Page 36 - Gi flipbook June/July 2018

IGEM NEWS | Young Persons Paper Competition 2017

SMART RISER JACKET

By Raymond Mung Yuen Wai, Assistant Engineer at the Hong Kong
and China Gas Company Limited and YPPC 2017 finalist

n Hong Kong, a typical gas riser
system consists of a base support, TABLE 1: Standard riser repair methods
the service main riser and the
service lateral, providing a reliable Methods Anti-corrosion tape Gas pipe leakage sealant
and safe gas supply to customers.
ISome risers can become
corroded due to prolonged exposure Gas pressure availability LPA-LPB LPA
to corrosive chemicals, mostly Curing time Instantly 24 hours
occurring in aging buildings. Required gas suspension No Yes
According to government statistics
from 2016, the number of buildings Durability Temporary repair Permanent repair
aged 30 years or more exceeds 21,000, Advantages Quick fix for emergency Stops gas leaks
and this number is increasing use only permanently

Limitations Trapped moisture can Only can be used on
FIGURE 1: A typical riser system aggravate corrosion thread gas leakage and
has a long curing time

considerably every year. The number of
riser replacements is also expected to FIGURE 3: Bending at the branch section
increase as more buildings age. Cost,
manpower and time are considerable
and critical factors in implementing
riser replacement.
Despite their suitability in certain
scenarios, the limitations of the usual
riser repair methods can constrain
their implementation in real life. In
that case, replacement of the
corroded riser becomes the only
solution to ensure a safe gas supply.
However, replacement, too, has its
drawbacks.

DOWNSIDES OF RISER
REPLACEMENT
FIGURE 2: Replaced riser Temporary gas suspension
To ensure a safe and reliable gas Material wastage
supply, replacement of the riser is The replacement of service risers
often unavoidable. However, it requires produces surplus material such as
interruption of the gas supply, causing extra pipe segments and couplings.
an inconvenience to users. In addition, For example, replacing a 0.3m
one week's advance notice is required defective section on a 3m service main
to inform gas users. This period riser means removing the whole 3m
between the notice being issued and section to ensure the remaining
the riser replacement poses a potential pipelines are not contaminated. Ninety
safety risk. per cent of materials are wasted in
order to recover a relatively small
Lateral service corrosion area. This is not a very
Removal of the main riser may induce a environmentally friendly approach.
downward pulling force on the lateral
service risers, which may become bent or SMART RISER JACKET
twisted. The bending stress can cause In order to avoid the typical pitfalls and
cracking at the backfill, trapping constraints of replacing defective risers,
rainwater and sewage and accelerating a new method called the Smart Riser
corrosion to the service lateral. Jacket has been invented.

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