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Turbine shaft seal with spring arrangement

IP.com Disclosure Number: IPCOM000114543D
Publication Date: 2005-Mar-29
Document File: 5 page(s) / 163K

Publishing Venue

The IP.com Prior Art Database

Abstract

A turbine shaft seal arrangement comprises a semi-circular spring extending circumferentially between the turbine casing and a shaft seal. It allows the shaft seal to move away from the shaft during low-pressure conditions in order to avoid damage. When the spring force is overcome with increasing pressure in the turbine the semi-circular spring is forced to move radially inward and assume a shape having several waves along its length. The spring is kept in contact with the seal by several pins or similar devices. The ends of the semi-circular spring are fixed by means of a stop plate arranged in the vicinity of the horizontal casing flanges of the turbine casing.

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Turbine shaft seal with spring arrangement

Rotating machinery such as steam turbines typically comprise labyrinth seals about their shaft in order to minimise leakage flows between static and rotating parts. Excursions from normal concentric running can occur at low-pressure conditions. Accordingly, the seals are designed to spring back away from the shaft in order to reduce damage to the seal and shaft. For this, known springs are designed either as individual plate springs arranged spaced regularly about the circumference or as radially mounted coil springs as disclosed for example in US 3,594,010. Other known labyrinth seals are spring loaded away from the shaft during low-pressure conditions as disclosed for example in US patent 5,934,684. Should the pressure load overcome the spring force, the seal moves to a running position on the rotor.

A new solution to avoid damage to shaft and seal is presented. It comprises semi-circular springs, instead of coil or plate springs, that extend circumferentially between the casing and a shaft seal and allow the seal to move away from the shaft during low-pressure conditions. Figure 1 shows the lower half of a turbine casing, the turbine rotor, and three segments of a labyrinth seal extending along the circumference of the casing between the casing and the rotor. The hatched area extending over the entire extent of the three seal segments indicate the position of the semi-circular spring S1. Several pins or similar devices give a point contact between the semi-circular spring and each seal segment and are plac...