If pumps break down prematurely, it is not always related to the granular sediment in the dirty water. This will literally reduce exposed parts such as the impeller. But often the pH value of the water is the real problem.
Clear, dirty and waste water pumps are designed for pumping water with a pH value within a defined range. In clean water, the value scatters around seven on the pH scale, which ranges itself from 0 to 14. The pH value indicates whether a solution is acidic or alkaline. The following applies: The more acidic the water, the more aggressive it is to other materials. Even above the average value, oxidation prevails: Free hydrogen ions attack metals, resulting in corrosion.
Even stainless steel, usually the pump material of choice, is only conditionally immune. If the protective oxide layer is damaged, e. g. by notches, the rust will soon bloom. In the case of aluminium, protection only exists in the core range of 4.5 to 8.5 on the pH scale. The fact that aluminium does not rust is a frequent misapprehension. Cast iron has many advantages but offers only limited protection.
More often than assumed, the pH value of water is in the problematic range. Rough rule of thumb for deep excavation, special deep excavation and raw material mining: the deeper it goes, the more problematic. PH values down to −3.6 have already been measured for mine water. In most cases, mixed water is the cause, and this is often the case elsewhere in construction.
The pump manufacturer Tsurumi Europe GmbH, Düsseldorf/Germany, has developed its new TM series (Figure 1) especially for these scenarios while focusing on mobility (frequent relocation). These are lightweight submersible motor pumps where all parts that come into contact with liquid are made of titanium. They effectively protect against the chemical attack of pumped media containing salt and chloride.
Titanium is 45 % lighter than steel and twice as strong as aluminium. The material forms an extremely resistant oxidic protective layer, which can be less sensitive to dents, scratches and notches. Titanium is the material of choice in many applications.
The TM series currently comprises three pump types providing up to 350 l/min on the one hand and 15 m head on the other. Due to the weight advantage of the titanium alloy used by Tsurumi, the pumps weigh only 7,8 kg dry. In addition to titanium, Tsurumi also uses GRP for secondary housing parts and ultra-hard silicon carbide for shaft seals. Like almost all pumps in the range, the TM also comes with encapsulated electrical conductors, a double inside mechanical seal and built-in motor protection.
By the way, a trick can reduce the vulnerability of many pumps: Externally mounted anode blocks made of aluminium or zinc divert the galvanic currents and thus largely discharge the corrosive attack.
Tsurumi Europe GmbH