by Dave Kinsey, Mechanical Projects Manager, Eraring Operations and Greg James, Sales Manager New South Wales, Queensland & New Zealand, Hydro Australia.
Eraring Power Station underwent a significant upgrade from 2010 to 2012, increasing the output of all four generating units from 660MW to 720MW each, and establishing Eraring as Australia’s largest power station.
Eraring Power Station, located in the coal belt area at Lake Macquarie on the central coast of New South Wales, began generating in 1982, with all four units commissioned between 1982 and 1984. Formerly state-owned under the banner of Eraring Energy until mid-2013, the station is now owned by Origin Energy, one of Australia’s largest electricity generators and retailers.
Condensate extraction pumps
The pumps are the standard arrangement of condensate extraction pump used in the power generation industry: underfloor, vertically mounted, canned design, four stages with a double suction impeller with inline suction and discharge ports. Each of the four generating units has two 100 per cent duty pumps, operating on a duty/standby arrangement, each driven by an 1850kW four pole electric motor.
For more than a few years, the life of the thrust bearing has been subjected to scrutiny, after causing numerous premature failures and constant concern for the station operators, maintenance engineers and management. The thrust bearing design was typical for the period that the pumps were manufactured, back to back tapered roller design incorporating both thrust and radial loads and the drive coupling configuration as part of the bearing cartridge.
Under the original bearing design, Eraring was experiencing two failures per year for approximately ten years, then three failures per year for the last two years leading up to the bearing upgrade. Each time a condensate extraction pump (CEP) failed, it took an average of five weeks to repair and cost many thousands per pump in spare parts (including replacing the destroyed bearing), labour and overhaul of the damaged wet end.
It also took a toll on the staff responsible for the CEPs, due to the inability to prevent or predict the failures, and the fear of losing two CEPs on a single unit, bringing that unit out of service for a significant interval. The reason for the failures appeared to be negligible design margin, and the initial dry start-up of the bearing (rollers above oil bath, requiring rotation of the pump to lubricate rollers, hence no lubrication at start-up, where highest thrust loads are placed on the bearing).
Station engineers had been researching the upgrade design options for a period of time, calling on the original equipment manufacturer, aftermarket service centres and bearing manufacturers for input and options to overcome this troublesome plant and work towards the best possible solution.
Eraring developed a draft bearing design after consultation with bearing manufacturers. Then three companies were invited to tender for confirmation of the design, supply of the bearing, overhaul of each wet end and installation of the upgraded pumps. All three companies had previously overhauled CEP wet ends for Eraring. The tenders were judged on price, previous experience at similar jobs elsewhere (references), technical expertise, safety performance and previous experience on site (conduct under previous orders/contracts with Eraring).
The project included a sizeable work scope including design and supply of a new white metal bearing cartridge with an appropriate pedestal and several other new components. The contract specifications required maintaining the same pump drive coupling, electric motor, mechanical seal cartridge and as many of the original pump components, meaning there was substantial engineering work required by the Hydro Australia engineers.
Hydro Australia, located in the Gippsland region in Morwell, Victoria, was awarded the contract late in 2012. Hydro Australia was awarded this contract for the following main reasons:
Relationship with Eraring – knowledgeable and friendly staff, easy to deal with, professional and courteous manner, open and always available for discussion on related technical matters. Equipment always returned on or ahead of schedule.
Technical expertise – high quality of service on previous wet end overhaul jobs, including professional reports, site visits by key technical staff to explain issues and develop strategies, willingness to have Eraring staff visit Morwell workshop to inspect job progress, meet staff and understand the processes Hydro undertake to overhaul/repair Eraring equipment.
Cost effectiveness – previous experience shows that Hydro job estimates are fully inclusive. Not always the cheapest quote, but always the highest quality job for the most competitive price. Where Hydro’s competition offer reduced initial pricing, Eraring experience shows that delays and variations have always caused the job to end up costing more than the initial quote from Hydro.
The contract runs for a period of four years, with the first pump installation completed in April 2013 and the final pump due for installation in 2016.
Additional requirements and spare pump
With the knowledge and experience of Hydro Australia with the supply of engineered spare parts, a major undertaking was to supply and complete new discharge head, a first for Hydro Australia. The 2.5m high, 1.7m wide discharge head is the most significant component of the pump, as it ties everything together. Other new components were manufactured by Hydro Australia including impellers, stage cases, wear rings, couplings and shafts. The new components complete with the stations spare parts, enabled a complete spare pump to be manufactured. This spare pump gives flexibility and relieves time critical exchanges and on the run maintenance.
