The Project

Energy Development Corporation (EDC) procured the BacMan power plants from National Power Corporation – Palayan 2 x 55 MW and Botong and Cawayan 20 MW plants. The plants needed major rehabilitation – Botong had been inundated by landslides on two occasions and cooling tower burnt down, Cawayan was destroyed by an overspeed event and a typhoon, and Palayan was in a very poor state after many years of very little maintenance.

Our Role

Thorndon Cook staff were involved as Owner’s Engineer for EDC to manage and engineer the rehabilitation of the Palayan facility, transfer the main equipment from Botong to Cawayan and its rehabilitation.

Our role included evaluation of the work required, development of contracting strategy, and preparation of specifications.

Multiple contracts were put in place, aligning the scope to contractor’s in-house capability to shorten the bid and award period. The contracts addressed the complexity and uncertainty in rehabilitation by dividing the scope into defined work, inspection work, work to be done in piecework rates basis, and a system for dealing with unanticipated work. By clearly allocating risk appropriately, a good tender response was received.

Results

The project faced severe challenges, with extreme rainfall and adverse weather during the first few months, contributing to delays in outdoor work.

More detailed inspections showed extra work was required such as complete replacement of the Palayan power plant main steam piping and gas extraction system steam piping.

Long lead times on items such as switchgear meant one unit’s existing switchgear was temporarily rehabilitated, followed by replacement at a later date for acceptable reliability.

The operator, BacMan Geothermal Incorporated is proud of their safety record during the project, achieving 2,000,000 hours without LTI.

Commissioning was achieved within 3 months of the original ambitious schedule, but a generator rotor earth fault took one of the machines out of service. After some months of operation a blade failure took out the second machine. All machines required generator rotor rewinding to return them to operation, and turbine blades were replaced. For long term operation EDC procured new turbine rotors.

Innovations

The rehabilitation included modifications to improve the performance and reliability, and cater for a 50% increase in non-condensable gas in the steam. The gas extraction system was modified to operate more efficiently by:

• repurposing redundant loop seals for use on the 2nd stage condensate drains
• expanding gas extraction capacity using Liquid Ring Vapour Pumps (LRVPs) so that the existing 2-stage ejector system could be operated in hybrid mode reducing steam consumption.

The cooling system was upgraded by converting the existing cooling towers from splash fill to counter flow fill, which also allowed lowering of the cooling water pipes and additional cooling water flow from the hot well pumps with the reduced head.

Capabilities

Disciplines:
process design, mechanical engineering, electrical engineering, project/program management

Roles:
conceptual engineering, feasibility studies, including economic analysis, front end engineering design, project planning and project management, tendering and procurement, site construction supervision, commissioning and start-up, owner's engineer roles