FIELD OF INVENTION:
The invention relates to method for building rotor for suspended type hydrogenerator at site. The rotor building is done in a service bay, thereafter the assembled rotor is erected in generator barrel and other assemblies are carried out in a appropriate sequence in the machine bay, where a machine bay pit is provided.
BACKGROUND AND PRIOR ART:
The hydrogenerators are broadly classified in four categories based upon speed, space, core length, critical speed etc. The generators are categorized as (a) Umbrella generators which have one thrust and guide bearing located below rotor, (b) Semi Umbrella generators which have an additional guide bearing above rotor as compared to Umbrella, (c) Suspended generators which have one thrust and guide bearing above rotor and a guide bearing below rotor and (d) Short Coupled generators with only one thrust and guide bearing above rotor.
In suspended type generators, the rotor which consists of shaft, spider, rim, pole etc is built in service bay, which is made of concrete. As per present practice, a pit has to be created in the service bay at considerable expense of money and time for rotor building purposes. This pit was made because no supports were there for supporting the bottom shaft on to the guide. The pit was covered after the building of rotor. This involved considerable expenses of money and time for rotor building purpose.
Since umbrella and semi umbrella generators have thrust bearings, the rotor building for such generators does not need shaft pit in the service bay (where the rotor building activity is completed) because the shaft can be lowered first and made to rest on the thrust bearing pads, as shown in Fig 1(a). For suspended type generator, as there is no thrust bearing to
hold the shaft in situ, a shaft pit is necessary to build the rotor in the service bay as shown in Fig 1(b). The hydrogenerators are huge in size, therefore, these are made in parts to facilitate transportation. The parts are assembled at site. The rotor which consists of shaft, spider, rim and poles, is also made in one assembly after building in service bay. It is already detailed out previously that shaft pit is necessary in service bay to build the rotor for suspended type generators as shown in figure-5. After building the rotor in service bay, it is lowered insitu along with shaft. This technology results in higher crane capacity and power house height in addition to shaft pit in service bay due to additional shaft length.
OBJECTS OF THE INVENTION;
It is the object of the present invention is to provide a method of rotor building in service bay, particularly for suspended type hydrogenerators, without erecting a shaft pit in service bay.
Another object of the invention is to provide a method of rotor building in service bay in which the rotor shaft is first erected insitu to eliminate the need of a shaft pit in service bay.
Yet another object of the invention is to provide a method of rotor building in service bay without erecting a shaft pit which reduces the cost and time for installation of hydrogenerators at site.
STATEMENT OF INVENTION
According to this invention there is provided method for building rotor for suspended type hydrogen era tor at site comprising of the top shaft is positioned on top end of spider, bottom, shaft is secured to the bottom end of the said spider by means of coupling studs, the assembly of said spider, top and bottom shafts are supported on a plurality of spider stools, characterised in that the said bottom shaft is lowered first in position in generator barrel and supported on to guide bearing support and placed insitu secured through supports, wherein supports comprising of assembly fixed to shaft by means of screws and provide resting of said shaft on the guide bearing support ring.
SUMMARY OF THE INVENTION
Accordingly there is provided a novel method for rotor building in service bay in which the rotor shaft is erected first insitu to eliminate need of shaft pit in service bay, according to the novel method, supporting the shaft insitu is first provided since the same has no provision in normal design for suspended type generators. For this purpose, an arrangement with a plurality of supports has
been developed including a step of providing a plurality of additional tapped holes on the shaft.
The support have been designed to suit the resting of the shaft on to the guide bearing support ring which is the integral part of bottom bracket. Thus the shaft is erected first insitu and held firmly therein, hence need of a shaft pit in service bay is eliminated for rotor building. The method comprises configurating the supports assembly on the shaft for lowering the shaft insitu. The step of configurating the support assembly further comprises welding and machining the supports, each support being tightened on to the shaft with typically two number supports, each support being tightened on to the shaft with typically two number screws of adequate strength. The shaft with support assembly is then lowered insitu resting on the guide bearing support ring. The jacks which are provided on to the bottom bracket, are thereafter positioned on raised condition. The rotor which has been built on the service bay is then lowered being supported on to the jacks. The shaft is pulled up using studs and tightened with the spider. The supports are removed at this stage and the jacks are released slowly.
