The conventional approach consisted of renewing the underground pipe systems. The second solution concept envisaged placing a pump station at each plant. In this approach, the slop products of the production plant as well as the resulting rain and surface water are pumped via an existing pipeline network on the pipe bridges to the central wastewater treatment. The second solution approach was awarded the contract.
PCK Refinery GmbH initiated discussions with various pump manufacturers. The composition of industrial wastewater can vary greatly, and corrosive substances can also enter the pits. Therefore, the minimum requirement for the material of the parts in contact with the medium was defined as Duplex 1.4462. The design temperature of 80 °C ruled out the use of submersible motor pumps. Ultimately, PCK specified submersible pumps with a dry-mounted IEC standard motor. The switch-on level for the pumps had to be chosen to avoid backflow into the inlet channels. This resulted in installation lengths of 2.5 to 5 m.
The Swiss pump manufacturer EGGER was one of these potential suppliers. As a pump manufacturer specializing in solid-laden fluids, EGGER was able to convince during the technical award. The patented Turo® Vortex hydraulics has an impeller completely retracted into the housing with a free ball passage the size of the pressure nozzle. Clogging can be virtually ruled out, and coarse solids such as stones, branches, screws, or other coarse materials can pass through the pump without any failure. Moreover, the pump is self-sufficient and operates without any external supply such as sealing fluid. The shaft seal as a single-acting mechanical seal sits directly behind the impeller. The slide bearings above are lubricated with a clean liquid supply and do not come into contact with the pumped medium. Through a water-glycol mixture, the pumps are additionally frost-proof, and the journl bearings are protected against corrosion.
In addition to these technical advantages, the very positive operational experience with already used pit pumps was the reason for placing the order for a total of 48 pumps of this type with EGGER in 1998. Two pumps were installed per wastewater station. The base load pump is operated via variable speed drive controlled by the liquid level. The second pump with fixed speed serves as a reserve and as an overload pump, which is switched on in parallel during heavy rainfall.
After over 25 years of operation, the EGGER shaft pumps of the SG type have proven themselves excellently. Subsequently, other application sites were also equipped with EGGER submersible pumps, including pits and tanks classified as Zone 0. Further very demanding applications followed, so that currently over 100 EGGER products are in use in the refinery.
