Turbine Rupture Disk CoverTurbine Rupture Disk Cover

Background

Turbine rupture disks (Figure 1) or diaphragms protect low pressure turbine casings from deforming or rupturing due to an accidental increase of the internal steam pressure. Due to stress, corrosion, and other causes, the diaphragms develop cracks or their assemblies cease being airtight and become a major path for air leakage into the vacuum part of a steam system. Subsequently, water and steam chemistry and cycle corrosion protection goes out of control and, in a case of severe air inleakage, condenser vacuum and cycle output and efficiency are reduced. Corrosion of lead and copper alloy rupture disks also introduces undesirable (promoting pitting and stress corrosion) lead and copper oxides into the steam cycle. Severe air inleakage is also a safety hazard for operators and maintenance personnel.

During operation, the loss of tightness of the rupture disks is impossible to correct. Unit shutdown for repairs is inconvenient and the cost of downtime is high.

Description

A typical Cover Assembly is shown in Figure 2. The airtight plastic covers fit most rupture disk housings. They can be installed while the turbine is running in about 20 minutes. When installed, they also serve as an indicator of leakage of the rupture disk assembly so replacement of the original disk can be planned.

The same type of cover can be used to seal manholes on turbines, condensers and elsewhere. The Cover Assembly consists of the cover, an indicator pad, and a clamp.

Figure 1. Turbine Rupture Disk without Cover

Figure 2. Turbine Rupture Disk with Jonas, Inc. Cover

Installation

• Check that the OD of the existing Assembly Housing is clean (without blistering or loose paint, dirt, or oil). Clean the surface and remove blisters if necessary.

• Place the Indicator Pad approximately in the middle of the existing Assembly.

• Slide the Cover on the existing Housing with the Indicator Pad in place.

• Slightly tighten the clamp around the Cover.

How to Order

Measure the OD of the rupture disk housing in four directions 45 degrees apart and the minimum height of the housing at OD (see Figure 1). Include these measurements with your Purchase Order.