Page 37 - Gi flipbook March 2018

automatic shut-off device, blocking closed, permanent magnets embedded shut-off plates in a symmetrical
water ingress in the gas pipe in the first in the plates attract the magnetised design create a tight seal against
place, long before the customer steel seats, closing the Aquashield and water ingress from both directions.
reports an interruption to their supply. the water flow downstream.
The main purpose of Aquashield is Before the Aquashield can be reset Easy to install and operate
to block the flow of water in the gas to the open position, a suction tube Aquashield can be installed in an
pipe. It effectively confines the must be inserted into the device to existing gas network easily without
affected area before anyone notices extract water from the cavity. A rod is modification to the current supply.
the water ingress, so interruptions to then inserted to push the buoy down The operation of Aquashield is simple
customer supply can be minimised. to its original position, meaning the and reliable and its internal parts are
Moreover, since the extent of the gas shut-off plates separate from the maintenance-free and easily reset.
network affected can be reduced, the metal seats and open the path for gas
size of the workforce and the amount resumption. (See Figures 5 and 6) SPECIAL FEATURES OF
of time needed for follow-up actions AQUASHIELD
like de-watering and gas resumption PE cross fitting embedded with
can be further reduced. FIGURE 5 Aquashield shut-off mechanism metal seats
There are two types of Aquashield; In order to avoid specially-made
a metal one was designed as an earlier fittings and to reduce on-site
version and an updated, PE device fabrication, Aquashield uses a factory-
provided a few improvements. produced, prefabricated PE cross
Simplicity is key. Aquashield’s design fitting with mechanical parts for easy
consists of mechanical parts housed in connection to the existing PE network
a PE cross fitting, including the by simple electrofusion.
counter rods, shut-off plate, cantilever, A pair of metal seats made of
metal seat, PE adaptor, guide rod and magnetised steel is embedded in the
buoy. It creates a self-triggered FIGURE 6 Aquashield re-opened PE cross fitting by interference fit,
water-blocking mechanism using which acts as a valve seat to the
buoyancy principles, a lever system shut-off plate. Once the magnets in
and magnetic force. the plate are brought to the metal
plates, a strong magnetic force
WORKING PRINCIPLES OF attracts the two together, blocking
AQUASHIELD the water flow from either direction.
Aquashield has been designed for use
in low pressure distribution networks. Shut-off plates
Its PE spigot ends allow it to be fused The plates are made of polycarbonate
directly onto the PE pipe. Under embedded with 20 permanent
normal circumstances, Aquashield is magnets, evenly distributed at the
fully open to allow the gas flow. DESIGN CONSIDERATIONS outer ring of the plate, to create a
Material selection magnetic force to the metal seats.
The self-triggered shut-off device is (See Figures 7 and 8)
FIGURE 4 Aquashield mechanism
initiated by the buoyancy force Polycarbonate was chosen as the
exerted on the buoy once water material because of its high impact
accumulates in the Aquashield cavity.
This means the components lifted up
by the buoyancy force must be made FIGURE 7 Aquashield PE cross fitting with
of lightweight materials. a pair of metal seats
The floating element itself, which is
made of expanded polystyrene foam,
has good buoyancy properties. Apart
(See Figure 4) Assuming water from the magnetised steel seats, the
ingress from either side of the gas pipe, other components are made of
as water enters the Aquashield, the lightweight plastic materials like
blocking mechanism is triggered polyoxymethylene (POM),
automatically by the buoyancy force of polycarbonate (PC) and aluminium.
the ingress water exerting on the buoy. Aside from this, the materials are
As the water level in the Aquashield rigid enough to withstand water and
increases, the buoy keeps rising. The gas pressure and good for preventing
guide rods ensure the buoy moves corrosion. FIGURE 8 Shut-off plate assembly
upward in a vertical displacement.
Once the buoy rises up to a certain Two-way blockage of water
position, the system hits on the The direction and location of water
counter rods and pushes the shut-off ingress can be unpredictable, hence
plates laterally and in parallel to the the Aquashield is designed to block
metal seats. water flow no matter which
When the shut-off plates are direction it comes from. Two

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