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Pumping against the tide to keep Royal Portbury Docks Moving
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When an urgent requirement
for hire pumps capable of
delivering a total of 40,000
cubic metres per hour came in
from Bristol Port Company, it was
Pump Supplies’ quick thinking
and proactivity that secured
them the job – and the ability to
supply a total of 34 Flygt
submersible B pumps and 21 N
pumps from its stockholding at
very short notice.
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Introduction
Royal Portbury Dock was constructed south of the River Avon at its confluence with
the River Severn, and to the west of Bristol. The construction works were completed
in 1977.
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The Port can handle ships of 130,000 tonnes dead weight. Motorway access is the
best of any port in the country and there are excellent rail connections to both
Avonmouth and Royal Portbury Dock. The Port is now recognised as one of the most
productive and technically advanced in Europe. The former local authority owned Port
was sold to a private company in 1991. Since then the tonnage throughput has
increased from 4m tonnes to 12m tonnes and annual revenue from £22m to more
than £60m. There has also been more than £450 million invested at the Port.
With a spring tidal range of over 12m, the Port experiences the second largest tidal
range in the world. The strong tidal currents create a highly dynamic environment.
The Portbury Dock, like the adjacent Avonmouth Dock, is impounded and the water
level within each Dock is maintained by lock gates and impounding pumps. The lock
at Portbury is the largest in the UK being 300m long and 40m wide and has three
pairs of interchangeable gates. The Dock water level is higher than all but the highest
tides and thus it is necessary when ships are entering the Dock from the estuary to
fill the lock with water from the Dock. Each time this operation happens, and it can
occur as many as four times on every tide, water is lost from the Dock and the water
level reduces. To recover the water loss and maintain an almost constant water level
in the Dock, impounding pumps are used to take water from the estuary and pump it
into the Dock.
Without impounding pumps the Royal Portbury Dock simply could not operate.
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 Layout of dock area
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The Problem
As part of a major development at Royal Portbury Dock, a tidal chamber was
constructed in the corner of the enlarged dock with capacity for six permanent 500kW
canister pumps to maintain the dock water level. The function of the pumps is
designed to recover all the water lost through the maximum number of lock
movements that the Port considers is achievable, now or in the future.
Throughout the commissioning stages of the permanent pumps, Bristol Port
Company’s required hire pumps and ancillary equipment to be supplied in the
short-term. This was to pump sea water with a static head varying from circa twelve
metres at low tide to circa three metres at high tide over a distance of 150 metres
from the sea water intake, and subsequently enable the dock to function efficiently.
Diesel or electric pumps could be used and the dock could supply electricity from
its existing facilities.
In the end the electrical submersible option was chosen powered by
temporary generators.
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 Incumbent canister pumps and overpumping equipment
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Solution 1 : East Pier
Due to its quick response to the client’s request, Pump Supplies and Bristol Port
Company reached an agreement to supply and install twenty 12” Flygt submersible
B2250 54 kW pumps each with 150 metres of 12” quick release tube at the dock’s
East Pier.
Because of Pump Supplies’ ability to mobilise plant and equipment very quickly, the
first of 15 articulated lorries delivering equipment to site began the next morning –
depositing plant and equipment on the edge of the dock side, an area exposed to the
elements with little manoeuvrability for lorries or stock holding.
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 Overpumping ancillary equipment
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Over the next few days Pump Supplies technicians began to place the pumps over the
quay wall and into operational position. Due to the dangers of working close to the
edge of the quay all operatives wore safety harnesses securing them to the quay wall.
The Port Company supplied labour for positioning the discharge lines and linking
them up, and built a temporary control room to house the starter panels, ultra-sonic
controllers and distribution panels. A further Pump Supplies team concentrated on
the M&E requirements using portable generators with 2,000 kva of power
(1 no. 1,000 kva generator and 2 no. 500 kva generators) in order to power the 20
Flygt pumps.
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Working around the clock from 0600hrs to 2400hrs, the Pump Supplies team worked
solidly for five days to set up and commission the pumps. The whole network was up
and running within six days.
The speed in which Pump Supplies was able to get the hire pumps up and running
was crucial to facilitate the smooth running of the dock area. Teamwork ensured that
Flygt pumps in batches of five could be brought on line together, until over the five
day period all twenty were operational.
At their peak, the peak flow rate of the East Pier pumps on high tide was
approximately 19,800 M3/hr (5,500 l/s or 51/2 tonnes of water per second).
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 Pumps lowered into position on East Pier
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Solution 2 : West Pier
Discussions continued between Bristol Port Company and Pump Supplies to provide
further capacity to pump more water utilising the West Pier area.
