FUGESCO

Radial Seals

Radial type seals are used in hydroelectric turbines, pump-turbines and large pumps.

The primary purpose of a mechanical radial shaft seal is to maintain a near watertight seal between the turbine shaft and the head cover. Depending on the pressure under the seal, two or more carbon segmented sealing rings are required. This seal is reliable, relatively simple to install and easy to operate and maintain.

All of our radial type shaft seals are fully split or non-split and specifically designed for hydropower generating turbines. The seal can be custom designed and adapted to the existing turbine configuration and specification in order to meet the operating requirements.

For small shaft diameters, these seals can be designed with anti-rotation pins positioned in the cover and in the lower chamber ring to maintain a low seal profile. For easier installation we recommend the use of an intermediate ring with the stop pins located between the two sealing rings in order to facilitate installation. If required, an inflatable seal can be supplied to allow maintenance without dewatering the turbine.

A basic turbine seal consists of a base ring and a cover ring forming the cavity that houses the sealing rings. The cover ring is secured to the base ring that, in turn, bridges the gap between the turbine shaft and the head cover and also serves to house the inflatable seal (if required).

The cover ring can also be designed to act as a reservoir to accumulate water on top of the seal to prevent a dry running condition of the top sealing ring in the event that the turbine is operating under vacuum conditions.

Each sealing ring assembly consists of overlapped and interchangeable carbon segments, compression springs and garter springs. The carbon segments are positioned around the shaft to perform the sealing function.

The sleeve is split into half rings or quarter sections. The sealing area of the sleeve is machined to a high precision surface finish. The sleeve rotates with the shaft by means of drive screws or a clamping system.

A flow of clean water free of abrasive particles must be maintained throughout the seal to provide cooling and lubrication to reduce wear of the sealing surfaces. Water should be filtered to ensure that impurities larger than 25 microns are removed. In order to prevent dirt from entering the seal from below, the clean water supply must be at a higher pressure than the water pressure underneath the seal.

All of our seals include eyebolts and jacking screws for use during assembly or disassembly. The seals also come with Hex keys for assembly of the housing components, an o-ring splicing kit, flange sealant, silicone grease and a piping connection identification plate. A copy of the installation, maintenance and operation manual are also provided with the seal.

In order to regulate the pressure differential between the shaft seal and the turbine, a seal water control panel complete with an automatic differential pressure regulator can be supplied with each seal. The positive pressure differential is necessary to prevent abrasives particles from entering the seal chamber (For more information about “Seal Water Control Panels” see Chapter 3 in this catalogue).