Expansion tanks are closed containers usually supplied as pressure vessels that incorporate an internal bladder and gas charge. They are designed to allow the gradual ingress/egress of liquid from the attached system in order to prevent over-pressure or vacuum conditions if the volume of the liquid in the system changes due to temperature, or some other effect.
Typically this type of vessel is designed to allow the ingress and egress of liquids at a much lower rate than might be typical for a surge vessel. Accordingly the inlet/outlet connection requirements are normally very different, with expansion tanks typically requiring much smaller connection than for a similar sized surge vessel.
Expansion tanks are normally provided with an internal bladder, or membrane to separate the process liquid from the gas charge. Bladders, or membranes are used because they separate the liquid from the gas and prevent absorption of the gas by the liquid. They also prevent escape of the gas charge from the vessel when the system is depressurised.
Internal bladders will be supplied in Butyl, Nitrile or Viton rubbers, depending on the compatibility of the process liquid with the rubber as well as the operating conditions in which the tank will work.
Sizing of the vessel will depend upon the demands of the system, as well as the working pressure range and temperature. Our engineers are able to assist in the correct sizing and selection of equipment should you require.