The invention will now be described with help of the following accompanying drawings.
BRIED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
FIGURE: 1(a)- Shaft support insitu for umbrella and semi umbrella type generators, according to prior art.
FIGURE: 1(b)- Suspended type generators having no provision for shaft support according to prior art.
FIGURE: 2 Assembly of supports on shaft of suspended type generators according to the invention.
FIGURE: 3 Lowering of bottom shaft of suspended type generators insitu according to the invention.
FIGURE: 4 Lowering of rotor (without shaft) of suspended type generators insitu according to the invention.
FIGURE : 5- Rotor building for suspended type generator with shaft pit according to the prior art.
FIGURE: 6- Rotor building of suspended type generator without shaft pit according to the invention.
Fig. 1(b) shows the general cross sectional view of a suspended type hydrogenerator, where, as per prior practice, the bottom shaft needs to be accommodated inside a pit in service bay, where it would hang during the rotor building.
This is detailed in Fig. 5 Top shaft (1) is positioned on top end of spider (2). Bottom shaft (3) is secured to the bottom end of said spider by means of plurality of coupling studs (4). The assembly of spider, top and bottom shafts is supported on a plurality of spider stools (5) placed on the service bay floor. The rotor building activity is executed in this position.
Fig.6 depicts the rotor building arrangement of a suspended type hydrogenerator as per the invention.
According to the invention, the bottom shaft (3) is first lowered into the pit in the machine bay and placed insitu, within the machine pit. For securing the bottom shaft so positioned a plurality of supports (8) have been designed as seen in Fig 2. The said bottom shaft is provided with a plurality of additional tapped holes on the shaft.
The supports (8), typically four such, have been designed to suit the resting of the shaft on to the guide bearing support ring (not shown). Thus, the invention provides for erection of the bottom shaft (3) first insitu, thereby obviating the need of a shaft pit in the service bay for rotor building. The method comprises configurating the supports assembly (7) on to the bottom shaft (3) for positioning the shaft in situ. The step of configuring the support assembly (7)

6-further comnrise welding and machning of the supports (8) each support being
tightened on to the shaft (31 with typically two screws (9) of adequate strength. After this, the said shaft is iowered tnsitu to rest on the guide bearing support ring which is an integral part of the lower bracket. The jacks (6), which ate provided on top of bottom bracket, shown sn Fig1(a) are thereafter positioned on raised condition insitu. The shaft (3) is pulled up using screws and tightened with the spider. The supports (8] are removed at this stage and the jack is
, released slowly.
For the rotor building as per invention, the rims need to be supported at the bottom end. As shown in fig 6, numerous special firn stools (10) are positioned on the servics bay In circular placement to support the weight of the rim Tne invention reduces crane cleara nce m the service bay and machine bay as the bottom shaft (3) is already lowered nsitu.
The insitu lowering of the bottom shaft along witti support assembly is shown m Figure-3. The rotor is built paraiieiiy sn service bay without a shaft pit as shown in Figure 6. Thereafter the rotor is lowered insitu which rests on brakes under jacked condition and tightened with shaft, as n Figure 4.
The invention thus provides for a novel method for building rotor for suspended type hydrogenerator wherein the top shaft is positioned on top end of spider, bottom shaft is secured to the bottom end of the said spider by means of coupling studs, the assembly of said spider, top and bottom shafts being supported on a piuraiity of spider stoois, the said bottom shaft being placed in situ secured through supports fixed on to the shaft by means of screws, said supports enabling the resting of the said shaft on to the welded guide beartng support ring with bottom bracket characterized in that the said bottom shaft is held firmiy insitu.

WE CLAIM;-
1. Method for building rotor for suspended type hydrogenerator at site comprising of the top shaft (1) is positioned on top end of spider (2), bottom shaft (3) is secured to the bottom end of the said spider by means of coupling studs (4), the assembly of said spider, top and bottom shafts are supported on, a plurality of spider stools (5), characterised in that the said bottom shaft is lowered first in position in generator barrel and supported on to guide bearing support ring and placed insitu secured through supports(8), wherein supports (8) comprising of assembly (7) fixed to shaft (3) by means of screws (9) and provide resting of said shaft on the guide bearing support ring.
2. Method for building rotor for suspended type hydrogenerator at site substantially as herein described and illustrated.