By Beate Zaschke
A new Elephant House is replacing Cologne Zoo's oldest building, a Moorish design constructed in 1863, to improve the environmental conditions of elephants living in the facility. Two waterfalls feature prominently in the new design, which won an architectural competition in 1999.
ACO Passavant Gebäudeentwässerung GmbH of Phillipsthal, Germany, developed the pumping system layout for water drainage in the facility. The company used Spaix® PipeCalc and Spaix® Classic pipe calculation software from VSX - Vogel Software of Dresden, Germany, to determine the operating points (lift height and flow quantity) and to select appropriate pumps.
Various pump shafts are required in the new Elephant House for two waterfalls and other functions. Pumping capacity must be calibrated precisely for the operating point with throttling provided by orifice plates or gate valves. The submersible pumps used must be constantly underwater because the pumps run approximately 12 hours per day. Other pump shafts are intended for reservoirs in the enclosure. These pumps have to run approximately once a year to drain the reservoirs. During the draining phase, these pumps will run continuously for 36 hours. Here again, the inlet quantity and pump capacity must be brought into agreement so pumps remain constantly underwater to ensure sufficient cooling.
"The Spaix system of programs helped us calculate and select the appropriate pumps, which we calibrated for the optimum duty point by trimming the impellers. Using this system of programs saved us considerable time compared with the usual calculation methods," according to Manfred Schäfer of ACO Passavant, who oversaw the project.
Waterfall 1 provides an illustrative example of determining operating points for pump shafts. A submersible pump continuously circulates water. Flow rate is determined by the flow speed and water amount of the waterfall, namely 61.2 m3/h. Spaix PipeCalc determines the resulting lift height. First, the type of medium must be defined, which is domestic wastewater with no faecal content. The total flow of 61.2 m3/h is entered and the desired number of pumps defined as "1." The geodesic height, which at six metres corresponds roughly to the height of the waterfall, enters the calculation. To determine the loss of each component in the piping system, the material, nominal width, pipe length and roughness must be entered. The pipe systems consists of 10 metres of straight pipe length and four elbows, both grey cast iron and DN 100, an expander from 80 to 100 millimetres, a DN 80 slide valve and a DN 80 check valve. Loss is calculated for each individual component. The resulting total head loss is determined from the previous calculation, which is 3.7 metres. The geodesic height and friction loss results then in a total head loss of 9.7 metres.
The next step is to select the hydraulically optimised pump for Waterfall 1. The determined operating point of H = 9.7 metres and Q = 61.2 m3/h is entered directly into the Spaix pump selection software, which contains hydraulic and technical product data for ACO Passavant's pump and lift equipment. Using the specified operating point, the program searches the pump database for the appropriate hydraulics. The software suggests the SAT-Q 400/80/D as the optimum pump. Given Q = 62.3 m3/h and H = 9.8 metres, the operating point of the pump agrees precisely with the specification. The program supplies the pump diagram and all information and technical details about the product, such as various installation views, the bid solicitation text, materials and photo, which documents the project. Finally, the complete bid documents are printed on prepared data sheets.
Spaix PipeCalc is a leading program for operating point calculation of centrifugal pumps in the field of drainage and domestic utilities. It helps determine the required pumping capacity for selected applications according to international standards in addition to calculating pipeline losses. Spaix PipeCalc determines flow rate and quantity for drainage systems according to EN 12056 and ATV 118, and for drinking water supply systems according to DIN 1988.
Pipeline loss calculations allow for unbranched pipeline systems and branched systems with identical, parallel branches. When the flow rate is known, the pressure loss of the pipeline system and thereby the required lift height for the pump are determined according to pipeline loss components from straight pipe lengths, fittings, shaped parts and exit loss.