[ Heating ]
[ Heating ]
When replacing outdated heating systems in existing buildings , masonry chimneys must be retrofitted with a liner due to the lower flue gas temperatures . Stainless steel systems , which are installed from above , are not only durable and impermeable , but also avoid major construction work inside the building . Photo © Joachim Nicolaus
For old chimneys that are not completely straight , a flexible stainless steel liner can follow the required passage . Photo © Cheminées Poujoulat condensate and acidic flue gases attack and deteriorate the mortar joints , which allows wetness , dangerous gases , and smoke to get into the house . Therefore , they require a lining . However , many older heating systems have significantly deteriorated liners or no lining at all . Modern liners are often double walled generally with an insulation between the walls . Type 316L stainless steel is now used as a high performance flue liner for the inner wall . This grade resists acid condensate as well as acidic flue gases and high temperatures . The outer liner can be of the same material or Type 304 stainless steel in mild environments . A stainless steel flue liner with its smooth surface finish makes it more difficult for soot to adhere to , allowing smoke to exhaust faster . Lessening soot build up also reduces the risk of fire .
Hot water , coming from the boiler , enters the hot water tank through the coiled heat exchanger tube . It thereby transfers its heat to the water which is stored inside the stainless steel tank . Photo © Viessmann
Comparatively light and easy to install , stainless steel is suitable for lining both existing chimney flues and new installations . A wide range of shapes and diameters of sleeves and chimney outlets are possible with Type 316L stainless steel . Compatible with all fuels , the alloy is ideal for wood , oil , and gas-fired boilers , and allows dry or damp smoke to evacuate at high and low temperatures . Traditionally double walled stainless steel liners were used to avoid dangerously hot pipes in the house and to maintain the flue gas temperature to ensure a good draft and avoid condensation . However , with condensing boilers the insulation solves a different problem . The flue gas temperature is so low , that it has almost no natural draft , and therefore maintaining its temperature is extremely important to allow the gases to escape . Double walled stainless steel pipes can also be used by themselves , without a traditional masonry chimney for support . This solution is cost effective , light and easy to install , it saves space , and can add a beautiful and dramatic element inside or outside the house .
Hygienic stainless steel hot water tanks Hot water tanks store heated water , mainly for domestic use in bathrooms and kitchens . Type 316L stainless steel meets the highest requirements for hygiene and durability and can withstand most corrosion risks from all types of potable water . Unlike enameled steel tanks that require regular replacement of their magnesium anode , Type 316L stainless steel requires minimal maintenance . Just like with a chimney flue , a stainless steel tank lining is smooth , which mitigates scale build up and thereby reduces maintenance and prevents premature aging of the water tank . Heat exchange coils , also made of Type 316L stainless steel , offer the same advantages in addition to good thermal conduction . In chloride-containing hot water , stress corrosion cracking ( SCC ) is always a risk . To mitigate against SCC , Type 444 ferritic stainless steel with 2 % molybdenum and 2205 duplex stainless steel with 3 % molybdenum are also popular for the lining and heating coils of hot water tanks . Thanks to its high strength , duplex stainless steel hot water tanks are also much lighter than conventional tanks . The most efficient heating systems available today are all moving towards designs with molybdenum-containing stainless steel . Type 316L stainless steel is used across a range of heating applications , improving the efficiency and durability of boilers , chimney fittings , sleeves , and outlets , flue pipes and liners , hot water tanks , and tank heat exchange coils . Additionally , in some models 904L austenitic stainless steel , Type 444 ferritic stainless steel , and 2205 duplex stainless steel are used for specific applications . Having said that , with emission-free electric heat pumps enjoying double-digit growth rates , home heating is now quickly moving away from burning fossil fuels – but not from molybdenum-containing stainless steels . Their corrosion resistance and hygienic properties are essential for heat pumps as well – however , that is for another article .
Reproduced with the kind permission of the International Molybdenum Association ( IMOA ). IMOA is a non-profit trade association representing the majority of the molybdenum industry worldwide . For information , visit www . imoa . info
40 Stainless Steel World May 2024 www . stainless-steel-world . net