Across a great many industries where fluids are contained in open and closed pits/sumps or tanks located below or at ground level, it is inevitable that pumps will be required to empty or transfer the fluids to other locations. However, the pump type employed will have to satisfy the demands of the application, so consideration has to be given to pump selection and specification. Horizontal pumps and submersible pumps may well accommodate a substantial number of applications and operating conditions, but for more challenging applications vertical suspended immersion pumps can be the best answer.
Low-pressure suspended pumps are designed for vertical wet installation in a closed tank under atmospheric pressure. In contrast to submersible pumps, where the motors are encased and immersed in the fluid being pumped, the motors and associated critical components of vertical suspended immersion pumps do not come into contact with the fluid. This is because they are located in the pump motor stool on a plate attached to the top of the pit/sump or tank. It is a significant advantage because it removes the requirement for sophisticated motor monitoring devices and contributes to lower maintenance costs resulting from extended service intervals.
A further advantage is realised where flammable fluids are being pumped. Transferring fuels is not a problem because the electrical components are separated from the mechanical components.
The impeller is fully immersed in the fluid at the bottom end of the pump shaft, which is contained within the robust support column, to which is attached the discharge pipe. This design and construction means that the whole unit takes up minimum floor space, making it suitable for installing in confined spaces.
Ander Ochoteco, KSB Estigia Product Manager explains that: “Suspended immersion pumps are most suited to trouble-shooting solutions where some specific applications and operating conditions are challenging. Here, we are looking at pumping flammable liquids, condensates, high temperatures, cavitation and the potential for low NPSH. In pits and tanks where fluids are coming from different processes, there can be an unknown mix of chemicals and concentration of solids. These are conditions where self-priming and submersible pumps would struggle.”
Ander stresses that for many applications, it is the robustness of the Estigia pumps that have proved to be successful. “We have examples of applications in a wide spectrum of industries where high temperatures are encountered and highly toxic and hazardous chemicals are treated. At a plant treating animal fats at 60 ⁰C contained in tank in an ATEX T4 atmosphere our answer to the challenge was a version with a round base drilled according to DIN and ANSI for sealing the tank. The pumps supplied were stainless with an immersion depth of 3m and double cartridge mechanical seal with API52 PLAN and closed impeller. Another example was at a plant renovating its condensation evacuation coke and gas systems. The application involved pumping a potentially flammable fluid solution with a concentration of 18% benzene. For a major European vehicle manufacturer, we replaced submersible pumps with units for the supply of general cooling water extracting the water below ground level. Where long suction lines are involved and large amounts of air require evacuating, changing to an immersed pump can result in reduced pumping times”.
“The markets in which this pump is established include industrial wastewater, chemicals, seawater collection, sulphuric acid, paper, surface treatment, automotive and marine,” continues Ander. “The Estigia series is characterised by high efficiency and low operating costs. These attribute result from its ease of installation, accessibility for maintenance without entering the pit or tank, longer intervals between servicing and its ability to be retrofitted with the minimum of disruption.”
Recognising that industrial processes and requirements are ever-changing, KSB has now introduced in a new variant to its Estigia series, which reflects the growing requirements for vertical suspended immersion pump technology. This new development builds on the flexibility of its original design, bringing different types impeller, materials of construction, varying immersion depths and compatibility with many emerging mechanical and electrical accessories. This new version is available with a choice of three types of impeller, namely: closed, semi-open (channel) and vortex in diameters up to 300 mm.
Depending on the pump version specified, flow rates of up to 1200 m³/hr at pressures up to 16 bar are attainable. “The advantages over other makes of suspend immersion pumps lie in the details that KSB has introduced to the new pump,” says Ander. These include higher pressure capabilities, together with a wide range of accessories to accommodate special requirements and pump customisation. For the installation depth, various lengths ranging from a minimum of 852 mm to a maximum of 6402mm are available and three discharge pipe diameters can be selected for each pump size.”
When the immersion depth exceeds 2400 mm, a special design element between the support column sections and the discharge pipe makes for significantly reduced vibrations. The casing cover of the pump is fitted with a product-lubricated plain bearing made of high-grade, wear-resistant silicon carbide. The pump set is easy to install and dismantle with its integrated cover plate serving as the tank cover. The material variants on offer are cast iron, stainless steel and duplex steel. Replaceable casing wear rings prevent possible wear on casing and impeller.
The pump set can be supplied with shaft bearings lubricated by the fluid handled, an external liquid or an electric grease pump. A so-called cantilever design is also available. This version is designed to ISO 5199, with flexible coupling and grease-lubricated rolling element bearings arranged outside the fluid handled. The pump is suitable for fluid temperatures of -30 °C to +140 °C. It can be driven by variable speed and fixed speed electric motors, with or without ATEX approval.
Vertical suspended immersion pumps have been shown that they can play a significant role in fluid handling operations where submersible pumps and self-priming horizontal pumps may not be able to satisfy the users’ needs. Immersible pumps provide an alternative solution that offer a robust technology for the safe and effective emptying of pits/sumps and tanks.
Here you can find even more information, documents and downloads (in German) about these pumps: www.ksb.de/estigia
