• Materials of Construction.
• Solid Copper - type CS: Copper is virtually impervious to attack by aggressive water. In the few areas where water is known to attack copper the calorifier can be protected by a sacrificial aluminium anode. this leaves a protective coating on the copper and does not need replacing. the copper thickness required for a calorifier increases with pressure and diameter. above a certain size copper lined steel is more economical.
• Copper-Lined steel - type CL: Carbon steel lined internally with copper. none of the steel is in contact with the water. the steel gives great strength, the copper prevents corrosion. special techniques have been developed to ensure a close fit of copper to steel, to allow thermal expansion and contraction of the lining and to test the lining. it is fitted as standard with an anti-vacuum valve to prevent partial vacuum damaging the lining. Even so care should be taken during drain-down to ensure adequate venting of the calorifier. the cold feed must never be restricted during draw-off.
• Galvanised steel-type GS: Hot dip galvanising deposits a zinc layer which provides excellent protection against corrosion if the water is hard. galvanised calorifiers should not be used with copper pipe-work or soft water. the copper causes electrolytic action and releases particles of copper which deposit in the calorifier, causing localised electrolytic action and corrosion. soft water prevents formation of a protective scale. the copper tube bundle rapidly gets a film of scale because of its higher temperature. this prevents electrolytic action and corrosion. For added protection a magnesium sacrificial anode can be fitted. this must be replaced when exhausted. also the copper tube bundle can be electro-tinned which reduces the electrochemical potential.
• Stainless steel-type SS: Stainless steel calorifiers can suffer chloride attack at welds. most water supplies contain enough chloride to cause problems. heat treatment after all welding is completed solves the problem but is expensive. If the water supply is chloride free (e.g.de-ionised water) then stainless steel calorifiers will be acceptable.
• Glass/Polymer lined steel-type PL: An alternative to copper-lined steel. the lining was developed for arduous conditions in industrial processes. It is generally more resistant to abrasion, chemical attack and impact damage than
traditional glass linings. if damage occurs, the surrounding coating will not be affected and the damage can be repaired. In the lining process minute glass flakes are combined with a special polymer, applied to the steel, cured and electrically tested. the lining is WRC approved for use with hot water. other materials available on request. Please contact us for any enquiries you may have.
* System Considerations.
• Secondary vent: Calorifiers can be supplied for open vented or unvented (sealed) systems. in open vented systems, the vent pipe allows escape of air from the calorifier, ingress of air during drain-down, thermal expansion of water and (in the event of control failure) escape of steam from the calorifier. the vent pipe should never be blocked. No valves should be fitted to it except, where more than one calorifier share a common vent, special 3-way vent/bypass valves. This ensures that the calorifier is always open to atmosphere.
• Unvented systems: When it is not practical to fit a vent, an unvented system will be used. certain additional precautions and equipment are necessary to ensure that an unvented system will be safe:
√ The calorifier must be designed for the maximum working pressure - after thermal expansion of the water.
√ A Temperature (or combined Pressure/Temperature) Relief Valve must be fitted in case of control failure.
√ An automatic air vent.
√ An anti-vacuum valve
√ An expansion vessel.
A water booster set may be required to provide water at the required pressure and flow rates.
• Secondary return: Most large systems circulate DHW around a building and back to the calorifier. this ensures that all draw-off points have hot water available quickly. the pipe-work should be lagged and the re-circulation rate minimized to reduce heat loss. the heat loss should be taken into account when selecting a calorifier.
• Thermal insulation options.
√ Type MA consists of 50mm mineral wool with dimpled aluminium cladding. this gives good thermal insulation and a quality finish. for some installations there will be a high risk of damage to the factory fitted insulation. in these instances it is preferable to insulate on site.
√ Type UF For sizes up to 1000 liters or 250 kg dry weight (approximately) we can offer Type UF semi-rigid urethane foam insulation. this is sprayed on in a standard thickness of 25mm (up to 60mm on request). Its ozone depletion potential (ODP) is zero, it does not support combustion and it resists water penetration. uniform thickness is not guaranteed.
Enamelled Storage Cylinders.
Storage cylinders for central heating systems up to 25 bar and 100 °C,and domestic hot water up to 10bar and 90 °C. |