Hydro Australia had a long relationship with the Eraring Power Station, having refurbished several condensate extraction pump hydraulic wet ends and several main boiler feed pump cartridges over the previous five years. All the Hydro repair methods, procedures, inspection parameters, reporting formats and attention to detail that the Eraring engineers have become accustomed to in the previous Hydro Australia refurbishment work will be used to the utmost detail in this contract.
New design bearings
Hydro Australia worked closely with Michell Bearings in the UK during the tender process and settled on a water-cooled AV series bearing design from their standard range with a few additional customised inclusions to suit. The bearing cartridge includes all the instrumentation typical on new plant including RTDs imbedded in the thrust and journal bearings, oil temperature sensors in the oil chamber, oil level alarms and trips, cooling water temperature sensors and a proximity probe located adjacent to the bearing cartridge.
With the power station design, difficult location of the pumps plus the size and weight of the pumps, removal and installation was a long procedure requiring the pumps to be partly dismantled in-situ. The pumps (without motors) are approaching seven metres long and weighing 10,700kg. Removal and reinstallation is a lengthy process which requires removing the motor, splitting the pump in two parts, removing the discharge head first, then the wet end.
Hydro Australia’s engineers came up with several designs to make life easier, quicker and safer. The first modification was to cut the shaft in two pieces making the handling of the hydraulic wet ends easier and to reduce the possibility of damaging the costly shaft when handling and transporting, this requires the use of a hydro designed sleeve style muff coupling.
Installing the pump in two pieces, setting the end float, setting up the bearing, mechanical seal and drive coupling all in a difficult location can be a cause of error and concern. The site of the installation is difficult because the pumps are several levels below the crane that lifts the pump through an opening in the floor. Hydro Australia engineers, working with the site contractors, PPI, and the station engineers devised a way of installing the fully assembled pump in one piece thus enabling the entire pump to be built, setup and ready to go in the hydro workshop. Only the motor is fitted in-situ now. The method saves over a week of disassembly, assembly and set up time on site on each pump change.
Attention to detail
Another Hydro Australia solution was manufacturing a testing jig to check the concentricity and parallelism of the 2.5m tall discharge heads. After 30 years in operation, a concern was that some of the discharge heads may be found to have become distorted. Since inception, Hydro Australia has pushed the need on multistage pumps for concentricity and parallelism of all components to ensure the entire pump rebuild is set up perfectly. This custom built testing jig saves a significant period of time on every rebuild and can be used time and time again long after the contract is finished.
The first pump completed on the contract was built up with site spares and some of the newly supplied components manufactured by Hydro Australia. The pump was successfully upgraded and installed during an outage in April/May 2013. Following this, pumps have been installed in September 2013 and April 2014, all three on time and operating as well as anticipated with low vibration levels measuring around 50 to 70 micron on all the pumps, a very pleasing result to all concerned.
Eraring is very happy with the high quality service from Hydro Australia under this contract. Technical discussions with Hydro Australia’s engineers have led to many improvements, including single piece CEP removal, spare discharge head and spool piece manufactured to allow a full spare pump overhaul. Hydro’s experience with the nuts and bolts of site works has also added great value to the site installation process. The process of the overhaul and upgrade is continually improving, which is a credit to Hydro that they are not resting on their laurels after the first successful installation, but are seeking to improve with each pump. Regular catch-up phone calls and site visits show that Hydro Australia is genuinely keen to get the best result for Eraring.
According to Eraring’s Project Manager, David Kinsey, the performance from the three installed upgraded CEPs has been above expectations. 1A CEP has seen over 12 months service (approximately 6,000 service hours). The only faults experienced have turned out to be red herrings, caused by incorrectly calibrated instrumentation or operator lack of familiarity with the new equipment. CEPs no longer gain attention as a critical, high risk failure item of plant at Eraring Power Station – this is the best possible outcome for this project.
The trust and open communication between the Eraring Power Station and Hydro Australia staff, working together in partnership toward a common goal, has been extremely beneficial to the project. A long standing relationship has been further built on by this contract and hopefully far into the future.
Pump design, materials, components and specifications have come a long way in the past 30 years. Initial instinct when a piece of equipment has failed is to replace like for like. With the advances in technology, materials, components and the experience of Hydro Australia being one of the most experienced non OEM pump rebuild companies worldwide, there are always options to improve, upgrade, build to a better standard and prolong the life of existing pump equipment. Hydro has proved this sentiment time and time again all around the world.