Keep it moving
Avoiding blockages is more important than efficiency

Wastewater pumps have never had it easy. The media place high demands on the materials and the hydraulics. Users expect maximum availability and long service life. The selection and dimensioning of wastewater pumps affect more than the problem-free flow of water in a water treatment plant. Getting the performance specs right has a significant influence on investment and operating costs. It is worth doing your homework up front.

When it comes to costs, pump manufacturers often point to the efficiency of their pumps, which is undoubtedly an important parameter that highlights the hydraulic quality of a pump unit. However, this is not the end of the story in the wastewater industry. There are additional important aspects to consider, for example low susceptibility to blockages and rugged design. When you are talking about wastewater pumps, reliability is more important than high efficiency. Users also appreciate simple, low cost maintenance which enables them to get a pump back in working order more quickly. ABS Pumpen shares this view. The company believes that if you focus on efficiency, you have to expect that you will spend a lot of money clearing blockages. The reason for this is that higher efficiency comes at the expense of smaller cross-sections, and this increases the risk of blockages. The AFP-ME series from ABS is designed for wastewater and sewage treatment applications. Models are available in the 9 to 160 kW (50 Hz) or 185 kW (60 Hz) range. These immersion pumps offer non-clogging operation (contra block system with large opening for solids), high reliability and efficient motors. The units are also easy to maintain, and the original efficiency level can be restored on site without the need to replace any parts.

Rubberized pumps a success
Herborner Pumpenfabrik appears to
have a reliable solution for handling really tough jobs at the intake stations in water treatment plants. The aggressive, sandy sludge in the intake basins is extremely hard on conventional pumps. The housings and impellers are unable to withstand the stress for very long. The manufacturer has been conducting a long-running test on a rubberized pump at a water treatment plant near Berlin. The test has been running since 2001, and the results are very respectable. This particular water treatment plant uses immersion pumps. Due to the high concentration of sandy substances in the water on the bottom of the basin at the intake station, the pump was installed about one meter above the bottom. This increased the service life of the pump, but mineral deposits have to be removed manually at least twice a year. For technical reasons, cleaning can only be carried out on weekends. A Univers-T immersion pump has now been installed. A rubber coating has been applied to the free flow impeller, the pump housing and the cover to make the pump suitable for mounting on the bottom and to prevent the build-up of new deposits. (The alternative, a stainless steel design, would have been twice as expensive as the current solution.) The user is satisfied with the pump’s durability so far.
Rugged eccentric screw pumps and hose pumps
Allweiler has developed the new AENZ series of eccentric screw pumps, which are ideal for pumping media with a high solids content. An inlet funnel guides the media to a screw. The new pump replaces two previous series, and the manufacturer is convinced that the new version offers industrial users a number of advantages. The maximum allowable solid content is
38 percent, which is twice the limit on the previous design. The new pump, which is made of standardized components, also reduces investment and operating costs. Spare parts and high-wear parts are more readily available, and spare parts management is less complicated. The manufacturer also has a double-screw pump to handle media which contain even more
solids.
The rugged Elro hose pumps from
Crane Flow are designed for media that contain solids. High pumping performance at low speed is a special feature of the XP series. Models running at moderate speed (60 RPM max.) pump between 3.2 and 46.0 m3/h. The advantage of low speed operation is reduced wear on the hose material, which extends service life. Because the units have a very large hose inner diameter (91 mm on the XP 800), they are
suitable for pumping media that contain long fibers and solids up to a diameter of 40 mm. The new T300 series was designed for mobility. This compact model pumps up to 18 m3/h at a maximum pressure of 1.5 bar. The pump can even handle high viscosity media with the aid of a patented vacuum system. The T300E has a powerful 3 kW electrical motor. If no electrical
power is available, the user can choose the T300B instead, which comes with a Honda gasoline motor (3.7 kW).
No need for cooling at 300 m3/h
The Grundfos SE series of wastewater pumps offers users a range of practical
features. The primary and secondary mechanical seals are designed as replaceable cartridges. When the need arises, the user can replace the seal without any special tools. The pumps are suitable for wet well and dry well installation. They can deliver up to 300 m3/h without motor cooling. A solid-block stator housing conducts excess heat to the medium in the pump housing. Temperatures remain below the critical level even during continuous operation. Heat is exchanged directly without the need for cooling ducts, and there is no risk of blockages which can occur with conventional designs. In wet well installations, a polyurethane-filled stainless steel cable entry creates a hermetic seal and prevents fluids from running down the cable into the motor. Single-channel and super vortex impellers allow solids up to 100 mm to pass through. This reduces the risk of blockage and minimizes interruptions. The units feature a flexible design. The motor assemblies can be removed quickly, and they fit pumps with single-channel (SE1) and SuperVortex impellers (SEV).
Telesolutions: Internet-based pump diagnostics
KSB offers Internet-based remote diagnostics. The services are called Telesolutions, and they include notification of service personnel when a fault occurs. Pump and system status information is presented on-screen or in report format. According to the supplier, the information helps the user perform status-based maintenance and drive down operating costs. The system is based on the Pumpexpert diagnostic device, which is available for all of the main series of pumps which are used in water or wastewater management applications. The device captures available information from sensors on the pump and in the system (pressure, flow rate, temperature of the medium and vibration). The various signals along with changes over time provide information on the status of the pump. Pump-specific rules and limits are pre-configured by the manufacturer. The user receives a clear-text message and a recommendation on what action to take if a fault occurs (bearing damage or dry running). Pumpexpert also provides information about the operating mode of the pump and the system and any significant changes. This is important, because deviations from the operating point or from the pump running time are a reliable indicator that problems are likely to occur.
Sample wastewater pump problem
During system trials which were run on a large wastewater pump, a frequent but apparently random “excessive external vibration” warning was issued. The data from the machine and the adjacent machine which were displayed in graphics format were used to quickly identify the problem. Heavy vibration was induced by the adjacent machine via a common pipe when the machine slowly ramped up to speed and inlet pressure was particularly low. It only took a few minutes to reduce the ramp up time by 50%, and this solved the problem, preventing early bearing failure and unscheduled maintenance. The customer can use the administration mode on the web front end to manage users, pumps and messaging. KSB has no doubt that this technology will significantly increase the efficiency of maintenance activities. Early warning about potential problems can eliminate significant follow-on damage and unscheduled maintenance. Continuous pump monitoring and analysis of current and historical data enable users to extend inspection intervals.