Australian Water Management Review Vol. 1 2014 | Page 24

shannon creek daM sWitches to
custoM anti-cav control valve
solution to handle excessive
head loss across its inlet valve
Authors:

andrew Parker, Director with ToTaL Flow control

mark Gimson, Business Development and marketing manager with Singer Valve

S

hannon Creek Dam and pump station is
the core feature of the Regional Water
Supply scheme, a joint venture of the Coffs
Harbour City Council and the Clarence
Valley Council. With an inundation area
of 37 square kms, the reservoir provides 30,000
mega litres of supplementary water supply to
The Clarence Valley and Coffs Harbour, located
on the mid-north coast of New South Wales,
Australia. This award-winning project will secure
water supply to an estimated 220,000 people in
the region over the next few decades. The dam
crest can be raised a further 10 meters to increase
storage a further 45,000 megalitres.
The Nymboida River supplies the Shannon Creek
Dam with its water and has an inlet weir at the river
takeoff that is approximately 128m above the pipe
work in the valve pit. The dam delivery head is 33m
making the normal head loss across the valve 95m.
This can increase to a maximum of 105m when the
Nymboida River is at its maximum level as a result
of heavy rainfall.
Clarence Valley Council (CVC) who manages the
scheme, has an operating license that allows for
up to 54 mega litres/day which amounts to 624 l/
sec flow into the dam. This can increase to 94
mega litres/day (1087 l/sec) in certain emergency
situations. The dam inlet control valves have to be
able to operate between closed and maximum flow

18 | AustrAliAn water man age m e nt re v ie w

rate, depending on current rainfall in the catchment
area, and levels in the Nymboida River.

its components, and connected pipework resulting
in the failure of the main inlet valve.

Since commissioning and start up, CVC has
experienced ongoing cavitation problems and seal
failures of the main inlet control valve. The original
installation included an inlet valve – DN750, PN35
double flanged butterfly valve, along with a DN250,
PN35 low flow bypass butterfly valve. The problem
was the DN250 bypass valve would cause severe
noise and vibration when operated, which lead to
the DN750 valve doing the majority of the work. It
was operating at approximately 8 to 9% open to
achieve the normal required flow rate of 250 l/sec
into the dam. This is really not an ideal situation
for a butterfly valve, as the butterfly valve’s original
design is for fully open or fully closed.

During discussions regarding these problem valves,
CVC provided TOTAL Flow Control and Singer Valve
with specific flow ranges, inlet pressure ranges and
outlet pressure requirements enabling Singer to
offer and recommend an engineered solution to their
specific application.

After the second valve seal failure on the main
valve that resulted in severe leakage when closed,
CVC contacted TOTAL Flow Control to provide
a solution that would deliver to CVC long term
operating reliability and control. It was determined
that with the significant head loss across these
valves and the variable flow range required, the
installed DN750 butterfly valve was oversized, and
was an inappropriate valve type for this application,
resulting in severe cavitation damage to the valve
seats, leaf and seal. The consequences of cavitation
are numerous and included loud noise, extreme
vibrations, choked flow, erosion of the control valve,

Singer’s Anti-Cavitation technology contains two
heavy stainless steel sliding cages that maximize