What is applied to an exchanger gasket, when allowed by the plant, to enhance the seal to the gasket surfaces?

Graphoil tape is commonly used to enhance the seal in an exchanger gasket. This material is made from a combination of graphite and other materials, which provides a flexible and durable seal that can help accommodate the varying pressures and temperatures encountered in heat exchangers. Its properties allow it to conform well to surface irregularities, which helps prevent leaks and promotes better sealing performance.

Moreover, graphoil tape is chemically resistant and can withstand high temperatures, making it suitable for numerous industrial applications where traditional sealing materials might fail. This adaptability and effectiveness in ensuring a tight seal is why it is preferred in many plant operations.

Other materials mentioned, such as silicone sealant, PTFE paste, and varnish, while they serve sealing purposes in certain applications, may not offer the same performance characteristics or compatibility with various fluids and operating conditions found in heat exchangers as graphoil tape does.