of every 100, when they were called to work, they operated. The study also demonstrated a 99% effectiveness so when they operated, they controlled or extinguished the fire 99 times out of 100. When called on to operate, sprinklers are very effective at controlling fires. 95% of fires involve five sprinklers or less while 65% of fires involved one sprinkler only. So, this notion that all the sprinklers go off in the building is unrealistic and the data from real fires confirms this.

 

In reality only a very small amount of water being delivered from those sprinklers is needed to control the fire quickly. The notion of widespread water damage is also not supported by these figures.

 

Financial impact of Sprinklers

The findings of this UK study are consistent with the data from property insurer FM global. This reveals that sprinklered fires show a reduction in damage of 80 to 85% and it is repeated again and again across the globe. On average the properties without sprinklers suffer fire damage that is 7 times greater than those with sprinklers.

 

Building Users

So, what are some of the other benefits of using sprinklers? For the building user sprinklers protect occupants, limit fire damage and therefore minimise interruption to the continued use of the building.

 

Useable Space

When we think about usable space building regulation guidance recognises that effective sprinklers reduce a potential fire. This is reflected in guidance to allow and increase compartment sizes and open up design opportunities. As previously noted, this same thinking also is considered in standards on the design of means of escape.

 

Effective Fire Resistance

The increased ability to tackle fire with sprinklers can be used to balance the active and passive Fire Protection measures. Along with reducing the potential fire size we can also look at how we can optimize the fire resistance in certain components of a building. Similarly, if we are considering a smaller fire within a compartment this can impact how we look at fire spreading between buildings. The amount of heat that's being generated and passed to another building will be considerably less. 

 

Effective Land Use

Sprinklers can therefore have a beneficial impact on the separation distances and boundary conditions. This has an impact on effective land use. If you can place a building closer to a boundary and building larger compartments you make more use of the land that's available to you.

 

Building Design Freedoms

With the trend towards more open plan spaces Atria and larger side-lines sprinklers increase the level of active Fire Protection, so that design freedoms can be achieved. These design freedoms also reflect the ability of people to enjoy a building based on use of the space and access to light.

 

Summary of the Benefits of Automatic Fire Sprinkler Systems

When you add these components together for the total view sprinklers can add impact beyond just the pure cost. They can reduce the impact of fire increasing sustainability, they can increase the flexibility of use of a building, they can offer freedoms in terms of the land, internal layout and fire safety systems. The value of the additional benefits need to be weighed against the cost of installing the sprinkler system.

 

Design Considerations: Offices

All of that is easy to say, so we worked with a fire engineering consultancy to look at offices. Could the consideration of sprinklers accrue some commercial or monetary benefits?

 

Methodology

In the first instance they reviewed our regulations and looked at the guidance and available codes of practice for examples where the inclusion of automatic fire sprinklers could lead to differing outcomes. For example, if automatic fire sprinklers were installed, what would be the impact on factors like; exit widths, fire resistance of structural elements, and compartment sizes. They then looked at the capital cost of those items with and without the capital cost of automatic fire sprinklers in the design of offices.

 

Worked example #1

The first example is a 6 storey office building in London with a gross internal area of 15,000 square meters. The design guidance used was BS9999 and looked at 2 design cases with and without automatic fire sprinklers. The two examples in the image show 50 by 50 meter offices on 6 stories, which are below the threshold at which automatic fire sprinklers would normally be guided. The other element for buildings such as these would be boundary conditions. We looked at separation distances which for London are quite generous. On the northern side 20 metres, eastern side 10 metres, southern side 10 metres, and the western side 5 meters. In common with a lot of buildings in London we looked at the opportunity for glazed facades. When you start to consider the space separations between the boundaries this leads to a noticeable change in the amount of fire rated facade that will be requested for this building. In a situation without sprinklers on the right the fire rated facade required for the building is 800 square meters. This reduces to just over 400 square meters in a situation with sprinklers. While sprinklers add approximately £328,750 to the cost of the building, the fire rating of the facade can be adjusted, saving in excess of £2.75 million. Structural fire resistance can also be adjusted, saving a further £320,000. The introduction of sprinklers is extremely positive in this example and is over £2.75 million cheaper due to the reduction in the use of fire rated facades.

 

Worked example #2

For balance let's look at a small footprint of 20 metres by 20 metres with four stories on a less congested site in Manchester. The generous boundary conditions on the northern side were 11 metres, the eastern side 20 metres, the southern side 12 meters, and the western side 50 metres. Once again, a glazed facade was proposed and is common to what we will see in many buildings and office buildings up and down the country. Without automatic fire sprinklers the need for the use of fire rated facade reduced to 40 square meters. There was no requirement for a fire rated facade as shown on the right hand side, when using automatic fire sprinklers. This was a huge difference to the last worked example. Sprinklers add £97,600 to the cost of the building, while the boundary conditions are not as dominant in this example, the addition of sprinklers means that the rating of the facade for fire exposure can be adjusted, saving in excess of £44,000. In addition, structural fire resistance can be adjusted saving a further £15,000. Overall the costs of the sprinkler system cannot directly be offset by these features, but the sprinkler building is only £39,000 more expensive. So, by working through the numbers it becomes clear that sprinklers can offer opportunity and is not simply a pure cost. This work is available on the business sprinkler alliance website to download.

 

Case Studies

 

Liverpool Car Park

Some recent fires have highlighted the case for sprinkler protection. A Liverpool car park fire on New Year's Eve 2017 made the headlines. Packed full of cars for a horse show Merseyside FRS had the initial fire surrounded, but it spread to other floors destroying the structure and more than 1000 cars. The financial impact is in the region of £50,000,000 in reconstruction costs, on top of which is a further £20,000,000 worth of vehicles in this building. This is a building type which has no guidance for automatic fire sprinklers within our regulations. In one incident alone we're looking at an impact of more than £70,000,000. In contrast if sprinklers had been provided in this building, it would have contained the fire to one or two cars. As no one was injured this would have been deemed a success by our regulations. The impact is still being felt in the local area as temporary car parking has been built.

 

Daventry Industrial Park

One of the largest fires seen in Europe in recent years are brand new un-sprinklered warehouse in Daventry was completely destroyed following a fire in March 2018. Losing £20,000,000 of stock, add to this the cost of rebuilding and the losses are over £50,000,000. It was undoubtedly a well-engineered building receiving BREEAM ratings. However, the facility was only opened for four months before it completely burned to the ground. The building was effectively brand new having only been completed in December 2017. The business operating from these premises subsequently went into administration and was taken over by a competitor. There were no sprinklers in this building. Again, no one was injured in this event. It could be viewed as a building regulation success however it is clear the outcome could have been so much different if sprinklers were operating in the building.

 

Conclusions

In conclusion sprinklers are effective at containing fire and have an impact beyond property protection. They have costs but offered design and layout opportunities are layered approach to fire safety and assist people to escape a fire. They also allow for a combination of active fire suppression with passive protection and can lead to the creation of successful and innovative buildings.

Thank you very much for your attention.

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