STEAM TURBINE ASSIGNMENT

Anchoring in a 660 MW DONGFANG/GE turbo generator.

NAME: ABHISHEK NEGI

ROLL NO: 03815303713

SEMESTER: 5TH SEM

COURSE: B.TECH

ANCHOR POINT OF TURBINE In designing the supports for the turbine on the foundation, attention must be given to the expansion and contraction of the machine during thermal cycling. Excessive stresses would be caused in the components if the thermal expansion or contraction were restricted in any way. The method of attachment of the machine components is also a decisive factor in determining the magnitude of the relative axial expansion between the rotor system and turbine casings, which must be given careful attention when determining the internal clearances. The fixed points of the turbine are as follows: - The bearing housing between the IP and LP turbines. - The rear bearing housing of the IP turbine. - The longitudinal beam of the I.P turbine. - The thrust bearing in rear bearing casing of H.P turbine.

Casing Expansion The front and rear bearing housings of the HP turbine can slide on their base plates in an axial direction. Any lateral movement perpendicular to the machine axis is prevented by fitted keys. The bearing housings are connected to the HP and IP turbine casings by guides which ensure that the turbine casings maintain their central position while at the same time allowing axial movement. Thus the origin of the cumulative expansion of the casings is at the front bearing housing of the LP turbine. The casing of the IP turbine is located axially in the front area of the longitudinal beam by fitted keys cast in the foundation. Free lateral expansion is allowed. The center guides for this casing are recessed in the foundation crossbeams. There is no restriction on axial movement of the casings. Hence when there is a temperature rise the outer casing of the IP turbine expands from its fixed point, towards the generator. Differences in expansion between the outer casing and the fixed bearing housings to which the housings for the shaft glands are attached are taken up by bellows expansion joints.

Rotor Expansion

The thrust bearing is incorporated in the rear bearing housing of the HP turbine. Since this bearing housing is free to slide on the base plate the shafting system moves with it. Seen from this point, both the rotor and casing of the HP turbine expand towards the front bearing housing of the HP turbine. The rotor and casing of the IP turbine expend towards the generator in a similar manner. The 1.P. turbine rotor is displaced towards the generator by the expansion of the shafting system from the thrust bearing. The magnitude of this displacement, however, is reduced by the amount by which the thrust bearing is moved in the opposite direction by the casing expansion of the IP turbine.

Differential expansion

Differential expansion between the rotors and casings results from the difference between the expansion originating from the bearing housing behind the HP turbine and that from the thrust bearing. This means that the maximum differential expansion of the HP and IP turbine occurs at the end furthest from the thrust bearing. Differential expansion between the rotor and casing of the IP turbine results from the difference between the expansion of the shafting system, originating from the thrust bearing, and the casing expansion originating from the fixed point of the I.P casing on the longitudinal beam members.

Anchoring and Aligning the Stator Frame and End Shields to the Foundation:

The stator frame is anchored to the foundation with anchor bolts in conjunction with aligning

elements and sole plates set in grout on the foundation. The leveling screws are screwed into

the support foot of the frame and permit a rapid and exact alignment of the stator. To ensure

a uniform transmission of forces they are arranged symmetrically about the anchor bolts. The

spherical portions of the leveling screws ensure complete contact and thus a rigid connection between stator and foundation. The stator end shields are aligned on the machine sole plates

with shims. Different thermal expansions of the stator and foundation result in differential

movements between the frame and machine sole plates. The stator is therefore fixed in

position in a manner allowing for expansion while retaining alignment. Fixed keys located at

the feet in the middle of the stator frame secure the frame axially in a central position.