These expansion tanks are mainly used to absorb the fluid which is expanding and it has the capacity to maintain the pressure. ASME is a certification that ensures safety, quality and durability and this is achieved by incorporating a standard design. This certificate has a great value and it is the proof for quality. A blow down tank is required to reduce the pressure or temperature of the boiler. The temperature of the water coming through the blowdown system will be low. According to the ASME certification there should be a minimum shell thickness. Heating the water can expand its size and thus it will be double the size because of the increase in density. If this water gets heated in a closed plumbing system there is a chance for an accident. There is a possibility of failing of internal parts and internal flue or water connections. Many toxic gases like carbon monoxide can be released and when this enters the living area it can lead to big accidents. The water heater may explode when the relief valve is blocked. The expansion tank must meet certain conditions and specification in order to get ASME specification. Normally the expanded water has the tendency to come out and this excess water goes to the pre pressurized tank. When this water gets cool this is sent back to the system. We should be very careful while selecting the expansion tank.
Certain product guide and principles are adopted while selecting the expansion tank. In some cases multiple tanks are used to accommodate the higher thermal expansion. Fresh water should be added to the expansion tank if there is over pressure due to any blockage. There are both open type and closed type expansion tanks. Most of the open type expansion tanks are kept at a higher position of the circulating system. Close type expansion tank are used for thermal expansion of hot water. The pressure created can release through the relief valve if these closed type expansion tank is not used. Most of the closed type expansion tanks contain glass assemblies, air charge fittings etc. The expansion tanks must be allowed to drain when it seems to be heavy and after drainage of water, air will automatically enter the tank. It should be taken care to safely drain the water out as it will be hot.