Inherent to the design of all Heat Recovery Steam Generators is the internal liner systems,
internal seismic restraints, and miscellaneous internal supports. These types of components
necessary and must be attached directly to the HRSG cold casing by means of pins, studs,
scallop bars and/or other components. Due to this fact, some amount of conducted heat is
unavoidable and expected. In some of these localized areas, temperatures will exceed the
specified casing temperature.
In conjunction with these items mentioned above, casing pipe penetrations and piping
expansion joints will also experience heat conduction that is unavoidable. In fact, the
stainless steel piping expansion joints are designed to operate under these specific
conditions and insulation of the expansion joints will result in joint failures.
These areas of high casing temperature are not indications of equipment or material
breakdown, or inadequate design and will not compromise the longevity or integrity of the
HRSG. High temperature areas may be noticed due to small areas of discolored paint.
Overall HRSG appearance and discoloration of paint caused by these hot areas is highly
affected by the choice of paint / coating. Paints should have a continuous temperature
exposure limit of 500 degrees F. Vogt Power recommends a zinc rich primer. If a top coat is
required in high temp areas above 500 degrees F continuous, such as a bypass dampers,
etc. a suitable high-temperature coating, such as silicone acrylic or silicone aluminum, is
recommended. High-temperature coatings may have limited color availability, depending on
the type of coating and the manufacturer.