Page 36 - Gi flipbook March 2018

IGEM NEWS | Young Persons Paper Competition 2017

Aquashield to mitigate

water ingress of gas pipes

By Rita Chiu, Assistant Engineer at the Hong Kong
and China Gas Co Ltd and YPPC 2017 finalist FIGURE 2. Gas pipe (top) damaged by water
jet from adjacent leaking water pipe
ong Kong is a busy and interruption to their gas supply. This
densely populated city. means water ingress into a gas pipe
While the road surface can affect a large number of
is congested with customers before any action is taken.
buildings and traffic, The longer the time lapse, the greater
H the ground beneath is the extent of the gas network
also suffocating with utility pipework. affected. Minimising the time between GAS PIPE
Due to the congested conditions the actual water ingress and the
underground, utilities are constantly incident report time is crucial to
fighting for space, making use of every containing the incident, as well as
available inch for their pipes. This arranging resources for de-watering WATER PIPE
means gas and water mains always and gas resumption.
neighbour each other, as their buried
depths are similar. Action to contain the affected area
To avoid water ingress to gas mains, Due to the quick spread of water
there is a requirement of at least ingress within a gas network, current FIGURE 3. Internal structure of Aquashield
300mm clearance between the two practice dictates that a large workforce
types of pipe. In reality, the pipes is required to locate the exact water 1st Generation (metal iron body)
sometimes have less clearance due to ingress point, and this can take a long
space limitations. time. Immediately after arriving on site,
When vigorous excavation activities the emergency team has to determine
are combined with pipes in close the extent of the affected area by
proximity, this can lead to burst water checking the syphons, saddles, risers
pipes and one of the main causes of and governors along the affected area.
water ingress into gas mains. The team will check the site
When a water pipe bursts near a environment as well as the timing and 2nd Generation (PE body)
gas main, the high pressure water jet location of customer reports. If the 1
(usually 6-8bars) together with sand situation is uncontrollable, gas valves 2
and rock create a grinding effect, and risers will be closed to confine the
which damages the nearby gas pipe affected area, causing gas interruption 3 5
over time. The water jet then enters to customers. 4
the eroded gas pipe and creates a gas
supply interruption for a considerable Locating the water ingress point and
number of customers. (See Figure 1) follow-up actions 6
(See Figure 2) The possible location of 7
water ingress has to be identified by
THE CURRENT CHALLENGES checking the nearby governors and 1. PE cross fitting
2. counter rods
OF HANDLING WATER INGRESS syphons, if any. Ground conditions and 3. metal seat (magnetized steel)
Delays in reporting the speed of ingress may provide hints 4. shut-off plate
The point when water ingress occurs for identifying the water’s source and 5. cantilever
is unpredictable and usually is only location. If the leak is small, it can take 6. guide rod (stainless steel)
noticed when customers report an some time to identify its exact 7. buoy

location. Once the ingress point has
FIGURE 1 Small clearance of water pipe and other utilities been identified, dewatering and repair
of the gas pipe, and subsequent gas
resumption will also require a huge
amount of resources and time,
depending on the pipe material and
the area affected.
(See Figure 3) To mitigate the effect
of water ingress to a gas pipe, and
solve the above challenges, Aquashield
has been designed to work as an

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