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A gland leak on a valve operating in a high-pressure steam system is more than a maintenance issue. Apart from the continuous loss of steam and energy, an uncontrolled leak can create a serious personnel-safety concern and may progressively affect the surrounding valve components.

At a major power plant in India, a severe steam leak developed from the gland area of a 3-inch Angle Seat Piston Valve. The leakage was traced to the gland packing around the valve stem.

The valve was part of an operating system and immediate isolation or shutdown was not considered feasible. The plant therefore required a repair method that could control the leakage while the valve remained in service.

Nicco Engineering Services Limited carried out an engineered Online Leak Sealing (OLS) intervention to arrest the leak without interrupting plant operation.

Operating Conditions

• Equipment: Angle Seat Piston Valve

• Nominal Size: 3 inch

• Leak Location: Valve gland / gland packing area

• Process Medium: Steam

• Operating Pressure: 195 kg/cm²

• Operating Temperature: 100°C
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• Existing Packing: Metallic gland packing

• Leak Sealing Compound: NES Compound 7A

The Engineering Challenge

Gland leaks present a different sealing challenge from conventional flange or pipe-joint leaks.

The leakage path exists around a moving valve stem, and any sealing intervention has to control the escaping process medium without damaging the stem, restricting its movement, or placing uncontrolled loads on the gland assembly.

In this case, the challenge was intensified by the high operating pressure.

The repair therefore had to address several factors simultaneously:

• containment of the escaping steam;

• retention of the sealing material within the gland region;

• controlled introduction of compound into the leak path;

• protection of the valve stem and gland assembly; and

• safe execution while the system remained pressurised and operational.

The Online Leak Sealing Approach

Before beginning the sealing operation, the gland arrangement and accessible sealing geometry were assessed by the service engineering team.

The existing metallic gland packing formed an important part of the sealing arrangement and provided the necessary mechanical resistance within the gland region.

A suitable injection arrangement was then established around the gland.

NES Compound 7A was introduced through a single injection point under carefully controlled injection pressure.

Rather than simply forcing compound into the gland, the injection was progressively controlled so that the material could migrate into the available leakage path and establish an effective seal around the stem.

As the compound occupied the leak path, the escaping steam was progressively reduced until the gland leakage was arrested.

The work was completed online, without shutting down the operating system.

Result

The intervention successfully restored containment at the valve gland.

Following completion:

• the steam leakage was arrested;

• the valve remained in continuous service;

• an unplanned plant shutdown was avoided;

• steam and associated energy losses were stopped;

• the immediate personnel-exposure risk around the leaking valve was substantially reduced; and

• the valve could remain operational until a permanent inspection and maintenance opportunity during a planned shutdown.