When time is of the essence

When CS Energy needed to quickly refurbish a cooling water pump at the Callide Power Station in Queensland, they knew Hydro Australia was the company best equipped for the task ahead.

 

CS Energy’s Callide Power Station is located near Biloela, 120km south-west of Gladstone, Queensland. Victorian-based Hydro Australia was successful in winning the tender to repair and refurbish one of the power station’s cooling water pumps during an April 2015 outage. Hydro Australia had successfully carried out the same work during previous outages in 2013 and 2014. Refurbishing a split case water pump is a relatively straightforward exercise, however this project had a number of challenges to be managed.

The pump

First up, the pump is large, with 1,400mm diameter flanges, axially split case, 3.5m x 3.5m x 3m high, and weighing in at near to 24,000kg, it requires a low loader to transport. Also, due to the oversize dimensions of the pump, the transportation can only be carried out during daylight hours. This means three days’ travel each way between Biloela and Morwell.

The timing

Due to time constraints with the unit overhaul program, the pump was required to be in and out of Hydro Australia’s workshop in 13 days. Any later and the unit’s return to service would be delayed, something that neither CS Energy or Hydro Australia wanted to happen.

The work scope 

The refurbishment had a fairly typical work scope. Grit blast and coat the casing, upgrade the bearing housing to accommodate new labyrinth seal designs, new components consisting of bearings, shaft sleeves, throat bushes, mechanical seals and casing wear rings, balance the rotor and assemble.

Preparation

Knowing the job details well in advance made the process easier. Hydro Australia were able to purchase in all the components required, and raw materials were pre-machined for components including the throat bushes, case wear rings and shaft sleeves. The decision was made early to have a dedicated project manager walk the job through from the start, a decision that proved very worthwhile when the timeframe kept dropping.

The obstacles

On top of the time delay in getting the pump removed, a few other obstacles arose once the pump was stripped and assessed. Firstly, the casing required line boring past the erosion/corrosion damaged areas under the case wear rings. This was accompanied with new oversized stainless steel wear rings in excess of 1,100mm in diameter.  The next issue was the impeller – a missing/broken suction vane in the impeller eye, 17 cracks in the impeller, with many cracked through, and severe cavitation on all suction vanes.

Moving forward

After careful consideration and formalising the weld procedures and repair methods, the impeller repairs were successfully carried out by Harvest Engineering in Melbourne. Once the impeller was repaired and inspected, work started on the rotor with dressing of the weld repaired areas, skimming the wear rings and rotor balancing. Consecutively the casing was blasted, line bored, inspected and coated internally in preparation.

Completion

After only eleven days, the pump was completed and ready for the long trip home, two days ahead of schedule. In such a short time the pump was rebuilt to a high standard and will provide  reliable service for the power station.

Hydro Australia has representatives for Australia and New Zealand based in Sydney, Perth and the Morwell head office. For more information on Hydro Australia visit www.hydroaustralia.com.au or email [email protected].

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