Increased amounts of pipelines and water contained in them were absorbed by the very structure of the system, located in the uppermost point of capacity.
This reservoir served a dual function – a safety valve pressure caused by temperature changes and supply point for the new water with natural losses in its hardware. This type of installations created many problems caused by oxygen received through an open container and constantly circulating with water. The evaporation of water, it is not timely substitution also increased the percentage of dissolved salts, which cause the formation of scale, especially in small diameter PEX pipes, radiators, boilers and reduced the effectiveness of the system.
Installing an open vessel at the highest point building assumed that the tank will be placed directly under the roof of the house ie in the most vulnerable to changes in temperature and location, thus, remained a possibility of freezing water contained in the tank during the inactivity of the unit itself.
Corrosion and rapid scale formation in pipes, boilers and radiators forced the owners to the continuous maintenance of installations and replacement units.
For these reasons, almost a century reigned undisputed advantage for the production of cast iron boilers and radiators for rust resistance.
The evolution of materials, reduction of prices of production and installation, additional equipment, the use of Taco circulation pumps and smaller in size but more efficient boilers – have reduced the diameter PEX pipe.
Improving the quality of the production of heating systems clouded the old concept of open systems, the oxidation products continually harmed equipment.
The transition to closed systems. The solution was to completely close the system and find an acceptable way to accommodate the volume changes due to, the natural expansion of the water temperature increases.
Fifty years ago, went on sale first expansion tanks equipped with a diaphragm.
This type of tanks that are still being made, decided two main problems:
a) Compensation for expansion warmed water;
b) Excluding the possibility of contact of water with oxygen in the air.
This significant result was achieved by a simple manufacturing of metal tank, which consists of two parts, separated by a sealed diaphragm made of rubber. One of the two parts could be filled with compressed air, the other part is connected with the flow of the free circulation of hot water heating system.
Until now, the majority of heating systems is assumed that the hot water from the boiler circulates around the perimeter of the scheme, and the tank is located at the highest point of the structure. Mains supply the radiators, where the water gives off heat, warming the environment. Chilled water was out of the radiator from its lowest point, going down the secondary range of circulation of the heating system. Under this scheme, water is returned to the boiler to be warmed again and start a new cycle.
The ability to change the internal pressure of the system allowed to place radiators on an arbitrary height, with very low material costs, reducing the need for a long and fruitless pipelines that would lead to significant heat losses, or would require significant cost to their insulation.
Possibility to create a heating system under pressure allow greatly simplifies their design, allowing you to apply the optimal solutions as a cost for the equipment, and the time of installation.
Summarizing, we can say that the Expansion tank with a diaphragm was a necessary decision to produce more efficient energy-saving and less costly in terms of installing the heating system.
Current situation
Tanks with a diaphragm made in large quantities, and to this day, the simple design allows you to maintain a more cost-effective prices, in comparison with other, more modern expansion tanks with a replacement membrane.
Their disadvantage is the need to replace the entire tank in case of damage to the membrane.
In USA, due to difficulties in supplying the internal membranes, are in high demand and used by even the expansion tanks understated dimensions.
