The Tough get Going: An Overview of Pumps for Sludge Drying and Thickening Applications

A standard AODD pump is typically limited to the pressure of the supplied air, which is often insufficient to fill the press. For this reason, it can be necessary to increase the pressure, for which there are three very different technical solutions:

• The first variant uses one of the diaphragms on a standard pump to generate additional pressure. This force is transferred to the feed diaphragm via the internal connection, enabling it to work with double the pressure. This is rarely used anymore, as it leads to high pulsation, low feed rates and high air requirements and is more likeable to break.

• Another variant is to operate a pump with an air pressure amplifier. This process is limited by the fact that a standard pump is used most of the times, which is typically designed and built for significantly lower pressures. Additionally, the increased pressure from the “booster” pulsates strongly, which can influence the flow of the product. Boosters also seem to reach their limits in maintaining pressure as they are almost always too small.

• The third variant is a pump with internal pressure conversion. The increased surface area — typically twice as large or more — causes the compressed air to generate a corresponding increased force. This acts on the feed diaphragms with increased (double) pressure. The entire construction is designed for the high strain of maximum pressure, as well as the typically abrasive sludge. For this reason, the pump housing is built from materials such as stainless steel or polyethylene (PE-UHMW). This tough material is a decisive factor for durability.