FIELD OF INVENTION
This invention relates to an improved stay ring of a turbine with cast stay vanes
weld-joined to upper and lower stub vanes integrally cast to respective belts.
More particularly, the invention relates to an improved cast-welded large size
stay rings with variable horn radii and horn heights in which middle vane, upper
belt with upper stub vanes and lower belts with lower stub vanes are cast
separately and joined together by welding.
BACKGROUND AND PRIOR ART OF THE INVENTION
The large size stay rings of a turbine with variable horn radii and horn heights
are difficult to manufacture as the integral casting of the stay ring is beyond the
capacity of any foundry to cast or too many dies are required for fabrication.
Stay ring is an essential component of hydro turbines and consists of upper and
lower belts connected together by streamlined columns called the stay-vanes to
guide the water to guide vanes. It is designed to withstand the hydraulic thrust
and the weight of the superimposed parts. The upper and lower belts have

flanges that are machined for bolting with the top-cover and pivot ring
respectively. The stay-vane profile is designed to provide streamlined flow for
minimizing hydraulic loss and meet the strength requirements. The horn radii
and horn heights are points where the stay ring is welded to the spiral casing.
As shown in fig.l and 2 of prior art, large stay rings (1) were made of fabricated
construction in which the upper (5) and lower belts (4) were made in segments
by cutting, rolling and bending boiler quality carbon steels plates in required
shape, and the stay vanes (2) being made of casting. The each segments of the
belts were welded together to form complete ring. The stay vanes (2) have
upper and lower stems which are then inserted into the matching shaped
grooves (8) in the upper and lower belts and finally welded (6,7) (refer Fig.2).
The main problems in this design was that of making expensive dies for bending
each of the belt segments and finally inaccuracies in setting the design angle of
the stay vanes (2) with respect to the axis cannot be ruled out while welding to
the grooves (8) in the upper (5) and the lower belts (4).
OBJECTS OF THE INVENTION
Therefore it is an object of the invention to propose an improved stay ring with
cast stay vanes weld-joined to upper and lower stub vanes integrally cast to

respective belts which is capable of manufacturing the stay ring with a much
simpler design.
Another object of the invention is to propose an improved stay ring with cast
stay vanes weld-joined to upper and lower stub vanes integrally cast to
respective belts which eliminates the use of expensive dies and thus makes the
manufacturing cost effective.
Yet another object of the invention is to propose an improved stay ring with cast
stay vanes weld-joined to upper and lower stub vanes integrally cast to
respective belts which are able to maintain accurate angle of stay vanes with
better location.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig.1 - shows a sectional arrangement of a hydro turbine showing the location of
stay ring according to prior art.
Fig.2 - shows the fabricated stay ring according to prior art.
Fig.3 - shows the cast-welded stay ring in accordance with the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
As shown in fig.3, according to the present invention the upper (4) and lower (5)
belts along with some portion of stay vanes i.e. stub vanes (9,10) are cast
separately maintaining the design angle and profile (13). The advantage of this
design is that the angle of the stay vanes (2) can be maintained accurately. In
the present invention the stay vane (2) is split into a middle vane (12) and upper
and lower stub vanes (9,10). The middle stay vanes (12) or the main portion of
the stay vanes (2) are cast separately. These cast middle vanes (12) are welded
(11) to the stub vanes (9,10) which are cast integrally with upper and lower belts
and thus form the complete stay ring (1).
These cast welded stay rings (1) with variable horn diameter (D) and horn
heights (H) are formed in joining separate castings of middle stay vanes (12),
upper belt (4) with stub vanes (9) and lower belts (5) with stub vanes (10) by
welding. The horn diameter (D) and the horn heights (H) are points where the
stay ring (1) is welded to the spiral casing (3).
This design is successfully implemented in the stay ring of a hydraulic turbine
being installed in Uttarakhand state of India.

WE CLAIM
1. An improved stay ring (1) with cast stay vanes (12) weld-joined to upper
and lower stub vanes (9,10) integrally cast to respective belts (4,5)
comprising:
an upper belt (4) being cast integrally with stub vanes (9);
a lower belt (5) being cast integrally with stub vanes (10);
a middle stay vanes (12) being cast separately;
characterised in that the middle vanes (12), upper belt (4) with stub
vanes (9) and lower belt (5) with stub vanes (10) are joined together by
welding to form the complete stay ring (1) maintaining the design angle of
the stay vanes (2) accurately.
2. An improved stay ring (1) as claimed in claim 1, wherein the middle stay
vanes (12) is the middle and main portion of stay vanes (2).
3. An improved stay ring (1) as claimed in claim 1, wherein the stub vanes
(9,10) are a portion of the stay vanes (2).

An improved stay ring (1) with cast stay vanes (12) weld joined to upper and lower stub vanes (9,10) integrally cast to respective belts (4,5) consists of an upper belt (4) being cast integrally with stub vanes (9), a lower belt (5) being cast integrally with stub vanes (10) when a middle stay vanes (12) is cast separately. The middle vanes (12), upper belt (4) with stub vanes (9) and lower belt (5) with stub vanes (10) are joined together by welding to form the
complete stay ring (1) maintaining the design angle of the stay vanes (2) accurately.