The marine centrifugal pump casing is generally cast from cast steel and tin bronze. Although the properties of bronze are superior to those of cast iron and cast steel, they are subject to excessive stress due to mechanical stress during the long-term operation, which may cause cracks. Secondly, if the method is improper when handling and disassembling the pump body, the pump body will be damaged. In addition, the flow path of the pump body may be damaged under the action of liquid corrosion and scouring.
1.Pump casing crack
Check the crack of the pump casing, usually by first tapping the casting with a hand hammer, and the sound is clear and crisp. If the sound is hoar, the casing has cracks. The crack position is then further determined by the kerosene-white powder method. If the crack is not subjected to pressure or seals, in order to prevent the crack from continuing to expand, a hole of 3 mm in diameter can be drilled at the beginning and end of the crack to prevent the crack from continuing to expand. If the crack appears in the pressure part, repair welding must be performed.
2. Pump body flow corrosion and erosion
Depending on the pump material and working conditions, the causes of corrosion and erosion damage in the flow path are not the same, often for the following reasons:
1 The fluid pressure in the pump is high, and the flow rate is fast, causing erosion damage;
2 fluid damage to the chemical corrosion of the flow channel;
3 The pump body runner structure is improperly designed or damaged by the selection of materials.
For the case of 1 should change the working conditions of the pump; if the situation of 2, change the fluid chemistry or replace the adaptable centrifugal pump; if the case of 3, replace the pump or pump of better material. According to the experience, cast iron cast steel has the worst corrosion resistance and erosion resistance, tin bronze is better, 1G18 NitI is the best, followed by Cr13 steel. At present, the most effective repair method for the pump flow passage is chrome plating on the inner wall. After repairing in this way, it can guarantee no scouring and corrosion marks for 2 years of operation. If the condition does not allow chrome repair, weld repair can be used. Repair with epoxy resin.
