Low pressure steam turbine seal arrangement
View Patent ↗A seal arrangement is installed between confronting co-planar portions of a low pressure steam turbine exhaust hood and a circular bulkhead that forms part of an exhaust duct structure of a steam turbine module. The seal arrangement forms a vacuum seal between the interior and exterior of the exhaust hood and comprises a flexible gasket in the form of an annular diaphragm. This diaphragm has a radially inner circumferential portion that seals with the bulkhead, a radially outer circumferential portion that seals with the exhaust hood, and a radially median resilient portion. Sealing is achieved by providing radially inner and outer clamping flanges operative to sealingly clamp inner and outer circumferential portions of the gasket to the bulkhead and the exhaust hood respectively. To enable quick access to the interior of the exhaust hood, the clamping flanges comprise upper and lower halves and the upper part of the gasket is sealed to the upper parts of the exhaust hood and the bulkhead by an arrangement of flanges and counter-flanges, the counter-flanges being releasably secured to outside surfaces of the exhaust hood and the bulkhead.
1. A vacuum seal arrangement installed between confronting co-planar portions of a low pressure steam turbine exhaust hood and a circular bulkhead that forms part of an exhaust duct structure of a steam turbine module, the vacuum seal arrangement comprising:
a flexible gasket in the form of an annular diaphragm with a radially inner circumferential portion sealingly secured to the circular bulkhead by releasably secured segmented flanges;
a radially outer circumferential portion sealingly secured to the exhaust hood by releasably secured segmented flanges; and
a radially median resilient portion extending therebetween;
wherein the segmented flanges comprise diametral joint lines between flange segments coincident with a sealing plane between lower and upper parts of each the exhaust hood and the circular bulkhead; and
wherein an upper part of the gasket is releasably secured to the upper part of each the exhaust hood and the circular bulkhead by an arrangement of segmented flanges and counter-flanges.
2. The vacuum seal arrangement of claim 1 , wherein the radially median resilient portion of the gasket comprises a portion convexly curved to approximate a semi-toroidal shape.
3. The vacuum seal arrangement of claim 2 , wherein the radially median resilient portion is convexly curved toward an interior of the exhaust hood.
4. The vacuum seal arrangement of claim 1 , wherein:
the segmented flanges are releasably secured to inside surfaces of the counter-flanges, and the counter-flanges are releasably secured to an outside surface of the upper part of the circular bulkhead;
the segmented flanges are releasably secured to inside surfaces of the counter-flanges, and the counter-flanges are releasably secured to an outside surface of the upper part of the exhaust hood;
an inner circumferential portion of the upper part of the gasket is sealingly secured between the segmented flanges and the counter-flanges; and
an outer circumferential portion of the upper part of the gasket is sealingly secured between the segmented flanges and the counter-flanges.
5. The vacuum seal arrangement of claim 4 , wherein the lower part of the gasket is releasably secured to the lower parts of each of the exhaust hood and the circular bulkhead by the segmented flanges releasably secured to an inside surface of the lower part of the circular bulkhead;
the segmented flanges releasably secured to an inside surface of the lower part of the exhaust hood;
a radially inner circumferential portion of the lower part of the gasket releasably secured between the segmented flanges and the inside surface of the lower part of the circular bulkhead; and
a radially outer circumferential portion of the lower part of the gasket releasably secured between the segmented flanges and the inside surface of the lower part of the exhaust hood.
6. The vacuum seal arrangement of claim 5 , wherein the flanges are releasably secured by bolts or the like.