Pumping of extremely abrasive media, e.g. mixtures of iron ore and water, poses major challenges to mine operators all over the world. In order to improve lifetime and increase MTBF (Mean Time Between Failure) values, reliable and well-proven technological concepts are required, especially in terms of wearing part resistance. The Mulitsafe double hose-diaphragm pump offers a proven technology for these highly abrasive applications. The only real wearing parts of this pump are the suction and discharge valves. To guarantee continuous improvement of the already high valve lifetime, a special test rig has been installed at the Feluwa works in Mürlenbach/Germany. Daniel Nägel and Philipp Werhan are describing, how this test rig (Fig. 1 – with pump type TGK 250 3 DS 35, performance data: Q = 14 m³/h, p = 130 bar(g) ) allows testing of customer-specific media under real conditions.
The first test series started in 2017 with a mixture of iron ore (67 per cent by weight) and water to test the material resistance in terms of abrasiveness. The density of the dry material was 2500 kg/m3. The test was carried out with 9000 litres of test medium with a density of 1731 kg/m3 and a dynamic viscosity of 24 mm2/s (cSt). The pump was discharging a volume flow of 14 m³/h at a pressure of 130 bar(g) against full load.
The test compared standard material combinations for valve parts which are typically used in pump industry with alternative and, amongst others, new materials, such as valve balls made of aluminium oxide or valve seats made of hard metal or stellite. Each material pairing was subject to valve tests over a period of 80 operating hours against full load. The measured mass loss permitted conclusions on the resistance of the different material pairings.
The first analyses of the material pairings that have been tested so far show that the standard valve parts already do have a high stability, but that the alternative pairings offer great potential. The material pairing of aluminium oxide ball and stellite valve seat serves as an example. The overall lifetime achieved by this combination is almost 5 times longer than that of the reference material pairing consisting of a 1.4571 valve ball and a 1.4112 valve seat (Fig. 3).
It goes without saying that components made of such materials are more costly. However, life cycle costs for valve parts made of the above-mentioned material pairing are 50 % lower than for the standard pairing (Fig. 2). Pump availability is significantly increased thanks to the improved lifetime of the components and plant shutdowns for maintenance are reduced.
The tests clearly show a trend that the lifetime of individual components develops similar to the lifetime of their wear partners. The expected service life of a ball made of 1.4571 in combination with a valve seat made of material A is almost 50 % higher than the expected service life in combination with a valve seat made of material B.
By way of conclusion, the comparison of the equipment used on the test rig emphasises the outstanding lifetime of the Feluwa valve technology. During the test a steel deflector plate with a thickness of 30 mm, which was used to deflect the mixture of iron ore and water, was penetrated within 20 operating hours (Fig. 4), which shows that the Feluwa wearing parts that have been used so far fulfil highest requirements, even under the most extreme conditions and thus guarantee maximum operation times of Feluwa Multisafe double hose-diaphragm pumps.