CaseStudies

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Pumping against the tide to keep Royal Portbury Docks Moving
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.
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.
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.	Layout of dock area
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.	Incumbent canister pumps and overpumping equipment
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.	Overpumping ancillary equipment
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.
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).	Pumps lowered into position on East Pier
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.	West Pier Discharge Flows
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.
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).	At work in the tidal chamber
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.	Storm damaged pumps
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