Rodolphe Winiarski explains how choosing the right products from the outset can avoid problems of sway, settlement and seismic activity, affecting fire protection in high-rise structures.
MANY DIFFERENT factors come into play when installing sprinkler heads. In any installation, ensuring that the sprinkler heads are properly aligned with the ceiling surface is vital to the effective functioning of a fire protection system, yet is often overlooked. This becomes even more of an issue in high-rise installations where ceiling alignment can shift due to building sway or settlement.
Recent figures from the National Fire Protection Association (NFPA) show that in the US alone, 42% of instances where sprinklers have not been effective were due to inadequate water reaching the fire. This figure could be improved by ensuring correct sprinkler head positioning.
A properly installed sprinkler head needs unobstructed airflow access from the space being protected. If a sprinkler head is not properly aligned with the ceiling pane, the sprinkler will not be exposed to heat and airflow, leaving the ceiling to act as a heat deflector and potentially delaying or preventing the sprinkler from activating in time to control the growth of a fire.
Rigid piping, to connect the branch with the sprinkler, does not move with the ceiling plane. This means that while suspended ceilings may move with time due to ceiling creep, the sprinklers themselves remain in a fixed position as the ceiling slides slowly away. So, if the ceiling drops, there is a danger that the sprinkler will sit too high and be isolated from airflow in the room.
Ease of installation
Research shows that top performance, dependability, ease of installation and access are all key requirements of customers in selecting fire protection products. These are intensified when dealing with high-rise structures.
When installing fire protection piping, the choice of coupling can significantly affect the ease and speed of installation. Couplings with installation-ready technology can be fitted twice as rapidly as standard couplings and offer contractors an easy way to increase productivity, efficiency and profitability on site. They are delivered on site as single units with no loose parts and require no disassembly to install. Such couplings are proving very popular on projects throughout the world where speed and reliability is critical.
With growing demands for fire protection systems that will accommodate building height and address space issues within the mechanical room, ease of system installation must go hand-in-hand with functional suitability. A case in point is the Shanghai World Financial Centre, which at 492.3m, presented many fire protection installation challenges.
To maximise usable space in the building, the smallest – and lightest – available valves were selected. Victaulic FireLock NXT deluge valves were chosen for use throughout the fire protection system, as they operate under high pressure and offer ultra-fast trip times, while utilising lower operating pressures to provide faster water delivery to sprinkler systems.
A mix of flexible and rigid couplings was used to reduce the impact of seismic and wind forces. Their use ensured the necessary freedom of motion without compromising system integrity, to keep the critical fire protection system operating safely and efficiently throughout the building’s lifespan.
Sway and creep
Vertical riser piping in tall buildings is often subject to deflection due to wind loads that cause the building to sway. Where the pipe is rigidly fixed to the building structure, freedom of motion must be designed into the piping system, allowing it to move in unison with the building.
The anchoring of the systems by storey and the use of flexible couplings between anchors provide the necessary freedom of motion to enable the pipe to move with the building structure.
As with thermal transients, deflection or linear movement imposed on a piping system may occur due to building creep – the common term for the amount a building will move due to settlement over a specified period of time.
Accommodating building creep can be addressed in different ways when using mechanical piping systems by employing a flexible system, a rigid system or a combination of both.
In a grooved system using only flexible grooved mechanical pipe joints, risers are installed with anchors at the top and bottom, with the piping being guided every other pipe length to prevent angular deflection at the joints within the piping run. A sufficient number of flexible couplings must be used to accommodate the anticipated movement. Pipe gapping of the pipe ends within the coupling is required to allow the riser to compress as the building settles.
In those systems that use only rigid grooved mechanical pipe joints, risers can be treated in a similar way to a welded system and, where movement is required, expansion joints or offsets can be designed into the riser to accommodate the expected movement and to prevent damage to system components. By designing risers with a combination of both rigid and flexible grooved joints, engineers can use rigid couplings to reduce guiding requirements, and flexible grooved joints to accommodate the expected movement required.
Therefore, although fire protection installation in high-rise structures presents a range of challenges for the installer, by ensuring that a flexible system is specified from day one, building sway and settlement, limited plant-room space and increased pressure issues can all be overcome, ensuring a fully functional system for many years to come
Rodolphe Winiarski is fire protection market manager for Victaulic. For further information, visit www.victaulic.com