Aiming for peak boiler performance in Hong Kong

T he A and B stations at Castle Peak in Hong Kong (pictured above) have a combined installed capacity of 4100 MWe. As part of a comprehensive modernisation programme, Foxboro I/A Series control systems are being progressively installed at the 2700 MWe unit B station (on the right).

The first phase of the project has been completed. This involved the upgrade of one of four 680 MW boiler units at the 2700 MW Castle Peak B station. The station Hong Kong's largest - is owned by Castle Peak Power Company Limited (CAPCO), a 60/40 venture of ExxonMobil Energy Ltd and CLP Power Hong Kong Limited. The latter is the principal subsidiary of CLP Holdings which is listed on the Hong Kong Stock Exchange and is one of the largest investor-owned power businesses in Asia.

CAPCO owns three power stations in Hong Kong. Alongside Castle Peak B, there is its sister plant Castle Peak A, a 1400 MW coal fired station, and also the 2500 MW gas fired Black Point station. All three are operated and maintained by CLP Power.

As the largest electricity utility in Hong Kong, CLP Power provides electricity to 2.1 million customers, about 80 per cent of Hong Kong's population, in its supply area covering Kowloon, the New Territories and most of the outlying islands, including Lantau where Hong Kong International Airport is located. CLP Power's parent company, CLP Holdings, also invests in energy-related businesses on the Chinese mainland and the Asia Pacific region.

Both Castle Peak stations are based on British design and technology widely adopted by the Central Electricity Generating Board (CEGB). Privatised over a decade ago, the CEGB was responsible for the design, construction and operation of all power stations in the UK and in many of the former overseas territories.

Move to DCS

To avoid potential problems in obtaining spares for the boiler control system on which the vendor had ceased to provide support, CAPCO management decided to move to a modern distributed control system (DCS).

Against the backdrop of strong competition from other reputable control system suppliers, Invensys had to satisfy CAPCO of its capabilities in the power industry, with particular emphasis on its refurbishment skills. "Although we had never worked with Invensys before, based on their previous experience at other large power stations around the world, we were confident that the company could deliver both the technology and expertise we needed," said KB Lam, Generation Projects Manager of CLP Power Company Limited.

In addition to assuring CAPCO about Foxboro products and the value of its own experience, Invensys had to satisfy a number of other demands in order to beat the competition. These included presenting the best project execution plan, the best risk management strategy, and provision of a product with the lowest lifecycle cost yet one with proven backward compatibility and scalability. At all times, the company also had to prove that it had a complete understanding of the issues and concerns affecting CAPCO.

At the same time, CAPCO had its own set of objectives for the project:

• Non-obsolescence of replacement control system.

• Improved control system reliability.

• Improved life cycle cost as a result of reduced operating and maintenance costs.

• Improved operational effectiveness.

• Enhanced plant performance.

Scope of supply

Invensys' scope of supply included the Foxboro I/A Series system for the boiler modulating and sequence control, plus a range of auxiliary controls such as those for the soot blowers, valve positioners, some actuators, UPS, training skid and large screens. It also called for improvements and modifications in the control room and installation of all the necessary cabling etc.

The company had also to remove the existing control system along with hardwired back-up control panels in the control room and all other pieces of existing hardware that had been made redundant as a result of the refurbishment work.

In a more consultative role, Invensys was expected to provide value-added services that would improve the performance of the boiler units. To deliver this, the company performed a benchmark test to set up the baseline for improvement. Furthermore, the company had to improve on the original control scheme, provide 100 per cent testing during system staging and plan for a complete changeover to the new control system over a shutdown period of not more than three months.

To meet these rigorous requirements, Invensys undertook a number of initiatives. One of the first was to form an ad hoc team made up of experts in sales, engineering and customer service in order to focus more clearly on CAPCO's needs. Another was to emphasise the value of the partnership approach to the project and how this went hand in hand with the company's commitment to a long term winwin relationship.

As well as investing time to provide the customised solution, Invensys made sure that the project manager designate was involved in the negotiation and clarification meetings during the sales phase. This in particular was seen as a critical factor in the success of the project as CAPCO was keen to ensure both that there was continuity from the sales phase to engineering and that it could be confident an experienced project team had been put in place.

Another critical factor was the ability to draw on worldwide power support. Invoking the involvement of the FoxMass Global Power Engineering team was seen as crucial in giving CAPCO a high degree of confidence in Invensys' capability and resources devoted to the successful execution of this project.

Project success

In the end all of CAPCO's objectives were met, particularly in terms of improved boiler unit performance.

As with any plant rehabilitation project, the accuracy of 'as built' drawings is crucial and CAPCO undertook the very important role of data validation. As a result, project risk was significantly reduced and the partnership approach resulted in the unit being put into service one day ahead of schedule despite a very tight timetable. "The successful completion of this first boiler unit against a demanding schedule has justified our confidence in Invensys," noted Lam.

The original contract was awarded on 3 April 2001, with the first boiler unit completing its provisional acceptance test on 20 July 2002. The second unit was delivered at the end of last year. The third and fourth units, both currently in the engineering phase, are due to be delivered at the end of this year and the beginning of next year respectively.

Ultimately, the multi-million Castle Peak dollar modernisation contract calls for the installation of the Invensys Foxboro I/A Series automation system in all four units to overcome the ageing problems associated with the prior system. The new control system will provide a higher level of automation that is expected to reduce unit start up times and improve thermal efficiency. The new systems will also minimise maintenance effort and material costs.