“Tai Ah Wan (Daya Bay) Nuclear Power Station has installed two sets of GEC-A produced 900MW steam-driven turbine electricity generator. Each steam-driven rotor has a high-pressure rotor and three low-pressure rotors. The steam-driven turbine machine has four rotors, which coupled with the rotors in the generator by four pairs of couplings. The system started working since 1994 and has a total of four outages. On the 2nd outage in December 1995 to March 1996, both generators used Pilgrim radial fit bolts to replace the original GEC-A bolts.
On the 1st main outage in December 1994 to May 1995 and on the 2nd outage, the dismantling of the original bolts has encountered great difficulties especially on the 2nd set of rotors during the 2nd outage, three pairs of bolts were in ‘seized’ position. Normal ways of dismantling were impossible and the bolts had to be machined out in order to remove them. For this reason, three extra days were spent on outages.
Due to the change of bolts to Pilgrim radial fit bolts on the 3rd outage in December 1996 to May 1997, the dismantling and replacement of the bolts were easy. For example, in each machine, there are four sets of rotors and each set have sixteen bolts and the outage on two machines were completed in a day and hence saved time.
With the above comparisons (GEC and Pilgrim), our opinion is that Pilgrim radial fit bolts should be used in the power station steam-driven generator system. The new nuclear power station called Lin Au Power Station which is undergoing construction, has two sets of 900MW system installed has already used the Pilgrim radial fit bolts.”
YE NENG QIAN – Head of Service Engineering Division