Gaskets are part of every boiler and steam or hot water system. They’re used around the many handholes and manholes provided for access and inspection, to prevent leaks in exhaust ducting, and wherever pipes are joined. If a boiler gasket fails the consequences are usually serious. Hot water, steam, or exhaust gas leaks are dangerous and reduced efficiency increases operating costs. That’s why safety experts recommend boiler gaskets be inspected regularly and replaced every year.
Every boiler consists of a burner or heating element and some form of heat exchanger. Water, often chemically treated to prevent corrosion, enters the heat exchanger and is heated to a target temperature. In a steam-producing boiler temperatures and pressures can exceed 380°F and 180PSI.
Exhaust gases go up a flue and steam or hot water enter the piping system. In steam systems the vapor condenses as it cools and the condensate returns to the boiler to be reused. Condensing boilers tend to produce a corrosive condensate, (actually carbonic acid,) in the exhaust stack.
Shutting down a boiler is expensive and disruptive, so it’s always better done as part of scheduled maintenance rather than in response to a leak. Most boilers benefit from an annual inspection and clean. Removing accumulated soot and scale improves efficiency and components should be checked for correct operation. As that involves opening handholes and manholes, it’s also a good opportunity to replace gaskets, even if they show no sign of leaks. (And never reuse a gasket as that could lead to an unplanned shutdown!)
Boiler Gasket Materials
On the fire side of the boiler gasketing is usually done with fiberglass rope or tape. This can handle temperatures of more than 1,000°F. Another option is graphite foil, often formed into a spiral wound gasket for sealing flanges.
On the water side the primary consideration is tolerance to steam. Secondary requirements are good tensile strength, (to resist the internal pressures,) and resistance to corrosive acids and water treatment chemicals. Heat and oxygen tend to oxidize many elastomeric gasket materials, and this should also be considered when selecting boiler gaskets.
All-in-all, the water side environment usually leads to EPDM gaskets. They have a wide temperature range, good compressibility, and the excellent steam resistance that’s needed.
Boiler Gasket Selection
Downtime is expensive, so it’s important to ensure the new gaskets will provide at least 12 months of trouble-free service. Boiler gaskets should be selected based first on performance and secondly, on ease of installation and replacement. A well-made gasket will fit comfortably, providing good coverage of the mating surfaces. Contact a Hennig specialist today to ask what’s recommended for your boiler.