Pump Supplies’ solution was to install another twenty Flygt pumps around the
peninsula of West Pier. This comprised 12 Flygt B2250 54kW 12” pumps and eight
NS3300 44 kW storm pumps, also 12”. As with the East Pier they were hung over
the wall with similar operational duties.
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 West Pier Discharge Flows
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The West Pier pumps had the potential to pump at a peak flow rate on high tide
approximately 18,000 M3/Hr (5,000 l/sec or 5 tonnes water per second).
Within three weeks of attending site, Pump Supplies had all 40 pumps operating
simultaneously. However the pumps were barely keeping up with the levels set out in
the brief because of the dock’s entrance lock itself. Once the first gate began shipping
movements the West Pier pumps had to stop pumping to enable the lock to
receive ships.
In addition, tugs set out at low tide to meet incoming ships from as far out as
Barry Island in Wales, therefore with the lock gates opening and closing throughout
the day, the water that the West Pier pumps was putting into the dock was being lost,
as was the additional 2,000 kva of generated power to control the pumps.
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Solution 3 : Tidal Chamber
As a result, Pump Supplies again assessed the site to see what else could be supplied
to facilitate the pumping requirements. Pump Supplies installed a further 15 Flygt
pumps comprising 13 NS3300’s 44 kW and two B2250’s 54 kW in the dock’s tidal
chamber. To initially install the pumps, the remaining two metres of water in the
chamber was drained to two inches at low tide to allow safe working.
Once commissioned, the 15 Flygt pumps were used to pump water into the Dock
with between 3-9m static head (depending on whether it was high or low tide).
The pumps in the tidal chamber were automated with ultra-sonic level controllers to
read the water levels which proved to be an effective solution. Better flow was
achieved for a shorter uninterrupted pumping duration, using 1500 kva of power from
super-silent generators.
The pumping capacity of the tidal chamber was a peak flow rate on high tide of
16,000 M3/hr (4,444 l/sec or 4.4 tonnes water per second).
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 At work in the tidal chamber
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Setbacks
One month later, the temporary pumping configuration at Portbury Dock was
interrupted by a severe storm which damaged 12 out of the 20 pumps on the East
Pier. Because they had only the discharge line for stability, they were picked up and
smashed against the wall by the severity of the storm. Two were swept away but later
recovered by the Port’s divers.
The challenge was back on to find 12 new hire pumps to replace the battered pumps
and control panels.
It took Pump Supplies just five days to remove and replace the affected pumps.
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 Storm damaged pumps
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De-Commissioning
All 55 submersible Flygt pumps continued to run in tandem until the pumps on the
West Pier were de-commissioned (because they could not match the pumping levels
required as a result of the entrance lock system).
The pumps on the East Pier and in the tidal chamber – 35 in total –
remained operational for a further three months. The 20 pumps on the East Pier were
then off-hired. The following month the six permanent canister pumps were installed
and commissioned, and the 15 pumps in the tidal chamber were finally off-hired.
In total the hire project lasted seven months.
Evaluating Success
In total 55 Flygt pumps were supplied, installed and commissioned by
Pump Supplies, achieving in excess of 40,000 m3 per hour and meeting
Bristol Port Company’s requirements whilst operating in a highly demanding, harsh
and exposed environment.
They were all provided by Pump Supplies from its network of UK depots in Gloucester,
Port Talbot, Bodmin and Winsford. During that time the company continued to service
its existing client portfolio and maintain customer relationships. No ships were turned
away throughout the life of the hire project and a smooth changeover for the
permanent canister pumps was witnessed.
The Flygt equipment supplied by Pump Supplies operated intermittently on demand
for a period in excess of 5,760 hours (approx 240 days) throughout the life of the
project without operational failure. The only pump failures were due to storm or
shipping damage.
John Chaplin, Director of Engineering for Bristol Port Company says,
“Pump Supplies provided an outstanding service throughout the duration of its works.
It was able to respond quicker than other suppliers, which was crucial at a time when
the operation of the Port was dependent upon the company’s expertise and the
performance it delivered.
“All the temporary pumping facilities proved reliable and on the occasions when ship
or storm damage occurred, Pump Supplies was prompt to rectify the damage.
The Pump Supplies team was approachable and had a detailed and comprehensive
understanding of the equipment it was providing.
“Overall Pump Supplies was proactive in its approach and prompt to address any
changes and modifications as and when they were required by the Port.”
Vital Statistics
Total kW of pumps installed – 2760
Total number of generators – 8
Total kva of power used – 5,500
Total amount of fuel used at peak utilisation – 2,000 gallons per day
Total length of pipeline used – 5.2 kilometres
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