Research And Insight

Diaphragm tank

The volume of the water in a pipe system will vary depending upon its temperature. An expansion tank is used to ensure the absorption of excessive volumes of water. This normally consists of a closed tank, where a flexible membrane absorbs the excess pressure.

The gas-filled side of the tank contains nitrogen. Its pre-set pressure must correspond to at least the static pressure plus 0.5 bar. Breaks or explosion of the pipe work due to excessive pressure can occur if a diaphragm tank is not included.

In booster applications, diaphragm tanks can be used on both the discharge and the suction manifold. Connected to the suction manifold, a tank serves to counteract fluctuating inlet pressures.

Pressure in low flow periods:
Diaphragm tanks are commonly used on the discharge manifold to provide water storage for the system in very low flow situations. It decreases the running time of the booster pumps, thereby making the system more energy effective.

Eliminates water hammer:
Since the diaphragm is flexible, it is able to adjust to sudden pressure changes, thus counteracting water hammering.

When to use diaphragm tanks:
If low or no-flow conditions are expected, a diaphragm tank should be used to work in conjunction with the Stop Function of the booster system.

In areas where inlet pressure fluctuates, diaphragm tanks are often installed on the suction manifold to reduce damaging peak pressures.  

The Grundfos Hydro MPC range of pressure boosters are ideal for energy-efficient and safe operation together with a diaphragm tank for applications in commercial buildings, and also for the smaller pressure-boosting requirements in domestic buildings.